Cordgrass Prcduction,
   /   UtiIiZatiQn, and
Nutritional Value 
  / Follcwing
Burning

/ I
 A, Y
/ l? 3/3/ 977
'   '\v  M l versit %
, \ I

    
   
 
         

 

 

  

 GRICULTURAL EXPERIMENT STATION
M, ECTOR, COLLEG ATION. TEXAS
AVYA8<M UNIVERSITY SYS M

Contents

SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

MATERIALS AND METHODS . . . . . . . . . . . . . . . . . 5

RESULTS AND DISCUSSION . . . . . . . . . . . . . . . .. 6

Soil Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 6

Physical and Chemical Components . . . . . . . . 6

Soil Moisture Trends . . . . . . . . . . . . . . . . . . . . . 6

Foliar Cover Replacement Following
Burning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Production and Utilization of Gulf Cordgrass
Following Burning . . . . . . . . . . . . . . . . . . . . 1O

Protein, Phosphorus, and Digestible Energy
Levels of Gulf Cordgrass Herbage

Following Burning . . . . . . . . . . . . . . . . . . . . ll

Protein . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11

Phosphorus . . . . . . . . . . . . . . . . . . . . . . . . . . . .. l2

Digestible Energy . . . . . . . . . . . . . . . . . . . . . . . l6

CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

LITERATURE CITED . . . . . ." . . . . . . . . . . . . . . . . . . . 19

ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . .. 19

APPENDIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Summary

l
Gulf cordgrass, a highly productive species, form‘
almost solid stands on the Coastal Prairie. In its matur
state, the grass is coarse and unpalatable to livestoc
However, when immature, the plants are grazed by ca
tle, suggesting the possibility of improving utilizatio
with certain range management practices. Production
utilization by cattle, and nutritional value of gul
cordgrass after burning on different dates wer
evaluated from February 1975 to February 1976 nea
Armstrong, Texas. Utilization of gulf cordgrass regrowt
was greatly increased following burning compared to us
of unburned sites. Since gulf cordgrass afforded forag
during the winter months, cattle concentrated on th
burned areas. Grazing use maintained the regrowth in
young tender state throughout the winter. Howeve
utilization of gulf cordgrass tended to decrease durin
the spring when other grasses and various forbs becam
available on adjacent range sites. New growth of guy
cordgrass following burning was higher in protein, pho
phorus, and digestible energy content than matur
growth on unburned areas. The primary benefits
burning gulf cordgrass, a temporary increase in forag
quality but a prolonged increase in utilization by live
stock, varied according to site characteristics, precipita
tion, and date of burning. Utilization of mature gu
cordgrass was negligible throughout the study perio
and standing crop on unburned sites did not vary appr
ciably over a 1-year evaluation period. Management di
rectives to increase utilization and quality of gul
cordgrass should be aimed towards burning of product
tive sites during warm, moist periods, and preferablyl
immediately prior to seasonal reductions of other avail‘
able range forage. 

v

  

Gu

/ \.

   
  
  
    
    
  
  
   
    
    
    
   
  
  
   
  
  
   
  
   

  

R. D. Oefinger and C. I. Scifres*

(Oastal Prairie and Marshes are comprised of
ely 3.8 million hectares‘ of valuable range-
the Texas Coast. Stands of gulf cordgrass
artinae (Trin.) Hitch.], better known t0
n the southeastern portions of Texas as “sac-
 common in this area (Figure l). Entire pas-
‘be occupied by almost pure stands of gulf
uch pastures have unique management re-
as contrasted to typical Coastal Prairie since
cordgrass forage is coarse, tough, and not
d by livestock. However, because of the
inance of certain sites almost to the exclusion
ies, there is often localized overgrazing of
es not supporting gulf cordgrass. The sites
only occupied by gulf cordgrass are periodi-
ated and support few alternative species that
ceptable forage for livestock under such
tal conditions. In fact, when mature stands
grass are destroyed, the areas may become
1 with other species of a lesser forage quality,
y certain salt-tolerant plants. Since gulf
, so well adapted to the Coastal Prairie, more
nagement techniques are needed to op-
iitllization.

pecies of Spartina commonly occur in Texas,
cordgrass occurs in such extensive areas as
bstantial economic importance as forage for
The other two species common t0 the Gulf

to convert metric to English units.

, research associate, The Texas Agriculture Experiment
(le, and professor, The Texas Agricultural Experiment
artment of Range Science).

trademark or a proprietary product does not constitute a
a warranty of the product by The Texas Agricultural
tation and does not imply its approval to the exclusion of
_ _ " that also may be suitable.

If Cordgrass Production,
/ .

Utilization, and

Nutritional Value

Following
Burning

Coast, smooth cordgrass (S. alterniflora Loisel.) and
marshy cordgrass [S . patens (Ait.) Muhl.] are restricted
to areas immediately adjacent to the coastline and are

most often found growing in or near coastal saline waters
(16).

Gulf cordgrass is a native, perennial, bunchgrass
with large, dense tufts of stout, glabrous culms (12). The
leaf blades are narrow and strongly involuted, tapering
to sharp and spinelike tips. The plant may be 1 to 2
meters tall with dense, cylindric inflorescences 1O to 3O
centimeters long (16).

A reliable estimate of the distribution of species of
Spartina is not available. However, the range of gulf
cordgrass is undoubtedly extensive, and it has high po-
tential for producing a large quantity of forage (28). Gulf
cordgrass has been reported to grow along the Gulf and
Caribbean coastlines of the United States and Eastern
Mexico. The grass has also been found inland in Argen-
tina and Paraguay (6). Within Texas, thousands of hec-
tares of land comprising the Coastal Prairies and
Marshes in extreme eastern Texas and eastern portions
of the Post Oak (Quercus stellata Wang.) Savannah and
South Texas Plains support almost pure stands of the
grass (11). Inland areas as far as Gonzales County sup-
port stands of gulf cordgrass (6). Gulf cordgrass most
frequently occurs on moist, saline soils (13), and al-
though is it most common on poorly-drained soils, the
grass may occur on sandy-textured soils.

Although excessive wetness inhibits root growth
and development of most grasses, species of Spartina are
well adapted to wet soils and may require periods of soil
saturation for maximum community development (10).
Gulf cordgrass generally occupies lowland areas periodi-
cally inundated, but above sea level (12). The grass gen-
erally grows at intermediate elevations between the true
marsh and highland ridges (25). On the Coastal Prairie,
it usually occurs between marsh associations dominated
by species such as clubbed cutgrass (Leersia Hexandra

3

Figure 1. Gulf cordgrass, coarse and un-
palatable in the mature state, dominates
large areas of the Coastal Prairie to the ex-
clusion of other range forage species.

Swartz.), cattail (Typha sp.) and upland “chaparral” 0r
mixed brush? With continued disturbance of gulf
cordgrass communities, seashore saltgrass (Distichlis
spicata Greene) and other salt-tolerant species may in-
vade the drier sites (1). These invaders are less produc-
tive than gulf cordgrass and are not desirable livestock
forages.

Salinity is one of the major limiting factors in ag-
riculture (32). Species of Spartina are evidently adapted
to high salt spray concentrations. Daily spray applica-
tions of salt water to foliage of cordgrass had no apparent
adverse effects on plant growth (21). Evidently, herbage
of species of Spartina possess thick cuticular layers allow-
ing the plant to tolerate salt spray. Gulf cordgrass grows
abundantly where soil salinities range from about 0.6 to
2.1 percent and the water table is from l0 to 2O cen-
timeters below the ground surface. Where soil salinity is
slightly less than 1 percent, gulf cordgrass may grow in
water 2 to 3 centimeters deep (l). The apparent adapt-
ability of gulf cordgrass to saline environments charac-
terizes the grass as a halophyte.

Gulf cordgrass is one of the most important grasses
of salt marsh succession and is almost always used as a
forage for livestock (1). Although the grass rates only fair
as range forage, apparently due to the coarse, tough na-
ture of the mature herbage, cattle may be forced to con-
sume the mature plants when other rangeland vegeta-
tion has been severely overgrazed.

As a result of his many activities, which include
periodic burning of wetland areas, man, of all biotic fac-
tors, has the greatest influence on the marshland ecosys-
tem (23). Growth characteristics of gulf cordgrass give
rise to its apparent adaptability to fire. Regrowth follow-
ing burning progresses rapidly, thus quickly rendering
succulent regrowth acceptable as forage to domestic
grazing animals (6). Young regrowth is typically lower in
lignin and fiber content than mature grass shoots and,

’McAtee, I. W. 1976. Unpublished data. The Texas Agricultural Ex-
periment Station (Department of Range Science).

4

 

 

therefore, is more tender and succulent (19). In add

tion, gulf cordgrass only rarely produces a heavy see
crop if left undisturbed. However, the grass may readily
flower, sometimes in abnormal numbers, the first o
second season after burning (9). Prescribed burning,
therefore, has apparent potential for improvement o
gulf cordgrass range. '

The increased attraction of grazing animals for veg
etative regrowth following a fire and the high nutritive
quality of young grass shoots usually improve livestoc
gains (9). Vallentine (30) cites the benefits of burning 

increasing the nutrient content of forage, particularl I

protein and phosphorus, in early growth stages. Im
provement of palatability and nutrient content of grasse
by burning, if only small areas are burned, may result i
overgrazing of preferred species. Therefore, entire pas
tures should be burned and stocking rate adjusted accord A
ingly (27). I

Young shoots of cordgrasses have nutritive level
comparable to those reported for coastal bermudagras
[Cynodon dactylon (L.) Pers.] (4). For instance, protei
content of the young grass shoots may exceed 13 pe
cent. Herbage of mature grass is always lower in protei
and phosphorus than immature, actively growing shoot 7
Even when the soil is not deficient in phosphorus, 
ture forage may not supply enough of the nutrient t
meet animal requirements (19). Soils and forages i
much of the Coastal Prairie are deficient in phosphoru
which is usually supplemented in the water.

Confidence in predicting results of burning range
land vegetation has been established through experi
ence. However, the effects of fire in any given area ma
be highly dependent upon certain soil characteristic
(15). Fire was once thought to be damaging to the soil b
reducing organic matter and nitrogen content due to th
high temperatures during burning (27). However, ther
are no experimental data available to justify such losses;
The soil profile (other than organic debris and humus) o
most burned areas is not degraded, and if erosion do
not take place in significant proportions, fertility is im

 
 
 
  
  
 
  
 
  
 
  
 
  
  
  
 
 
  
 
  
  
 
  
 
 
 
  
 
 
  
  
 
 
  
  
 
  
 
  
 
  
  
 
  
  
 
  
  
  
 
 
  
 
  

tleast temporarily (9). Soil horizons below sur-
" : ic layers are usually only slightly affected by
no more than the upper portion of the humus is
by burning (8). In addition, vegetative regrowth
nitiated 1 to 3 Weeks earlier in the spring on
an on unburned areas. Shoot initiation is evi-
mulated by the brief but sharp increase in soil
emperatures during burning. Also, following
blackened and unshaded soil is considerably
than unburned areas during the day, providing
nmental stimulus for early growth (30).

tability, the plant characteristic derived from
v imal preference among two or more available
is an important factor in considering manage-
gulf cordgrass range. Forages, no matter how
s or abundant, have no value unless grazing
consume them. If an economical method of har-
could be developed and palatability improved,
might become a valuable source of protein (28),
for range livestock. Benefits from improved
(quality and palatability are most likely to be
th forage species which are aggressive, highly
e, and persistent (31). Gulf cordgrass appears
these criteria, and prescribed burning has po-
o ecoming an integral part of the range man-
lan for gulf cordgrass range.

- te the relative importance of gulf cordgrass in
Prairie, little research data have been ac-
~ concerning its ecology and management.
u ent of gulf cordgrass has traditionally focused
j g of mature stands to enhance palatable re-
‘ ere usually has been no management plan
i with the burning efforts. Landowners burn
7i ass at their convenience or when supplemen-
is critically needed rather than on a systemat-
basis.

urpose of the research was to study the
nsumption, and nutritional value of gulf

herbage after burning as related to selected
i teristics.
v V objectives of the research were to
' uate gulf cordgrass herbage production and
ization by cattle as influenced by date of
rning;
elate edaphic characteristics (pH, salinity,
isture, and texture) with gulf cordgrass de-
opment following the burns; and
' aluate the nutritional value based on protein
ent, phosphorus content, and digestible
rgy of gulf cordgrass herbage at various time
ezvals following burning.

MATERIALS AND METHODS

study area was located on the Armstrong Ranch
p,“ Kenedy County, approximately 68 kilometers

Kingsville, Texas. Five sites supporting almost
ds of gulf cordgrass were selected for study.
covering at least 3 hectares, were burned on
slates by ranch personnel. An adjacent, un-

burned area on each site was used as a control for com-
parisons. The sites were subjected to periodic flooding
but usually not to prolonged inundation.

Vegetative responses were evaluated relative to
changes in foliar cover, herbage production, and utiliza-
tion“ by cattle, and herbage quality at time-lapse inter-
vals following burning; these were compared to the same
criteria on the unburned areas. Soils on each site were
characterized relative to selected chemical and physical
characteristics. The study areas were evaluated, based
on the selected variables, approximately at monthly
intervals for a year beginning on February 20, 1975.

Soil samples from each site were recovered from 0-
to 8-, 8- to 15-, and 15- to 30-centimeter depths at each
sampling date. Soil moisture content, determined
gravimetrically, was compared with rainfall received
during each grazing period and related to extent of gulf
cordgrass topgrowth development. In addition to
monthly moisture content estimates, soils were charac-
terized relative to pH based on a 1:2 to 1:5 slurry (22);
salinity on aqueous extracts (3); textural components by
the hydrometer method and/or by size class separation
by weight (18); and organic matter content by acid diges-
tion and titration (20).

Foliar cover, the amount of ground surface area
covered by gulf cordgrass foliage, was estimated within
burned plots with permanent line transects as described
by Canfield (5). Three lines, approximately 30 meters
long, were established within the burned plots at each
site at the initiation of the study. Foliar cover was re-
corded at monthly intervals on burned areas for the first
4 months of study, then on a bimonthly basis thereafter
to 1 year after burning. Estimation of foliar cover on
adjacent, unburned plots was derived from gulf
cordgrass density and average plant foliar area on each
site. Foliar cover of unburned plots was estimated at the
beginning and end of the 1-year evaluation period.

Utilization of gulf cordgrass by livestock was esti-
mated through the use of grazing exclosures. The exclo-
sures, constructed from lO-gauge wire having 10- by
10-centimeter openings, were approximately 2 meters
tall and were held securely in place by steel stakes.
Eighteen such exclosures were placed in each plot, 12
per burned area and six per adjacent unburned area. The

gulf cordgrass herbage within burned areas was bar-j

vested to a 2.5-centimeter stubble height at monthly
intervals for the first 5 months of study, then on a
bimonthly basis thereafter to 1 year after burning. Har-
vests were made from 0.25-square meter plots within
the center of each protected area (ungrazed) and at least
2 meters away from the exclosure in the grazed areas.
Immediately following each harvest, the exclosures were
moved approximately 3.5 meters to begin the next sam-

ple grazing period. A paired-plot method as described

“The term “utilization" is used throughout to encompass forage remov-
a1, whatever the cause. It should be understood that although inges-
tion by cattle is probably the major cause of removal, substantial losses
also occur due to trampling, weathering, use by wildlife and insects,
and to other natural factors.

by Scifres et al. (24) was used to estimate utilization of
gulf cordgrass for each grazing period. Differences in
weight of air-dry (65 degrees centigrade) gulf cordgrass
herbage within protected plots and corresponding
grazed areas were used to estimate utilization of gulf
cordgrass for each grazing period.

Production estimates of gulf cordgrass regrowth fol-
lowing burning were derived from harvests of plots, 0.25
square meter, within protected areas. Estimates of
production were adjusted at each sampling date by sub-
tracting the previous month’s utilization estimate, thus
allowing determination of actual production from one
sampling date to the next.

Utilization estimates of unburned gulf cordgrass
stands were made from a protected plant and compara-
bly sized unprotected plant and were collected from one
site each month for a 5-month period beginning with the
initiation of study. Production estimates of unburned
gulf cordgrass plants were obtained from a double-
sampling method (volume versus weight) at the termina-
tion of the study (17).

Due to the aggregation of gulf cordgrass plants oc-
curring over the study areas, it was necessary to adjust
utilization and production estimates of burned areas to
average basal area and plant numbers on each site.
These adjustments were made after it was determined
that there were no differences in numbers of regrowth
shoots per unit area of gulf cordgrass bases surviving the
fire, and that, within an evaluation date, there were no
differences in shoot heights. Each production and utili-
zation value was then adjusted to the average basal
diameter of gulf cordgrass plants within burned areas on
that site to convert all estimates to a common base.

At each sampling, green gulf cordgrass herbage was
harvested in both burned and unburned plots for esti-
mates of protein, phosphorus, and digestible energy
levels. Crude protein content was determined using the
Kjeldahl procedure for nitrogen determination (2);
phosphorus was determined spectrophotometrically
(14); and digestible energy was determined as outlined
by Tilly and Terry (29). Monthly nutritional values were
then interpreted in light of soil moisture levels, rainfall,
and production of gulf cordgrass for that grazing period.

Density (number of plants/unit area), plant height,
and canopy diameter of gulf cordgrass regrowth in un-
burned areas were periodically evaluated using the

point-center-quarter method as outlined by Cottam and
Curtis 

Variation in gulf cordgrass production, utilization,
and protein content was sorted among sites and dates of
sampling with appropriate statistical techniques. Re-
gression equations were derived from production and
utilization estimates to allow prediction of rate of change
as influenced by time after burning (26).

The pastures were stocked with approximately one
animal per 8 hectares as a cow-calf operation during this
study. Burned areas were estimated to constitute less
than 10 percent of the total area of each pasture, and gulf

6

 
  
 
 
 
  
 
 
  
  
   
 
  
  
   
  
 
 
 
 
 
 
 
 
  
 
  
  
    
  
   
  
  

cordgrass constituted approximately 80 percent of the
area available to grazing animals.

RESULTS AND DISCUSSION

The study areas were of similar topography and
physical features. All areas were lowlands susceptible t0
periodic inundation. Gulf cordgrass dominated the vege-
tation on all sites, but other grasses and forbs were in-
terspersed within the stand during early to mid-spring,
“green up." Honey mesquite (Prosopis glandulosa Torr.
var glandulosa) savannahs typical of sandy, inland areas
of the Coastal Prairie bordered the lowlands. This vege-
tation type grades into “chaparral” (mixed brush domi-
nated by honey mesquite and species of Acacia) on the
uplands to the west.

Soil Characteristics

Physical and Chemical Components

The loamy sand sites, burned in fall 1974 wer
characterized by a near neutral soil surface, becoming
more basic to 3O centimeters deep (Table 1). Soluble
salts averaged 0.28 percent or less in these soils regard
less of depth. Organic matter was consistently greater o
the loamy sand site, regardless of sample depth, than o
other sites. Surface soil of the loamy sand site burned
October 23, 1974, was acid and contained the greatest
amount of organic matter, 2.1 percent, of the study
areas.

Soil salinity on the alkali sandy loam site burned in
spring 1974 was higher than for other study areas, par-
ticularly at the 8- to 30-centimeter depth (Table 1).
Crusting and salt accumulation on the soil surface was
apparent throughout the study, especially during drier
periods. With increased precipitation, soluble salts were
probably leached into underlying soil, thus accounting
for increased salinity levels at lower depths at those
times of sampling. Salt accumulations virtually elimi-
nated forbs and grasses which occurred seasonally on the
more mesic sites and favored salt-tolerant species such a
shoregrass (saltgrass) (Monanthochloe littoralis
Engelm.). Soil pH was basic regardless of depth, an
organic matter accumulation never exceeded 0.44 per
cent. Soil texture was sandy loam to 8 centimeters dee
and sandy clay loam at 8 to 30 centimeters deep.

Soil salinity of the alkali loamy sand, burned i
winter 1975, ranged from 0.043 percent in the 0- t
8-centimeter layer, increasing to 0.68 percent at 15 to 3
centimeters deep (Table 1). Soil reaction was basic re-
gardless of depth, and organic matter accumulation di
not exceed 0.41 percent. Soil texture was loamy sand t
8 centimeters deep, increasing in clay content and be-
coming sandy loam and sandy clay loam at 8 to 15 cen-
timeters and 15 to 30 centimeters deep, respectively.

Soil Moisture Trends

Upon initiation of the experiment in late February
1975, all study areas were inundated with 0.5 to 2 cen-
timeters of standing water. However, the water did not

 EDAPHIC CHARACTERISTICSOF SITES WHERE cuu= CORDGRASS RESPONSE TO BURNING WAS EVALUATED oumwc;
, HARMSTRONQTEXAS-

so" Organic com-hfffiteunrf; (%)
depth Salinity carbon Textural5
Burned (cm) l%) pH 1%) Sand Silt Clay class
Oct. 1, ~ 0-8 0.025 7.6 0.55 83 5 12 Is
1974 8-15 0.053 8.0 0.27 85 4 1 1 ls
15-30 0.141 9.2 0.21 76 7 17 sl
Oct. 23, 0a 0.523 6.6 2.10 12 9 19   sl
1974 8-15 0.461 7.2 0.69 69 8 23 scl
15-30 0.685 8.8 0.39 65 6 29 scl
Nov. 9, y 0-8 0.020 7.2 0.87 82 6 12 ls
1974 8-15 0.018 7.2 0.16 82 7 11 ls
15-30 0.027 7.9 0.23 . 79 5 16 sl
Avg O-8 0.189 7.1 1.17 79 7 14 ls
8-15 ~ 0.177 7.5 0.37 79 6 15 sl
15-30 0.284 8.6 0.28 73 6 21 sl
Spring, 0-8 0.410 8.5 0.44 77 9 14 sl
p‘; 1974 8-15 1.232 9.0 0.23 70 6 24 scl
 - 15-30 1.632 9.0 0.24 69 7 24 scl
Winter, 0-8 0.043 8.7 0.41 82 6 12 ls
1975 8-15 0.553 8.4 0.28 77 5 18 sl
15-30 0.680 8.8 0.18 70 6 24 scl

t average of three loamy sand sites and from one alkali sandy loam and alkali loamy sand sites.
completed from October 1 to November 9, 1974.
_ ducted during early May.
i ducted on January 6.
classes, ls = loamy sand, sl = sandy loam, and scl = sandy clay loam.

cover the surface of most of the burned gulf cordgrass
bunches. There was no rainfall from that time to the
April 1975 sampling (Figure 2). The greatest single ac-
cumulation of rainfall for the study period, 12 centime-
ters, was recorded from April 23 to May 23. Rainfall de-
clined from May to June but increased to 10.9 centime-
ters, the second highest amount received, during July.
There was little variation in rainfall from July to Sep-
tember. After September, however, precipitation began
to decrease steadily, with no rainfall recorded at the
November sampling. Only 1 centimeter of rainfall was
recorded in December, but precipitation increased to
2.8 centimeters in early February 1976. Precipitation for

Soil moisture content corresponded directly to
available rainfall as would be expected, except at the
October 27 sampling when soil moisture content of all
sites increased to the highest levels for the study, while
recorded precipitation decreased (Figures 3,4,5). Rain-
fall during the night preceding the morning of the sam-
ple collection date is responsible for this occurrence.

. , , , , , , , , Average moisture content of soils on the loamy sand
 15a. M: page Jgp Azure. sggt 02¢;- hligv. geac. Ffv- Pa? sites for the study period was 10 percent (Figure 3). The
 0A 1E site burned (October 23, 1974, maintained the highest

average soil moisture content, 14 percent, of the three
loamy sand sites. The lowest average soil moisture of the
sites for the study period occurred on the area burned in
November 1974. Soils on the alkali sandy loam site aver-
aged the highest moisture content for the study, 14 per-
cent (Figure 4). Soils on the alkali loamy sand site aver-

Splpitation (centimeters) during study of gulf cordgrass
 lng during 1975 and 1976.

7

the study period averaged 4.68 centimeters per month. .

DEPTH

LOAMY SAND SITES

 

 
 

as - _l.°_'“_l
i ° -8
II 3 —15
_ nun 
32 "I 0 -3O AVG
E} 28% 

l- 2

Z :

Ill ~ '

'5 24" s

Q I

o I

i‘ 2o I

a P

P"

‘L’

g 1e - _

-| h,“ P:

6 \ ‘nu,’ X i‘

"’ 11 - \   / _ 

ll—|_| |_'|'g"|$|—| “:‘@|_Qh."|1l—|—|?\‘! . |—|—|—| '?".I"—N.I':"I::‘m:,fll.m':—|—|—|—
8 " Q‘? n u Minn" “\\\“$ lhu":
. |,"“.“\\\\
\ Figure 3. Soil moisture
4 ’ content (percent of dry
weight) on the loamy sand
= - 1 1 1 r 1 1 1 1 1 1 c sites, 1975 and 1976.
FEB. MAR APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC. FEB. FEB.
2O 13 23 28 25 2O 27 25 27 19 18 4 26
D A T E
DEPTH
1cm) ALKALI SANDY LOAM SITE
I I 8 I15
nun. 
32 III O "-30 AVG

   

   

 
  
     
        

»- 28
<3
I'-
E
.324 -
~ i
s 2*»
D
i-
‘L’
O 1 -
S 6
i —I$|—|—|_|—|—|—|—|$l l—l—l—l—c‘a,l_fl'lfil.fl_|rlilq
8 u-
Figure 4. Soil moisture con- i
4 ' tent (percent dry weight) on g
the alkali sandy loam site, j
1 1 1 1 1 1 1 1 J 1 1 1 4  and  
FEB. MAR. APR. MAY. JUNE JULY AUG. SEPT. OCT. NOV. DEC. FEB- FEB.
2O 13 23 28 25 2O A2_'Il_ 27 19 18 4 26

aged 12.5 percent moisture content for the evaluation
period (Figure 5).

Foliar cover was monitored as an index of gulf
cordgrass foliar growth, expansion, and regrowth rate in
conjunction with herbage production following burning.
Foliar cover trends on burned areas were fairly consist-
ent for all sites. Expansion in foliar cover of regrowth of
gulf cordgrass following burning was significantly differ-
ent among sites and among sampling dates. F oliar cover
estimates of unburned, mature gulf cordgrass plants did
not vary appreciably from initiation to termination of

8

l

study, regardless of site. Average foliar cover of matun
unburned gulf cordgrass plants on the loamy sand s
was approximately 76 percent, and foliar cover avera
 on theallcalisl
loam and alkali loamy sand sites were 80 percent and
percent, respectively.

 
   
 
 
 
 
  
  

The average rate of foliar cover recovery under gr
ing for the period of evaluation on the loamy sand si
burned in fall 1974 was 5 percent per month. Aver
rate of foliar cover recovery for the evaluation period
the loamy sand site burned October 23, 1974, 5.5 p
cent per month, was significantly greater than on
other loamy sand sites. The greatest increase in fol’

 

  
 

DEPTH
12.").

j 0-—8

-_ 

nun 

"I 0'30 AVG



t  .
is

 
       
  
 
 
 

ALKALI LOAMY SAND SITE

|$|—|1|—|$|$|_|—|_|_|q

&“;nu}“uun""
u“ '“'"lr
Figure 5. Soil moisture con-

tent (percent dry weight) on
the alkali loamy sand site,

  
 
  
   
 
 
  
  
  
  
   
   
  
   
   
   
    
   
 
 
  
  

 ong sampling dates on the loamy sand sites, 46
 occurred from May to July, 7 to 9 months fol-
burning (Figure 6). Apparently, cattle grazing on
p’ forages during the mid to late spring period re-
 reduced grazing pressure on the gulf cordgrass
p  and allowed rapid foliar expansion. During the
g lf-r-rmonths, other available forage became limited,
more uniform grazing pressure was applied to the
i grass on burned sites. In late February 1976, 15
‘tenths following burning, average foliar cover of
;gulf cordgrass on the loamy sand sites was 6O
 only 16 percent below the average foliar cover
 ent unburned sites.

l“: cover variation across sample dates on the
l. dy loam site, burned in spring 1974 followed
f] general trends discussed for the loamy sand
figure 7). However, for the first 4 months of
Wliar cover of gulf cordgrass on the burned area
1T8- iderably lower than that on other study areas.

i‘; in July 1975, 14 months after burning, foliar
 the area increased to greater than that for other
 . Evidently, until substantial amounts of rain-

y ed, gulf cordgrass plants on this site suffered
g siological drouth because of the soil salinity.
st average foliar cover (l percent) occurred in
A, 9 months following burning, on the alkali
'9 site. The greatest average foliar cover for the
jpercent, was recorded in November, approxi-
Y3 months after burning. The greatest change in
 sion on the alkali sandy loam site, 6O percent,
y, from May to July when other alternative forage
 i le to the cattle. Average foliar recovery rate of
 lf cordgrass regrowth on the site was 6 percent
 . At the termination of the study, 21 months

 | l n l l L I l 1 - L I  and 
 FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. NOV. DEC. FEB. FEB.
1 2o 13 2a 2a 25 2o 27 2s 19 1a 4 2s
' o A r E

following burning, average foliar cover of burned gulf
cordgrass regrowth on the alkali sandy loam site was 75

percent, only 5 percent less than the foliar cover of adja-
cent unburned gulf cordgrass.

Growth form of gulf cordgrass on the alkali sandy
loam site differed considerably from that of plants on

a‘ LOAMY SAND SITES

77 uuaunuso-Q

TOT
56L

49-
42-

3ST

28-

FOLIAR covsn (96)

 

a  t
 2 l -
FEB. MAR. APR. MAY JULY sen.
2o 1a 2a 2a 2o 2s 1s
DATE

Figure 6. Foliar cover (percent) following burning of gulf cordgrass
in fall 1974. (Means followed by the same letter are not significantly
different at the 95-percent level of probability among dates accord-
ing to Duncan's Multiple Range Test.)

ALKALI SANDY LOAM SITE
UNBURNED

FOLIAR covsn (96)

MAY JULY SEPT. NOV. FEB-
4

MAR. APR.
13 23 28 2O 25 19
D A T E

FEB.
20

Figure 7. Foliar cover (percent) following burning of gulf cordgrass in
spring 1974.

other sites. Mature plants were not as large, relative to
basal diameter and height, as the mature gulf cordgrass
plants on other sites. Average height of mature plants 0n
the alkali sandy loam site was 25 centimeters compared
to 108 centimeters and 78 centimeters for plants on the
loamy sand site and the alkali loamy sand site, respec-
tively. Average basal diameter of mature, unburned gulf
cordgrass plants on the alkali sandy loam site was 32
centimeters compared to 40 centimeters for both the
sandy loam site and the alkali sandy loam site. Also,
plants on the alkali sandy loam site grew more erect than
plants on the other sites, their leaves drooping only after
growth had attained near maximum height.

The highest foliar cover, 53 percent, on the alkali
loamy sand site occurred in November, approximately
10 months following burning in winter 1975 (Figure 8).
The lowest foliar cover percentage, 13 percent, on the
site was recorded in February 1975, 1 month following
burning. Average rate of recovery of gulf cordgrass foliar
cover on the burned alkali loamy sand site was 4 percent
per month. The greatest rate of recovery, 29 percent,
occurred from May to July, 4 to 6 months after burning.
Average foliar cover of burned gulf cordgrass on the al-
kali loamy sand site was 52 percent at the termination of
the study in late February 1976, 13 months following
burning. Foliar cover of the site at the termination date
was 27 percent less than that estimated for the adjacent
unburned gulf cordgrass.

Production and Utilization of Gulf
Cordgrass Following Burning

Standing crop of unburned gulf cordgrass on the
loamy sand sites averaged 1,250 kilograms per hectare at
initiation of the study and was 1,356 kilograms per hec-
tare at termination of the study. The slight increase in

10

8 ALKALI LOAMY SAND SITE
4 l-
UNBURNED-i
17 —
1o
s3
__ 5s -
A 5 49
>
o
0
u. 42 -
<
3
E as -

no no
-\ an
I T

14"

   

FEB. MAR. APR. MAY JULY SEPT. NOV.
2O 13 23 28 20 25 19

DATE

FEB.
4

Figure 8. Foliar cover (percent) following burning of gulf cordgra
in winter 1975.

standing gulf cordgrass crop was probably due to norm,
seasonal variation and measurement error. Standi l’

crop of mature, unburned plants on the alkali sandy lo {A

site averaged 1,050 kilograms per hectare at the begi
ning of the study and 980 kilograms per hectare at thy
end of the study. Standing crop of unburned stands op
the alkali loamy sand site in March 1975 was 1,323 kil
grams per hectare and 1,273 kilograms per hectare at
final sampling in February 1976. a

Utilization of gulf cordgrass foliage from unbum
sites was negligible regardless of evaluation date. Vari
tion in utilization values was considered a product =_
sampling error since only occasionally were a few le
tips of unburned plants grazed.  

The numbers of gulf cordgrass plants per hectare o
the loamy sand and alkali loamy sand sites were simila
Average gulf cordgrass densities were 2,450; 2,500; an
7,000 plants per hectare, on the loamy sand, alkali loam
sand, and alkali sandy loam sites, respectively. Thou
the alkali sandy loam site supported greater numbers I
gulf cordgrass plants, the plants were shorter, explainin
differences in weight of standing crop. Average bas
area of burned regrowth was 59 square centimeters p
plant on the loamy sand sites, 49 square centimeters p
plant on the alkali loamy sand site, and 17 square ce f‘
timeters on the alkali sandy loam site. In addition, ave
age basal area for mature, unburned gulf cordgra
plants was 1,257 square centimeters per plant for
loamy sand and alkali loamy sand sites and 804 squad
centimeters per plant for the alkali sandy loam site. x

The first significant increase in growth rate based If
herbage production of gulf cordgrass following burni
on the loamy sand sites occurred in August followi A
fairly consistent rainfall for a 3-month period (Figure ‘p,
Herbage production was reduced significantly in D

"r '2“WJPWI-"r'"-wwrr'-wwnmfifnza'sfwfifl 

  
    
  
   
 
  
   
   
 
   
  
   
 
  
  
   
   
  
  
   
   
   
   
   
 
  

to a level not significantly different from that in
,7,» August. The most rapid growth rate, based on
production on the loamy sand sites, 104 kilo-
 hectare per day, occurred from December
‘gtlate February 1976 (Figure 9). Average growth
_ lfcordgrass within burned areas on the loamy
f  for the entire period of evaluation was 5 kilo-
 hectare per day. Burning followed by grazing
 production of over 21,500 kilograms per hec-
f lf cordgrass herbage on the loamy sand site.
 be compared to the end-of-season standing
liijmburned areas of 1,365 kilograms per hectare.
  “if, the productivity of gulf cordgrass range was
 hanced by burning.
 utilization averages for the three loamy
 following burning generally followed produc-
(Figure 9). Average utilization from February
e was not significantly increased in August,
lding to the significant increase in production

1%

golf-o Average utilization levels from August to

 of the study were not significantly different.

age utilization on the site burned October 23,
“Y significantly greater than on the other loamy
. Utilization of gulf cordgrass regrowth by cat-
 g burning on this site was probably greatly
i" by a watering facility located on the site. Cat-
 an estimated 3 kilograms per hectare per day
i, rass herbage on the loamy sand sites. Based
Qirement of 12 kilograms per day air-dry forage
 an animal unit, carrying capacity for the 12
 about 1 animal unit per 4 hectares (1 animal
hi0 acres). The greatest utilization following
 the loamy sand sites occurred on the Feb-

 Lomv SAND SITES
 o-romnowm PRODUCTION
Log (wt) = 2-60+-0047(time lallsmdays)

_= lo- UTILIZATION
 Loq (m) = 2 .30 +.0049(time lapsedays)

‘Q:

'0
0
. h,"

\\\\ " 1
_ "u"! IIIII n‘ l l l I
l l l l l

 lPR. MRY Jlli NLY AUGLSEPI OCT. NOV. DEC. FEB. FEB.
1 23 28 25 20 27 25 27 19 18 4 26

 one or nmvssr

ative production and utilization (kilograms per hec-
gulf cordgrass topgrowth on the loamy sand site,
$74.

ruary 26, 1976, sample collection date, 32 kilograms per
hectare per day over a 70-day period.

Herbage production average for the period of study
on the alkali sandy loam site burned in spring 1974 was 4
kilograms per hectare per day (Figure 10). The greatest
herbage production of gulf cordgrass on the area oc-
curred on the February 26 sampling, approximately 21
months following burning. Trends in herbage produc-
tion on the alkali sandy loam site followed those on the
loamy sand sites. However, only about half as much gulf
cordgrass was produced on the alkali sandy loam com-
pared to the loamy sand.

Utilization of gulf cordgrass herbage on the alkali
sandy loam site varied as on the loamy sand sites (Figure
10). Greatest utilization rate was 34 kilograms per hec-
tare per day from December 18 to February 26, 1976,
approximately 21 months following burning. Average
utilization of burned gulf cordgrass regrowth for the
period of evaluation was.2.5 kilograms per hectare per
day on the alkali sandy loam site.

Average production of gulf cordgrass herbage on the
alkali loamy sand site, burned in winter 1975 was 6 kilo-
grams per hectare per day (Figure 11). Trends in pro-
duction were similar to those for other sites. Greatest
growth rate of gulf cordgrass on the alkali loamy sand
site, 46 kilograms per hectare per day, was recorded
from December 18 to February 26, 1976, 13 months
following burning.

Utilization of gulf cordgrass regrowth by cattle aver-
aged 4 kilograms per hectare per day on the alkali sandy
loam site for the period of evaluation (Figure 11). As was
with other sites, the greatest utilization of gulf cordgrass
topgrowth by cattle on the alkali loamy sand site was in
late February 1976, 13 months following burning.

Protein, Phosphorus, and Digestible Energy Levels of
Gulf Cordgrass Herbage Following Burning

Protein

Since gulf cordgrass tissues were clipped at a 2.5-
centimeter stubble height, nutrient variations in burned
and unburned plants were highly dependent upon the
quantity of older growth present at the date of sampling.
From initiation to conclusion of the study, as the amount
of older growth increased, protein levels decreased.
Early in the study, however, particularly during March,
utilization by cattle was apparently adequate to maintain
the gulf cordgrass in an immature state.

Crude protein content of gulf cordgrass herbage
varied considerably within and among loamy sand sites
but generally declined with increasing age of regrowth
(Figure 12). The highest average protein content for a
single date, 11.2 percent, occurred in March 1975, the
first date of sampling but 5 months following burning of
the site. Protein content of gulf cordgrass from one of the
three sites averaged 13.7 percent at that time. This in-
crease in protein content was not apparent in April, the
spring following burning. Average crude protein content
of gulf cordgrass regrowth on the loamy sand sites
burned in fall 1974 was 5.23 percent compared to 5.08
percent for green tissues from unburned mature plants.

11

CUMULATIVE PRODUCTION AND UTILIZATION (kg/ha)

23400 ALKALI smov LOAM SITE
' o-—TOPGROWTH PRODUCTION
n- Log (w1)= 2.90 +.0029(1ime lapse. days)

o-UTILIZATION

 P nu Log  2.451‘  |apse,day$)

19,000)
10,000 l-
1s,200 -
14,400 -
12,600 -
10,0001-

9,000 r-

2200

5,400

3,600

1,000

, l 1 1 1 1 1 1 1 1 1 m | 1
FEB. MAR. APR. MAY JUP£ JULY AUG, SEPT. OCT. NOV. DEC. FEB, FEB.
20 13 23 28 25 20 27 25 27 19 18 4 26

DATE OF HARVEST

Figure 10. Cumulative production and utilization (kilograms per
hectare) of burned gulf cordgrass topgrowth on the alkali sandy loam
site, burned in spring 1974.

The highest average crude protein of gulf cordgrass tis-
sues, 5.52 percent, occurred on the site burned on Oc-
tober 23, 1974. Average crude protein content of green
tissues from adjacent unburned plants for the study
period was 5.10 percent. Variation in protein content of
herbage among sampling dates was similar among the
areas burned in fall 1974. Site and treatment were not
significantly different; however, date of sampling and
treatment by date interaction were significant.

Protein content of gulf cordgrass regrowth following
burning was significantly greater than levels of unburned
gulf cordgrass tissues on loamy sand sites in March and
May (Figure 12). Crude protein content, however, in
gulf cordgrass regrowth following burning did not signif-
icantly exceed that of burned plants at any other sam-
pling date. Apparently, the lack of spring rainfall did not
allow rapid growth of burned plants, thus lowering pro-
tein content of regrowth in April. In addition, during the
early to mid-spring, other grasses and forbs became suf-
ficiently available to provide grazing animals with alter-
nate forage. With decreased grazing pressure, gulf
cordgrass herbage consisted of maturing regrowth with a
concomitant decrease in nutritional components.

The alkali sandy loam site was burned approxi-
mately 3 months prior to burning of the loamy sand sites,
and therefore supported the oldest vegetative regrowth
of the sites studied. Average protein content of gulf

12

ALKALI LOAMY SAND SITE
o-JOPGROWTH PRODUCTION ‘
II Log lwtl = 2.42+ .0052 ltime lapse. daysl

m- Lqg iwtl : 2.14 +.0050 ltime lapse, daysl

23,400 '-

19,0001-
1a,000 -
16200 P’
14,100-
12500 -

10000 -

9,000

1200-

CUMULATIVE PRODUCTION AND UTILIZATION (kg/ha)

5,400 -

l

I FEB. MAR. APR. MAY JUNE JULY AUG. SEPTOCT. NOV. DEC. FEB. =~

20 13 23 28 25 2O 27 25 27 19 18 4 26

DATE OF HARVEST

Figure 11. Cumulative production and utilization (kilograms per g A
tare) of burned gulf cordgrass topgrowth on the alkali loamy sand f
burned in winter 1975. 1

cordgrass plants from the burned and unburned al f

sandy loam was 5.38 and 4.67 percent, respectiv‘
(Figure 13). As with the other sites, protein cont
within burned and unburned areas on the alkali san
loam site coincided with variations in soil moisture, a y.
and quantity of herbage produced. Therefore, regro
on burned sites contained significantly more prot
only in March and in Iuly (Figure 13). i

Evaluation of the alkali loamy sand site was initia g
approximately 2.5 months after burning on January
1975. Crude protein content in gulf cordgrass herb
from this site averaged 5.45 percent following burn‘
and 5.06 percent in green tissues from the unburn
area (Figure 14). As with other sites, protein content
herbage was responsive to rainfall and to top removal p
grazing. Protein levels in regrowth of burned g
cordgrass exceeded those of green tissues from mat f
plants only in early spring (March) (Figure 14). Hi
ever, it is assumed that this increase in protein cont 1
occurred throughout the winter, a critical time relati
to nutritional needs of the livestock.

Phosphorus

Phosphorus deficiency is a common problem ,
southeast Texas. Variations in phosphorus content of g1
cordgrass herbage generally followed the same trend
for protein content. Phosphorus content was sign’,

   
    
 
    
  
  
   
 
  
    

SAND SITES

5 aurm

UNBURN

— AVG aunu 5.23%
..- AVG uuaunu s.oa%

Figure 12. Protein content

 

 

     

(percent) of unburned gulf
cordgrass topgrovvth and of
regrowthfollowing burning
in fall 1974 on loamy sand
sites. (Means followed by
the same letter are not sig-
nificantly different at the
95-percent level of proba-
bility among dates accord-
552;;   ing to Duncan’s Multiple

~ g -:- 5:215:51 5215121 '~'51-1-= 1+5? -:~:~5~:- 151515555 ‘Z5515 “I:  Range T881.)
' inn. MAY JUNE JU LY AUG. s: PT. NOV.
  :3 20 25 20 27 25 27 19
» o A r e

 i. smov LOAM sms
 a g aunn
 U uuaunn
 — AVG aunu 538W,
f; -- AVG uuaunn 4.67%

Figure 13. Protein content
(percent) of unburned gulf
cordgrass topgrovvth and of
regrowth following burning
 in spring 1974 on the alkali

ll.l lll l l lll l l ll Il l.ll ll lll l l ll l llll | Il ll
llllllll.l l l l.l l l. l lillll"lllllllllllllllllllllll
lllllglllllllllllllllllllllllylllll lllllll
llllllllllllllllllllllllllllllllll

5551f l’ -****  51155 sandY loam site.

 -t among sites, sampling dates, and, for the

 , by site interaction. However, there was
yzv-difierence in P levels as a result of burning

f1’ content of gulf cordgrass herbage over
f period on the loamy sand sites burned

 0.116 percent (Figure 15). Average P

 ture grass from the same area was 0.108
 horns content was apparently highly de-
e with enforcement of regrowth by burn-

z
n}
O
°<
o
3m
n
‘T!
rn
m
‘l’!
"m
“m

ing causing only a slight difference. Regrowth on burned
loamy sand sites contained more phosphorus than ma-
ture tissues in the spring (March) and fall (September
through October) of 1975 and winter (February) of 1976.
Regrowth of gulf cordgrass on the loamy sand site
burned October 23, 1974, tended to contain the greatest
amount of P, 0.128 percent, for the study period. The P
content of unburned stands of gulf cordgrass on the same
area averaged 0.123 percent, indicating the influence of
site apparently to be of more importance than burning

13

2 EBURN LOAMY SAND SITES
E Uuuaunn
o,“ E - AVG eunu 0.116% ___
' i -- AVG uneunn 0.100% § E
5E a g
$0.1»- E 5 1'2"‘ 
"1 E, é E E "5' E
’g°‘°l' 2 2 2 2 2 2
U El E I g g. E
Figure 15. Phosphorus 300w  i E i g g
content (percent) of un- S ' g]   g g y §
burned gulf cordgrass top- é 5f f g I‘; ;
growth and of regrowth fol- g OWL g ; ; g g ;
 lowing burning in fall 1974 e ' :15; I; g i 5 i
on the loamy sand sites.   5   a =
(Means followed by the i‘ » _    
_ l " i g l L; :
51*  2  2*
  2 2 2 2

g aunu

ALKALI LOAMY SAND sms

11 - unauau (y.
_ Ava eunn 5.45% ‘

10- "'AVG uuaunu 5.06% A.

      
 
 
 

lllll.l. l!

   

PROTEIN content (9a)

iigl l I.
ll!" 1111115100
"""|""'||||lIll|l| "l|' "lllll|' lll"l!!!"

   

Figure 14. Protein content
(percent) of unburned gulf
cordgrass topgrowth and of
regrowth following burning
in winter 1975 on the alkali
loamy sand site.

 
  

 

lllilll-il.l-l.i.il}llllll.lllllKi-lIl-l-lll

  
   

l.l.l.l.l-1'_]“ll_'l'ltl,i_t

OCT. NOV.

E lllll‘"'.' l,'l," l

 

same letter are not signifi-
cantly different at the 95- g‘
0 oz

,ll

percent level of probability
among dates according to
Duncan's Multiple Range
Test.)

l.lll"llllll""llllfil"""l‘llllllllllllll"ll"
mmmmimiifizmiii

     

SEPT. OCT.
25 27

MAR. APR. MAY JUNE JULY
13 23 28 25 20

treatment. However, average P content of gulf cordgrass dropped in the fall (November) after a dry period and A

herbage from the loamy sand site burned November 9, the beginning of seasonally cool temperatures (F igu l
1974, was 0.125 percent for the burned area and 0.102 15) 
Pement f0? herbage from the unburned 31' @3- The P content of herbage on the alkali sandy lo‘
Average P content from the loamy sand sites burned site burned in spring 1974 tended to follow soil moistu ‘
in fall 1974 never attained the O.18-percent on a 90- availability and grazing trends, except on March 
percent dry-matter basis recommended for wintering when P content of unburned plants tended to be high .
mature beef cattle during pregnancy (27). The highest than that of burned regrowth (Figure 16). The highe
average P content on the loamy sand sites, 0.161 per- level of P was attained in September in regrowth on t  a
cent, occurred during September within burned areas burned area, approximately 16 months after burnin
after2 months of fairly constant rainfall and after burning and after a 2-month period of fairly constant rainf 
the previous fall in the late October or early November. Phosphorus levels of plants on the burned area d)
The P content of gulf cordgrass herbage on burned areas creased with decreased precipitation in October, and l

14

 gulf cordgrass herbage from unburned areas increased levels during warm, moist periods and within

  

 

  

 

     

    

   

 

 abruptly in November when there was no the burned area. However, during drier periods, it was
iiainfall. not uncommon for P content of mature gulf cordgrass to
 e P content of new growth following burning exceed that of regrowth from the burned area. Apparent-
 ' loamy sand site in winter 1975 was 0,092 ly, P content of gulf cordgrass regrowth, as with protein,
iivhile P content of green tissues from mature decreased as the age of tissues increased. When soil
 s plants averaged 0.097 percent (Figure 17), moisture was adequate to support rapid growth, nutrient
 tlevel of P occurred in March but, in contrast content of gulf cordgrass was increased and utilization by
 onse on other sites, the highest P level‘ oc- cattle increased. Increased utilization maintained a de-
gljiioliage from mature gulf cordgrass plants. Ex- gree of immaturity within burned gulf cordgrass plants.
 at period, trend in P content was towards When grazing pressure was reduced as alternative forage
 E guflfl y ALKALI SANDY LOAM SITE
 m uuaunu
 — AVG BURN 0.125%
 -- AVG unaunu 0.101 °/,,
E 
 it. gt gs g g jE-fv . Eff Figure 16. Average phos-
-.% E1 i] E E E11 ; E2’ phorus content (percent) of
5i '51 E, if fir‘  E, unburned gulf cordgrass
"51 g if g f; A ‘g? topgrowth and of regrowth
g, g E; g §  E following burning in spring
   g g g  g 1974 on the alkali sandy
+14»: -:~:-:~: flzfll iii? lffif-Z . _“‘I. :3‘ 3  
APR. MAY JUNE JULY AUG. SEPT OCT. NOV DEC FEB. FEB
23 28 25 2U 27 25 27 19 18 4 6
D A T
a BURN ALKALlLOAMY SAND SITE
unsunu
_Avc BURN 0.092%
-- AVG uusunn 0.091%
 i a
  Figure 17. Phosphorus
   3;; content (percent) of un-
  E.  burned gulf cordgrass top-
 i}; 2 if growth and of regrowth fol-
  gi lowing burning in winter
 115;} is Z 1975 on the alkali loamy
 APR. MAY JUNE JULY AUG. SEPT. ocr. NOV.
3; 23 28 20 27 25 27 19
 o A r E

15

became available on upland sites, the gulf cordgrass was
allowed to mature slowly with a concomitant decrease in
nutrient levels. i

Digestible Energy

Variation in digestible energy content of herbage
from unburned gulf cordgrass plants and of regrowth
following burning was not significant among sites. Dif-
ferences in levels of available digestible energy, how-
ever, were significant due to burning treatment and
among sampling dates. Highest levels of digestible
energy were generally attained in regrowth within
burned areas of gulf cordgrass during the first 2 to 3
months of evaluation. Digestible energy levels were re-
duced, however, 3 to 4 months after evaluation as time
after burning increased. .

Average digestible energy of gulf cordgrass herbage
for the study period on the loamy sand sites, burned in
fall 1974 was 1,799 kilocalories per kilogram compared
with the significantly lower level, 1,688 kilocalories per
kilogram, from green tissues of unburned gulf cordgrass
plants (Figure 18). The greatest digestible energy con-
tent, 2,382 kilocalories per kilogram, occurred in gulf
cordgrass herbage on the sandy loam site burned Oc-
tober 23, 1974. This level of digestible energy was at-
tained during March, approximately 5 months following
burning. The digestible energy of burned gulf cordgrass
regrowth from the loamy sand sites, however, was re-
duced during the early dry period and when spring
“green up” reduced topgrowth utilization by cattle. Di-
gestible energy levels within gulf cordgrass topgrowth
dropped, though not significantly from the previous 3

  
 
    
  
    
   
   
  
 
  
 
 
  
  
 
 
 
  
 
  
  
 

months, beginning in November and were maintain r
reduced levels during the winter when growth was s;
pressed by cool temperatures. With warming temp
tures in late February 1976, digestible energy of g!
cordgrass regrowth tended to increase on the loamy §
site. l
Average digestible energy of gulf cordgrass on,
alkali sandy loam site, burned in spring 1974, was 1,
kilocalories per kilogram compared“ to 1,733 kilocalo
per kilogram in mature herbage (Figure 19). The hig
level of digestible energy in gulf cordgrass herbage
the alkali sandy loam site occurred in March on l
burned area, approximately 1O months following b
ing. After March, however, digestible energy conte i
gulf cordgrass regrowth on the burned site was red l;
until late February 1976, when levels again increasg

Average digestible energy of burned gulf cord y‘
regrowth on the alkali loamy sand site, burned in wi
1975, was 1,786 kilocalories Dyr kilogram (Figure A
Average digestible energy within green tissues from
jacent unburned plants on the same site was I
kilocalories per kilogram. The highest level of diges l‘
energy of topgrowth from the alk 1i loamy sand site
2,075 kilocalories per kilogram which occurred in A
approximately 3 months following burning. Digest
energy of gulf cordgrass herbage on the burned a
loamy sand site remained well above energy leve
mature gulf cordgrass on the adjacent unburned A l
through September. Digestible energy content of
cordgrass regrowth following burning was similar to A
of the mature unburned gulf cordgrass tissues on the f.
through the winter. A

390° g aunu
§ UNBURN
2750 - Avg 3mm 1800Kcal/kg
II AVG UNBURN1688Kcal/kg
2500
2,250

<8
8

LOAMY SAND SITES

c‘
N
0|
o

DIGESTIBLE eusncv (Kcqllkg)
'8 f3
s a ‘é

750

Figure 18. Digestibl’
ergy (kilocalories [
kilogram) of unburn
cordgrass topgrowt A
regrowth following b l
in fall 1974 on the l-
sand sites. (Mean
lowed by the same lett
not significantly differ
the 95-percent Iev
probability accordi
Duncan's Multiple 
Test.)

 
  
 
 
 

__§17'-=-"=I=lll.ll||l|ll||l|

uumug
S'\D_

AUG.
27

DATE

16

ALKALI SANDY LOAM SITE

 

_ AVG aunu 191s Kcal/KQ
Qi- AVG unaunu m4 Kcal/kg

E

Figure 19. Digestible en-
ergy (kilocalories per
kilogram) of unburned gulf
cordgrass topgrowth and of
regrowth following burning
in spring 1974 on the alkali
sandy loam site.

Figure 20. Digestible en-
ergy (kilocalories per
kilogram) of unburned gulf
cordgrass topgrowth and of
regrowth following burning
in winter 1975 on the alkali
loamy sand site.

17

ALKALI LOAMY SAND SITE

=._====__=_=====____=_____________________=======

27
DATE

r___________________________________________=__________________ W

  

_==_E_=_=m====_====_______==______________________________

___.___________________________________________=_====_=====_

1756 Kcal/kg

grave was
iAVG uuaunu 1sa2 Kcal/kg

CONCLUSIONS

Trends for gulf cordgrass herbage production were
similar across all sites although burning date varied.
During periods when adequate soil moisture was avail-
able for gulf cordgrass regrowth, herbage production was
greatly enhanced. However, the rate of recovery, re-
gardless of burning date, was highly dependent upon
site characteristics which provide optimum growth con-
ditions. Generally, rate of herbage production on similar
sites burned at different times would be expected to be
greater on later burns, due to younger plant regrowth.
However, substantial increases in production occurred
in the early spring and during the year after burning
regardless of the burning date. Apparently, until op-
timum foliar expansion is reached, herbage production is
only moderate.

The extent of utilization of gulf cordgrass herbage
following burning is apparently regulated both by date of
burn and by site characteristics. However, when alter-
nate forage is available to cattle, utilization of gulf
cordgrass is reduced regardless of burn or site charac-
teristics. Herbage utilization following burning, how-
ever, was similar among sites. As the age of burn in-
creased, utilization generally decreased as foliage be-
came coarse and unpalatable until forage on adjacent
sites became seasonally limited. When other forage was
not available, utilization of gulf cordgrass regrowth was
increased on all sites following burning regardless of
burn date or site characteristics, though the degree of
utilization varied among the sites and burn dates.

Foliar cover trends were similar to those for herb-
age production and utilization. However, since line
transects were placed in grazed areas, foliar cover also
reflected use of the grass by cattle. Decreases in foliar
cover also reflected greater herbage utilization in rela-
tion to production from February to April. Generally,
after April and May, cumulative utilization began to de-
crease in respect to herbage production, and foliar cover
began to increase.

Nutrient content of gulf cordgrass herbage de-
creased as the quantity of older growth increased at each
sampling date. After 4 or 5 months of active growth fol-
lowing burning, protein content of herbage was re-
duced. During ]une, protein levels from gulf cordgrass
burned in the, fall and that from adjacent unburned
plants were nearly equal, after which protein of treated
plants was consistently below those levels within the
unburned plants. It was at this time, 7 months after fall
burning, that the herbage utilization began to slow in
relation to production. Phosphorus levels were generally
below maintenance levels for cattle, and variations in
this nutrient were not significantly affected by burning.
Digestible energy of gulf cordgrass regrowth following
burning may attain almost 2,800 kilocalories per kilo-
gram.

Lack of rainfall and availability of alternate forage
for the first 3 months of study were reflected in reduced
gulf cordgrass herbage production and utilization, nutri-

18

tive value, and foliar cover. Growth of gulf cordgrass 
affected by moisture stress in April but resumed in‘
sponse to rainfall and decreased abundance of other 
age. The alkali sandy loam site, burned in spring 1
averaged the greatest soil moisture content for  
period. However, because of accumulations of sol 
salts within the soil profile, gulf cordgrass grew a.
dantly only following rainfall and subsequent impr
soil moisture conditions. Burning of saline areas .

prior to the wetter seasons of the year would help en

adequate soil moisture to overcome the high salt.

cumulations.

The greatest production, nutritive content lei
and utilization of gulf cordgrass herbage occurred on‘
loamy sand site burned October 23, 1974. Soils on
site evidently were better suited to optimum gro v

gulf cordgrass. Apparently, salinity was not high ens

to prohibit production of grasses and forbs during;

spring, but growth of other vegetation was not so a
dant as to restrict growth of gulf cordgrass by com  
tion for soil moisture and nutrients. Sites of lower s;
ity appeared to support abundant forb and grass gr,
during the spring. Such abundant growth of other v]

tation obviously increased competition for soil mois’
and soil nutrients, as well as provided alternate fora

the cattle.

Burning gulf cordgrass in the early fall allowe

growth development for grazing cattle throughout
winter when other range forages were dormant. r
nutritional components are reduced with time follo A
burning, the young regrowth provided a good wi
range. During early spring, prior to abundant grow =,
other grasses and forbs, stands of gulf cordgrass regr
supplied ample amounts of protein to grazing ani =
With spring “green up,” however, various other f0

became available, and utilization of gulf cordgra

cattle was reduced. When grazing pressure was red
on gulf cordgrass, the regrowth was allowed to I
maturing, and nutritional components and palata
were reduced.  

Range sites which maintain adequate soil moi
and supply ample nutrientsfor regrowth are opti
for consideration of burning as an improvement to
gulf cordgrass range. Also, sites having salinity l;
that do not restrict gulf cordgrass growth but th
limit growth of other vegetation may be desirable p
total production potential is considered. Burning of
productive sites on a rotational type system could i
bly supply grazing animals with palatable, nutr'
range forage on a year-round basis. Burning in the 
desirable from the standpoint that palatable fora
available to cattle during the winter. Also, regrow
productive sites during the spring, following burni
the fall, is conducive to increased nutritional val
gulf cordgrass, thus supplying grazing animals wit‘
tritional forage prior to the availability of alternate
age.

    
   
  
  
  
  
   
   
 
 
  
   
  
    
  
  
  
   
  
  

 1950. Ecological basis for land use planning in Gulf
 hlands. I. Soil and Water Cons. 5:57-67.

_; 1960. Official Methods of Analysis (9th Ed.). Assoc. of
 u Washington, D.C. 832 pp.

 A., and L. V. Wilcox. 1965. Soluble Salts. In. C. A.

 Methods of soil analysis. (Part II.). Amer. Soc. Agron.,

‘iifwis. 936-931.

 P. R. 1956. Studies in the nutritive value of Spartina

 the marsh areas of Coastal Georgia. Bull. Torry Bot.

 -534-

 R. H. 1941. Application of the line interception method
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 . S., and M. C. Johnston. 1970. Manual of the Vascular
 exas. Texas Res. F ound., Renner, Texas. 1881 pp.

 ., and I. T. Curtis. 1956. The use of distance measures

U iological sampling. Ecology 37:451-460.

 e, R. F. 1967. Plants and environment; A Textbook of
ecology. Iohn Wiley and Sons, Inc., N.Y. 422 pp.

l: ire, R. F. 1968. Ecology of fire in grasslands. In Adv. in

1 5=209~2e6.

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Lppp.

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 ege Station, Tex. 653 pp.

ԤW., and T. W. Box. 1965. Grasses of the Texas Coastal

' A&M Univ. Press, College Station, Tex. 189 pp.

 j .3, and I. Hacskaylo. 1963. Methods and Procedures for

emical and Physiological Research. Texas AézM Univ.

iStore, College Station, Tex. 81 pp.

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 N.Y. (2 vols.). 1051 pp. -

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‘iyield of gulf cordgrass from basal diameter and volume

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Kilograms per hectare
Centigrade l

18.

19.

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22.

24.

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26.

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32.

LITERATURE CITED

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ACKNOWLEDGMENTS

The authors are grateful to Tobin Armstrong,
Armstrong Ranch, for providing land and assistance for
the conduct of this study. Also, the help of Iim Mutz,
Ierry McAtee, Rob Gordon, Lynn Kitchen, and Orvin
Bontrager in data collection is greatly appreciated.

APPENDIX
English Equivalents of Metric Units

Metric English

Unit Equivalent
Centimeter 0.39 inch
Meter 3.28 feet
Kilometer 0.62 mile
Hectare 2.47 acres
Cram 0. 0022 pound
Kilogram 2.2 pounds

0.89 pound per acre
(9/5 Fahrenheit) + 32

19

ALL PROGRAMS AND INFORMATION OF THE TEXAS AGRIC
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REGARD TO RACE, COLOR, RELIGION, SEX, AGE, OR NATIONA

THE TEXAS AGRICULTURAL EXPERIMENT S'
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