This publication on soluble salts is dedicated to Dr. Paul Lyerl Resident Director of Texas A&M University Agricultural Research Cent at El Paso. From his arrival at the Center in 1942 until his death in 197i Dr. Lyerly was totally dedicated to the advancement of agricultur During this period, salinity emerged as a major agricultural proble = Although it continues to plague Texans, there is now a better understan ing of the problem and how to minimize its adverse eillects on soils . i crops. Bulletin 876 -— published August 1957; revised October 1959; October 1962,- ]une 19 Contents i—-r-w—-r—i—v—l i-Ikwmo-IOO >-¢r—~>-Ir—- COO5UIUI 2O 21 21 21 21 23 23 26 27 28 28 29 29 29 29 30 30 31 31 31 32 33 33 34 2020100000 -\l®®UlCJ1Ulr-I> SUMMARY INTRODUCTION SOLUBLE SALTS IN WATERS AND SOILS Where Salts Come From Kinds and Amounts of Salt How Salt Problems Develop Definition of Terms CHARACTERISTICS OF SALT-AFFECTED SOILS Saline Soils Saline-Sodic Soils Sodic Soils Definition of Terms EFFECTS OF SALTS ON PLANT GROWTH How Plants Absorb Water How Salts Reduce Available Water Visible Effects of Salinity Salt Tolerance of Plants Definition of Terms QUALITY OF WATER FOR IRRIGATION Total Salt Content Sodium Content Other Water Quality Considerations — Borates, Bicarbonates, Nitrates Definition of Terms SALINITY CONTROL AS AFFECTED BY MANAGEMENT Preventing Accumulation of Salts Establishing Good Drainage Planting Under Saline Conditions Using Best Water for Germination Applying Plenty of Water — Leaching Percentage Maintaining Good Soil Structure Using Amendments if Needed Managing Fertility While Controlling Salinity Definition of Terms RECLAMATION OF SALT-AFFECTED SOILS Assessing the Situation Reclamation of Saline Soils Reclamation of Saline-Sodic and Sodic Soils Reclamation Using High-Salt Waters Definition of Terms SAMPLING SOILS AND WATERS FOR SALINITY ANALYSIS Soil Sampling Water Sampling Definition of Terms ACKNOWLEDGMENT REFERENCES APPENDIX Summary This bulletin attempts t0 set forth the concepts of salinity andrsalinity control in a simple, concise form that is easy to read and readily understandable by farmers, small landowners, gardeners and townspeople. Soluble salts can, in some way, become a problem for anyone engaged in the growing of plants. These problems are most prevalent in the more semiarid and arid regions of the State but are not confined to those areas. The homeowner with sickly shrubs, flowers or vegetables in East Texas also may be faced with some type of salt problem. ' This affliction is subtle and can develop in many different ways: from application of salty water, from low soil permeability, from high ground water tables, from not applying enough water, from inadequate drainage, from not understanding salt-tolerance in plants, from simple mismanagement and at times from over- fertilization, particularly with potted plants and flower beds. The problems of salinity are already serious and are becoming more so in Texas because the acreage of irri- 4 gated lands is constantly increasing while our availa water supplies are decreasing. This will necessitate l of poorer quality water and less desirable land for riculture in the future. Many thousands of acres of once-productive land Texas are already “salted out.” Many thousands m already are experiencing reductions in yields because excess soluble salts. These yield reductions often are recognized as being caused by salinity because ot factors—diseases, insects, weeds, weather——are eas to see and more likely to be blamed for the trouble. An understanding of salinity—how it can devel how it affects plant growth and how it can controlled-should be of value to all persons concern, with producing finer crops, vegetables, fruits, nu flowers or shrubs anywhere in the State of Texas. Mention of a trademark or a proprietary product does not constitu guarantee or warranty of the product by The Texas Agricultural Ex iment Station and does not imply its approval to the exclusion of 0 products that also may be suitable. ' ‘ More than one-fourth of the irrigated farmland of _ nited States is affected to some extent by excess soil A ter salinity. In the I7 western states, more than 18 a1 acres of irrigated land are salt affected. In Texas, problems are more extensive and more serious lmost people realize. Soluble salts are a serious and uing problem in the 200,000 irrigated acres west of ecos River where most agricultural waters are very Actual and potential salt problems exist along the length of the Rio Grande River from New Mexico v Gulf of Mexico. Production throughout the lush. I Rio Grande Valley winter garden area is continu- I endangered because many of the crops grown (cit- F d vegetables) are very sensitive to salts. ong some parts of the heavily populated Gulf f, accelerated pumping of ground waters for indus- I d municipal needs is resulting in the encroach- ' of ocean water into these aquifers.‘ Rice farmers a e encountering salt problems in pumping waters "ayous, inlets and rivers in periods of low tide or river flow. In North Texas, production of irri- g valley lands along the Red River has been reduced ~: yyears by the high salinity of the ground waters l“ area. Many wells in the smaller irrigated areas of . ,1. L _ paper by C. Godfrey (27) and recent unpublished studies by the ‘ Water Development Board and U. S. Geological Survey. f‘ ively, associate professor, TheiTexas Agricultural Experiment l; , Corpus Christi; and resident director and professor (de- ), The Texas Agricultural Experiment Station, El Paso. Control of Soluble Salts in Farming and Gardening D. E. Longenecker and P. J. Lyerly* West Central Texas contain enough soluble salts to affect crop growth. In the extensive High Plains irrigated area, gradual depletion of good quality ground waters means that sooner or later farmers may be forced to use waters of poorer quality, which in places underlie the good waters of the Ogallala formation. Only the northeast portion of the State, with its predominantly sandy soils and high rainfall, will continue to remain free from salt problems in the future. The acreage of irrigated or supplementally irrigated land in Texas is constantly increasing, whereas water supplies are not. This means that the hazards caused by salinity will continue to_ increase as waters of poorer quality must be utilized. Perhaps the most serious aspect of salinity is that itaifects crop yields on some of the most productive land in the State—the nearly 10 million acres now under full or partial irrigation. Field crops, vegetables, fruits, nuts, flowers, shrubs—all are susceptible to salt injury. This publica- tion is intended to inform all persons engaged in growing these plants of the many ways in which salt problems may develop and how these problems often can be rec- ognized, minimized or even eliminated by good man- agement or simple know-how. SOLUBLE SALTS IN WATERS AND SOILS Where Salts Come From All waters from surface streams and wells contain dissolved salts. The original source of these salts is the 5 I PERCENT SALT SOLUTION ONE LITER WATER IO GRAMS SALT earths crust. As a result of weathering, small amounts of salt are dissolved from the rocks and carried away by water. Mountain streams usually contain only small quantities of salt. As the streams enlarge into rivers and move toward the ocean, they accumulate more and more salt in solution because evaporation, constantly occur- ring, removes only pure water, leaving the salts behind (Figure 1). Drainage waters from irrigated lands, ef- fluents from city sewage and industrial waste waters also are diverted back into the rivers, gradually increasing the salt load. In some instances underground waters pass through beds of salt, dissolving appreciable quantities before they emerge and enter the rivers. Ocean waters, much too salty for irrigation, contain about 3 percent salt, or about 4O tons of salt per acre-foot of water. This is the result of millions of years of salt accumulation from rivers, together with constant evaporation which each year lifts billions of tons of pure water vapor into the atmosphere to fall again somewhere as rain or snow. _ Kinds and Amounts of Salts Generally, salt is thought of as table salt; however, hundreds of different salts are known. Examples of common salts usually found in irrigation waters are table salt (sodium chloride), Epsom salt (magnesium sulfate), gypsum (calcium sulfate), street salt (calcium chloride), Glaubefs salt (sodium sulfate) and baking soda (sodium bicarbonate). In this publication all of the salts will at times be referred to collectively as “soluble salts.” The kinds rof salts normally found in irrigation waters, their chemical symbol and the relative propor- tions of each salt usually present are shown in Table 1. It should be emphasized that this is a hypothetical water only. The proportions of each salt vary considerably in waters from different areas and often differ appreciably in waters from the same area. Usually sodium salts make up a large percentage of the total salt present. The kinds, amounts and proportions of the various dissolved salts are very important in all aspects of salinity. All salts, when dissolving, separate into very mi- nute, invisible charged particles called ions. Thus sodium chloride forms an equal number of positively charged sodium ions (Na '4‘) and negatively charged 6 ONE HALF WATER EVAPORATED t | \ \ | l \ l I 1 \ \ \ ‘ , ‘l,’ \ \ l I 1 ‘ \ "1 ‘\\\“"'I1 \ \\\l|ll/] ". .': “a Figure 1. Effect of water evaporation on the concen- tration of salts in solution. A liter is approximately 1 quart. Ten grams is about 1 teaspoonful. 2 PERCENT SALT SOLUTION chloride ions (Cl T). A salty irrigation water therefore is actually composed of millions of submicroscopic ions, all charged, and all mixed uniformly throughout the water. Many of the ions are required by plants for normal, healthy growth. These should be thought of as essential nutrients. Some of the essential ones are calcium, mag- nesium, potassium, sulfate and nitrate. Sodium, usually present in largest amounts, is not essential for plant growth. Irrigation waters therefore contain both essen- tial and nonessential ions. However, salinity always re- fers to too much salt. Even essential ions like calcium, magnesium or sulfate can be quite harmful when present in too large quantities. How Salt Problems Develop Salt problems usually develop in one or more 0 three ways: (1) From salts already present in the soil, (2) from high ground water tables or (3) from salts added in TABLE 1. KINDS OF SALTS NORMALLY FOUND IN IRRIGA TION WATERS, WITH CHEMICAL SYMBOLS AND APPROXI MATE PROPORTIONS OF EACH SALT1 Approximate pro- ChEmiCHl portion of total Chemical name symbol salt content Sodium chloride NaCl Moderate to large I Sodium sulfate Na2SO4 Moderate to large Calcium chloride CaClz Moderate Calcium sulfate (gypsum) CaSO4 - 2H20 Moderate to small A Magnesium chloride MgCl2 Moderate Magnesium sulfate M9804 Moderate to small Potassium chloride KCl Small Potassium sulfate K2804 Small Sodium bicarbonate NaHCO3 Small Calcium carbonate CaCO3 Very small Sodium carbonate Na2C_O3 Trace to none Borates BO3_ Trace to none Nitrates N03- Small to none lWaters vary greatly in amounts and kinds of dissolved salt This water fairly well represents many used for irrigation in Texa p ‘gation water. Salts added in the water are by far p st frequent cause of trouble. . ' e problem of salts already present in the soil is ; y limited to arid 0r semiarid areas where rainfall is flicient to dissolve and leach these salts below the A of the root zone. If any question exists as to the ntent of the soil, samples should be taken for 4t analysis. Generally, even in arid regions, well- » soils are fairly low in soluble salts. alt problems often develop from the presence of “g ound water tables. Ground waters in many areas I ite salty, and in river valleys are often near the soil '- unless adequate drainage systems have been Water containing dissolved salts moves up- into the soil above a water table through the fine jres or capillaries. The extent of upward capillary ‘ ent of water and salts depends upon the texture of il. In coarse sands with large capillaries such up- (movement will be less than 3 feet. In medium- d soils (loams) with smaller capillaries, total up- movement can extend 5 to 1O feet above a water ‘ In clays and clay loams, which contain many very apillaries, salts have been known to accumulate 2O feet above a water table over a long period of time. ner the soil texture and the finer the capillaries, the ‘r the moisture and salts can move, but the rate of f d movement slows rapidly as capillaries become a . l) 0st salt problems develop directly from salts 5- in the irrigation water. This is usually a gradual . because large amounts of salt must accumulate e effects become visible. It is almost always the ulated salts which affect plant growth. Plants ab- I and give off (transpire) much water. Additional i is evaporated from the soil surface. In both pro- 1 , pure water is removed, and the salts are left d t0 accumulate. This is illustrated simply in Fig- _j If 10 grams of salt are dissolved in 1 liter of water, yevaporates, a 2-percent solution is created. Both ration and transpiration are high in arid regions humidity is low and temperatures are high. e amounts of salt added to a soil by irrigation as over a 6-year period when 3 acre-feet (36 inches) I er are applied each year are shown in Table 2. Salts umulate very rapidly. The water containing 1 ton f per acre-foot is generally considered to be good water, yet in 2 years enough salt could accumu- l» harm salt-sensitive plant species, and in 4 years rops could be seriously affected. Municipal water 'es in many western states, including some Texas , contain as muqh=as 1 ton of salt per acre-foot. alts added to the soil must be removed before ulation becomes serious. The only way this can be is by leaching; that is, washing the salts down l; the soil below the bottom of the root zone. Thus, i g and drainage become essential in control of ve a l-percent salt solution. If half of this water’ salinity. Leaching of ‘salts can be done by applying extra water with every irrigation, but this is unnecessary, expensive and wasteful of water. Most farmers in irri- gated areas leach the soil once each year with a heavy irrigation applied before planting. Salt injury to flowers, shrubs, vegetables and fruit trees is a common occur- rence with townspeople in low rainfall areas. They do not understand that even municipal water supplies may con- tain enough salt to make periodic leaching necessary. Contrary to general belief, harvested crops remove very little salt from the soil in comparison to the amounts generally added in the water. Some approximate values are given in Table 3. Total quantities of salt removed are seldom more than 300 pounds per acre per year. Thus, leaching is necessary regardless of the crop grown, un- less irrigation waters are exceptionally low in salt. Rainfall can help to reduce salt accumulation, but amounts falling in arid regions are too little and too unpredictable to be of much help. Some areas are excep- tions, however. In the irrigated subtropical Lower Rio Crande Valley of Texas, rainfall each year is sufficient to keep salts leached from su-rface soils even though saline ground water tables often are less than 1O feet deep. Without this rainfall, salt problems in that area would soon become much more serious. Definition of Terms absorb—to take in or assimilate. acre-foot—amount of water to cover l acre to a depth of 12 inches (43,560 cubic feet). arid—very dry; desert or semidesert. capillaries—fine pores or openings in soil which can contain either water or air or both. chemical symbol-——each individual atom comprising all matter has been given a symbol (abbreviation) for chemical purposes. concentration—refers to the amount of a substance dissolved in, or mixed with, another liquid or material. constituent—one of several substances making up the whole ofa mater- ial. dissolved—a substance which in solution attains true molecular or ionic form (true solution). TABLE 2. QUANTITIES OF SALT ADDED TO THE SOIL BY ANNUAL APPLICATIONS OF 3 ACRE-FEET OF WATER OF VARIOUS SALT CONCENTRATlONSl Tons of salt Tons of salt added to the soill per acre-foot of 1 2 y 3 4 5 6 water applied year years years years years years 0.5 1.5 3 4.5 6 7.5 9 1 3 i 6 9 12 15 18 2 6 12 18 24 3O 36 4 12 24 36 48 6O 72 6 18 36 54 72 9O 108 lThese amounts wil_l accumulate in the soil if not leached down- ward with extra water. TABLE 3. APPROXIMATE POUNDS OF SALT IONS REMOVED FROM THE SOIL EACH YEAR BY VARIOUS CROPS IN THE EL PASO AREA Crop Pounds removed by crops yield, pounds Crop per acre Sodium Calcium Magnesium Sulfate \ Chloride Total l: Sweetclover hay 8,000 17 156 104 69 33 379 Sudangrass hay 10,000 21 34 69 199 67 39 Alfalfa hay ‘8,000 42 60 49 52 55 258 Barley straw 2,000 14 8 3 28 15 q Corn silage 30,000 72 5s 103 97 103 j" 43 Barley grain 10,000 2 1 1 3 7 A Sorghum grain 4,000 6 3 5 8 17 Cottonseed 1,500 3 2 5 8 16 Average 7,938 22 40 42 58 39 202 drainage waters——refers to that water which is removed mainly through gravitational forces. earth’s crust——materials which make up the surface of the earth, usually to a depth of 5-10 miles. essential nutrients—th0se particular atoms, ions or molecular groups necessary for normal plant growth. excess salts—more salt than is needed 0r desirable in soils, plants or waters. gram—unit of weight in the metric system. One pound equals approx- imately 454 grams. ground water table—that point below the soil surface at which free gravitational water exists. humidity—refers to the relative amount of water vapor present in air at any time or location. hypothetical—similar to something, but which does not really exist in exact form. ion—charged atom (or group of atoms) which is formed when sub- stances dissolve in a liquid. leach—wash down through the soil. liter—unit of volume in metric system. Contains 1,000 cubic centime- ters of liquid—l.057 quarts.‘ loam—refers to a soil which contains coarse, medium and fine particles in fairly equal proportions; a good soil. percentage—-expression based on 100 as the total—l0 percent (10%) means 10/100 of the whole. pores——openings within the soil which can be large or small, and which can contain either air or water; very small pores are called capillaries. , proportion—a part or fraction of any wholefmaterial. salinity——refers to too much total salt. salt-sensitive-—-refers to plant species which are easily injured by ex- cess salts. semiarid—usually thought of as dry areas which do not receive enough rainfall for crop production without aid of some irrigation. sewage eflluent—treated municipal waste water after solid sewage materials have been removed. silage-crops cut before full maturity and stored in containers (silos) which exclude air and prevent spoilage. soil texture—refers to the relative proportions of large (sand), medium (silt) and fine (clay) particles which make up the whole soil. » submicroscopio-too small to be seen even with the aid of a micro- soluble salts—salts which can readily dissolve in water. species—refers to the classification of plants as developed by botanists to separate various types or groups. scope. transpire—leaves give off (transpire) water by evaporation, through millions of tiny openings in the leaf surface. ' weathering——gradual decomposition of materials through action 0 climatic factors such as wind, rain, freezing, thawing. CHARACTERISTICS OF SALT-AFFECTED SOILS p Salt-affected soils can be divided into three groups, depending upon the kinds and amounts of the variou salts present. It is important to understand these differ ences because they determine, to a great extent, ho these soils should be managed or reclaimed. Saline Soils A saline soil is one which contains sufficient solubli salts to injure or reduce the growth of many plants. Sodium salts are present but not excessively high i proportion to calcium and magnesium salts. Saline soil may be recognized by white crusts or brown fluffy are \ on the tops of the beds or high spots, but these are no always present. Plant growth may be stunted, and stand of crops may be spotty and irregular because of the effec of salts on seed germination (Figure 2). Ordinarily th pH (soil reaction) is below 8.5. Saline soils generally ar flocculated (friable), and their permeability to"water similar to that of nonsaline soils of similar texture. The principal effect of salinity is to reduce th availability of water to the plants, and this is noticeabl primarily in poorer seed germination, slower growth an a generally stunted condition of crops. Leaf color unde highly saline conditions may be bluish green. Total sal content of saline soils may vary considerably, but thei main distinguishing characteristic is not the amount 0 salt present, but the fact that the quantities of solubl calcium and magnesium salts are high enough to main tain good soil tilth and offset the adverse effects 0 sodium salts. ' i 2. Spotty stand of 'tton growing on ‘l. Good yields can ed from mature 1 but germination 1 ously reduced by ate, fluffy salt ac- tions on tops of $0diC SOilS e saline soils, saline-sodic soils contain sufficient ' ties of soluble salts t0 reduce the growth and yields yplants. S0 long as an excess ofall salts is present, ‘ysical properties of these soils are good and similar k of saline soils. The pH is seldom higher than 8. 5. irrigated with salty waters, their permeability is reduced but not seriously so. Saline-sodic soils from saline soils in that the relative proportion of to calcium and magnesium is appreciably higher; g comes obvious after heavy rains or after irrigation ' ow salt (good quality) water. en heavy rains occur, most of the soluble cal- d magnesium are washed out of the surface soil, ‘it effect of the sodium (much of which remains ed to the clay) quickly becomes evident. The pH .11. ove 8.5, the soil becomes dispersed and permea- to water virtually ceases. Rainwater often stands on soils for many days until it evaporates. Aeration to ‘roots is cut off, and the shock of the sudden change _ chemical and physical conditions often results in i‘ ete shedding of leaves and even death of the plants R 3). The danger of the excess sodium often goes gnized until these events occur. These soils re- amendments to remove the excess sodium (see i: s on salinity control and reclamation). a Soils odic soils (often called nonsaline sodic soils) are ely low in soluble salts but contain much sodium ed on the clay particles of the soil. These soils tend i ain in a dispersed condition, impermeable to both _ d irrigation water. They are of very poor tilth -—- ; and sticky when wet and prone to form hard clods i sts upon drying. When wet they have a charac- l smooth, slick loqkcaused by the dispersed condi- i. igure 4). "*- ese soils are very poor for growth of any plants. i pH is too high, usually ranging between 8.5 and i lamation is necessary before crops can be grown, al recovery to normal, friable, well-aerated condi- tions often is a slow process, requiring several years and much expense. Sodic conditions tend to develop in low areas of fine-textured soil periodically subject to flooding with high sodium waters. They also can develop from continued application of waters high in sodium and low in calcium and magnesium. They usually do not contain impermeable zones within the root area. Definition of Terms adverse——undesirable. aeration—refers to ability of air to penetrate into soils. Roots need air to survive and grow. amendment——material added to soil or water to improve the physical and chemical properties of soils. availability—refers to the ability of plant roots to extract soluble mater- ials from soils. clay—the finest particles in the soil. Too small to be seen with an ordinary microscope. clod—clump of soil of large size cemented together, usually in poor physical condition. dispersed—refers to soils in which the individual sand, silt and clay particles are separated, not aggregated or flocculated: a very undesirable physical condition for plant growth. flocculated-—opposite of dispersed. Soil particles are grouped together and permit intake of air, water and roots. friable——easily workable, not cloddy or crusted. pH—refers to acidity or alkalinity of soils or waters. pH of7 is neutral, below 7 is acid, above 7 is alkaline. Plants grow best in pH range of 6.0-8.0. physical properties—those properties of soils relating to density, pore space, texture, water and air permeability. plastic-—easily molded, like putty; an undesirable soil condition related to high clay content, low water permeability, poor aeration and dispersion. i proportion—-a part or fraction of any whole material. salt-aifected——refers t0 soils containing too much salt, or to plants injured by too much salt. soil reaction——same as pH (see above). tilth-—ease of workability of soil in seedbed preparation, planting, cultivation and so forth. A good soil is a soil “in good tilth." 9 EFFECTS OF SALTS ON PLANT GROWTH How Plants Absorb Water To understand how soluble salts affect plant growth it is necessary t0 know how soils hold water and how plants obtain this water. After a heavy rain or irrigation, the soil within the plant root zone becomes filledwith water. Some of this water in the larger pores drains out of the soil within 2 or 3 days. That water remaining is held within the many smaller pores or capillaries. Most of this water is availa- ble to plants and is taken in through tiny hairs near the tips of the rootlets. A single plant may have thousands of rootlets and millions of tiny root hairs. Most of this water passes through the plants and is lost from the leaves by transpiration (evaporation). Some soil water rises by capillarity and is evaporated from the soil surface. As soils become drier and drier, the water remaining in them is held more and more tightly and becomes more difficult for the plant roots to extract. This holding force 1O an‘ ‘.4’; Figure 3. Half-grown cotton growing saline-sodic soil killed after heavy rain. Fl caused soil dispersion, waterlogged co . tion, sodium toxicity and high pH. (El .. Valley, 1957.) is called soil moisture tension. The moisture content two soils as related to moisture tension is shown , Figure 5. After a heavy rain or irrigation, the moist tension is very low, and the amount of water in the soil i at a maximum. The clay loam holds more water than t sandy loam because soil particles in the clay loam . much smaller; therefore, the capillaries or pores k, finer. The finer the capillaries, the more water a soil ; hold. ' Plants permanently wilt when the available water almost all gone or when the soil moisture tension . proaches 10-12 bars (atmospheres). At this point so hold water so tightly that plants cannot get enough. the sandy loam soil, only about 9 percent water (from 0 15 bars) is available to plants, whereas in the clay lo soil nearly twice as much (about 16 percent) is availa (Figure 5). F iner-textured soils therefore hold mo available water than sandy soils. Most of the available water in the sandy soils is h) at low soil moisture tension, which makes it easy for r Figure 4. Sodic soil area in cotton field caused by high sodium water. Note spotty condition of the area, poor germination and slick look caused by the dispersed soil. s to absorb. Above 5 bars tension, hardly any availa- HQW Salts Redlwe AVailable water water is left in the sandy soil (note vertical rise in i‘ e, Figure 5). Plants growing on sandy soils therefore 0' water rapidly for a short time, and then suddenly in to wilt. In finer textured soils, water is removed re gradually, as the curve shows. More water is avail- p , but plants also use it more slowly. Often a crop on “loam soils can grow 3 to 4 weeks without wilting, jereas the same species on sandy loam soil would need ‘mating much more often. Plants absorb water and dissolved nutrients from the soil through the root hairs partly by a physical pro- cess called osmosis. Water can move from the soil into the root hairs only so long as the osmotic pressure of the root hairs is greater than that of the soil water. Salts, sugars, nutrients and other soluble materials within the plant cells contribute to their osmotic pressure or solute content, which is always present, not only in the roots but in all plant tissue. Any increase in the soluble salt content of the soil raises the osmotic pressure (OP) of the soil solution; as a result less water flows from the soil into the plant. For example, the OP within the root hairs of most plants growing on nonsaline soil is usually about 2 bars. After a heavy rain (pure water) the OP of the soil solution would be near zero, and water would flow readily into the roots because the difference in OP was 2 bars in favor of the plant. Water always flows from lower to higher osmotic pressure, and the greater the difference the greater the rate of flow. 4.’SANDY LOAM SOIL QFCLAY LOAM SOIL If the soil should be irrigated with water containing 2,000 ppm soluble salt, the OP of the soil solution would be raised to about 1 bar. The difference between the root 12¢» g l . OP and the soil solution OP would then be only 1 bar, "° 5 ‘éf '5 2° V25 and the rate of water movement into the roots would be 5m‘- MOSTURE CONTENT ' PERCENT slower. If the salt content of the irrigation water was even higher, or if the soil itself contained accumulated salts, isture retention differ. Sandy soil holds less water than finer- the QP ofthe Soil Solution Cpuld easily rise above 2 barsj ed clay loam, but this water is more easily extracted by plants At thls PQmt» flow Qfwater m“) the mots wOuld themetl‘ 1e it is less tightly held. cally cease, and the plant should wilt regardless of the 11 5. Soils of different texture showing how moisture content amount of water remaining in the soil. This is the major effect of excess soluble salts 0n plant growth. They re- duce the amount of soil water available t0 the plants. Plants growing in three s0ils—one nonsaline, one mod- erately saline and one highly saline—are depicted in Figure 6. In the nonsaline soil about half of the total soil water could be used before the plant wilted. At moderate and high salinity, smaller and smaller amounts would be available, and the plants would suffer for water sooner. Visible Effects of Salinity The most obvious visible effects of excess salinity are reductions in both rate 0f growth and total plant size: Forage and seed yields are also usually reduced. Corn (moderately salt tolerant) growing in pots irrigated with waters of increasing salt content is shown in Figure 7. The seed were germinated with low salt water, and the salt treatments were begun about 2 weeks after emergence. The plants are about 8 weeks old. The five salinity levels were 1,000, 2,000, 4,000, 8,000, and 16,000 ppm total mixed salts in the water. Excess water was applied at each irrigation to prevent any salt accumu- lation. From the l,000- to 16,000-ppm salt levels, plant growth was successively reduced. Yields were slightly lower at the 2,000 ppm level, greatly reduced at 4,000 ppm, and no grain at all was produced at the two highest salt rates. Leaf color was bright green at the lowest salt level, gradually assuming a bluish-green cast as the salt content increased. Firing or scorching of leaf edges be- came noticeable at 4,000 ppm, was greater at 8,000 ppm, and at 16,000 ppm the plants died before tasseling. A similar growth reduction with castorbean, also classed as moderately salt tolerant, is shown in Figure 8. This response of corn and castorbean is rather typi- cal of most plant species. It is apparent that there is no sharp point at which growth ceases as salinity increases. The adverse effects simply become more obvious at higher and higher salt levels until the plants die. The question therefore arises as to why the crops did not wilt and die immediately as the osmotic pressure of the soil solution rose above 2 bars (4,000 ppm salt), where intake of water should cease (according to the previous discus- ‘WAILABL? WATER NONSALINE MODERATELY SALINE HIGHLY SALINE SOIL SOIL SOIL Figure 6. Diagram showing that as the salt content of the soil in- creases, the availability of the water to plants decreases. In a non- saline soil, about half the water is available. ln a highly saline soil only about one-tenth of the water is available. [From Bernstein, Fireman and Reeve (1) ]. I2 sion). The answer is that all plant species are able, within reasonable limits, toincrease their internal osmotic pres- sure given sufficient time t0 adjust t0 a higher salt g situation: The words “within reasonable limits” are re- lated to salt tolerance. The earliest stages of plant growth (seed germina- tion and seedling establishment). are usually the most critical. Most plants are more sensitive to salt at this tim a because the tissues are tender and root systems ar shallow. Thus, spotty or skippy stands are a typical visi ble symptom of excess salinity (Figure 2). Of course skippy stands can occur due to other reasons. Often, ' plants survive the germination and seedling stages, ‘the may make fairly normal growth and yields (Figure 2).. This is especially true of species with some degree of sal tolerance such as cotton, alfalfa, corn and sorghum. It ha often been said by farmers in high salt areas that “gettin a stand is half the battle won. ” (For techniques for obtain l. ing better stands, see the section on salinity control.) Another visible symptom of salinity is a lack of re, sponse to applied fertilizers. Most inorganic nitroge and potassium fertilizers are soluble salts, and whe salinity is the principal factor retarding growth, fertiliz ers often add to the problem and sometimes do mor harm than good. In saline areas much fertilizer is waste each year because the chief factor limiting growth i salinity even though fertilizer nutrients (nitrogen, phos phorus, potassium) may be deficient. Salinity must firs be reduced before crops will show an economic respons to fertilizer. Some organic fertilizers (fresh manure) als contain soluble salts which could aggravate a salini .- situation. Since most inorganic fertilizers are soluble salts, it ii possible for salt problems to develop directly and solel from over-application of fertilizers. This is particularl true of greenhouses, flower beds and potted plants where rapid growth is desired, and it is easy to add to much fertilizer. Soil samples sent to the Texas A6: University Extension Soil Testing Laboratory (see foot note 2) from greenhouses, flower beds and gardens .1 well as from high salt areas are tested for soluble salts . well as for nutrient content. Recommendations based 0 fertility alone can be completely inadequate and mi‘ leading because salinity may be the main factor limitin growth. ' Visible symptoms of salinity on saline-sodic so' may be similar to those for saline soils; however, aft heavy rains, serious changes may occur. In these soil rains can cause dispersion of the surface soil with drast’ reductions in water permeability. This in turn can brin about waterlogging of the soil and inadequate root aer tion. In addition, toxic effects from excess sodium an high pH levels may become evident. This results ' wilting, yellowing or complete shedding of leaves an sometimes death of the plants (Figure 3). Salt Tolerance of Plants Plant species vary tremendously in their ability tolerate saline or sodic conditions. This is called “s Figure 7. Corn growing in greenhouse pots with in- creasing concentrations of soluble salts in the irriga- water. Crop is about 8 geeks old. tolerance,” “natural adaptation t0 salt” or “adjustment t0 galinity.” Some species are very sensitive t0 salts, many moderate tolerance, while a few types seem t0 saline soils. The mechanisms and factors involved salt tolerance are many and not yet well understood. appear to be related to either one or both of two ditions: (l) the ability of the plant to restrict the trance of salts or certain salt ions into its roots with the eater or (2) the ability to tolerate or adjust to salts after “ey are taken into the plant. Soluble salts and other mineral nutrients enter the twith the water as it moves through the root hairs. living tissue of root hairs of different plant species varying degrees of capacity to restrict the entrance of attain ions-—the reasons are not fully understood. As Bermudagrass and the wheatgrasses grow a on saline soils, yet do not absorb harmful amounts of ble salts. Their mechanism of tolerance could be led restricted absorption: Other grasses such as ,1.» -,_ ‘s? e 8. Castorbean ing in greenhouse f-with increasing con- _ ftions of soluble salts irrigation water. Crop g t8 weeks old. Rhodesgrass and alkali sacaton can absorb large amounts of salt, yet still grow well on saline soils. Their living tissue is able to tolerate or adjust to these salts by increas- ing its osmotic pressure, and by other means. This mechanism could more truly be called salt tolerance. These two mechanisms of either restricted absorp- tion or tissue tolerance form the basis for present-day classifications of plant species into what are called salt tolerance groups; that is, sensitive, moderately tolerant, tolerant and highly tolerant (Table 4). These tolerance ratings are of necessity rather general because other factors such as management practices, environmental conditions, new crop varieties, or types of rootstocks used in propagation of fruit trees can affect tolerance. Some low tolerance species are able to survive on saline soils, yet their growth and yields are greatly reduced. Others have varying degrees of sensitivity at different stages of growth.‘ Beets are quite sensitive to salt in the germination and seedling stages but become much more l3 tolerant as they mature. Hadishes and green beans ger- minate well under saline conditions but become more sickly the longer they grow. Alfalfa germinates well, but irrigation with salty water during the two- to four- leaf stage will often kill it. As its root system deepens, it becomes more salt tolerant. Some species are sensitive to specific ions such as sodium or chloride. This is true of the stone fruits and citrus. The tolerance ratings (Table 4) should therefore be used only as general guides. In this respect they can be quite helpful. TABLE 4. GENERAL SALT TOLERANCE RATINGS OF VARI- ous CROPSl Moderately2 Very Sensitivez tolerant Tolerant2 tolerant2 ECx103 ECx103 ECx103 ECx103 2.0- 4.0 4.0- 6.0 6.0- 8.0 8.0- 12.0 FIELD CROPS Field Bean Soybean Wheat (grain) Barley (grain) Castorbean Oats (grain) Rye (grain) Sesbania Safflower Sugar Beet (seed) - Rice (grain) Cotton Flax Sunflower Guar Sorghum (grain) Corn (field) FORAGE CROPS White Reed Hardinggrass Bermudagrass Dutch Clover Canary Grass Alsike Clover Oats (hay) Kleingrass Wheatgrass Red Clover Orchard Grass Buffelgrass Barley(hay) Ladino Clover Brome Grasses Alfalfa Rye (hay) Crimson Clover Big Trefoil Birdsfoot Panic-grass Trefoil Burnet Grama Grasses Hubam Clover Alkali Sacaton Meadow Foxtail Sour Clover Dallisgrass Rhodesgrass Milk Vetch Tall Fesque Saltgrass Timothy White Sweet Clover Sudan-Sorghum Yellow Hybrids Sweet Clover Sorghum Perennial (forage) Rye Grass Corn (forage) Wheat (hay) Johnsongrass ' (hay) VEGETABLE CROPS Carrot Lettuce Tomato Asparagus English Pea Corn (sweet) Beet Radish Potato Kale Celery Squash SDlTIBCh Green Bean Onion Broccoli Lima Bean Sweet Potato Cabbage Kidney Bean Yam Cauliflower Cucumber Bell Pepper Watermelon Rhubarb Hot Pepper Blackeye Pea Muskmelon 14 Table 4. (continued) FRUIT, NUT AND VINE CROPS?’ Grapefruit Pecan Pomegranate Date Palm Orange Peach Fig Lemon Apricot Olive Avocado Grape Pear Quince Apple , 1F Cherry l "f Plum Walnut Blackberry Raspberry y. Strawberry =5 Boysenberry ORNAMENTAL SHRUBS ‘ Viburnum Spreading Oleander Purple Sage . Juniper , Arbor Vitae Bottlebrush Lantana Pyracantha Privet Japonica lData taken from many sources but primarily from publications n7 the U. S. Salinity Laboratory, Riverside, California. (Ratin assume use of reasonably good production practices as suggest in section Salinity Control As Affected By Management.) 2Electrical conductivity (EC x 103) values listed at tops of colum _ are values of soil saturation extracts at which some reductioni growth and yields can be expected. A 3Ratings may vary somewhat depending upon the particular roo stock used for propagation. Many species, especially flowers, have never bee a adequately evaluated for salt tolerance because of th continual development of new varieties that may differi I: tolerance ratings. In helping to determine the salt toler ance or adaptability of trees, flowers, fruits, vegetable or shrubs in a particular area, the following suggestion should be helpful: 1. Have soils and waters tested for salt content t learn the magnitude of the salinity situation. ' 2. Contact your local County Extension Agen nurserymen or garden clubs. Their knowledge, much r it gained through experience, is valuable. 3. Examine the soil to learn something about i) texture, its depth and its internal drainage characteri . tics. 4. Carefully read the section “Salinity Control . Affected by Management.” 5. Begin with limited planting to avoid large _ nancial losses if the crop is not adapted or will not tole ‘ ate the salt conditions. ' Definition of Terms adapted—refers to ability of a plant type or species to grow well a produce good yields under a given set of conditions. aeration—plant roots need air for good growth. Aeration refers i ability of soil to supply air to roots. ’ aggravate-to make worse. le—refers t0 ability of plant roots to take up water 0r nutrients from the soil. p a unit ofpressure or resistance t0 pressure (or suction). One bar is equal to one atmosphere of pressure. TH 'ty—the ability of water t0 move through (or wet) a soil by physical forces other than the downward pull of gravity. ntration—refers to the amount of a substance dissolved in, 0r mixed with, another liquid 0r material. rsion—condition in which individual soil particles (sand, silt, clay) are no longer held together in clumps or aggregates; an undesir- able condition. lishment—term used to describe the emergence of seedlings after germination. T; (scorching)——condition where plants affected by too much salt develop dead regions along edges of leaves. i’ - . ic—not considered derived from organic living material such as plants or animals; mineral in nature. al drainage—refers to movement of water downward by gravity ’ through a soil. ism—a procedure or process. alts——more than one kind of salt mixed or dissolved together in soil ,or solution. i re retention—ability of soil to withhold water against various forces seeking to extract it. Snt—an atom, ion or molecule which aids a plant to grow. l: is—a physical force whereby water passes through semiperme- I able membranes (root hairs) into solutions of higher solute content within the root. ‘tic pressure—term used to denote the magnitude or force of p. osmotic movement of water, usually from the soil, into the root hairs (expressed in pressureunits). ic-considered to be living or dead plant or animal tissue. I super million (ppm)——chemical term describing concentration in I terms of weight. One ppm is one part by weight in a million parts 0f the substance or solution. refers to acidity or alkalinity of soils or waters. A pH of 7.0 is i, neutral, below 7.0 is acid, above 7.0 is alkaline. pH is the i’ negative log of the hydrogen ion concentration. ceIl—alI plants are composed of tiny units of living matter called cells. One leaf may contain millions of cells. hairs—-tiny protruding cells near root tips which absorb water, nutrients and salts from soils. lt-a very small root. '_zone-—that soil area normally occupied by roots. I lerance——the ability of a plant to withstand the adverse effects of ,V “soluble salts. “isture tension—a holding force (or negative pressure) by which v soils hold water against removal by plants or by physical forces. ' Usually expressed as atmospheres or bars of suction necessary f to remove it. any material or substance dissolved in a liquid. '4' 1,,‘ Y refers to the classififiation of plants by botanists into various I types or groups according to their genetic similarity. usually refers to the satisfactory or unsatisfactory emergence of * a crop after seed germination and after losses to seedling dis- I eases, weather, salts and so forth. pie-to live without necessarily making any growth. tolerate—to be able to withstand or live with. toxicity—toxic substances or conditions injure or kill plants, depending upon the amount present. transpiration—evaporation of water from leaves by passage of water vapor out through millions of tiny openings (called stomata) on the leaf surface. water-logged—refers to a soil completely saturated with water; injuri- ous to plants. QUALITY OF WATER FOR IRRIGATION! Since most salinity problems are caused by salts dissolved in the irrigation waters, a knowledge of what constitutes good, fair or poor water quality is very impor- tant. The classification of waters requires a chemical analysis which can be performed by either private or State laboratories? Unlike soil tests, the results of these water analyses sometimes are returned without specific statements as to the quality of the water or recommenda- tions for its use unless the testing agency has knowledge of the kinds of crops and types of soil for which the water is intended. The final decision as to whether the water is good or bad often is left for the user t0 decide. To make the decision, he should understand what constitutes a water analysis and how he can determine its quality. Total Salt Content Irrigation waters are usually analyzed for total salt content and the concentrations of sodium, calcium, magnesium, potassium, chlorides, sulfates, bicarbonates and carbonates. For an additional fee, boron or nitrates can also be determined. The total salt content of waters is expressed in vari- ous terms (Table 5). It is measured by passing an electric current through the water (Figure 9) and its salt content is usually expressed as micromhos per centimeter (cm) or millimhos per cm. One millimho equals 1,000 mi- cromhos. Farmers like to have salt content stated as tons per acre-foot of water (TAF). Chemists prefer it as parts per million (ppm), and pharmacists and those dealing with household water often use the term “grains per gallon.” For water quality classification purposes in this publication, the electrical term micromhos per cm is used. Classification of irrigation waters is based on the assumption that the waters will be used under average conditions with respect to soil texture, permeability, drainage characteristics, amounts of water applied and salt tolerance of the crops grown. Therefore, where con- ditions deviate widely from these averages, the water should be used with caution, or an expert should be consulted. ' The graph used to classify waters in terms of both salinity hazard (horizontal line) and sodium hazard (ver- 2Water or soil samples for analysis can be sent to the Texas A&M University Soil Testing Laboratory at College Station, Texas 77843. The local County Extension Agent can provide information about sampling fees and forrns which should be filled out and sent with the samples. 15 tical line) is shown in Figure l0. Consider first only the salinity hazard, which is based 0n total salt content. In this classification, waters are placed in one of four categories (Table 6): Class l, designated C1 on the graph, is very low in salt and has a very low salinity hazard. Class 4 (designated C4) is very high in total salt and has a high salinity hazard. The micromho value from the analysis will determine into which of the four classes the water falls. Class 1 (C1) — Low Salinity Water: This water is safe to use on practically all crops and soils with little chance of saline conditions developing. Class 2 (C2) —Medium Salinity Water: Waters in this class can be used to irrigate those soils which are relatively permeable and to grow plants which have - moderate salt tolerance. Generally, special management practices for salinity control will not be required unless the soils have very low permeability. Class 3 (C3) — High Salinity Water: This class of water should not be used on soils which have inadequate internal drainage (low permeability). Salt-tolerant plants should be grown and additional drainage facilities should be installed ifsaline spots occur and cannot be improved by leaching. Special attention should be given to leach- ing of accumulated salts (see subhead “Leaching Requirement”). Class 4 (C4) — Very High Salinity Water: Waters in this class require special management practices which include their use only on sandy, permeable soils and the planting only of tolerant or very tolerant crops. Addi- tional required practices may include furrow or double- bed planting. Internal drainage must be good, and enough water must be applied at some time during each year to leach out most of the accumulated salts. Special management will be needed during the seed germina- “tion period to obtain satisfactory stands. Sodium Content In addition to total salt content, the water should be rated as to “sodium hazard.” High sodium is not only toxic to many crops but also acts to disperse the soil, making it less permeable to water and a poorer medium for root growth. It is the combined effect of total soluble salts and sodium which determines whether a water is of good, fair, poor or unusable quality. TABLE 5. TOTAL SALT CONTENT OF IRRIGATION WATERS y EXPRESSED IN VARIOUS TERMS Electrical Tons of salt Parts per Grains conductivity per acre-foot million per gallon Micromhos Millimhos of water (TAF) ppm gpg 565 0.56 0.5 368 21 1 ,130 1.13 1 785 43 2,260 2.26 2 1 .470 86 4,520 4.52 4 2,940 I73 6,780 6.78 6 4,410 258 I6 Figure 9. Electric conductivity meter used for rapid determination 1i " total soluble salts in solution. Charged salt ions carry electric curren The more salt, the greater the current; I In determining the sodium hazard, a value calle the Sodium Adsorption Ratio (SAR) first may need to b evaluated. This is simple if the analysis reports the c0 ' tent of sodium, calcium and magnesium in equivale ‘ values—either milliequivalents per liter (meq/liter) r equivalents per million (EPM), which mean the sam Values reported in parts per million, tons per acre-foo pounds per acre or percentages are n91 equivalent qu tities and must be converted to such before being use The Extension Soil Testing Laboratory at College St tion (see footnote 2) calculates the SAR value and repo g it on the water analysis sheet. or The nomogram (Figure ll) explains how to detei mine the SAR value. A straight line drawn from t TABLE s. CLASSIFICATION o1= THE TOTAL SALT come OF IRRIGATION WATERS ON THE BASIS OF ELECTRIC CONDUCTlvlTYl s Conductivity Salinity Parts per p hazard range million i micromhos ppm Low—C1 100 - 250 70 - 175 Medium-CZ 251 - 750 176 - 525 i High-C3 751 - 2,250 526 - 1.575 Very high—C4 above 2,250 above 1,57 lBased upon classification standards adopted by the U. S. Salini Laboratory at Riverside, California, 1954. (29) i i concentration (left vertical line) t0 the calcium- )‘ agnesium concentration (right vertical line) inter- (the diagonal SAR line at some point——this is the ipalue of the water. e SAR value indicates the quality of the water [espect to sodium. Salts, when they dissolve in separate into positively and negatively charged ach microscopic clay particle in soils has small A e electrical charges which attract the positively salt ions (sodium, calcium, magnesium, potas- y much as a magnet attracts iron filings, and hold fto the clay. Therproportions, or percentages, of , calcium and magnesium held by the clay be- fafter a time, proportional to the amounts of these f the applied water. The SAR value is» an approxi- _l of the percentage of sodium held on the clay. As "(rcentage gets higher, the tendency of soils to j e and become less permeable increases. Thus, a I00 2 3 4 5 6. 7 8 I000 2 4 5000 E; T i i r I i i i r i ' Y o I 30 i v w 2e _ ci-sa A 26s c2-s4 ~ a: Q n x 24 ~ a C3-S4 22 T c4-s4 i! CI—S3 \ < _ _ O \ 2 20 5 z 4 S g ‘f C2'$3 g 5 u (l) I6 — -i u —- a’ = E no c: '4 __ = 3 i 2 2 ci-sz “'53 O l Q z l2 r- _ C2 — S2 3 '0 m‘ c4-sa a a '- 63-32 d z - 6 - - -' c4-s2 Cl—Sl _ 4 »—- _ Q‘ C2-Si 10. Chart used for classification of , waters based upon salinity hazard g _. ca‘ s‘ __ jum hazard. Salinity is expressed as 04- 5| l conductivity (micromhos/cm) and o l l l l l l l is expressed as sodium adsorption l l l 1 1 jSAFi). [From USDA Agriculture c, I00 250 750 22 5Q p§i<5° (29) 1- (4% CONDUCTIVITY - MICROMHOS/CM. (EOMOS) u 25° c. i‘ I -2 a 4 LOW MEDIUM HIGH VERY m5" SALINITY HAZARD high SAR means poor quality, and a low SAR means good quality with respect to sodium. -In the graph (Figure 10) SAR values are rated as low (S 1), medium (S2), high (S3) and very high (S4). Find the point on the vertical SAR line corresponding to the water’s SAR value. Now move directly across the graph to the point exactly above the previously determined electrical conductivity (total salt) value. This point will place the water in one of the four SAR categories on the graph. Class 1 (S1) —L0w Sodium Water: This water can be used on most soils and crops with little danger of sodium injury. It is ‘possible, however, that on fine- textured soils (clays or clay loams), sodium-sensitive crops might accumulate enough sodium in their tissues to be harmful to growth. Class 2 (S2) —Medium Sodium Water: There is a good possibility ‘that with continued use of this water, 17 No* Go*'+fMg+* Meq._/l. Meq/l. 2o 7 o enough sodium could accumulate in finer-textured soils t0 injure sodium-sensitive crops (citrus, avocados, stone-fruits, beans). An application of several tons of gypsum per acre to these soils every 4-5 years would reduce the danger of sodium injury. On coarse-textured soils with good internal drainage, S2 water can be used on most crops with little likelihood_of adverse effects, particularly if the soils are calcareous (contain free car- bonates or lime). ‘ Class 3 (S3) —High Sodium Water: Continued use of this water could eventually increase the proportion of sodium on the clay to rather high levels. Sodium- sensitive crops should not be planted where these waters are used. Even with less sensitive crops, special man- agement practices may be necessary to maintain soil permeability. Reductions in permeability could cause further accumulation of sodium and other harmful salts. If such water must be used, soils should be coarse- textured and should contain both gypsum and free car- 18 0.25 0.50 0.75 l.O sodium and “calcium-plus-magnesium’ concentrations in the solution. A water co taining 5 meq/liter of sodium (Na*) and meq/liter of “calcium-plus-magnesium’ B above 3. [From Bloodworth (9) ]. bonates. Only salt-tolerant crops should be grown. Class 4 (S4) — Very High Sodium Water: Thi water is generally not satisfactory for irrigation purpose unless (1) it is low in total soluble salts, (2) the soils ar medium to coarse-textured and (well-drained, (3) th soils contain both gypsum and free carbonates and (4 only sodium-tolerant crops (wheat grasses, Rhodesgrass, barley, cotton) are grown. This water applied to fine) textured soils could soon create sodic conditions, whic would then make costly reclamation procedures neces sary. These irrigation water classifications on the basis O‘ salinity and sodium hazards are not so simple as they ma appear. Where problems concerning water quality a», velop, changes in many management practices may be, come necessary, and such problems must often be solve on an individual basis with full consideration of all factor involved. Figure 11 . How to calculate the Sodium A I5 sorption Ration (SAR) of irrigation waters Vertical lines A and B give the equivalen 2O (Cafi + Mg") gives an SARvalue slightl ; re 12 is a nomogram similar to Figure 11 but for _ with saturation extracts obtained from soil ‘l. Values for Ca”, Mg” and Na* are higher I-soil extracts usually are higher in salt content ‘the waters applied to them. (It is included only hy those with access to the suction apparatus obtaining soil extractslas described in USDA W; re Handbook No. 60 (29). , ater Quality Considerations-Borates, nates, Nitrates 'g ain ions, when present in irrigation waters or “ very toxic to plants. Boron is probably the most f ts sensitive to boron may be injured by as little boron in water or soil solution. Although all be regarded as sensitive to boron, some are ‘s: erant than others. Some species arranged into .%1.253 >250 >3,75 r». a t lFrom USDA Agriculture Handbook No. 60. (29). 2< Less than. 3> Greater than. irrigation waters has both good and bad aspects. Ni trogen is a fertilizer nutrient, and any nitrates in wate should reduce the need for applied nitrogen. Some ters in West Texas contain enough nitrate to supply th. entire needs of the crop (28). One adverse effect is th nitrates may stimulate vegetative growth when suc growth is no longer desirable, such as on cotton i.n la summer. Even within a given irrigated area, nitrat content varies considerably among different wells fro year to year. In areas where nitrates are known to occu annual water analyses for this nutrient should be mad It could save hundreds of dollars normally spent i. nitrogen fertilizers, or permit farmers to use lower n trate‘ waters in late summer or on certain crops, if su other waters are available. Definition of Terms boron——mineral nutrient whose soluble compounds (borates) are to f to plant growth when present in more than trace amounts. calcareous——soils which contain free calcium carbonates (alkaline soil carbonates-—compounds containing the CO3 group—usually calciu magnesium or sodium compounds. ' disperse—to separate into individual particles. electrical conductivity—method used to measure amounts of solub salts in solution. Each charged salt ion carries electric curren equivalent——chemical term meaning “equal in combining power." equivalents per million (EPM)—same as milliequivalents per liter. chemical term expressing amounts or weights ofions in terms their combining power. ' free carbonates—refers to virtually insoluble salts of calcium and/ magnesium carbonate present in alkaline soils. grains per gallom-pharmaceutical term used to denote ion or s concentration in solution. Grains per gallon x 17.1 = parts I million. gypsum—calcium sulfate-—CaSO4 o 2HQO. hazard-—danger. internal drainage——refers to ability of water to move downw through soils by force of gravity. lime—term which is sometimes used for compounds ofcalcium such calcium carbonate or calcium hydroxide. - I medium—composition of the material used to support the root growth of plants. icromhos/cm—electrical unit of conductance used t0 denote the conducting ability of salt solutions. microscopie-cannot be seen without the aid of a microscope. milliequivalents/liter—same as “equivalents per million” (see above). millimhos/cm——see micromhos/cm; one millimho = 1,000 micromhos. nom0gram——diagra1n used to simplify the determination of certain mathematical calculations. ' permeability—the ability ofa substance to permit the passage ofother substances (air or water) through it. ppm—(parts per million), chemical term used to report concentrations in terms of weight. One part by weight in a million parts of substance or solution, is one ppm. SAR— (sodium adsorption ratio), a mathematically derived term used to express the approximate proportion (percentage) of sodium held by the clay particles 0f a soil. goil saturation extract—water extracted from soils by use of suction in ‘I analysis of soils for soluble salt content. [See USDA Handbook N0. 60 (29)]. - ific—pertaining only to certain conditions, individual salts or indi- vidual ions. AF—tons of salt per acre-foot of water. ‘i8XtllTG—-I‘6f€I‘S to the relative content of coarse (sand), medium (silt) p and fine (clay) particles composing a soil. i0xic——harmful or dangerous. SALINITY CONTROL AS AFFECTED BY MANAGEMENT Preventing Accumulation of Salts The best way to avoid salt problems is to prevent them from developing in the first place. Too often land is . purchased and put under irrigation before it is realized 1 that the water is too salty or the soil too fine-textured '1 (clay) to prevent salts from accumulating. Often land purchased for residential subdivision is that which was least suitable for agriculture—the major reason it was sold by the farmer to the developer. Before land to be used for irrigated farming or gar- dening is purchased, the irrigation water should be analyzed for salt content and the soil profile examined in depth. This means digging holes to depths of at least 4-5 feet to be sure that restrictive zones, particularly clay layers, are not present to obstruct drainage (Figure . In farming areas the USDA Soil Conservation Ser- vice usually has the soils mapped and classified as to their itability for agriculture. Local SCS work unit person- ' lot other sources of professional help should be con- lted before land is purchased for agricultural use. p; eir advice may save many years of struggle and frustra- t1 ow $23 i‘ 3a Deep moderately I-jpérmeable soils (sandy loams, _¢ s, silt loams) are the most desirable where saline ters must be used. If the purchaser has no understand- t; of soil texture or is unable to dig holes to determine emal drainage characteristics, water infiltration rates ‘F: be used as an alternative (Table 9). A portion of the surface soil (not less than 200 square feet) should be leveled, bordered and flooded to a depth of 10 to l2 inches. The rate of infiltration in inches per hour should be measured at l-hour intervals over a period of at least 24 hours. Land having very rapid average infiltration rates (greater than l0 inches per hour) or very low aver- age infiltration rates (less than one-half inch per hour) should be avoided. The high rate indicates coarse sands with a very low fertility and low water-holding capacity —the low rate indicates clays which are hard to manage and difficult to leach and which can accumulate salts quickly. Establishing Good Drainage Good internal soil drainage is essential for satisfac- tory crop growth where salty waters must be used for irrigation. The only way to remove salts from the soil is by leaching them down below the bottom of the root zone. It is almost always the accumulated salts which injure plant growth. As previously mentioned, salts may accumulate in a number of ways. In each case pure water is removed, and the salts remain behind to accumulate. Soil zones (clay layers, hardpans, plow soles) which restrict the downward movement of water often can be broken up by deep plowing (Figures l3, l4). In the situation shown, a 12- to I4-inch clay layer greatly re- stricted drainage and leaching, which eventually re- sulted in high salt accumulation and low crop yields. After deep plowing and leaching, yields were more than doubled, and a poor soil was permanently transformed into a good soil.‘ Farmers often resort to chiseling or subsoiling, but this gives only temporary improvement because the restrictive zones are not permanently broken up and tend to reseal. Where restricting zones are present and deep plow- ing or chiseling are not practical, other means of estab- lishing drainage must be found. In lawns and gardens and under trees and shrubbery this usually means dig- ging holes through the impermeable layer and filling the holes with sandy soil. Holes need not be more than 3-4 inches in diameter but should be spaced uniformly over the area to be irrigated. Bucket-type augers are ideal for this purpose. and can save much backbreaking labor. Where the restrictive layer is deep, installation of lateral tile drains directly above this layer is sometimes necessary. This is an expensive operation requiring technical knowledge and should be performed only after consultation with agricultural experts. Planting Under Saline Conditions When a dry soil is wetted, the soluble salts already in the soil move with the water because they dissolve and are carried along with it. It is very important to know how salts move and where they accumulate. Germinat- ing seed and seedlings are sensitive to salt. Knowing ‘Shallow soils underlain with caliche should never be deep plowed to depths which allow mixing of the caliche with the plow layer. 21 Figure 13. Heavy impermeable clay layer in field soil broken up by deep-plowing operation. This layer prevented leaching of salts and caused big a M‘ reductions in yields because of accumulated salts. Deep plowing restored permeability and soil productivity. where t0 plant often means the difference between get- ting a good stand, compared to a poor stand or none at all. It also means that early plant growth will be faster, crops will be healthier and yields should be higher. TABLE 9. TYPICAL INFILTRATION AND PENETRATION RATES OF WATER INTO SOILS OF VARIOUS TEXTURAL CLASSES, AND APPROXIMATE AMOUNTS OF WATER AVAIL- ABLE1TO PLANTS FOLLOWING A HEAVY IRRIGATION OR RAIN Average Hours for water Water water to penetrate 3 available Soil infiltration feet with 4o plants textural rates standing water Inches per class Inches per hour on surface foot of soil Coarse sands 10.00- 15 3 - 2 0.8 - 1.1 Sandy loams 2.00-4 18-9 1.2- 1.7 Silt loams 1.00- 3 36 - 12 1.7 - 1.9 and loams Clay loams 0.50 - 1 6O - 3O 1.9 - 2.3 Clays 0.25 - 0.50 144 - 72 2.1 - 2.7 lAll values listed here are only approximations and should be used simply as guides. 22 How soluble salts move and accumulate when soils are surface irrigated in a bed and furrow type system is shown in Figure 15. Where single-row beds are used and g every furrow is irrigated, salts in the soil and water movef from both sides and accumulate in the tops and centers of the beds. Furthermore, every subsequent irrigation car- a ries more salts into these zones of accumulation. Thus, 1 even though waters may be only moderately saline, ac» cumulation can continue until eventually plant growth is affected. Where waters are quite saline (2,000 ppm total“ salt or higher), one heavy irrigation can cause enough salt, to accumulate in the bed tops and centers to reduce or even prevent seed germination and to seriously injure growth of seedlings that manage to survive. With single-row beds the seed are usually planted in these areas where salt accumulations are highest, and quite? often the result is poor stands, sickly growth and lo yields. Figure 16 shows cotton planted on single-ro beds preplant irrigated with salty water (3,500 ppm). g The result was complete loss of stand and a total cro, failure. With wide double-row beds, movement of solubl salts is similar. After a good preplant irrigation, greates salt accumulation again is in the centers and tops of th beds. However, the shoulders of the beds a few inche [Vie 14. Deep plow in "on. Many stratified roan be permanently a ed by mixing of soil eaking up hardpans, s and other strata. the surface show very little salt accumulation. ers in saline areas plant their seed 0n the bed ders. The result is usually good stands, growth and I S if salt-tolerant crops are grown. Figure 17A shows ‘ l, ent growth of cotton planted on the shoulders of le-row beds in the Pecos area where salty pump is the only water available. l, igure 17B shows an almost complete loss of cotton water in the El Paso Valley. Borders are used to Tl water on these level soils, and many farmers i‘ the borders in double-row fashion—one row on shoulder. In this field the border-planted cotton up to a perfect stand. ith surface irrigation the areas of lowest salt ac- i ation are directly under the furrows (Figure 15). y, rs forced to use very salty waters often take advan- f this by planting in the furrows (Figure 18). This e usually gives good stands but has some serious antages. Soils in the furrow are colder, emergence f: ly growth are slower, seedling diseases are worse, i 'ns after planting and before emergence can cause to form, preventing seedling emergence. When ppens, replanting is necessary. Early cultivation is i‘; icult, and first summer irrigations must be di- igdown the seed rows. This increases the crusting Adding problem, which in some soils seriously ts plant growth. _ with single-row beds using highly saline (4,000 _ Using Best Water for Germination Where a choice of different quality waters is availa- ble, it is a good practice to use the best quality (lowest salt) water for the first (or preplant) irrigation. Once plants are past the seedling stage, waters of higher salt content can be used with less risk of adverse effects because root systems have become deeper and more extensive, and most plant species have had time to adjust somewhat to saline conditions. With certain salt-tolerant crops which normally re- quire less soil moisture during the fruit or seed matura- tion period (cotton, small grains, grass and legume seed, safflower, sorghum) it may even be desirable to apply saline water for the last summer irrigation. The added salinity would make the water less available to plants by increasing the osmotic pressure of the soil solution. Thus, plant moisture stress would be moderately in- creased without letting the crop suffer badly from lack of water, which often occurs on sandier soils or when irriga- tions are unduly delayed. Applying Plenty of Wateré-Leaching Percentage One of the most-common causes of salt accumula- tion in soils is failure to provide enough water to leach salts below the bottom of the root zone. This is particu- larly true in watering lawns, trees and shrubbery, where it is difficult to judge the amount of water being applied. Some sprinklersfican operate a long time without apply- ing much water. 23 SINGLE ROW BEDS We've'~'»'»'¢';‘3*Z3 35s .?_§s!+?+'.~9c‘:§9’9.99?+?" a». ‘s LOW SALT WGH SALT ACCUMULATION ACCUMULATlQN VERY HIGH SALT ACCUMULAUON MODERATE SALT ACCUMULAUON ti] m T0 “leach salts below the bottom of the root zone” means leaching them deep enough so they will not rise into the root zone again by capillary action during evap- oration between irrigations. This means wetting soils to a depth of 3-4 feet when waters containing appreciable amounts of salt (1,000 ppm or higher) must be used. Frequent light irrigations in hot dry areas can be more harmful than less frequent heavier ones because the light irrigations give little or no leaching. Salt accumulation therefore can build up rapidly even though the applied water may be fairly low in salt content. Figure 16. Cotton planted on tops of single-row beds after irrigation with salty water. Salt accumulation in seed row prevented germina- tion and caused complete loss of stand. 24 Figure 15. Single-row versus double-row beds showing areas of salt accumulation fol-g lowing a heavy irrigation with salty water. Best planting position is on the shoulders of the double-row bed. . A guide showing the approximate amounts of extra g water required in addition to crop .needs is presented in; Figure 19. This extra water is the leaching water. —usually called the “leaching percentage. ” The leaching percentage depends upon the salt content of the water‘ and the salt tolerance of the crop. With sensitive crops,‘ more water must be applied because little or no salt accummulation in the root zone can be permitted. F 01; water containing 1, 3 and 5 tons of salt per acre-foot the leaching percentages for sensitive crops should be ap-y’ proximately 20 percent, 45 percent and 65 percent, re if spectively. To use this information intelligently, th grower should have some knowledge of the availabl water-holding capacity of the soil he is irrigating l. approximately how much of this available water has bee used since the last irrigation. A Assume an application of water containing 2,2 ppm salt to a moderately salt tolerant crop on a loam o: silt loam soil. Table 9 shows these soils can hold 1. 7 to 1. ‘§ inches of available water per foot—assume 1.8 inches i, Assume further that if the crop has been managed nor mally about half of this available water will have bee l’ used up (transpired or evaporated) since the last irrig‘ tion. It therefore should need about 0.9 inch of water pe foot of soil just to replace what has been lost. For 3 feet i, soil this will be 7 inches. According to Figure 19 aboii 25 percent extra water will be needed for leaching pup’ poses: 2.7 x 0.25 = 0.68 inch 2.7 + 0.68 = 3.38 inches A total irrigation of approximately 3.38 inches of wate will be required to do a good job of leaching with th’ water on this soil with this crop. ' 'i a l e 17A. Excellent stand and growth of cotton planted on shoulders of wide double-row beds after irrigation with salty water. (Pecos, Texas, "l965.) ', 17B. Excellent stand of cotton on double-row border, compared to a very poor stand in rest of field, which was planted on single-row beds. n water contained about 4,000 ppm total salt. 25 The leaching percentage values in Figure 19 are only approximate because salt tolerance ratings of crops are not precise, water-holding capacity of the soil is approximate, and the amount used since the last irriga- tion must be estimated. The important things to realize are that (1) extra water does need to be applied and (2) the saltier the water and the more sensitive the crop, the more extra water is required. This practice, even though wasteful of water, is essential, since no other way has been found to prevent salts from accumulating. Soluble salts cannot be “deactivated,” “deionized” or “neu- tralized” in the soil—they must be leached out. This can be done at every irrigation or it can be done with one heavy application each crop year. For use in estimating water measurement, Table 9 shows the approximate time required to wet 3 feet of soil while maintaining standing water on the surface (flood- ing). With the loam soil of the preceding example, a minimum time would be 12 hours and a maximum time 36 hours, depending upon the rate of infiltration. Fine- textured soils (clays and some clay loams) cannot be satisfactorily leached during the growing season because serious adverse effects on some crops would result from prolonged waterlogging. Soil probes (thin metal rods with a handle) also can be used to measure depth of water penetration. The probe can be pushed easily through wet soil but requires more effort when dry soil is con- tacted. In both farming and gardening, a satisfactory, uni- form, efficient job of leaching or irrigating cannot be done unless the land has first been carefully leveled as shown in Figure 20. High spots are continually under- irrigated and tend to accumulate salts. Periodic leveling is therefore an essential part of the farming operation in areas of saline water. Leveling, of course, would not be necessary where sandy soils are sprinkler irrigated; how- ever, sprinkling with salty water is risky unless it is known the crop being grown will not be injured by salts applied in this manner. Figure 18. Cotton Iister-planted in furrows after preirrigation with highly saline water. Good stands were obtained, but other factors may contribute to low yields. 26 Maintaining Good Soil Structure Soil texture, which refers to the proportions of the different size fractions (sand, silt, clay), is a permanent characteristic of soils and cannot easily be changed. Soil structure, on the other hand, refers to the arrangement‘ or grouping together of the soil particles into aggregates or granules. These aggregates mpy be large or small, and their stability (ability to hold together) may be weak or’ strong. Good structure or granulation in soils is very. desirable, particularly in the finer textured classes (clay loams and clays), because it facilitates the movement of.‘ air and water into and through a soil and consequjentlyigi promotes root penetration. With good soil structure; root systems are larger, more extensive and better able; to extract the moisture and nutrients necessary for op- timum growth. ' Many factors are involved in the development an maintenance of soil structure, but the most important growing soil-improving crops which add plenty of or ganic matter (Figure 21). The regular addition of organi matter, whether from crops, manure or compost, is th best possible insurance of good soil physical conditio)“ and a safeguard against the adverse effects of sodium. 7 A distinction should be made between good soi structure with organic matter and good soil structure without organic matter. In the absence of organic mat- ' ter, a soil may be well aggregated and have good struc- ture, but this structure is largely dependent upon a high percentage of calcium and magnesium held on the clay, with a minimum of adsorbed sodium. It is largely al chemical type of structure. This kind of structure begin to break down, and soils begin to disperse whenever th i proportion of adsorbed sodium (SAR) rises above 15-2 percent. The more sodium in proportion to calcium an magnesium in the soil or water, the more readily the so' tends to disperse and assume an undesirable condition. When soils contain plenty of decomposing organi matter, their structure is less readily broken down b; sodium or use of heavy farm equipment. They remai open and permeable to water and air because the organi matter physically prevents the dispersed soil conditio from becoming a serious factor. This is a physio biological type of structure, more stable than th calcium-magnesium type discussed previously. Organic ‘matter also has other advantages. It stim 5 lates biological activity, which slowly decomposes t organic material and converts the nutrients into solub form. Organic matter is a good source of fertilizer é cause it contains all the essential elements, and the elements are released slowly and are not so readi leached out as are chemical fertilizers. Its decompositif also results in formation of much carbon dioxide (C I which combines with the soil water to form carbonic ac (HzCOs). This acid helps to reduce the alkalinity of t t soil, which can become excessively high with too mu sodium. I Since plant residues and organic matter deco I pose, they disappear in a few years and must be replac §sALT content OF ;|Rm0An0N WATER §r TON PER ACRE FT ~ ECX lO3=|l5 735 PPM. §3 tons PE ACRE FT ;* Ecx m = -345 2200 PPM. § TONS PER ACRE FT r EC x :03 = 57s 3675 PPM. v conditions] re. Herein lies the ‘value of good crop rotations. f-frotations, soil-improving crops are grown periodi- , {and organic material is automatically restored. nother way to maintain or improve soil structure Ies letting the soils dry out occasionally. This is best _y fall plowing and letting the plowed soils remain f‘ rbed during the winter. The combination of dry- ‘eezing and thawing definitely improves structure. Qimum amount of tillage and other tractor opera- ould be used, and tractors should be kept out of lds when the soils are wet. Uniform level soils are essential for efficient irrigation and ching of salts. Shown is a good stand of cotton on beds irrigated with saline water. APPROXIMATE LEACHING NECESSARY ' FOR SENSVHVE CROPS FOR MODE RAT ELY TOLERANT CROPS FOR TOLERANT CROPS "19. Approximate percentages of the applied water necessary for leaching of accumulated salts. Leaching percentages are greater for 1 sitive crops and for waters of higher salt content. [Based upon leaching percentage formulas (29) but modified to better fit Texas soils and Using Amendments if Needed When the percentage of sodium exceeds 65 to 7O percent in waters, or the SAR of waters or soil saturation extracts exceeds 15, addition of amendments may be- come necessary to maintain good soil structure. This is particularly true for fine-textured soils that do not con- tain much gypsum or organic matter. The purpose of using amendments is to increase the amounts of soluble calcium or magnesium which in turn counteract the bad effects of too much sodium. This can be done directly by adding such amendments as gypsum or calcium chloride to either the soil or water, or indirectly by adding acidifying materials such as sulfur, sulfuric acid, lime-sulfur or iron or aluminum sulfates to the soil, provided the soil contains free carbonates. Soils of most arid and semiarid regions are calcare- ous and often contain thousands of pounds of calcium or magnesium carbonates per acre. However, these carbo- nates are almost insoluble in water and therefore cannot effectively counteractthe effects of too much soluble sodium. Sulfur, sulfuric acid, lime-sulfur and iron and aluminum sulfates combine with these carbonates to form gypsum, which is more soluble. (See Reclamation of Salt-Affected Soils). To determine whether soil amendments are needed, and the kind to apply, the soils and waters 27 Figure 21. Forage sorghums grown in a crop rotation program can add tremendous amounts of organic matter after being chopped, disked and incorporated. should be tested to learn (l) the sodium percentage and SAR of the water, (2) the SAR of the soil extract, (3) whether the soil contains gypsum and (4) whether free carbonates are present. An agricultural expert should interpret the test results and make recommendations. Application of amendments can be expensive if any large acreage is involved. Cost of amendments varies greatly depending upon location. The kind, amount and method of application are important. The cheapest may not be the most effective kind to use. Managing Fertility While Controlling Salinity Under conditions of high salinity there may be little or no response to applied fertilizers because excess salts may be the main factor limiting growth. When the excess salts are removed by leaching, much of the soluble fer- tilizer is leached out with them. The problem then be- comes how to remove soluble salts yet still maintain necessary fertility levels. This is not easy to do, particu- larly on sandy soils. The best way is to leach out most of the accumulated salts before the fertilizers are applied. Most irrigating farmers do this with a heavy preplant water application in the spring. After planting, nitrogen (and potassium if needed) is top-dressed or side-dressed to the crop before the first summer irrigation. Phosphate can be applied at any time because it is not leached from soils. Another very effective way to maintain fertility is to depend upon crop residues, manure or compost to sup- ply most of the fertilizer needed. These materials de- compose slowly in soils and can supply ample plant nutrients if enough material is incorporated. In farming, crop residues are generally used since manure and com- post are usually unavailable. The kind of residue is im- portant. Nitrogen is the fertilizer element most easily lost by leaching. Some crop residues contain plenty of nitrogen—some contain very little. Alfalfa and the sweet clovers are good soil-improving crops under saline con- ditions because they are both salt-tolerant and high in nitrogen. These legumes take their nitrogen from the 28 air, and in such rotations, nitrogen seldom needs to be applied to any of the other crops. A Residues from nonlegume crops (small grains, sor- ‘ ghum, corn, cotton) contain very little nitrogen. When‘ these are incorporated, nitrogen should be applied to aid A in decomposition and to assure that the following crop will have an adequate supply of nutrients. a -~_ Definition of Terms acre-foot—amount of water to cover one acre to a depth of 12. inches—43,56O cubic feet. W,‘ I adsorbed—attached to or held in some way to the surface of an objegct. i Usually refers to ions adsorbed on clay surfaces due to electrical forces of attraction. aggregates—small clumps of soil held together by various means. A desirable condition permitting air and water entrance. calcareous—soils which contain slightly soluble free calcium and mag- nesium carbonates—pH usually above 7.0. ‘ caliche—common term for calcareous white subsoils in low-rainf y areas. capillary action—water moving through very small soil pores (capil: laries) due to forces of attraction greater than that of gravity. Causes lateral and upward movement of water in soils. clodding—refers t0 large chunks or blocks of soil difficult to break up 0 g work into a smooth seedbed. ‘ compost-—partially decayed organic material of all types formed fro A leaves, soil and other plant residue, when piled up and moist to permit decomposition for periods of 6-12 months. crop rotations——system of rotating thekinds ofcrops planted in succe sion on a field, with the purpose of improving physical an chemical conditions of the soil. deactivate (deionize, neutralize)—terms used by salesmen selling pr ducts claimed to reduce the adverse effects of salts in soils. if dec0mposition—refers to the gradual breakdown and destruction i. organic material in soils by soil organisms. facilitates—aids or assists. flocculatiom-opposite of dispersion. Soil particles tend to cling i, gether in -floccules-—first step in the desirable process of aggr _ gation. l free carbonates—term given to almost insoluble calcium and m) nesium carbonates when present in soils. A granules—similar to aggregates. A desirable condition where soil pf ticles are clumped together by various forces. Permits good and water penetration. gypsum—partially soluble calcium sulfate—CaSO4 o ZHQO‘. incorporation—refers to disking in or plowing under of various mate als grown or applied to the soil surface such as cover crop fertilizers, manure, amendments. ' infiltration—movement of water from surface into a soil. leaching percentage—the amount (%) of extra water over and n" crop needs necessary to leach soluble salts down through a so’! i legume—species of plants able to extract nitrogen from the air y means of symbiotic bacteria growing on the roots. ' lister-planted—planted in furrows using furrow-openers (sweeps discs) directly in front of planting mechanism. a maturation period—period after seed or fruit have formed and are the ripening stages. - , pressure—pressure developed in a solution by passage of f’ ater only through the wall of the container into the solution. sed to refer to pressure developed on inside wall of imipermeable cell membranes. 'nl(water)——essentially the same as infiltration; movement of ater into a soil. ' iological-term used to describe physical changes in soil _ ught about by the presence or activity of living or once-living terial. -.ture stress—when plants suffer from lack of water, moisture __ide the plant is under tension or stress due to difficulty of raction from the soil. _ e-—slows down, prevents or inhibits. 0 %,diseases—a number of diseases, mostly caused by fungi, .ich attack, injure and kill germinating seed or young seed- Li: Ins-refers to soil texture and to the relative proportions of d, silt and clay in a soil. it ment—a material, not classed as a fertilizer, which is applied ,1‘ ‘(soils usually to improve the physical condition. g 'ng crop—any crop which, upon harvest or incorporation, ults in an improvement in the physical, chemical or fertility j; dition of the soil. I lds together; not easily broken up. f‘ ndition in which layers of different texture (sand, silt or v_ )lie more or less parallel in soils and can be sharply defined abrupt changes with depth. k g—condition in which a soil is completely filled with water; gundesirable condition which cuts off air to plant roots and tes toxic substances. i MATION o|= SALT-AFFECTED sons i‘ ng the Situation ‘ word “reclamation” assumes that the soil is o badly salt-affected that special procedures are T» to restore productivity. Many thousands of fsalted out” soils exist in Texas, most of them in s-Pecos Region. lamation of anysoil first requires an assessment _ ation: how bad it is, the causative factors, how lean be reclaimed and whether it is worth l g.‘ The first two are relatively simple to deter- analyses of soil and water samples, by a careful ion of the soil profile and by establishing the l; the water table. Salted-out soils can be of any but are usually deep, fine-textured soils with 1 poor drainage. (The causes of “salting out” ussed in previous sections.) I analyses will determine the kinds and amounts esent and whether the soil contains gypsum carbonates. It will establish whether the soil ; saline-sodic drzsodic in nature. The profile '0n will determine soil permeability charac- d the relative difficulty of leaching the salts. ‘affected soils cannot be economically reclaimed because of a ‘ to an excessive depth, lack of good quality water or the ‘*= of establishing adequate drainage. If it has been determined that a soil can be economi- cally reclaimed, the next step is to examine and perhaps establish drainage facilities for carrying away the leached salts. This is usually the most expensive operation. If sand, silt or gravel layers are encountered at depths of less than 12 to 15 feet, the most common practice is to dig large deep parallel open drains through the area to be reclaimed, with some means of disposing of the drainage water at the lower end of the irrigated area. Distance between drains should be determined by an irrigation specialist. Needless to say, any impermeable or restric- tive zones above this 12- to 15-foot depth should be eliminated, if possible, or alleviated in some manner before leaching is attempted. Reclamation of Saline Soils Salty soils which do not contain an excess of sodium usually have good structure and are not difficult to leach unless they are very fine textured. Reclamation of these soils consists simply of applying enough water to thoroughly leach the soil. The water applied should preferably be low in sodium but fairly saline (1500 to 2000 ppm total salt), as this helps in keeping the soil permeable during the leaching process. As much as 4 acre-feet of water may be needed to reclaim 1 acre of highly saline soil. Preferably the water should be applied in several applications, allowing time for the soil to drain well after each application. After reclamation, only good quality water should be used for irrigation. Reclamation of Saline-Sodic and Sodic Soils These soils require additions of amendments to supply soluble calcium before the beginning of the leach- ing operation. Reclamation of these soils not only re- quires removal of soluble salts but also removal of much adsorbed sodium which has caused the sodic condition to develop. Even though soils may contain gypsum, more gyp- sum may be needed for reclamation. If the soils do not contain enough gypsum but do contain free carbonates, sulfuric acid is the most rapidly reacting amendment to use, if available. Waste acid from refining plants can sometimes be obtained at very low cost. Sulfuric acid reacts quickly with free carbonates to produce gypsum according to the following chemical formula: H2504 + CaCCL; + 2H2O S ulfuric Calcium Water Acid Carbonate = CaSO4 . 2H2O + H2O + C02 Gypsum Water Carbon a Dioxide (gas) The carbon dioxide (CO2) escapes immediately as a gas. One advantage of using sulfuric acid is that the gypsum formed is in very fine particles. It reacts more 29 quickly t0 replace sodium because it is more soluble than applied gypsum. Sulfuric acid is a very corrosive liquid and is difficult and dangerous to handle; extreme care in using it is necessary. If the soils contain no source of calcium (gypsum or free carbonates), then gypsum or a soluble calcium ma- terial such as calcium chloride should be applied.“ If the soils contain free carbonates, other amendments than gypsum can be used——(in addition to sulfuric acid) sulfur, lime-sulfur or iron or aluminum sulfates (Table l0). These react with the free carbonates to eventually pro- duce gypsum, but the reactions are much slower than with sulfuric acid. Sulfur sometimes takes several years to oxidize completely into sulfates and gypsum and is the slowest-acting of all amendments. Because iron and aluminum sulfates are relatively expensive, they are not used unless they offer some advantage, such as a local source of supply. Lime-sulfur contains some soluble cal- cium, but its chief effect is due to oxidation of the sulfur to produce gypsum, a very slow process. With saline-sodic and sodic soils, the reclamation procedure usually consists of a series of stages—first reclaiming the surface soil, then adding more amend- ment to reclaim it to greater depths. To reclaim deep; fine-textured sodic soils in one operation would be virtu- ally impossible, since water would remain ponded on the Foil surface for many months with undesirable side ef- ects. TABLE 10. KINDS OF SOIL AMENDMENTS AND APPROXI- MATE AMOUNTS REQUIRED TO AID IN THE RECLAMATION OF SODIC AND SALlNE-SODIC SOlLSl No. pounds (approximate) required to _ 2 supply 1000 Chemical PUmV pounds of Amendment formula % soluble calcium Gypsum CaSO4 " 2H2O 100 4,300 Sulfur S 100 800 Calcium chloride CaCl2 - 2H2O 100 3,700 Sulfuric acid H2804 95 2,600 lron sulfate FeSO4 " 7H2O 100 6,950 Aluminum sulfate Al2(SO4l3' 18H2O ' 10o 5,550 Lime-sulfur4 Calcium 24 A 3,350 solution polysulfide lFrom USDA Agriculture Information Bulletin No. 195. (l) 2With purity lower than indicated above, additional amounts would need to be supplied. 3Assumes free carbonates present to react with those amendments which do not contain calcium. 4Purity of lime-sulfur expressed as sulfur content. “Calcium chloride, if used, should be thoroughly leached out during reclamation to insure removal of soluble salts. 30 The amendment first is applied to the soil surface and usually disked in; then 10 to l2 inches of water is applied to bordered areas. There is no good way to calculate the amount. of amendment needed for re- placement of the sodium because the leaching process is slow, solubility and reactions of the amendments are different, and the conversion of carbonates to gypsum is incomplete. The usual procedure is to apply reasonable amounts of amendment at each stage. The approximat a amounts of each amendment needed to supply 1,0 pounds of soluble calcium, assuming fairly complet reaction in the soil, are given in Table 10. This amgun should be applied at each stage of reclamation. In some cases, attempts are made to seed ber mudagrass or barley after the first or second stage of th operation. These are grown for a while, then disked in and the added organic matter aids in the conversio process. As reclamation proceeds to greater depth soil-improving crops can be grown to maturity. How ever, the reclamation process is not complete until m0 of the sodium is removed from at least 4 feet of soil. Eve . then much more time is required for restoration of g l< soil productivity because soil structure,once completel destroyed, is slow to return to a normal condition. Reclamation Using High-Salt Waters This method for reclaiming salt-affected soils w proposed by the U.S. Salinity Laboratory in 1960 (25). i’ is most effective when the soils still retain some degree permeability. The method operates on the principle th very saline waters keep a soil open and permeable ev though much sodium may be present in both soils a f water. It utilizes a dilution technique and consists several stages. Very saline water is first applied to lea out most of the accumulated salts. Then this saline wat is somewhat improved by dilution with better quali (lower salt and sodium) water in the second leach’ operation. The third operation utilizes even better q . ity water, and the fourth (last) stage uses good qual' low-salt water. For best results, gypsum should be . plied to the soil at the start of reclamation. The syst requires a source of very high-salt water—water in range of 10,000 to 20,000 ppm total salt, and this _ quirement limits its usefulness. a Definition of Terms acre-foot—enough water to cover one acre to a depth of‘ inches-43,560 cubic feet. adsorbed-attached to or held to the surface of a material usuall forces of electrical attraction. calcareous-a soil or material which contains relatively insoluble cium and magnesium carbonates. pH usually above 7.0. corrosive—attacks metals, clothing and other substances by oxid A Sulfuric acid even is corrosive to concrete ditches. dilute—to make weaker, usually by adding more water. dispersed—condition in which the soil is no longer aggregat flocculated, each particle separated from the other. A undesirable condition. facility—ability or means to do something. b0nates—see calcareous above. I very coarse mineral particles larger than 2 mm in size. l’ —partially soluble calcium sulfate CaSOi Q 2HgO. (sulfur)—certain microscopic soil organisms utilize sulfur and in j doing so cause its oxidation from “S” to S02, S03 and S04, in which latter forms it reacts with calcium carbonate to form gypsum. C3804 0 2O. w 'vity—refers to the inherent ability of a soil to produce crops of s. value. » same as pH. A soil reaction of 7.0 is neutral; below this it " becomes increasingly acid and above this increasingly alkaline. I —to restore to some semblance of its previous productive capacity. ' cuff-term used to refer to soils which contain so much salt or sodium that no crops will grow. f il mineral particles with size diameters from 2.0 mm to 0.02 mm. l-i iects—other chemical or physical reactions brought about unin- j tentionally. (mall soil mineral particles ranging from 0.02 mm to 0.002 mm in ' size. Very difficult to see with the naked eye. ‘ eability characteristics—refers to those characteristics which alfect the movement of water and air into and through a soil. LING SOILS AND WATERS FOR SALINITY fl ANALYSIS -_». analyses are to be meaningful, samples must be of the soil or water they are intended to repre- If a field contains both productive and unproduc- eas (Figure 22), an analysis of one soil sample ing a mixture of soil from the entire field would ;_f 'ttle meaning. Salt content varies widely within the rofile-usually it is highest in the centers of beds “fps of ridges and lowest under the furrows (Figure I e magnitude of this variation depends on many f , such as type of planting bed, management prac- (soil permeability and salt concentration of the ion water. A ten- to twentyfold increase in salt intration from furrow to the top of the bed is not al. jgSampling ;The proper procedure for sampling soils for salinity p sis depends on the specific purpose for which the flees are taken. If the purpose is to determine the “A a salt or sodium content of the soil, the entire soil i should be represented; however, it is best to the tops of ridges where there are abnormally high 5ncentrations. An exception is salt problems in ts or rice, where it_is_ sometimes desirable to have es of surface soil crusts analyzed. Where crops are 1 anted, sampling sites should be selected away from rders, and high spots and depressions should be ed. With irrigated row crops, sampling of either Tor furrows could give misleading information be- I of the great variations in salt content between p“, s and tops of beds. The best time to sample proba- bly is after land preparation and just before listing or preplant irrigating. If, however, the purpose is to determine salt buildup in the beds or its effect on seed germination, sampling should be restricted to the beds, and particu- larly to the area of seed germination. Samples should be taken within the seed zone, after first discarding the surface inch, and should be taken at planting or time of germination. To sample barren or unproductive spots in a field, separate samples should be taken from adjacent produc- tive as well as the unproductive areas so that compari- sons can be made (Figure 22). It usually is desirable to sample both surface soil (0 to 12 inches) and subsoil to a depth of at least 3 feet. Salinity or low productivity often is a result of restricted permeability deep in the soil. Dense or impervious layers 6 to 8 feet below the surface may be responsible for salt accumulation or even total crop failure. In special cases, various segments of the subsoil should be sam- pled. All soil samples submitted for analysis should be composite samples. Individual samples often vary widely in salt content; therefore, a number ofsamples from each depth at different locations should be composited, or mixed together, before extracting an average sample for analysis. Composite samples should be composed of 5 to l0 subsamples taken from one general area. Do not attempt to composite samples from too large an area. Where differences in soil texture or crop productivity exist, separate composites should be made from each area. In some instances it may be advisable to obtain the advice of a soils specialist before sampling. Sampling is most satisfactory when done with a sampling tube orbucket-type auger. Augers, with exten- sions, can penetrate 10 feet or deeper. Where these are not available, a shovel can be used to sample the top I to 4 feet as follows: first, each hole should be dug to the full sampling depth desired and then 1/2- to l-inch slices taken from the side of the hole. Samples from several sampling sites should be collected in a bucket or other container, mixed thoroughly, and a composite of about 1 quart extracted and labeled. If samples are to be shipped by mail they should first be air-dried, then packaged carefully to avoid breakage. Water Sampling Water samples are comparatively simple to take, but several precautions should be observed. When sam- pling pump water, samples always should be taken at or near the well and only after the pump has been operating for one-half hour or more. Samples never should be taken of stagnant water or from ditches where the water is not flowing. Surface water sources should be sampled from the running stream as ‘near the point of field application as possible. Containers should be approximately 1 pint in 31 Figure 22. Barren areas in alfalfa field caused by excessive soil salinity. Spotty areas are typical of saline conditions, even though entire field isp affected. ' size and throughly clean. Plastic bottles are ideal for water sampling since breakage is eliminated. If dependable recommendations or opinions about the analyses are expected from the laboratory, informa- tion about the problem observed, kind of crops grown, fertilizers used, past management practices, and other relevant factors is essential. Texas County Extension Agent offices have appropriate information forms and boxes for shipping soil samples and can supply other advice if needed (see footnote 2). Definition of Terms adjacent—near to or close by. analysis—to separate by chemical or physical methods. 32 barren——unable to produce crops of any value. Usually devoid of alm » all vegetation. bucket-type auger—auger with a metal tube near the base which til 1 with soil when auger isrotated by hand. composite—a mixture of a number of samples taken from nearby if similar locations. dense—very tight—almost impervious to water or air or roots. depressions—low areas in field. impervious—water (or air or roots) cannot penetrate an impervio _ ZOH€. salt concentration—refers to the amount of salt in a soil, or the amou of soluble salt in wateror soil solution. segment—portion or part of. site~—a particular chosen location in a field. file—refers to the nature of the soil material from the soil surface down t0 parent material or bottom of root zone. xture—pertains to the relative proportions of large (sand), medium (silt) and fine (clay) particles making up a soil. l, t—-refers to water that has been standing exposed to the ele- ments for some time until algae or other growth develops. a general term used to refer to that soil underneath the surface soil—usually below 12 inches in depth. water——any water lying on 0r flowing over the surface of an ~ area. ACKNOWLEDGMENT aMuch of the information in this bulletin is based on ch done at the U. S. Salinity Laboratory, River- California. The authors are greatly indebted to scientists, and particularly to Leon Bernstein and Bowerfor their helpful suggestions. Some research ‘ gs have been slightly adapted to better fit the soils, 1 , crops and climatic conditions of Texas. lSpecial thanks is expressed to Charles Welch and ray of the Texas AlSzM Extension Soil Testing v . tory for twice carefully reviewing the manuscript Jg the process of its preparation. REFERENCES rnstein, Leon, Milton Fireman and R. C. Reeve. Control of inity in the Imperial Valley, California. USDA. ARS Report 4, 1955. vmstein, Leon, and H. E. Hayward. Physiology of Salt Toler- _ ce. Ann. Rev. Plant Physiol. 9:25-46. rnstein, Leon. Salt Tolerance of Grasses and Forage Legumes. DA Agric. Information Bul. 194, 1958. . fmstein, Leon. Salt Tolerance of Vegetable Crops in the West. I DA Agric. Information Bul. 205, 1959. lmstein, Leon. Osmotic Adjustment of Plants to Saline Media. "Steady State. Amer. Iour. of Botany 48: 909-918, 1961. ‘n Bul. 283, 1964. Imstein, Leon. Salt Tolerance of Fruit Crops, USDA Agric. l, rmation Bul. 292, 1964. ,rnstein, Leon. Reducing Salt Injury to Ornamental Shrubs in ‘Iv West. USDA Home and Gardening Bul. 95, 1964. l: oodworth, M. E. Some Principles and Practices in the Irriga- of Texas Soils. Texas Agric. Exper. Sta. Bul. 937, 1959. i. er, C. A. Chemical Amendments for Improving Sodium l} USDA Agric. Information Bul. 195, 1959. l. er, C. A. Prediction of the Effects of Irrigation Waters on I ils. Proceedings, Teheran Symp. on Arid Zone Research, 1961. 9x11: Imstein, Leon. Salt Tolerance of Plants. USDA Agric. Informa- 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. Ehlig, C. F. Salt Tolerance of Raspberry, Boysenberry and Blackberry. Proc. Amer. Soc. Hort. Sci. 85:318-324, 1964. Hausenbuiller, R. L., C. D. Moodie andH. W. Smith. Saline and Alkali Soils Under Irrigation in Washington. Washington Agr. Exper. Sta. Circular 302, 1957. Irelan, Burge. Extent and Quality of Ground Waters in Texas. Proceedings Texas A&M Univ., Salinity Conference, Iune 1960. Lagerwerif, I. V., and Gen. Ogata. Plant Growth as a Function of Interacting Activities of Water and Ions Under Saline Condi- tions. 7th Inter. Cong. Soil Sci. Madison, Wis. 1960. Lagerwerff, I. V., and H. E. Eagle. Osmotic and Specific Effects of Excess Salts on Beans. Plant Physiol. 36:472-477, 1961. Longenecker, D. E., and P. I. Lyerly. Some Relations Among Irrigation Water Quality, Soil Characteristics and Management Practices in the Trans-Pecos Area. Texas Agric. Exper. Sta. MP 373, 1959. ' Longenecker, D. E., L. Thaxton, Ir., and P. I. Lyerly. Cotton Production in Far West Texas with Emphasis on Irrigation and Fertilization. Texas Agric. Exper. Sta. Bul. 1001, 1963. Longenecker, D. E., E. L. Thaxton and P. I. Lyerly. Nutrient Content and Nutrient Ratios of Irrigated Cotton on Fertile Soils. Texas Agric. Exper. Sta. MP 728, 1964. Longenecker, D. E., E. L: Thaxton, Ir. and P. I. Lyerly. Salt Tolerance of Seed of Six Upland Cotton Varieties During Germi- nation as Agected by Salinity Conditions During Seed Produc- tion. Texas Agric. Exper. Sta. PR 2376, 1965. Longenecker, D. E., E. L. Thaxton, Ir., I. I. Hefner and P. I. Lyerly. Variable Row Spacing of Irrigated Cotton. Texas Agric. Exper. Sta. Bul. 1102, 1970. Lyerly, Paul I., and D. E. Longenecker. Salinity Control in Irrigation Agriculture. Texas Agric. Exper. Sta. Bul. 876, 1962. Merkle, F. G., and E. C. Dunkle. Soluble Salt Content of Greenhouse Soils as a Diagnostic Aid. Iour. Amer. Soc. Agron. 36:11-19, 1944. Pearson, George A. Tolerance of Crops to Exchangeable Sodium. USDA Agric. Information Bul. 216, 1960. Reeve, R. C., and C. A. Bower. Use of High-Salt Waters as a F locculant and Source of Divalent Cations for Reclaiming Sodic Soils. Soil Sci. 90:139-144, 1960. Richards, L. A. Availability of Water to Crops on Saline Soils. USDA Agric. Information Bul. 210, 1959. Texas A&M University Staff. Soil and Water Salinity Workshop. Proceedings of Workshop, Iuly, 1968. Texas Water Commission Staff. Water Levels and Chemical Analyses from Observational Wells in the Dell City Area, Huds- peth and Culberson Counties, Texas, 1948-1964. Texas Water Commission Circ. 64-01, 1964. U. S. Salinity Laboratory Staff. Diagnosis and Improvement of Saline and Alkali Soils. USDA Agric. Hndbk. 60, 1954. Utah State University Foundation. Characteristics and Pollution Problems of Irrigation Return Flow. U. S. Dept. of Interior, 1969. ‘ 33 Appendix i.‘ -. v- FORMULAS FOR CALCULATING WATER DEPTH, VOLUME AND IRRIGATING TIME. These formulas do not take into consider;- tion ditch loss, loss of tail water or uneven water penetration. Allowance must be made for such factors where pertinent. é cubic feet per second x hours or gallons per minute x hours acres x 1.008 acres x 452.5 1. Acre-inches per acre = _ cubic feet per second x hours gallons per minute x hours '2‘ Acremaet per acre _ acres x 12.1 or acres x 5,430 cubic feet per second x hours gallons per minute x hours 3. Acre-inches = 1.008 or 452.5 g 4_ Acrefleet = cubic feet peggieicond x hours or gallons persrlgizgigte x hours 5 Hours irrigating time = total acre-feet required x 12.1 or acre-feet required x 5,430 ' cubic feet per second gallons per minute 6 Hours irrigating time = acre-inches per acre desired x acres x 1.008 or acre-inches per acre desired x acres x 452.5 ' cubic feet per second gallons per minute EXAMPLES (1) How many acre-feet of water are pumped per day by a well producing 2,000 gallons per minute? Use formula 4: gallons per minute x hours ___ 2,000 x 24 = 48,000 = _ 5,430 5,430 5,430 8.84 acre feet (2) How many hours will be required to apply 4 inches of water to 100 acres 0f land when using 5 cubic feet of water per second? “ Use formula 6: acre-inches per acre desired x acres x 1.008 = 4 x 100 x 1.008 cubic feet per second 5 4°32 = 80.6 hours FACTORS AND CONVERSION FORMULAS1 1 cubic foot = 7.48 gallons 1 cubic foot per second = 7.48 gal/sec = 1 second-ft 1 gallon = 0.1337 cubic foot = 448.8 gal/min 1 liter = 1.057 quarts = 0.2642 gallon = 25923 gai/hour Water weighs: 8.35 pounds per gallon _ = 646,272 gai/day 62.43 pounds per cubic foot = 60 cu ft/min 2,719,450 pounds per acre-foot = 3,600 cu it/hour Soil weighs: 68 to 100 pounds per cubic foot 4,000,000 pounds per acre foot (average figure) = 86'400 cu ft/day _ _ = 0.992 acre-inches/hour One acre-foot of water contains: 43,560 cubic feet _ 238 aCieJnChGS/dav A 325329 gallons ' = 0.0826 acre-ft/hour 12 acre-inches _ 1 98 f/d 1 acre-inch of water: weighs 226,620 pounds _ _ ' 3cm t av 1,000 gallons per minute = 60,000 gal/hour contains 27,152 gallons contains 3,630 cubic feet = 1,440,000 QaVdaV 1 percent = 1/100 = 10,000 ppm = gz3zggziifti/tgieifiirste Meq/1 x equivalent weight = ppm ' Grains per gallon x 17.1 = ppm = 8'0” c“ ft/hour ppm x 0.00136 = tons per acre-foot of water = 1921504 c“ ft/daV EC x 103 (millimhos/cm) x 1,000 = EC x 106 (micromhos/cml _ = 2-21 acre-inches/hour Tons of salt per acre-foot of water x 735 = ppm _ = 53.03 acre-inches/day = 0.184 acre-ft/hour = 4.416 acre-ft/day 1Many of the factors given are in approximate figures. 34 35 888 88. 88. 2.88 .88 8.8 8.8 ...88 8888 88.8 8.8 8.8 8.8 88.8. 888.8 8.8 8.8 88.8 8. 88 .8. 8.88. 88.8 8.88 8.8 8.88 8.8 88.8 2.8 88.8 88 8.8. 88.8. 8.8 88.8 888.8 88.. 8 88 8.88 2.88 8.8 8.8 8.8 2.8 88.8 8.8 8.8 88.8 88.8. 88.8. 88.8 8.8 888.8 88.8 888.. 8 88. .88 88.8 8.8 8.8 88.8 88.8. 88.8. 88. 88.8. 8.2 88.8 8.8 8.8 88.8 88.. 88.. 88.8. 88 8.88 8.88 88 88. 88.8. 8.8. 8.... 8.8.8 888.8 88.8 8.8 888 28.8 88.8 88.. 888. 8.8. 888. 8. 8.888 8.8. 8.8 88.8. 8.8. 88... .88. 888.8 888.8 888 88.8 888.8 .88 8.8.8 88... 88. 888. 88. 8. 8.88 8.88. 8.88 88.8. 8... 8.2 88.8 888.8 .88 8.8 88.8 88.8 88.8 8.8 88.. 88. 888. 888. 8. 8.8.8 8.88. 8.8 8... .88. 8.8.8 88.8 88.8 888 88.8 888 888.8 88.8 88.. 8.88. 88. 88. 88. 8. 8.888 8.8. 8.8 .88. 8.2 .888 8.8 88.8 8888 88.8 88.8 888.8 88 8.8.. .88. 8.88. 88. 88. .. 8.888 8.8. 8.2 8.8.8 .888 888.8 88.8 8.88 88.8 888.8 8.8 88.8 88.8 88.. 888. 8.8. 8.8. 888. 2 8.888 8.8. 888. 88.8 8.8 88.8 888 88.8 88.8 888 28.8 88.8 .88 88.. 88. 888. 8.8. 88.. 8 8.88 ..... 8.8. 888 88.8 8.88 88.8 88.8 88.8 888.8 88.8 88.8 88.. 88.. ..88. 88. 888. 888.. 8 88.8 2.8 8.8. 888 8888 88.8 88.8 88.8 888.8 .88 888.8 8.8.8 88.. 88... 888. 888. 888. 88.. 8 8.888 8.8 8... 88.8 88.8 888.8 888 888.8 .88 88.8 88.8 88.. 888.. 8.88. 88. 28. 88. 88.. 8 8.88 8.88 8.8.8 88.8 888 8.8 8.8.8 88.8 888.8 88.8 88.8 888.. 88.. 888. 8.8. 888. 888. 888.. 8 8.88 88.88 888 888.8 888.8 88.8 88.8 88.8 8.8.8 88.. 888.. 88.. 8.88. 8.8. 888. 88. 888.. 888. 8 8.8. 88.8 88.8 88.8 88 88.8 .88 88.. 88.. 88.. 88.. 8.88. 88. 88. 88. 88.. 88.. 88. 8 8.8.. 8.8 888.8 88.. 8.8.. 888.. 88.. 88.. 88... 8.88. 888. 8.88. 88. 888. 888.. 88.. 888. 8.8. 8 8.88 8.8. 88.. 8.88. .88. 888. 88. 8.8. 88.88. 88. 8.8. 888. 88. 888.. 888. 88. 8.8. 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