iBYJLLET | N 934 §JuLY 1959 Zzwéz/ IlI-IAIL DAMAGE-E EXPERIMENTS IN CCDT~TCDN TEXAS AGRICULTURAL EXPERIMENT STATION R. D. Lawns. DIRECTOR. COLLEGE STATION. TEXAS Summary Cotton grown on the High Plains and in the Trans-Pecos areas of Texas frequently is damaged by hail. The damage varies from a few punctured or destroyed leaves and fruiting structures to com- plete destruction of the stem and bark to ground level. A number of experiments have been carried out to simulate hail injuries. Spacing, defoliation, various stalk cutoffs, stem bruises and combinations of injuries have been inflicted by hand. The main features of the results of these treatments follow. Stands were thinned substantially from the aver- age stand found in the areas without reducing the yield. An‘ optimum stand was found to be two plants per foot of row. Total defoliation retarded recovery and delayed maturity. The cotton plant, however, was not af- fected markedly by removal of one-third or two- thirds of its leaves. Furthermore, the cotton plant regenerated new leaves rapidly. The terminal bud is not necessary for growth and fruiting of the cotton plant. Topping neither decreased nor increased yields significantly. PQ? Contents Summary .............................. ..; ...................................... .- 2 Artificial, Machine-made Hail Damage ....... .. Introduction __________________________________________________________________ __ 3 Experinlental Results """""""""""""""""""""""" Spacing ................................................................ Review 0f Literature ------------------------------------------------- -- 3 Effect of Defoliation 011 Yield _______________________ Experimental Methods _______________________________________________ __ 5 Recovery from Destruction of Terminal B t‘ Spacing ____________________________________________________________________ __ 5 Recovery from Stalk Cutoffs .......................... .. a Defoliation ________________________________ ___________________________ __ 5 5mm Damage ------------------------------------------------ ‘j Removal of Terminal Bud _________________________________ __ 6 Effect of Injuries on Fiber Properties """"" "I Stalk cutoffs ______________________________________ ________ __ 5 Combinatiml of Injuries --------------------------------- -- v _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 4 u 6 ------------------------------------------------------------ .'-..... I Stem Injuries ......................................................... _. 6 Literature Cited ..................................................... Effects on Fiber Properties ....... .._ ....................... .. 6 "Q? Early-season stem injuriesltljdid not affect ' and fruiting. Treated plants did not lodge _ boll crop was made. The cotton plant recovered after the st severed above the lowest node. The buds at r forced into growth and a new plant was r Early-season injuries did not reduce yield but considerable loss in yield resulted from" ments later in the season. Results of seve '_ stem at the middle joint were similar for early, ments, but this injury did not depress yields a8 as the low cutoff during the later stages. l A test of the effect of various levels of ti‘, tion in combination with other injuries reveal no large additional decreases resulted from t‘ binations except for the 100 percent level oft iation. The combination of any injury wit plete defoliation resulted generally in greater in yield than were obtained from either inj a arately. ' The effect of hail injuries on fiber pr” could not be evaluated reasonably. “$9 Acknowledgments .................................................... _Q_ é AILSTORMS no EXTENSIVE DAMAGE IN TEXAS. Crop- il insurance claims have approached 5 million dol- 1 in some years, although only about l0 percent of if crops in the State are insured. The annual dam- from hail is much greater and far exceeds that . sedby tornadoes j Hailstorms occur in all areas of the State but are frequent in West Texas. The annual frequency ties from 10 or more storms in the Panhandle to than one per season near the coast. Storms strike grevery month of the year but are most frequent and se more damage in the spring and early summer. farmers have had the unfortunate experience ‘ seeing their lush crops damaged or destroyed by >, Figure 1. With increasing costs of production, ll loss becomes of greater economic significance. Hail injury to cotton consists of leaf destruction, J bruises and cutoffs, bark and wood injury and truction of squares, flowers and bolls. The re- A 'ng losses are dependent on the severity of the in- lies, the stage of growth and seasonal conditions. amount of loss sustained from hail injury de- i; also on the structure of the particular crop t. Damage to cotton, as compared with some is, has been difficult to evaluate because of the re- ‘th ability of the plant. A project was started in 1953 with the objective ‘timating the effects of hail damage to cotton by ins 0f simulated hail-like injuries. The purpose _ is bulletin is to present the results of the simu- hail tests and a review of the structure and . th habit of cotton in order to provide a more iul guide to the survey of hail damage. Review of Literature 1 Simulated hail damage studies have been con- led on many important crop plants such as corn :2, 4, l0), soybeans (1, 9), small grains (5), flax , tobacco (15) , sugar beets (14) , potatoes (18) onions (7). The results of many of these tests f. a sound basis for estimating the effects of hail ies and have in some instances provided useful y ation on the gnanagement of damaged crops. a main objective of the tests was to develop practi- ides for the survey of hail damages, and detailed iological analyses for the most part are incom- v The results show consistently that injuries had ire pronounced effect at certain stages of develop- t of the crop plant than at other stages. SIMULATED HAIL DAMAGE EXPERIMENTS IN [PIUTTUN HARRY C. LANE, Associate Professor Department of Plant Phgsiologq and Pathology Eldredge (4) and Kiesselbach et al. l0) after several years work with corn found that leaf damage and destruction were of primary importance. Total defoliation near the tasseling stage resulted in nearly complete failure of the crop. Similar results were noted by Eldredge (5) for small grains and by Klages (ll) for flax. Hawthorne’s (7) report on simulated hail dam- age studies in onions has been particularly useful in determining hail losses to this crop. His report gave results for various levels of defoliation at different stages of bulb formation. The work of Pointer and Woltz (15) onitobacco illustrated the prime importance of timely and proper cultural treatment of a crop after it has been dam- aged. It was shown that tobacco fields which were judged as totally destroyed could recover and pro- duce large yields if the damaged fields were “cleaned up” after the storm. Weber and associates (1, 9) have continued ex- periments in soybeans and have reported on the effect of defoliation, stand reduction and stem breakage on seed yield, chemical composition of the seed and other agronomic properties. Stage of development of the plants at the time of injury was found to be of pri- mary importance. Defoliation became increasingly important as the plants reached the late flowering stage at which time 100 percent defoliation of the plants resulted in near total loss. Stem breakage alone caused a lowering of yields, but not on the or- der of that caused by defoliation. Defoliation also had a greater effect on other agronomic properties than did stem breakage. No simulated hail experiments had been con- ducted with the cotton plant at the time the present project was initiated. A reasonably good loss adjust- ment procedure had been devised by tediously cata- Figure 1. A hailstorm near Crosbyton, Texas, on June 22, 1958, completely destroyed this crop of cotton. loging damage and returning to the fields in the fall to observe the extent of recovery. Many of the re- growth characteristics of cotton were known, but ex- perimentation was required to substantiate these ob- servations. Since a knowledge of the structure and growth habit of cotton is of prime importance in assessing hail damage, a review of the two phenomena is pre- sented. In making this review, the works of Eaton (3), Loomis (13) and Hayward (8) were used ex- tensively. ' The basic architecture of the cotton plant is simple and rugged. Cotton is a woody plant with an erect, branching central stem and a strong taproot system. The leaves have long stems or petioles, the blades are large with three to five lobes and are ar- ranged spirally on the stem in an alternate fashion. The plant in profile is cone shaped. The plant is generously supplied with lateral buds. At the cotyledonary node, the buds are single, opposite, vegetative and completely capable of pro- ducing another stem of the same gross morphology as the mainstem. There are two buds (or a divided bud) in the leaf axil at all other nodes. The cen- tral axillary bud produces a vegetative limb much like the mainstem; the side axillary bud produces a fruiting limb. Fruiting limbs are initiated five to six nodes above the cotyledonary node in Upland varie- ties whereas vegetative limbs are usually formed be- low the sixth node. Fruiting limbs, after being dif- ferentiated from the ‘terminal bud, begin growth im- mediately. The growth of central axillary buds, or vegetative buds, does not start until four to six nodes separate them from the apical bud. \ FLOWER \ ) vm t/J \L~ ’",\r ->g\,\§ ( - i BOLL /%' m. 7 5D \ N .5; \ -.\__ . y‘, ’ \ A FRUITING LIMQ ‘ \ Figure 2. A fruiting limb of cotton. Note two-ranked arrangement of leaves and zigzag manner of growth. 4 There are several ways to distinguish be the vegetative and fruiting branches produced cotton plant, Figures 2 and 3. l. A fruiting limb is initiated at the side » than the center of the leaf axil as the '5 tative limb. i 2. A fruiting limb grows horizontally and 5 zigzag manner rather “than straightfoi and vertically as the vegetative limb. A 3. The leaves on a fruiting limb are two-r: rather than spirally arranged as on a’ tative limb. - 4. Most important, the fruiting structur attached directly to the fruiting limb b fruit stalk or peduncle. A vegetative 1')‘ sometimes confused for a fruiting limb; close inspection will reveal that a smal p" ond order fruiting limb is present (a a ample, limb from node 5, Figure 3). i The flower bud is covered by three large , and is called a square. The corolla is rolled w bud, but opens to a showy white to yellow b with five petals. The corolla turns reddish af day and usually sheds in 3 days. The fruit of v. is called a boll. It is a capsule with three t0§ separate chambers in which the seed and fibeif formed. A The cotton fiber is a single cell which init from the outer layer of the seed coat shortly v fertilization takes place. The fiber elongatesj. idly and reaches its full length in approximate; days. Following elongation the fiber goes thro ' phase of secondary thickening during which c0 tric rings of cellulose are laid down on the int walls of the fiber cell, adding body and stren i the fiber. Both the rate of elongation and the \- ner of secondary layering are affected by tem ture along with other factors. The time req for a boll to mature varies from 45 to 75 days. - Optimum temperature for the germination i growth of the radicle and hypocotyl is approxi ly 90° F. The interval from time of plantin emergence of the young plant varies from 5 c? days, depending on temperature and soil mois With optimum conditions, primary roots grow idly and a plant will develop a small taproot-g 12 inches long within a few days after germina A lateral root system is developed within the " few inches below the surface of soil. Additi lateral roots are developed at lower intervals ’_ taproot penetrates the soil. After emergence, the green cotyledons grow 3 produce food for the young plant. The first " leaf is visible within 7 to 15 days. Growth of, overall plant under field conditions followsth miliar bell-shaped or sigmoid curve. Rate of L; is slow the first days after emergence, but grad increases until it is sometimes phenomenal. i’ 5. Squaring starts about 1 month after emergence. reafter, the rate of fruiting is progressive and ited only by growth rate. Under optimum growth jitions the interval between successive fruiting 'bs (nodes on the mainstem after squaring has r f ed) averages 3 days. The interval between suc- fjive squares on a fruiting limb is 6 days. With imum stands and growing conditions, enough fruit - l § x £5 4o x a- x x 209 ’\‘ o X l JUNE L L JULY l‘ I4 l5'3O l'l4 |5'3O Figure 8. Mean yields in percent of undamaged plots resulting from low cutoffs for four crop years at Lubbock. growth and added injuries far exceed that of the interactions. Thus, most of the variation is due to these main effects, although certain of the interac- tions are important. ‘An examination of Tables 5-9 and Figure l2 shows that the main cause of variation in response to defoliation was the effect of 100 percent defolia- tion. Removal of two-thirds of the leaves caused some reduction in yield, but only 100 percent defoli- ation consistently reduced yield. Generally, the losses from 100 percent defoliation more than doubled that of two-thirds defoliation. One hundred percent de- foliation tended to kill the plants in the very early seedling stages, and to retard recovery in other stages. It was a serious injury at all stages of growth. The most critical times were the stages of flowering and boll growth. The interaction of years times defolia- tion was significant largely because of the early sea- son effects in 1953. However, another component of the interaction was the variation in results from 100 percent defoliation in the late stages of growth. The large mean square for growth stages indi- cated that injuries were more harmful at certain stages. The data show this was true particularly for the higher percentages of defoliation and for the more serious injuries at the later stages of growth, Tables 5-9. The effect of the topping injury was similar to that of the single test previously described. However, topping plus 100 percent defoliation was more dam- aging than either treatment alone, Figure l3. This was true for the very early stages and many of the treated plants died from this combination of injuries. Cutting the plants off at the middle joint re- duced yields from 30 to 50 percent compared to nor- mal controls. The early stage treatments reduced yields more in this test than in the single injury test previously described. One cause for this was that 9 TABLE 3. EFFECTS OF BARK AND STEM DAMAGE ON YIELD, LODGING. AND FRUITING OF COTTCN, LUBBOCK. 1958 Yield . Treatment Date percent Lodging 1?“? .Y m of check rumng Iune 1U 100 Check Iune 17 100 _ Iune 24 100 Iune 10 89 none none Bark Iune 17 102 none none Iune 24 98 none none Stem and Iune 1U 101 none none wood Iune 17 101 none none shattered Iune 24 84 some‘ none ‘Several plants were broken by a squall occurring shortly after the injury was inflicted on the morning of Iune 24. ‘stands were more dense in the combined injury ex- periments. The combination of the middle cutoff with one-third and two-thirds defoliation at the later stages of growth produced decreases above that of the stem injury alone, Figure l4. However, the middle cutoff and 100 percent defoliation caused a substantial decrease over that of either damage singly. This was also due to excessive killing by the combi- nation of the injuries. The year-to-year variation in response to the middle cutoff injury reflects the differences in posi- tion of fruit set relative to midjoint of the plants. Approximately two-thirds of the bolls set in 1958 were below the middle node of the plant, whereas in 1954 only half of the crop was below midjoint. ~ The removal of fruiting limbs at the earlier stages of growth did not reduce yields consistently. In contrast, yields were sharply reduced by removal of the fruiting limbs during the late growth stages. “T he reductions were greater with total defoliation at this stage, Figure l5. This showed that recovery or production depend on rapid growth of the term- Q inal and new fruiting and that time is short fOff recovery from August injuries which strip the t’ of fruit. The interaction of growth stage times , ed injury was consistently significant and refle largely the effect of removal of fruiting limbs at late stages of growth. if The interaction of added injury times def ation was not significant, butwcertain of the tr‘ towards greater reductions with!" defoliation in data have been mentioned for certain injuries. The results of bark injury showed no addedg fect over defoliation after the stem became wt Table 9. During the earliest stage, many of the pl s were actually cut off in the effort to scrape thro 1' [116 bark. A bonafide test of added injury times yearsfik teractions could not be made because of the cha in treatments. However, only small mean squ; were obtained for these interactions even though p’ treatment was altered. ;v The analyses of the combined injury tests shi that hail damage can be estimated reasonably by i proper evaluation of the main components: gro? stage, degree of defoliation and type of cutoffs. Ta 5-9 provide a practical key for the evaluation of h,‘ damage. Discussion Damages and losses resulting from a hailstorm‘ a cotton crop are difficult to estimate. Only by s tematic classification of injuries and by the appli cation of proper loss factors can accuracy be obtain A number of factors such as stage of growth, type injuries and seasonal conditions must be consider? An inexperienced person cannot accurately integr all these factors, and many acres of potentially ij cotton have been plowed up because of the incorr evaluation of hail damage. e Figure 9. Recovery from a low cutoff made in early June: (A) limbs growing from cotyledonary node, (B) treated plant j August and ( C) check plant in August. 10 it . TABLE 4. FIBER PROPERTIES OF SAMPLES COLLECTED FROM COMBINED-INIURY TEST. LUBBOCK, 1958 1 Added iniury £33,“ (5523:? None Topped Middle cutoff Severe bark damage '5' Mic.“ UHIVF Press.“ Mic. UHM Press. Mic. UHM Press. Mic. UHM Press. 15-day-old 3.9 .92 82 4.1 .95 82 4.1 .93 82 3.9 .88 88 Squaring 3.9 .96 80 3.8 .91 83 4.1 .98 86 4.1 .94 85 Flowering 3.6 .88 81 3.9 .94 82 4.2 .96 78 3.4 .94 80 Late boll 4.1 .96 74 3.9 .97 82 3.8 .95 79 3.6 .94 82 15-day-old 3.9 1.00 82 2.8 1.00 78 3.8 1.00 76 3.2 .95 78 Squaring 3.2 .94 76 3.7 .98 80 3.5 .94 78 3.1 .93 72 Flowering‘ 3.2 .94 77 2.8 .94 75 3.4 .98 78 3.2 .88 81 Late boll’ 2.4 .98 80 2.5 .89 84 2.4 .96 80 2.4 .93 80 ;'es resulted in 50 to 100 percent bolly crop. Qbolls opened prematurely. V‘ winds. g Some of the results of these tests should be ap- y ble t0 the estimation of hail damage. The spac- Tor stand of a crop is a frequent point of disagree- ‘t, but the results of numerous experiments on "ng of cotton have shown that a conservative .'ng of about two plants to the foot of row is op- In (l2, 16). In contrast, farmers on the High occasionally grow stands of four to twelve ‘ts per foot of row. Such a practice is without ex- _ental support. Actually, yields usually are lower- r a result of these thicker stands and undoubtedly g stands promote some of the immaturity in the i: Plains crop by delaying the nodal appearance of first fruiting limb.’ One of the reasons given by iers for extremely heavy planting rates is that it 5 some protection against hail loss. The prac- i actually defeats its purpose, however, because a 5. YIELDS AS PERCENT OF AVERAGE OF CHECKS TING FROM VARIOUS LEVELS OF DEFOLIATION MUTILATION AT DIFFERENT STAGES OF GROWTH. . LUBBOCK. 1953 1 micronaire, a measure of the weight per unit length of the fiber. = upper-half-mean, approximately equal to the classer's staple length. _, . = Pressley strength, a measure of the strength of a bundle of fibers of 1 inch _in cross section expressed in thousands more spindling plant is grown and fruiting is delayed in nodal position. Storms in July which top or cut- out the upper one-third, of plants do far more damage in the thickly planted cotton than in reasonably spaced plantings. The contrast between the maturity and position of fruit on an extremely thick stand" and on an optimum stand is shown in Figure 16. Another reason given for thick stands is that they facilitate machine harvesting. The consensus of work- ers who have measured machine efficiency is that a stand of two plants every foot of row (6-inch spac- ing) can be harvested satisfactorily by strippers or pickers (17). The results of the spacing tests reported here show that a 6-inch spacing of plants would be a fair and reasonable basis for the adjustment of stand losses by hail. TABLE 6. YIELDS AS PERCENT OF AVERAGE OF CHECKS RESULTING FROM VARIOUS LEVELS OF DEFOLIATION AND MUTILATION AT DIFFERENT STAGES OF GROWTH. LUBBOCK, 1954 jry all plants killed by treatment. . Added inlufY P Added injury Date M11111 Llmbs defoli- Date M-dd1 Llmbs 1 1 e . 5 99° None Topped cute“ mQeI-ed anon 518499 None Topped Cato; Inger-ed y 6/11 15 day old 100 96 70 102 6/22 15 day old 100 94 65 84 7/ 10 Squaring 100 93 59 96 7/5 Squaring 100 88 74 87 7/ 20 Flowering 100 97 68 96 0 7/ 23 Flowering 100 93 63 86 8/6 Young bolls 100 112 57 70 8/ 6 Young bolls 100 109 49 70 6/11 15 day old 186 88 86 96 6 22 15 d 1d 100 93 64 10o 1/10 Squaring 101 10o 5s s2 775 Squgggn‘; 90 85 74 84 7/88 Flowering 88 84 55 78 ss.s 1/2s Flowering s1 as as s4 8/8 Ysuns 5°18; 85 88 48 58 s/s Young bolls a1 1s s7 s5 6/ll 15 day old 109 81 82 115 7/18 Squdking 94 75 65 91] 6/22 15 day old 90 88 67 84 7/20 Flowéiing 101 a1 55 86 7/5 Squaring 88 85 65 87 g/g your, 1,9115 1115 35 34 53 66.6 7/ 23 Flowering 84 79 52 86 g s/s Youn bolls 12 1s 2s 7o s/11 1s day old 1o 291 7* as g 7/10 Squaring 80 59 49 67 5/22 15 d 1 75 52 43 1/20 Flowering 7o 5s 27 4s 7 ,5 Squgifluj d 67 77 50 3f, 8/8 Ywns bells 48 42 2 4 10o 1/2s Flowering ss s2 2s v 8/6 Young bolls 40 40 10 4 I00 ---- ,-----'--x ----------- "i""' X X , t BO x \x g x x_______ so i " X ‘é g 40 2o eaowrq STAGE I SEEDLING SOUARING FLOWERING YOUNG BOLLS Figure 10. Mean yields in percent of undamaged plots resulting from medium cutoffs for four crop years at Lubbock. Another feature of these results applicable to hail damage estimation is the differences observed between early and late-season injuries. An injury early in the season does not cause as much loss as a similar injury incurred later in the season. Crops have regrown and produced normal yields after ex- tremely heavy damage in June. Similar damage in july or August caused considerably larger losses in yield. The cotton plant has a remarkable capacity for growth after serious injury; if most of the grow- ing season occurs after the storm, the plant can re- cover to the point that the effects of the early hail damage are difficult to distinguish. Farmers are prone to worry about the “setback” to their crop by hail injury. The delay in fruiting and development Figure 11. An example of healing by an injured cotton stem. Number 1 is an example of healing after real hail in- jury. Numbers 2, 3 and 4 show healing after simulated injury. . ‘woo S:___q__-o-—|--0-0 8O *______________* l- s 6° \ Q Numborloovos _, '3?‘ s- q; removed = t‘- - w o O n‘ 4o o I13 x 2/3 i- all 2O GROWTH STAGE‘ soumme r-"towamue sous; Figure 12. The effect of various levels of defoli/ '1 different stages of growth on yields of cotton. SEEDUNG caused by hail damage often appears to be more I‘ it really is because injury to small plants destroys‘; dry matter than appearances indicate. The f loss in dry matter and the slowing down of grow ii plants reach maturity reduce the significance of; “setback” to the crop that seems so obvious on. day after the storm. Careful attention should be given to the ex of leaf and stem damage. A crop that is totallyf foliated and has the bark stripped on the stem in the season does not recover rapidly, and u; plants may fail to recover. On the other hand, small amount of leaf tissue remains undamagedg buds will live and recovery is more certain. Perl - the most severe injury overall to the cotton play total defoliation; but if a few leaves remain, g leaves will be regenerated in a short time. An i i terminal growing point is important in cases of h, defoliation as fruiting will occur much sooner. j, The terminal bud, with the exception s above, is not necessary for the regeneration of cotton plant. When the terminal is intact, it portant as it plays a predominant role in the devg; mént of the plant. After a plant is topped, axis buds become active and control growth. The low cutoff as described and reported common hail injury. It is a particularly trouble injury near the end of June as it leaves the crop l‘ ing totally destroyed. But the results of several y“ testing, and long experience with hailstorm in' show that the potential yield after low cutoffs in - is high, which warrants working the crop in cases rather than replanting either to sorghug‘ cotton. Early june losses as a result of the {g are not great but it would be even more difficult show a decrease in yield from cutoffs in May on Texas High Plains because so little growth is t‘ during that month. However, because of a d of uncertainty with damaged crops, and beca ‘l, - _ 1. YIELDS AS PERCENT 0F AVERAGE 0F CHECKS =11 TING FROM vamous LEVELS 0F DEFOLIATION MUTILATION AT DIFFERENT STAGES 0F anowm. .1 HALLS, 1954 Added injury ‘- nt ‘ i . Growth - _ 1) g . Limbs * . a e 51999 None Topped re- moved 6/ 22 Presquare 1UU 89 81 88 7/ 14 Squaring 1UU 92 67 89 8/11 Young bolls 1UU 98 4U 33 6/22 Presquare 94 92 79 88 7/ 14 Squaring 94 77 65 77 8/11 Young bolls 94 81 33 44 ‘ 6/22 Presquare 98 96 79 1U4 " ’ 7/ 14 Squaring 98 92 63 79 8/ 11 Young bolls 83 83 38 35 6/22 Presquare 75 5U 33 81 7/ 14 Squaring 83 71 44 27 8/11 Young bolls 6U 52 17 U r -_'n amount of replanting seems necessary from a ‘v of causes, farmers in the area invariably re- ‘t crops damaged in May. The practice is not ‘Yonable because the latter part of May is the al time of planting much of the cotton in the i It has been observed, however,.that crops sur- g early hail damage are often more mature at q than replanted ones. The low and middle cutoff injuries produced ar results when applied early in the season and . is no reason to distinguish between the types. j‘ presence of leaves, undamaged bark and a g y root system are more important factors than g pe of stem cutoffs in affecting recovery in early of growth. Later in the season the middle cut- id not reduce yield as much as the low cutoff. probable that the results from the middle cut- _ a. YIELDS AS PERCENT 0F AVERAGE 0F CHECKS - nus FROM vantous LEVELS 0F DEFOLIATION MUTILATION m‘ DIFFERENT STAGES 0F GROWTH, _~ LUBBOCK. 195s Added iniury ‘at Date Growth Middl Limbs 3 _ 51°99 None Topped e re- n cutoff moved 6/4 15 day old 1UU 91 7U 1UU 6/ 19 Squaring 1UU 89 65 99 7/ 1U Flowering 1UU 95 61 99 8/ 7 Young bolls 1UU 99 63 8 6/4 15 day 01d 1U5 1U6 75 1U2 6/ 19 Squaring 85 93 87 94 7/ 1U Flowering 8U 86 75 81 8/7 Young bolls 11U 1U6 6U 1U 6/ 4 15 dcflr bld 96 9O 61 93 6/ 19 Squaring 83 83 56 92 7/ 1U Flowering 81 68 6U 85 8/7 Young bolls 82 8U 53 9 6/ 4 15 day old 75 62 4U 9U 6/ 19 Squaring 87 82 5U 7U 7/ 1U Flowering 79 71 38 71 8/ 7 Young bolls 6U 56 33 U off at late season cannot be applied directly to hail damage as any storm severe enough to cause this in- jury would also likely destroy all the fruit below mid- joint. There is a tendency for plants severed at the higher nodes to produce several side branches. Such plants may be late in fruiting if excessive vegetative growth is made. Furthermore, this type of regrowth hinders machine harvesting. Early stem bruises caused by hail rarely result in the subsequent lodging of plants after a boll crop is set. Tissues continue growing and adding new wood during the healing of the cotton stem. A healed stem is often strongest at the point of injury. The practice of breaking stems by hand at the point of injury after a hailstorm is a poor indication that lodging will occur later. Plants that have grown several side branches from the lower nodes frequently split at the fork. This is not related to hail bruises. Although the results of the tests on the effect of stem injuries showed little reduction in yield, plants in- jured by hail in this manner are sometimes slow in recovery. Also, unexpected amounts of dying after hail injury have been associated with the severity of the stem injuries. The bark must remain intact and secure up to the position of living buds which re- generate the damaged plant. The initial foods re- quired for the growth of buds must be translocated from the root or stem and the movement of foods oc- curs through the bark tissues. Figure 17 is an example of the healing of a stem that was injured at an early stage by inserting a knife through the stem to separate the wood. The treated plants developed and fruited normally, Figure 17A. Figure 17, B and C, shows opposite sides of the in- jured point. Note the extra thickness of wood made in the healing process. TABLE 9. YIELDS AS PERCENT OF AVERAGE OF CHECKS RESULTING FROM VARIOUS LEVELS OF DEFOLIATION AND MUTILATION AT DIFFERENT STAGES OF GROWTH. LUBBOCK, 1958 Added injury Percent severe deioli- Date Growth M-ddl b k ation s“‘°° "m T°PP°d ciitoife dfi..- age 6/11 15 day old 1UU 1U3 7U 89 6/ 25 Squaring 1UU 97 9U 85 U 7/23 Flowering 1UU 89 78 1U5 8/21 Late bolls 1UU 1U1 76 1UU 6/11 15 day old 1U4 92 9U 1UU 6/ 25 Squaring 98 99 86 84 33.3 7/ 23 Flowering 84 92 8U 88 8/21 Late bolls 1U1 92 7U 8U 6/11 15 day old 98 98 83 81 6/ 25 Squaring 89 96 78 91 66.6 7/ 23 Flowering 91 79 52 1U3 8/ 21 Late bolls 8U 74 62 83 6/11 15 day 01d 99 67 43 63 6/ 25 Squaring 71 83 81 79 1UU 7/ 23 Flowering 6U 41 43 5U 8/21 Late bolls 54 58 72 64 “ o '0 o '/ 8Q ____§---x 6 O \g * \ Number leaves 4O removed O l/3 2/3 all PERCENT Ill v‘ 0 0 2O GROWTH STAGE o SEEDLING SQUARING FLOWERING BOLLS Figure 13. The effect of various levels of defoliation com- bined with topping at different stages of growth on yields of cotton. It is sometimes difficult to separate shedding re- sulting from hail injuries from natural shedding. In general, hail-induced shedding of a few squares and flowers during the beginning periods of fruiting is not harmful. Hail-induced shedding of the flowers and small bolls after a normal set of bolls is realized cannot be considered to affect yields since these struc- tures shed naturally. The results of the spacing ex- periments showed that the number of bolls set reach- ed a maximum number. This number of bolls seem- ed to be a function of the whole soil and climatic complex. As the maximum number of bolls set was reached, the subsequent flowers were shed. This same phenomenon occurs for other plants (9). The prin- ciples involved in the growth and fruiting activities of plants provide a basis for judging the significance of shedding caused by hail. Eaton and Loomis . (l3) have described these principles. The farmer's problem after his crops are dam- aged by hail is a difficult one. He must examine the IOQ 8O 21; 4o \*: P ERCENT I- Number leaves remaaved e 2o o l/S x 2/3 i- all GROlNTH smog I I O SEEDLING SQUARING FLOWERING BOLLS Figure 14. The effect of various levels of defoliation com- bined with middle cutoffs at different stages of growth on yields of cotton. 14 - sf damaged crop and decide what to do in order t; duce the best crop. One of the common m1 that is made after a hailstorm is the failure t_ amine the damaged plants closely. Farmers been observed replanting cotton that was dag superficially by hail. Near the end of the co planting season, this type of mistake could be! costly. p The following procedureiof examining and: ing for crops damaged in June has been used su ¢ fully on the High Plains. One should delay an amination to ascertain the extent of hail injury at least an accurate estimate of the number of p _ that will die can be made. In the meantime, ‘A necessary to give the damaged crop protection ;. blowing sand or crusting. Figure 18 shows a " - fighter” being used the morning following a evening storm. This storm occurred near Lub in 1958. Blowing sand burned the buds on “stubs" left in many fields and destroyed any y bility of recovery. In some areas where crusting; TABLE 1n. ANALYSIS or VARIANCE or comnmznl IURY rzsrs Mean square Combin" Source of df M . varmtwn 1953 1954 1956 1958 d! sq‘: Total 255 1.023 , ._ a Years 3 243. Reps 3 0.40 16.80 0.26 2.58 3 5 so Defoliation 3 8.69 42.99 8.13 18.89 3 6 YXD 9 3 ‘ Error A 9 0.18 1.38 0.32 0.26 45 1 Growth stage 3 1.98 17.02 10.62 3.09 3 26 l» G X Y 9 j G X D 9 0.35 1.87 0.29 1.12 9 1. G X Y X D 27 Error B 36 0.09 0.57 0.22 0.23 144 I - Added injury 3 6.33 32.57 12.50 6.62 3 40 7 A X D 9 0.15 0.79 0.30 0.27 9 0. , A X G 9 0.51 2.24 6.12 0.88 9 0 1. A X D X G 27 0.10 0.61 0.13 0.54 27 0. Error C 144 0.06 0.21 0.16 0.25 576 011 I00 o Q> Q Q “<11 / / ./ /! / l . // ../ 4° """:::.:,::s"= \* e O o l/3 at 2o x 2/3 u» all GROVIITH STAGE] l A ' SEEDLING SQUARING FLDWERING BOLLS I, Figure 15. The effect of various levels of defoliation A bined with removal of fruiting limbs at different stag growth on the yield of cotton. 5 graphed on the same day at Lubbock in 1958. ‘following rain or hail, it is important and neces- ‘to cultivate the damaged crop as soon thereafter ssible. j In examining a hail-damaged crop, all parts of fifield should be checked to determine if the dam- is uniform. Hail is often “spotty” in intensity some areas within a given field will be damaged e than others. Whether a field should be re- ted is often determined by the size of the area iving the most damaging injuries. It seems un- _1to plow up several good acres because a few are aged seriously. Also, it is not feasible to grow acres of another crop such as sorghum, for ex- flle, in the middle of a large acreage of cotton. As tioned previously, injured plants may continue to ffor several days. However, an accurate estimate e stand that will survive usually can be made in a week’s time. Stands can be thinned con- irably by hail without causing much loss, but the aining stand should be reasonably distributed. a The important step in the examination of hail age is that of determining whether leaves or es of leaves are still attached to the plants. The Q that only traces of leaves enable an injured plant ecover with more certainty than when all leaves destroyed bears re-emphasis. Figure 19 shows a iation where an abundance of leaves were left af- la hailstorm. Although the stems of these plants lebbadly bruised by a driving hail, the amount of f es remaining indicated the crop could regrow. We damaged crop was cultivated and it recovered Figure 16. The contrast in maturity between an extremely thick stand and an optimum stand of cotton. The stands were and made three-fourths of a bale of average grade lint per acre. If all of the leaves are destroyed by hail, a closer examination of the condition of the stem and buds should be made before a final decision about the crop is reached. Many cotton crops have recovered when all of the leaves were destroyed. Recovery is usually slower under these conditions and is dependent on whether the bark is intact and free from large breaks up to the point of living buds. If the bark and stem are free of bruises and breaks, the buds will swell and show signs of starting growth in a short time af- ter the storm. Inspection of plants sustaining a heavy beating by hail often revealed that the stem was shat- tered and the bark was loosened and broken to a point below the cotyledonary node. In such cases farmers were advised that recovery was very doubt- ful. After a hail-damaged crop starts to regrow, it is extremely important to protect the young shoots from the feeding of cotton insects. The aphid, thrip and fleahopper are most troublesome. These insects inter- fere with the initiation and establishment of squares, flowers and bolls. The failure to retain the earliest fruit is often the cause of plants making excessive vegetative growth. No definite rules on how to manage the irriga- tion of a damaged crop can be made. It can be sta- ted that the proper use of irrigation is necessary to the success of growing a damaged crop. In general, growth should not be forced by abundant watering _ Figure 17. Recovery from a stem injury made by inserting a knife blade through the stem when it was small: (A) the en- ‘plant, (B and C) opposite sides of the injured area of the stem. Figure 18. A. “sand-fighter” being used to reduce sand blowing after o hailstorm. as this will tend to interfere with or prevent the es- tablishment of the earliest fruit. Farmers in the High Plains area usually grow late-planted cotton with one summer irrigation. This practice would probably be better most of the time with the more seriously damaged crops. Crops that are damaged in july or August in this area are often more success- fully grown without additional irrigation. The results of the simulated hail damage ex- periments have demonstrated the regrowth potential of the cotton plant. At the same time, considerable variation was noted for some of the treatments. It is the variation in responses from season to season which has made learning by observation difficult. In fact, it is necessary to understand the growth respon- ses of the cotton plant to explain these variations. ln regard to future work, it would be most advan- tageous to investigate more thoroughly the responses of cotton to controlled variables of temperature and other conditions in order to provide a better basis for the explanation of the variation in the plant’s behavior. Another problem that 'may become more im- portant with time is the effect of hail injury on cot- ton quality. The purely empirical methods used in these studies failed to give a clear insight to the re- lation of hail injury to fiber quality. By no means is hail the cause of all the underdevelopment in the High Plains crop, and further basic work is required before general principles can be established. Per- haps closer examination of the relation of the age of plants at the time of injury to the maturity rea- lized would provide a partial answer to how hail damage affects the fiber. Cotton can be planted successfully for a period of about 30 days in most areas of Texas. In the long run, hail insurance to the farmer will be cheaper if a fair and equitable basis for replanting crops dam- aged in these intervals could be devised. Additional results on the effect of planting date on yield are needed for some areas. Literature Cited 1. Camery, M. P. and Weber, C. R. Effects of certain com- ponents of simulated hail injury on soybeans and corn. Iowa Agri. Expt. Sta. Research Bulletin 400: 1953. l6 Figure 19. A crop injured severely by hail but enough leaves left to assure recovery. 2. Dungan, G. H. Effects of hail injury on corn plant m ured." Ill. Agri. Expt. Sta. Ann. Rpt. 41: 1928. f 3. Eaton, F. M. The physiology of the cotton plant. A j Rev. of Plant Physiology 6: 1955. 4. Eldredge, j. C. The effect of injury in imitation of " damage on the development of the corn plant. Iowa Al Expt. Sta. Research Bulletin 185: 1937. U! damage on the development of small grain. Iowa Expt. Sta. Bulletin 219: 1937. 6. Flora, S. B. Hailstorms of the United States. Univ ~ of Okla. Press, Norman: 1956. 7. Hawthorne, L. R. Defoliation studies as a basis for W estimation of hail losses in onions. Texas Agri. Expt. Bulletin 682: 1946. 8. Hayward, H. E. The structure of economic plants. McM lan, New York: 1938. 9. Kalton, R. R., I/Veber, C. R., and Eldredge, j. C. effect of injury simulating hail damage to soybeans. Agri. Expt. Sta. Research Bulletin 359: 1949. 1o. Kiesselbach, "r. A. and Lyness, w. E. Simulated hail inj j of corn; Neb. Agri. Expt. Sta. Bulletin 377: 1945. l1. Klages, K. H. W. The effects of simulated hail injuries“; flax. Amer. jour. Agron. 25: 534-543. 1933. 12. Lane, H. C. Cotton spacing-A review and discussi: Texas Agri. Expt. Sta. Misc. Pub. 170: 1956. l3. Loomis, W. E. Growth correlations, growth and differ I ation of plants. Iowa State Press, Ames: 1953. 14. Morris, H. E. Simulated hail damage to sugar v.5 Mont. Agri. Expt. Sta. Paper 194. l5. Pointer, j. P. and Woltz, W. C. Investigations of ~i damage to tobacco. N. C. Agri. Expt. Sta. Tech Bull 123: 1956. 16. Ray, L. L., Hudspeth, E. B., and Holekamp, E. R. Cdt“! planting rate studies on the Texas High Plains. Agri. Expt. Sta. Misc. Pub. 358: 1959. 17. Southern Cooperative Series—Planting in the mechanizat” of cotton production. Bulletin 49: 1957. 18. Sparks, W. C., Woodbury, G. W., and Takatosi, F. Estimating hail injury in potatoes. Idaho Agri. Expt. Bulletin 274: 1957. Acknowledgments Acknowledgment is made to all agencies and individ d who aided the work reported. The Hail Insurance Adjust and Research Association of Chicago, and several agents j farmers in West Texas are due special acknowledgment. Eldredge, J. C. The effect of injury in imitation of l