Switchgrass (Panicum virgatum L.) has been proposed as a sustainable bioenergy crop because of its high yield potential, adaptation to marginal sites, and tolerance to water and nutrient limitations. A better understanding of the potential effects of biomass energy crop production practices on soil biological properties and organic matter,dynamics is critical to its production. Our objective was to evaluate changes in C pools under a warm-season perennial switchgrass in different soils compared to typically-grown crops collected at College Station, Dallas, and Stephenville, TX in February 2001. Sampling depths were 0-5, 5-15, and 15-30 cm. Switchgrass increased soil organic C (SOC), soil microbial biomass C (SMBC), mineralizable C, and particulate organic matter C (POM-C) compared to conventional cropping systems. Soil C concentrations were in the order: long-term coastal bermudagrass [Cynodon dactylon (L.) Pers.] > switchgrass or kleingrass (Panicum coloratum, L.) planted in 1992 > switchgrass 1997 > conventional cropping systems. Soil C concentrations tended to increase with increasing clay content. Greater microbial biomass C followed the order of Dallas > College Station > Stephenville, and ranged from approximately 180 mg C kg(-1) soil at Stephenville to 1 900 mg C kg(-1) soil at Dallas. Particulate organic C was more sensitive than other fractions to management, increasing as much as 6-fold under long-term coastal bermudagrass compared to conventional cropping systems. Our study indicated that conversion of conventional cropping systems into switchgrass production can sequestrate more SOC and improve soil biological properties in the southern USA.

Texas bluegrass has potential as a cool-season perennial pasture grass for the southcentral USA. Slow stand establishment in competitive environments is a limitation. Forage production of this grass increases with nitrogen (N), and rhizome growth increases with phosphorus (P). Stand responses by Texas bluegrass from three seed sources to seeding rate and a complete mixed fertilizer were assessed from 1997 through 2005 on a Louisiana Coastal Plain site. A linear response (R-2 = 0.39, P = 0.0001) to seeding rate in March 1998 persisted through 2005, even though stands at all seeding rates improved over time. Stands did not differ (P > 0.05) among seed sources. At only the higher seeding rates, rhizome mass increased with fertilization. Soil pH decreased with fertilization, and pH was positively correlated with the final stand rating in 2005. Direct stand responses to fertilization were not detected. Lack of competitive advantage, despite growth responses, and soil acidification with fertilization indicate that increased seeding rates and delayed fertilization may enhance initial establishment of Texas bluegrass in humid environments.

Crop ScienceVolume 45, Issue 5 p. 2124-2125 Registrations of Cultivar Registration of ‘Tejas 1’ Texas Bluegrass J.C. Read, Corresponding Author J.C. Read [email protected] Texas Agric. Exp. Stn., 17360 Coit Rd., Dallas, TX, 75252 Corresponding author ([email protected])Search for more papers by this authorJ.A. Reinert, J.A. Reinert Texas Agric. Exp. Stn., 17360 Coit Rd., Dallas, TX, 75252Search for more papers by this authorG.W. Evers, G.W. Evers Texas Agric. Exp. Stn., P.O. Box 200, Overton, TX, 75684Search for more papers by this authorW.R. Ocumpaugh, W.R. Ocumpaugh Texas Agric. Exp. Stn., 3507 Hwy 59E, Beeville, TX, 78102Search for more papers by this authorM.A. Sanderson, M.A. Sanderson USDA-ARS Pasture Systems and Watershed Management Research Unit, 3702, Curtin Road, University Park, PA, 16802-3702Search for more papers by this authorA.A. Hopkins, A.A. Hopkins Samuel Roberts Noble Foundation, 2510 Sam Noble Pkwy., Ardmore, OK, 73401Search for more papers by this author J.C. Read, Corresponding Author J.C. Read [email protected] Texas Agric. Exp. Stn., 17360 Coit Rd., Dallas, TX, 75252 Corresponding author ([email protected])Search for more papers by this authorJ.A. Reinert, J.A. Reinert Texas Agric. Exp. Stn., 17360 Coit Rd., Dallas, TX, 75252Search for more papers by this authorG.W. Evers, G.W. Evers Texas Agric. Exp. Stn., P.O. Box 200, Overton, TX, 75684Search for more papers by this authorW.R. Ocumpaugh, W.R. Ocumpaugh Texas Agric. Exp. Stn., 3507 Hwy 59E, Beeville, TX, 78102Search for more papers by this authorM.A. Sanderson, M.A. Sanderson USDA-ARS Pasture Systems and Watershed Management Research Unit, 3702, Curtin Road, University Park, PA, 16802-3702Search for more papers by this authorA.A. Hopkins, A.A. Hopkins Samuel Roberts Noble Foundation, 2510 Sam Noble Pkwy., Ardmore, OK, 73401Search for more papers by this author First published: 01 September 2005 https://doi.org/10.2135/cropsci2004.0595Citations: 4 Registration by CSSA. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume45, Issue5September–October 2005Pages 2124-2125 RelatedInformation

Optimizing feedstock production from switchgrass (Panicum virgatum L.) requires careful matching of genotype to environment, especially for southern U.S. regions. Nine genotypes from four combinations of ecotype and morphological type were harvested once yearly in autumn for 3 or 4 yr at five locations across Texas, Arkansas, and Louisiana that varied in latitude and precipitation. Genotypes were evaluated for dry matter yield (DMY), plant density, tiller density, lodging, and rust (caused by Puccinia spp.) infection. Genotype × environment (G×E) interactions were identified for most traits. Biomass yield of all genotypes tended to increase with latitude, but lowland morphological types may have been more sensitive than upland morphological types to differences in moisture availability. Yield (5.82 vs. 14.97 Mg ha−1, respectively) and persistence (final stand density, 3.99 vs. 5.96 plants m−2) were lower for upland than for lowland genotypes, particularly at higher rainfall and more southern sites. Lowland genotypes were often able to compensate for stand thinning by increasing individual plant size, but upland genotypes were not. Lodging and rust scores were higher for upland than for lowland genotypes. Yield (13.65 vs. 9.75 Mg ha−1) and final plant density (5.58 vs. 4.95 plants m−2) were higher for southern than northern ecotypes. The southern‐lowland combination exhibited the best yield and persistence over the study region, and genotypes within this group exhibited variability in yield among sites. Therefore, development of switchgrass cultivars for biomass production in the southern USA should focus on the southern‐lowland genotypes.

Simulation models for plant species important for biofuel such as switchgrass (Panicum virgatum L.) can be used to make management decisions related to biomass productivity and related to environmental impacts such as soil erosion and changes in surface and groundwater quality. The present study was designed to evaluate the accuracy of simulation of switchgrass biomass production by the ALMANAC (Agricultural Land Management Alternatives with Numerical Assessment Criteria) model at sites in Texas, Arkansas, and Louisiana. We used multi-year field data for Alamo switchgrass yields at each of five sites to evaluate ALMANAC. The model realistically simulated mean switchgrass yields at each of the locations and the total variability of all the data pooled, but did not perform as well in accounting for the year-to-year variability within some locations. Sensitivity analysis showed that changes in runoff curve number (CN) and changes in maximum stomatal conductance (GSI) had variable impacts on simulated values among the sites. A 15% change in CN changed mean annual biomass yield from 0% to 16% depending on location. Changing GSI from 4 to 8mms−1 changed mean annual biomass from 1% to 31% depending on location. ALMANAC shows promise as a tool to realistically simulate mean biomass yields and variability around the mean for multi-year runs of switchgrass at these diverse sites. Further research, with more extensive measurements of soil parameters including soil nutrients is needed to determine why the model reasonably simulated individual years’ yields at Stephenville, TX and Dallas, TX, but had difficulty at other sites.

Optimizing biofuel production and quality from switchgrass (Panicum virgatum L.) may require matching of ecotype and morphological type to environments, particularly in southern regions. Nine genotypes from four combinations of ecotype and morphological switchgrass type were harvested from 1998 to 2000 in five sites across Texas, Arkansas, and Louisiana that varied in latitude and precipitation. An additive main effects and multiplicative interaction (AMMI) method was used to evaluate genotype X environment interaction (G x E) patterns for traits important to biofuel production. Compared with upland genotypes across all site-years, lowland genotypes had greater lignocellulose yields (3.26 vs. 7.40 Mg ha(-1)), greater removal rates of soil N (41 vs. 83 kg ha(-1)) and P (6 vs. 12 kg ha(-1)), greater concentrations of moisture (394 vs. 452 g kg(-1)) and cellulose (388 vs. 394 g kg(-1)), and lower concentrations of N (6.3 vs. 5.7 g kg(-1)) and ash (48 vs. 40 g kg(-1)). Compared with northern ecotypes, southern ecotypes had greater lignocellulose yields (4.95 vs. 6.85 Mg ha(-1)), greater removal rates of soil N (60 vs. 76 kg ha(-1)) and P (8 vs. 11 kg ha(-1)), greater moisture concentrations (417 vs. 445 g kg(-1)), and lower ash concentrations (45 vs. 40 g kg(-1)). Lignocellulose yield paralleled dry matter yield (DMY) patterns. Switchgrass biofuel production efforts in the south-central USA should focus on improving DMY of southern lowland genotypes to maximize lignocellulose yields, but management factors may be more effective in optimizing moisture, ash, and mineral concentrations for combustion.

Dioecy is a breeding system that promotes cross-pollination in plants. The transfer of this trait into economically important self-pollinated cereal crops would revolutionize the production of hybrids in these species and provide a means for increasing yields because of heterosis. Texas bluegrass (Poa arachnifera Torr.) (2n = 8x = 56) is a polymorphic dioecious species that provides an opportunity to genetically map the dioecy locus. In this study, amplified fragment length polymorphism (AFLP)-based linkage maps were constructed for both the maternal and paternal plants used to develop a mapping population of Texas bluegrass. The maternal map contained 126 single dose restriction fragments (SDRFs), 31 linkage groups, 1744 cM, and an average marker spacing of 13.8 cM. The paternal map contained 210 SDRFs, 46 linkage groups, 2699 cM, and an average marker spacing of 12.9 cM. Approximately 76 to 81% of the Texas bluegrass genome was covered. Two AFLP markers (txbg7 and txbg154) mapped equidistantly (9.5 cM) on opposite sides of the dioecy locus (PDio1) on the paternal map. These markers provide a preliminary tool for studying sex determination and a framework for further characterization of the genomic region conferring dioecy in Texas bluegrass.

The fall armyworm, [Spodoptera frugiperda (J.E. Smith)] (Lepidoptera: Noctuidae), is a destructive pest of many species of cool- and warm-season turfgrass in the Americas and Caribbean Basin. Forty-seven cultivars and genotypes of Kentucky bluegrass, (Poa pratensis L.), were characterized for their resistance or susceptibility to fall armyworm larvae in no-choice experiments. The majority of the Kentucky bluegrasses (32 genotypes) provided 100% mortality before adult emergence. An additional seven cultivars provided > 90% mortality and two more produced > 80% mortality. The most susceptible cultivars were 'Glade' with 8.33% mortality, followed by 'PTDF22B2' (25%), 'Kenblue' (29%), 'Connie' (58%) and 'H86-386' (67%). Poa arachnifera x P.pratensis 'Reveille' was 100% resistant, characteristic of the parent, P. pratensis 'Huntsville,' as opposed to the parent, P. arachnifera 'Syn-1'. Overall analysis of the group of Kentucky bluegrass genotypes shows a gradation of resistance, with 'Wabash' killing 100% of larvae within 3 d feeding, an additional nine cultivars killing 100% within 9 d, 20 additional cultivars killing 100% by pupation and two additional cultivars provided 100% kill by adult emergence. The data indicates 'Walbash', 'Adelphi,' 'Eagelton' and 'Monopoly' (all producing > 92% mortality within 3 d feeding) present the greatest potential for transferring genetic resistance for the fall armyworm. Poa trivialis 'Laser' (33% mortality at adult emergence) was included as a susceptible standard.

The economic potential for soybean (Glycine max L. Merr.) as forage, compared to its potential as grain, creates a dilemma for soybean farmers in the southern Great Plains. To better understand these two potential uses, soybean cultivars differing in maturity and growth habit were planted in 14-inch and 28-inch rows on 11 May 2001 and 16 May 2002 near Dallas, TX. The soil was a Houston Black Clay (fine, smectitic, thermic Udic Haplusterts). Plant height, plate meter readings, and forage biomass were measured in July and August and grain yield determined in September. Forage (1.26 to 2.13 ton/acre) and grain yields (9.3 to 20.9 bu/acre) were relatively low and similar between row spacings and between cultivars. Forage quality traits ranged as follows (by dry weight): crude protein (8.7 to 17.2%), acid detergent fiber (24.1 to 33.6%) and neutral detergent fiber (33.2 to 48.9%), in vitro dry matter digestibility (69.2 to 78.6%), and relative feed value (120 to 196). Plate meter readings and plant height were each correlated to biomass in one season but not both. Because of its relatively high forage quality and low grain yields, harvesting any of the soybean cultivars for forage during mid-season would have been more profitable than harvesting for grain, given the hay and grain market prices when the experiments were conducted.

Crop ScienceVolume 44, Issue 3 p. 1023-1024 Registration of Cultivar Registration of 'Armadillo' Burr Medic W.R. Ocumpaugh, Corresponding Author W.R. Ocumpaugh [email protected] Texas A&M Univ. Agr. Res. Stn., Beeville, TX, 78102Corresponding author ([email protected])Search for more papers by this authorM.A. Hussey, M.A. Hussey Soil and Crop Sci. Dep., TAMU, College StationSearch for more papers by this authorW.J. Grichar, W.J. Grichar Texas A&M Univ. Agr. Res. Stn., BeevilleSearch for more papers by this authorJ.C. Read, J.C. Read Texas Agr. Exp. Stn., DallasSearch for more papers by this authorD.H. Bade, D.H. Bade Texas Coop. Ext., College StationSearch for more papers by this authorW.E. Pinchak, W.E. Pinchak Texas Agr. Exp. Stn., VernonSearch for more papers by this authorG.R. Smith, G.R. Smith Texas Agr. Exp. Stn., OvertonSearch for more papers by this authorR.A. Lane, R.A. Lane Sam Houston State Univ., Huntsville, TXSearch for more papers by this authorW.D. Pitman, W.D. Pitman LSU-Rosepine, LASearch for more papers by this authorJ.P. Muir, J.P. Muir Texas Agr. Exp. Stn., StephenvilleSearch for more papers by this authorS.W. Coleman, S.W. Coleman USDA-ARS, Brooksville, FLSearch for more papers by this author W.R. Ocumpaugh, Corresponding Author W.R. Ocumpaugh [email protected] Texas A&M Univ. Agr. Res. Stn., Beeville, TX, 78102Corresponding author ([email protected])Search for more papers by this authorM.A. Hussey, M.A. Hussey Soil and Crop Sci. Dep., TAMU, College StationSearch for more papers by this authorW.J. Grichar, W.J. Grichar Texas A&M Univ. Agr. Res. Stn., BeevilleSearch for more papers by this authorJ.C. Read, J.C. Read Texas Agr. Exp. Stn., DallasSearch for more papers by this authorD.H. Bade, D.H. Bade Texas Coop. Ext., College StationSearch for more papers by this authorW.E. Pinchak, W.E. Pinchak Texas Agr. Exp. Stn., VernonSearch for more papers by this authorG.R. Smith, G.R. Smith Texas Agr. Exp. Stn., OvertonSearch for more papers by this authorR.A. Lane, R.A. Lane Sam Houston State Univ., Huntsville, TXSearch for more papers by this authorW.D. Pitman, W.D. Pitman LSU-Rosepine, LASearch for more papers by this authorJ.P. Muir, J.P. Muir Texas Agr. Exp. Stn., StephenvilleSearch for more papers by this authorS.W. Coleman, S.W. Coleman USDA-ARS, Brooksville, FLSearch for more papers by this author First published: 01 May 2004 https://doi.org/10.2135/cropsci2004.1023Citations: 6 Registration by CSSA. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat References 1 Anonymous. 1956. Cogwheel bur clover. Texas Agric. Exp. Stn. L-285. Google Scholar 2Muir, J.P., Seeding rate and phosphorus fertilization effects on 'Armadillo' burr medic establishment. Agron. J. (2001) 93, 1269–1275 http://doi.org/10.2134/agronj2001.1269, 10.2134/agronj2001.1269 Google Scholar 3Ocumpaugh, W.R., M.A. Hussey, J.N. Rahmes, W.J. Grichar, Jr., D.C. Sestak, and R. Smith. 1997. Burr medic—A persistent cool-season legume for Texas. p. 59–63. In Proc. American Forage and Grassland Council, Georgetown, TX. Google Scholar 4Ocumpaugh, W.R., Coastal bermudagrass-legume mixtures vs. nitrogen fertilizer for grazing in a semiarid environment. J. Prod. Agric. (1990) 3, 371–376 10.2134/jpa1990.0371 Google Scholar 5Smith, G.R., Screening subterranean clover for persistent hard seed. Crop Sci. (1988) 28, 998–1000 http://doi.org/10.2135/cropsci1988.0011183X002800060027x, 10.2135/cropsci1988.0011183X002800060027x Google Scholar Citing Literature Volume44, Issue3May–June 2004Pages 1023-1024 ReferencesRelatedInformation

The literature on host plant resistance to insects and mites for both cool- and warm-season turfgrass is reviewed. Resistance to many insect and mite pests has been identified in most of the warm-season turfgrasses but reports of cool-season resistance are less extensive. Several successful turfgrass genetic improvement programs involve the combined efforts of plant breeders, entomologists and scientists in other complementary disciplines to develop improved cultivars with biotic and abiotic stress resistance. Turfgrass cultivars with multiple pest resistance, when deployed, help to alleviate the need for pesticides and indirectly reduce potential environmental contamination associated with their usage.

Black medic ( Medicago lupulina L.) has become naturalized in south-central USA where, in semiarid climates, it acts as a cool-season annual. Cultivation for wildlife and livestock forage and seed has not been fully realized as cultivars adapted to warm and dry climates have not been developed. This study evaluated forage yields and nutritive value of black medic accessions collected in Texas. March, April, and May forage yield, acid detergent fiber (ADF), acid detergent lignin (ADL), N, and P concentrations of 11 black medic accessions collected in Texas were compared with cultivar George at Stephenville, TX, during establishment and first self-reseeding years. Entries exhibited no frost damage and insignificant insect damage, but some Texas accessions were more vigorous in February and flowered earlier than other Texas accessions and George. Some Texas accessions were also more productive ( P < 0.01) than others as well as George. Forage yields among entries ranged from 0.6 to 1.5 Mg ha −1 yr −1 when averaged over years and harvest months. Harvest month affected all entry yields equally and peaked at 2.3 Mg forage ha −1 yr −1 during May of the first season but declined in the second, self-reseeding year despite greater rainfall. March ADF, ADL, N, and P concentrations tended to be lower than those of later harvests while the higher-yielding accessions also tended to have greater ADF and ADL concentrations. The results indicate that forage yield and nutritive value of naturalized black medic germplasm from Texas is variable and that a blend from the southern Great Plains should be developed.

Regulatory mandates have increased demand for best management practices (BMPs) that will reduce nutrient loading on watersheds impaired by excess manure P and N. Export of manure P and N in turfgrass sod harvests is one BMP under consideration. This study quantified amounts and percentages of P and N removed in a sod harvest for different rates of manure and inorganic P and N. Six treatments comprised an unfertilized control, two manure rates with and without supplemental inorganic N, and inorganic P and N only. The treatments were applied to 'Tifway' bermudagrass (Cynodon dactylon L. x C. transvaalensis Burtt-Davey), '609' buffalograss [Buchloe dactyloides (Nutt.) Engelm.], and 'Reveille' bluegrass (Poa arachnifera Torr. x P. pratensis L.) under field conditions. Comparisons among treatments revealed small variations of P and N content in clippings and the plant component of sod, but large variations in the soil component of sod for each turf species. In addition, 2 to 10 times more P and 1.3 to 5 times more N was removed in soil than in plant components of sod for the two manure rates with and without added inorganic N. Percentages of applied P and N in harvested sod were similar for the two manure rates with and without added N for each species, but differed among turf species for each P (46 to 77%) and N (36 to 47%). The large amounts and percentages of manure P and N removed by sod harvest support the feasibility of this BMP in efforts to reduce nutrient loads on watersheds.

ABSTRACTGovernment regulations to force water conservation have escalated the use of secondary water high in soluble salts for turfgrass irrigation in the arid and semiarid western USA, thus increasing the need for more salt‐tolerant turfgrasses. This study was initiated to determine the variability in salt tolerance within and among two Poa species and their hybrids. Two experiments were conducted during 2000 in the greenhouse at Fort Collins, CO, in solution culture to examine the effects of NaCl on leaf firing and shoot and root growth reduction of nine Kentucky bluegrass (KBG; Poa pratensis L.) cultivars representing three ecotypes, three Texas bluegrass (TBG; P. arachnifera Torr.) accessions, and five of their hybrids (P. pratensis × P arachnifera). In Exp. I, conducted during late winter through spring 2000, overall salt tolerance based on leaf firing and electrical conductivity (EC) of 50% shoot growth reduction (ECshoot 50) placed seven KBG cultivars in the most tolerant group. In Exp. II, conducted during summer though early fall 2000, overall salt tolerance rankings placed 4 KBG and 3 TBG cultivars in the most tolerant group. On the basis of percentage leaf firing and the salinity levels that caused 25 and 50% shoot growth reduction, compact (low, compact growth habit) and aggressive (aggressive, lateral growth habit) KBG ecotypes showed more salt tolerance than common ecotypes in both Exp. I and II. A broad range of variability in leaf firing and shoot and root growth reduction in response to salinity was found to exist within and among these Poa species and their hybrids, indicating that improvement in the salt tolerance of bluegrasses may be possible. Additionally, differences in salt tolerance of KBG and TBG between Exp. I and Exp. II suggested that environmental conditions could affect bluegrass salt tolerance expression.

Quantification of effects from factors known to modify vegetative development and growth in grasses is important in modeling biomass yield. The objective of this study was to measure the effects of increasing levels of N on leaf appearance (LAR) and lamina extension rates (LER) in switchgrass (Panicum virgatum L.) under field and controlled environmental conditions. Five nitrogen (N) fertilizer rates (0 to 268 kg N ha(-1)) were applied to a stand of "Alamo" switchgrass at Dallas, TX, and to potted plants (0 to 400 ppm) in a controlled environment. Quadratic regression models best described these responses to increasing rates of fertilizer N in both the field and controlled environment. In the field, LAR(-1) decreased to a minimum of 241 growing degree days (GDD) leaf(-1) at 163 kg Nha(-1) and LER increased to a maximum of 0.188 cm GDD(-1) at 164 kg Nha(-1). In the controlled environment, LAR(-1) decreased to a minimum of 155 GDD leaf(-1) at 90 ppm N and LER increased to a maximum of 0.272 cm GDD(-1) at 156 ppm N. Results demonstrate that LAR and LER are significantly affected by fertilizer N. Lamina extension rate responded to increasing levels of N in a manner typical of a classic yield response curve and was strongly correlated to plot yields, confirming its value as a potential indicator of yield.

Texas bluegrass Poa arachnifera Torr ., is a vigorous sod-forming perennial, dioecious grass, tolerant to heat. It is native to the Southern Great Plains. Genetic relationships existing among 28 Texas bluegrass genotypes were investigated using amplified fragment length polymorphism (AFLP) and randomly amplified polymorphic DNA (RAPD). A total of 3756 AFLP markers were generated on the 28 genotypes of Texas bluegrass. A wide range of polymorphism (23.08–85.33%) was observed among primer combinations with a mean of 64.11%. Among 441 RAPDs assayed, 335 were polymorphic with a mean polymorphic rate of 73.71%. Unweighted pair-group method using an arithmetic average (UPGMA) cluster analysis using AFLP and RAPD data separated the 28 Texas bluegrass accessions into two broad groups. With a few exceptions, the females clustered with females and males with males. These results indicate that, it may be possible to discriminate between males and females using molecular markers. Principal coordinate analysis of AFLP and RAPD data also indicated two distinct groups and revealed genetic variability among and within the groups. Based on their genetic similarity indices, high correlation was observed between AFLP and RAPD markers.

Texas bluegrass (Poa arachnifera Torr.) has shown potential for use as a cool-season perennial pasture grass in the southern Great Plains, where it occurs as a natural component of rangeland plant communities, and into the western Coastal Plain. Responsiveness of this grass to nitrogen (N) fertilization appeared to be limited to the spring growing period in initial evaluations in Louisiana. A field plot experiment was conducted to assess forage production and quality responses to season of N fertilization on the Syn-1 population of Texas bluegrass. Winter forage production responses to 50 kg N ha(-1) were obtained in the 1997-98 growing season but not in 1998-99 after stands had been depleted by summer drought. Greatest yield increases resulted from spring N application, however, fall plus winter fertilization provided the most uniform distribution of forage through the cool season. Forage fiber fractions, in vitro digestibility, and crude protein were not affected by N fertilization. Both amount and distribution of Texas bluegrass forage, but not forage quality, can be manipulated by time of N fertilization.

Switchgrass (Panicum virgatum L.) is a warm-season perennial grass indigenous to North America with excellent potential as a bioenergy crop. Our objective was to determine the yield potential and adaptability of switchgrass cultivars and germplasms in diverse Texas environments where the species might be used as a bioenergy crop. We determined the adaptability of several switchgrass cultivars and germplasms at five ecologically different locations (Beeville, College Station, Dallas, Stephenville, and Temple) in Texas in two experiments during 1992 to 1996. Alamo switchgrass was the best adapted commercially available switchgrass cultivar for biomass feedstock production in Texas in these trials with yields of 8 to 20 Mg ha−1. A single harvest in the fall maximized biomass yield and maintained switchgrass stands. Although very tolerant of moderate or even severe drought, switchgrass failed to yield under chronic extreme drought. At Beeville in 1996, there was no harvestable switchgrass growth because of extreme drought. Upland cultivars from the midwest matured early and did not produce as much biomass as lowland cultivars from the southern U.S. The predominant factor affecting switchgrass productivity in these Texas locations seemed to be rainfall amount. The highest biomass yield at each location generally occurred in years of greatest April to September rainfall. Soil type did not appear to have much influence on biomass production. Soil organic carbon increased from 11.1 to 15. 8 g kg−1 in the upper 30 cm of soil (average of four locations) during 1992 to 1996. These increases in organic carbon indicate a good potential for sequestering carbon through biomass production.

Crop ScienceVolume 39, Issue 2 cropsci1999.0011183X003900020059x p. 590-590 Registration of Cultivars Registration of ‘Reveille’ Hybrid Bluegrass J. C. Read, Corresponding Author J. C. Read [email protected] Texas A&M Univ. Res. & Ext. Ctr. (TAES), 17360 Coit Rd., Dallas, TX, 75252-6599Corresponding author ([email protected]).Search for more papers by this authorJ. A. Reinert, J. A. Reinert Texas A&M Univ. Res. & Ext. Ctr. (TAES), 17360 Coit Rd., Dallas, TX, 75252-6599Search for more papers by this authorP. F. Colbaugh, P. F. Colbaugh Texas A&M Univ. Res. & Ext. Ctr. (TAES), 17360 Coit Rd., Dallas, TX, 75252-6599Search for more papers by this authorW. E. Knoop, W. E. Knoop Texas A&M Univ. Res. & Ext. Ctr. (TAES), 17360 Coit Rd., Dallas, TX, 75252-6599Search for more papers by this author J. C. Read, Corresponding Author J. C. Read [email protected] Texas A&M Univ. Res. & Ext. Ctr. (TAES), 17360 Coit Rd., Dallas, TX, 75252-6599Corresponding author ([email protected]).Search for more papers by this authorJ. A. Reinert, J. A. Reinert Texas A&M Univ. Res. & Ext. Ctr. (TAES), 17360 Coit Rd., Dallas, TX, 75252-6599Search for more papers by this authorP. F. Colbaugh, P. F. Colbaugh Texas A&M Univ. Res. & Ext. Ctr. (TAES), 17360 Coit Rd., Dallas, TX, 75252-6599Search for more papers by this authorW. E. Knoop, W. E. Knoop Texas A&M Univ. Res. & Ext. Ctr. (TAES), 17360 Coit Rd., Dallas, TX, 75252-6599Search for more papers by this author First published: 01 March 1999 https://doi.org/10.2135/cropsci1999.0011183X003900020059xCitations: 30AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume39, Issue2March–April 1999Pages 590-590 RelatedInformation