Plains Bristlegrass Research Articles

Diet selection of Raramuri Criollo and Angus x Hereford crossbred cattle in the Chihuahuan Desert

Strategies to help producers cope with unpredictable forage production associated with low and variable precipitation patterns on arid rangelands are needed, particularly if global warming trends continue as projected. One option is to identify cattle biotypes compatible with less productive shrubby landscapes. One such biotype is the Raramuri Criollo (RC) from the Copper Canyon of northern Mexico. This small-framed animal exhibits travelling behaviors that allow it to exploit vegetation at a greater distance from water, although it is unknown whether RC have dietary preferences that differ from European breeds typically raised in the southwestern U.S.A. We examined diet selection of RC vs. desert adapted Angus x Hereford (AH) crossbreds typical of the region using DNA metabarcoding to determine the proportion of plant species in fecal samples. Fecal samples were collected from 10 cows of each breed in two adjacent pastures during two seasons (growing and dormancy; four weeks per season) for three consecutive years. Dominant plant species in fecal samples of both cattle breeds were Atriplex canescens (four-wing saltbush), Hoffmannseggia glauca (hog potato), Hopia obtusa (vine mesquite), Setaria leucopila (plains bristlegrass), Sporobolus spp. (S. contractus, S. flexuosus, and S. giganteus), Pleuraphis mutica (tobosa), and Bouteloua eriopoda (black grama), which is consistent with previous studies in the region using different techniques for assessing dietary plant composition of other breeds of cattle. Only a few differences were detected between breeds. Compared to AH, fecal samples from RC tended to contain a higher proportion of mesquite and Yucca spp. (P < 0.07) and less Ephedra spp. (P < 0.06). The only grass species that differed between breeds was black grama (P < 0.05), with AH fecal samples containing about twice as much as RC cows (∼8% vs. 4%). This finding could have important implications for conservation of black grama in the Chihuahuan Desert.

Medical Oxygen Concentrators for Releasing Seed Dormancy

ABSTRACTA new method is demonstrated for using concentrated oxygen (O2 gas) to release seed dormancy. Concentrated O2 gas in air is known to release seed dormancy in some seeds, including some foxtail (Setaria) species. New medical equipment makes O2 gas easier to work with than before, so laboratories working with dormant seeds can now use concentrated O2 gas as a seed treatment on a production basis. Use of medical O2 gas concentrators is simpler and safer than using O2 gas supplied by pressurized gas cylinders. Suitable medical O2 gas concentrators in new or used condition are readily available, operate on standard electrical current, and deliver O2 gas with low‐pressure tubes and fittings. Resealable plastic bags are inflated with concentrated O2 gas and then sealed as seed treatment chambers. This use of concentrated O2 gas is confirmed to significantly increase the germination of dormant seeds of giant foxtail (Setaria faberi Herrm) and plains bristlegrass (S. macrostachya Kunth).

Morphological and molecular characterization of populations of plains bristlegrass (Setaria macrostachya Kunth) in Chihuahua, M閤ico

Plains bristlegrass (Setaria macrostachya Kunth) is a native grass with forage value. However, due to the lack of grazing management practices, populations and thus genetic diversity, have been reduced. Morphological and gene... | Find, read and cite all the research you need on Tech Science Press

Dry Matter, Carbon, and Nitrogen Accumulation of Four Great Plains Grasses

ABSTRACTNative North American warm‐season bunchgrasses have the potential to provide both forage and cellulosic bioenergy in drier regions of the southern Great Plains. Almost no information is available on the potential accumulations of many of these species under forage, bioenergy, or combined system harvests. Multiflower false rhodesgrass (MFR; Chloris pluriflora Fourn.), pink pappusgrass (PPG; Pappophorum bicolor Fourn.), shortspike windmill grass (SSWG; Chloris × subdolichostachya Müll. Berol. (pro sp.) [cucullata × verticillata]), and plains bristlegrass (PBG; Setaria vulpiseta Scribn. and Merr.) were harvested during 4 yr at Stephenville, TX, USA. Seedlings were transplanted into a Windthorst sandy loam soil fertilized in Year 1 with 0 or 67 kg N and P ha−1 yr−1 plus 67 kg N ha−1 yr−1 in the spring of Years 2 to 4. Fertilizer improved N and dry matter (DM) accumulations (P ≤ 0.05) except for SSWG and improved (P ≤ 0.05) accumulations of October regrowth following July harvest in greater rainfall years. Multiflower false rhodesgrass produced greater (P ≤ 0.05) accumulation the first year (up to 4.38 Mg ha−1) while PPG had the most consistent accumulation across years with variable precipitation. Results indicate that MFR and PPG bunchgrasses native to the North American Great Plains have potential for bioenergy or forage and bioenergy production systems.

Selection of Seeds of an Exotic and Three Native Grasses by Northern Bobwhites (Colinus virginianus)

We used 24 captive northern bobwhites (Colinus virginianus) to compare relative preference of seeds of nonnative guineagrass (Urochloa maxima) to three native foods (switchgrass Panicum virgatum, Texas millet Urochloa texana, and plains bristlegrass Setaria leucopila). By mass, switchgrass was consumed more than other species; plains bristlegrass was least preferred. Selections of guineagrass and Texas millet were similar and intermediate between the other species. By volume, switchgrass and guineagrass were consumed equally. Switchgrass and guineagrass were higher in protein (16 and 18%, respectively) than the other species (13%). Texas millet had higher gross energy content and lower acid-detergent-fiber values compared to the other species. Plains bristlegrass had the lowest protein (13%) and lowest gross energy (3.72 kcal/g). Seeds of guineagrass were consumed and are similar to switchgrass in protein content.Usamos 24 codornices (Colinus virginianus) en cautiverio para determinar la preferencia relativa por la semilla de pasto de guinea (Urochloa maxima) no nativo comparada con tres alimentos nativos (pasto varilla Panicum virgatum, pasto alambre Urochloa texana y zacate tempranero Setaria leucopila). La semilla del pasto varilla por volumen fue la más preferida, y la del zacate tempranero fue la menos preferida. El consumo de U. maxima y U. texana fue similar e intermedio entre las otras especies. Las de pasto varilla y las de pasto de guinea fueron más altas en proteína (16 y 18%, respectivamente) comparadas con las otras especies (13%). La semilla del pasto alambre fue más alta en energía bruta y tuvo el menor valor de fibra ácida detergente comparada con las otras especies. La semilla del zacate tempranero fue la más baja en proteína (13%) y en energía bruta (3.72 kcal/g). Las semillas del pasto de guinea fueron consumidas y son similares a las del pasto varilla en el contenido de proteína.

North American Bristlegrass Seed Yield Response to Nitrogen Fertilizer and Environment

Information on field management practices for seed production of newly domesticated grasses native to the southern Great Plains of North America has not been well documented. This study was conducted to document seed yield responses of one accession of plains bristlegrass [Setaria vulpiseta (Lam.) Roem. &amp; Schult.] and three accessions of streambed bristlegrass [Setaria leucopila (Scribn. &amp; Merr.) K. Schum.] to 0, 50, 75, 100, and 140 kg N ha−1 yr−1 under irrigation at Stephenville and Beeville, TX, during 2005 and 2006. The soil at Stephenville was a Windthorst fine sandy loam, mixed, thermic Udic Paleustalfs and at Beeville a Parrita clayey, mixed, active, hyperthermic, shallow Petrocalcic Paleustolls. Seed yields across N levels at Stephenville in year of establishment ranged (p &lt; 0.05) from 57 to 753 kg ha−1 yr−1 October seed yield of accession 648 increased (p &lt; 0.05) 305% with 75 kg N ha−1 compared to the no‐N treatment at Beeville. Seed production peaked at 328 kg ha−1 for accession 648 and 352 kg ha−1 for accession 715 in spring 2006 at Beeville. Inflorescence density was positively correlated to seed yield (from 81 to 93%). Optimum bristlegrass N fertilizer management varied with accession, location, and year.

Evaluation of Herbicides for Restoring Native Grasses in Buffelgrass‐Dominated Grasslands

Abstract Buffelgrass (Pennisetum ciliare) is an exotic grass that threatens arid and semiarid ecosystems. The objective of this study was to determine effectiveness of several herbicides at reducing competition from buffelgrass to enhance establishment of planted native grasses. In Duval County, Texas, plots were delineated in two experiments in a buffelgrass‐dominated pasture and mowed on 2 September 2002. On 18 September 2002 and 7 October 2002, a 41% glyphosate (N‐(phosphonomethyl) glycine) herbicide was applied to all plots. A mixture of three native grasses—green sprangletop (Leptochloa dubia), plains bristlegrass (Setaria leucopila), and four‐flower trichloris (Chloris pluriflora)—was planted on 8 October 2002. On 9 October 2002, 1.12 and 2.24 kg/ha of a 80% tebuthiuron (N‐[5‐(1,1‐dimethyethyl)‐1,3,4‐thiadiazol‐2‐yl]‐N,N’‐dimethylurea) herbicide was applied preemergence to the first experiment, and all other herbicides were applied postemergence on 27 July 2003 to the second experiment. Percent canopy cover of vegetation was estimated with a 20 × 50–cm sampling frame during April, June, and October 2003 and August 2004. Postemergent herbicides had no significant effect on canopy cover of buffelgrass or planted species (p≥ 0.05). Canopy cover of native grasses did not exceed 8% on any treatment or sampling date, and buffelgrass cover returned to pre‐treatment conditions in less than 1 year; however, the 2.24 kg/ha rate of tebuthiuron suppressed (p &lt; 0.05) canopy cover of buffelgrass compared with controls and increased (p &lt; 0.05) native grasses almost 2 years past application. Tebuthiuron may have potential value in reducing buffelgrass canopy cover and increasing cover of native grasses, particularly Chloris spp.

Responses of desert grassland vegetation to mesquite removal and regrowth

The purpose of this study was to determine the long-term response of understory vegetation in the desert grassland of southeastern Arizona, USA, to removal and regrowth of mesquite Prosopis juliflora (Swartz) DC. var. velutina (Wooton) Sarg. trees. The study involved 3 treatments applied to mesquite in 1966; mesquite left intact (MI), mesquite removed (MR), and mesquite removed, sprouted, and regrown (MRS). Vegetation responses to 2 litter treatments, litter intact (LI) and litter removed (LR), also were examined. Cover of understory vegetation and juvenile mesquite (< 1.5 m height) were measured in canopy and open (intercanopy) locations. Major changes between 1967 and 1991 were increased cover of juvenile mesquite, shrubs, halfshrubs, bush muhly Muhlenbergia porteri Scribn., and Lehmann lovegrass Eragrostis lehmanniana Nees., and a decline in cover of Arizona cottontop Digitaria californica (Benth.) Chase, and plains bristlegrass Setaria macrostachya H.B.K. Arizona cottontop, plains bristlegrass, and bush muhly were more abundant in canopy locations; black grama Bouteloua eriopoda Torr. and Lehmann lovegrass were more abundant in open locations. Lehmann lovegrass cover was lowest in canopy locations of the mesquite intact treatment. Combination of the mesquite removed and sprouted and litter intact treatments favored increased cover development of native perennial grasses. Litter removal enhanced cover development of Lehmann lovegrass, most likely through increased amount of red light and increased soil temperature fluctuations. Low levels of understory cover (22% average) probably facilitated recruitment of mesquite and other woody plants. Our observation that the greatest cover of Arizona cottontop, plains bristlegrass, and bush muhly occurred in the canopy location of the mesquite intact treatment suggests a potential strategy for maintaining diversity of native perennial grasses. Mature mesquite should be examined as a refuge for native species.

Responses of desert grassland vegetation to mesquite removal and regrowth

The purpose of this study was to determine the long-term response of understory vegetation in the desert grassland of southeastern Arizona, USA, to removal and regrowth of mesquite Prosopis juliflora (Swartz) DC. var. velutina (Wooton) Sarg. trees. The study involved 3 treatments applied to mesquite in 1966; mesquite left intact (MI), mesquite removed (MR), and mesquite removed, sprouted, and regrown (MRS). Vegetation responses to 2 litter treatments, litter intact (LI) and litter removed (LR), also were examined. Cover of understory vegetation and juvenile mesquite ( 1.5 m height) were measured in canopy and open (intercanopy) locations. Major changes between 1967 and 1991 were increased cover of juvenile mesquite, shrubs, halfshrubs, bush muhly Muhlenbergia porteri Scribn., and Lehmann lovegrass Eragrostis lehmanniana Nees., and a decline in cover of Arizona cottontop Digitaria californica (Benth.) Chase, and plains bristlegrass Setaria macrostachya H.B.K. Arizona cottontop, plains bristlegrass, and bush muhly were more abundant in canopy locations; black grama Bouteloua eriopoda Torr. and Lehmann lovegrass were more abundant in open locations. Lehmann lovegrass cover was lowest in canopy locations of the mesquite intact treatment. Combination of the mesquite removed and sprouted and litter intact treatments favored increased cover development of native perennial grasses. Litter removal enhanced cover development of Lehmann lovegrass, most likely through increased amount of red light and increased soil temperature fluctuations. Low levels of understory cover (22% average) probably facilitated recruitment of mesquite and other woody plants. Our observation that the greatest cover of Arizona cottontop, plains bristlegrass, and bush muhly occurred in the canopy location of the mesquite intact treatment suggests a potential strategy for maintaining diversity of native perennial grasses. Mature mesquite should be examined as a refuge for native species.

Forage production and quality of 4 perennial grasses grown under and outside canopies of matureProsopis glandulosa Torr. var.glandulosa (mesquite)

Comparisons were made of dry matter production and forage quality of two coolseason grasses, Canada wildrye (Elymus canadensis L.), Virginia wildrye (Elymus virginicus L.), and two warm-season grasses, green panic (Panicum maximum var.trichoglume Eyles) and plains bristlegrass (Setaria leucopila Scribn. & Merr.), planted under and outside the canopies of mature honey mesquite (Prosopis glandulosa Torr. var.glandulosa). Green panic gave the greatest cumulative dry matter yield in both canopy (5120 kg ha−1) and open (3370 kg ha−1) locations, followed by plains bristlegrass under mesquite (1130 kg ha−1) and in the open (570 kg ha−1). One-time yields from Canada wildrye and Virginia wildrye, under and outside mesquite canopy, were 247 and 329 kg ha−1, and 272 and 268 kg ha−1, respectively. Dry matter production of green panic (p=0.001) and plains bristlegrass (p=0.026) was greater under mesquite only for the first of four harvests, although both warm-season grasses exhibited a trend for greater production under mesquite than in the open. Average nitrogen content of green panic was greater (p=0.0004) under mesquite than in the open, while plains bristlegrass exhibited a trend for greater crude protein content in the open than under mesquite. Overall, moisture content of the warm-season grasses was greater (p=0.0001) under mesquite than in the open, while Virginia wildrye was more (p=0.002) succulent under mesquite than in the open. Averagein-vitro dry matter digestibility of warm-season grasses was almost significantly greater (p=0.0501) in the open than under mesquite. Canopy soils contained significantly more organic C (p=0.0004) and total N (p=0.0001) than open soils, with differences of 8.3 Mg organic C ha−1 and 1.3 Mg total N ha−1. Correlations indicated that soil fertility was more limiting to grass production than light intensity.

The Effect of Polyacrylamide on Grass Emergence in Southcentral New Mexico

Seeding rangeland is a challenge for rangeland scientists, especially on those soils with tendency to crusting. Although some information is available on how soil conditioners affect emergence of certain comestible crops, little is known about the effect of synthetic organic matter on grass emergence. We examined the effect of polyacrylamide, a soil conditioner, on seedling emergence of blue panicgrass (Panicum antidotale Retz.), King Ranch bluestem (Bothriochloa ischaemum [L.] Keng), sideoats grama (Bouteloua curtipendula [Michx.] Torr.), plains bristlegrass (Setaria macrostachya H.B.K.), and 'salado' alkali sacaton (Sporobolus airoides [Torr.] Torr.) under field conditions. Emergence of blue panicgrass and sideoats grama was increased with polyacrylamide applications, even at the lowest concentration (10 kg ha-1) during summer 1987. No emergence response to polyacrylamide applications was found for King Ranch bluestem, and plains bristlegrass did not emerge in any experimental plots during summer 1987. During summer 1988, blue panicgrass and sideoats grama emergence was again increased with polyacrylamide applications. Emergence of 'salado' alkali sacaton and King Ranch bluestem was unaffected by polyacrylamide applications. Soil conditioners may be a feasible alternative for seeding some rangeland in areas where crusting is a problem.

Seedling emergence and root elongation of four grass species and evaporation from bare soil as affected by polyacrylamide

Seedling establishment is particularly difficult on range soils with a tendency to crust. Although application of organic matter can correct this problem, it is usually scarce on rangeland and, in general, in arid areas. Therefore, synthetic soil conditioners have become important in replacing the effect of natural organic matter. The objectives of this study were to determine the effects of polyacrylamide (PAM) on seedling emergence and root elongation of blue panicgrass (panicum antidotale), King Ranch bluestem (Bothriochloa ischaemum), plains bristlegrass (Setaria macrostachya) and sideoats grama (Bouteloua curtipendula), as well as on evaporation, infiltration and strength of soil with a tendency to crusting. Three trials were performed, with PAM doses of 0, 10, 20 and 40 kg ha−1. Polyacrylamide markedly improved emergence of sideoats grama, even at the lowest PAM application level, while blue panicgrass and King Ranch bluestem were unaffected. Plains bristlegrass had no emergence in any of the test plots and so statistical analysis was not performed. Roots of blue panicgrass and sideoats grama that grew in tubes treated with PAM were larger than untreated ones. Measurements of shear strength showed PAM reduced the crust on the soil surface. In general, as PAM concentration increased, shear strength values decreased. PAM reduced evaporation in the short and long term. Infiltration measurements were inconsistent. Results of this study suggest PAM may become important in rangeland areas because it can improve emergence as well as the root system of some grasses, reduce shear strength that is directly correlated with crust formation, and reduce evaporation.

Seedling Growth Responses of Buffelgrass (Pennisetum ciliare) to Tebuthiuron and Honey Mesquite (Prosopis glandulosa)

Tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} at 2 or 4 ppmw placed 0 to 3, 8 to 11, or 15 to 18 cm deep in soil columns reduced root and shoot weights of buffelgrass [Pennisetum ciliare(L.) Link # PESCI] 30 days after emergence. Plains bristlegrass (Setaria macrostachyaH.B.K.) seedling shoot weights were not reduced when 2 ppmw tebuthiuron was placed 8 to 11 cm deep or deeper. Effects of tebuthiuron at 0.13 to 0.50 ppmw on buffelgrass shoot and net tiller production were not moderated by the presence of honey mesquite (Prosopis glandulosa# PRCJG) in the pots. However, regardless of tebuthiuron dosage, average height and shoot weight of buffelgrass seedlings were greater when seedlings were grown in soil collected from beneath honey mesquite canopies compared to growth in soil from interspaces. Therefore, spatial variations in buffelgrass response to applications of tebuthiuron for control of invading shrubs may largely be attributed to soil changes induced by woody plants rather than to presence of shrubs.

Evaluation and Management of Grasses for Dual Livestock and Game Bird Use

Kleingrass 75 and Verde kleingrass (Panicum colortrtum L.), PI Similarly, selection of grasses for rangeland revegetation has been 217229 and PMT 4022 plains bristlegrass (Setoria macrostachya based largely on the ability to become established, persist, and H.B.K.) Nees), and commercial green sprangletop (Leptoehba produce an acceptable amount of forage. In Texas, game birds are ~(HJ.K.),wereshdicdforfoRgePndseedproduction.A~~an important or potentially important source of income from ty of seed was studied using caged bobwhite quail (Co&us virgini- hunting leases and a recreation resource for both rural and urban anus). Defoliation management practices had relatively little influ- populations. While grass seed plays a significant role in bird nutrience on forage yield. Forage digestibility declined rapidly when tion (Davidson 1949), bobwhite quail (Colinus virginianus) require defoliation was delayed, and the species responded differently in seed of more than one vegetation type to meet their nutrient the rate and pattern of decline. Seed yields were as high or higher requirements (Stoddard 1931, Casey 1965). Thus, grasses and with 30day interval harvesting as with deferred harvesting except management practices are needed that produce good quality forthat spring deferment increased kleingrass and summer deferment age for livestock and seed for bird use. increased green sprangletop seed yields. Green sprangletop also Wernecke (1977) identified grasses with seed production patproduced more seed by leaving a 20sm stubble than a lo-cm terns and seed characteristics that apparently make them acceptastubble. These indeterminate species apparently mature seed in ble for game birds. The genera included Panicum, Paspalum, and approxhnately 30 days, indicating that a management system that Setaria. Growth and forage quality in response to defoliation have leaves some tillers intact for 30 days or longer will result in some been reported for some species (Pitman and Holt 1983). This study seed formation. Seed production decreases to nil in 2 to 3 months was undertaken to evaluate selected management practices for following first maturity in an undefoliated stand. forage and seed production and to determine the acceptability of Bobwhite quail readily consumed kleingrass seed as a significant selected grass seeds to bobwhite quail. portion of their diet even in the presence of a high quality game bird diet. They subsisted for short periods on an all grass seed diet, but

Environmental Relationships with Forage Quality of Warm‐Season Perennial Grasses1

Seasonal patterns of digestibility of warm‐season perennial grasses in the southwestern U. S. A. generally show peaks in early spring and low values in mid‐summer. This research was conducted to determine if the patterns of digestibility of kleingrass (Panicum coloratum L.), green sprangletop [Leptochloa dubia (H.B.K.) Nees], and plains bristlegrass (Setaria macrostachya H.B.K.) were related to temperature, rainfall, relative humidity, and daylength under field conditions. Two selections of kleingrass (‘Kleingrass 75’ and Kleingrass 75‐25), and one each of green sprangletop and plains bristlegrass were harvested at 2, 4, and 8‐week frequencies during 1978 and 1979. Samples were separated into leaf and stem fractions with in vitro digestible organic matter (IVDOM) determined each fraction. From analyses with all four grasses combined, leaf and stem IVDOM was negatively correlated with temperature (r‐values from −0.353 to −0.419, all significant at 0.001 level) and daylength (r‐values as great as −0.378 with all significant at least at the 0.01 level). In general, leaf and stem IVDOM was positively correlated with measures of moisture conditions (r‐values up to 0.523 and 0.445 for rainfall and relative humidity, respectively).The environmental factors monitored were used in multiple regression models of leaf IVDOM, stem IVDOM, and percent leaf. Statistically significant models were obtained in most cases with R2 values up to 0.96. However, in a few cases less than 20% of the variation in IVDOM was accounted for by models maximizing R2 (with R2 values as low as 0.12). Distinct r elationships are apparent from these analyses; although, R2 values, partial regression coefficients, and individual environmental factors contributing significantly to the models were too variable for these models of leaf and stem IVDOM and percent leaf to be of general use. Overall trends in digestibility can be anticipated from knowledge of environmental factors, but forage digestibility cannot be accurately predicted from macroenvironmental factors.

Chemical Composition of Native Range Grasses Growing on Saline Soils of the South Texas Plains

Chemical Composition of Native Range Grasses Growing on Saline Soils of the South Texas Plains

Effect of Fire on Southern Mixed Prairie Grasses

Highlight: The long-term effect of fire was studied on the major grass species of west Texas when the winter-spring precipitation was 0 to 40% above normal. This and other studies indicate that sideoats grama and Texas wintergrass are harmed by fire. Buffalograss, blue grama, and sand dropseed were neither harmed nor benefited by fire. Vine-mesquite, Arizona cottontop, little bluestem, plains bristlegrass, and Texas cupgrass increased after burning for 1 or 2 years.

Nutrient Availability in Desert Grassland Soils Under Mesquite (Prosopis juliflora) Trees and Adjacent Open Areas

AbstractA pot‐culture technique was used to calculate relative yields for N, P, K, and S as an index of availability of these nutrients in soil from under mesquite [Prosopis juliflora (Swartz.) DC] trees and from adjacent open areas on a desert grassland site. Arizona cottontop [Trichachne californica (Benth.) Chase], plains bristlegrass (Setaria macrostachya H.B.K.), and bush muhly (Muhlenbergia porteri Scribn.), all native perennial grasses which grow abundantly under mesquite, were used as test plants.Relative yields for N were up to 15 times higher in soil under mesquite trees than in nonmesquite soil, whereas the level of total N was only three times greater. The soil under mesquite trees apparently provides a more favorable environment for supply of N than nonmesquite soil.Relative yields for S in mesquite soil were three times greater than in nonmesquite soil and were proportional to the difference in total S between soils, indicating that S is supplied more slowly than N under mesquite trees.Phosphorus showed a slight, although significant, difference in availability between soils, but total P was the same in the two soils. A threefold higher level of organic matter in soil under mesquite probably contributes to increased availability of P.Differences in total potassium and its supply to test plants were not detected between the two soils.

Germination Responses of Three Desert Grasses to Moisture Stress and Light

Lehmann lovegrass appeared very susceptible to physiological drought while Arizona cottontop and plains bristlegrass were not appreciably affected until osmotic tensions exceeded 12 atm. Lehmann lovegrass was the fastest and plains bristlegrass was the slowest to germinate. This study indicated that the adaptability and responsiveness of Lehmann lovegrass is due to its ability to germinate rapidly whereas the other two species require more time of moisture availability. Lehmann lovegrass and Arizona cottontop appeared adversely affected by constant darkness which suggests that they require a shallow planting while plains bristlegrass seemed to have the opposite response, which suggests that it requires a deeper planting

Influence of Fire on South Texas Chaparral Communities

Experimental fall burning of South Texas chaparral communities significantly reduced canopy of all brush species in untreated areas and in areas previously treated by roller chopping, shredding, and scalping. There was a highly significant (P &lt; .01) reduction in frequency of occurrence of lotebush (Condalia obtusifolia (Hook.) Weberb.), lycium (Lycium berlandieri Dunal.), and creeping mesquite (Prosopis reptans Benth. var. cinerascens (Gray) Burkart). Frequencies of occurrence of brasil (Condalia obovata Hook.) and Mexican persimmon (Diospyros texana Scheele) were significantly reduced (P &lt; .05). There was no sgnificant difference in total amount of grass on burned and unburned areas 1 year following the fire. Filly panic (Panicum filipes Scribn.), buffalograss (Buchloe dactyloides (Nutt.) Engelm.), and meadow dropseed (Sporobolus asper var. hookeri (Trin.) Vasey) were more abundant on burned than on unburned areas. Plains bristlegrass (Setaria leucopila Scribn. and Merr.) was less abundant on burned areas than on unburned areas. Forb production was significantly (P &lt;. 01) less on burned than on unburned areas, mostly because of reduction in western ragweed (Ambrosia psilostachya DC.) and Texas broomweed (Xanthocephlum texanum (DC.) Shinners). Fire could have been responsible for the creation of the brush mottes described by early explorers. The study substantiates the theory that fire suppressed brush on south Texas grasslands.