William R Ocumpaugh

Switchgrass as a sustainable bioenergy crop

Switchgrass (Panicum virgatum L.) shows potential as a sustainable herbaceous energy crop from which a renewable source of transportation fuel and/or biomass-generated electricity could be derived. In 1992, a new research program focused on developing switchgrass as a biomass energy feedstock was initiated by the U.S. Department of Energy in five of the southern United States. The multifaceted, multi-institution research addresses breeding for improved biomass yields, regional field tests, cultural practices, physiology and tissue culture. Recent progress is highlighted in this paper. Preliminary results from the breeding program indicate that recurrent restricted phenotypic selection could lead to development of new cultivars. A technique for regenerating switchgrass plants via tissue culture has been proven and new populations of regenerated plants have been established in the field. Performance trials at three regional cultivar testing centers in Virginia, Alabama and Texas have shown that ‘Alamo’ switchgrass has higher biomass yield and broader adaptability than other cultivars tested. Research on management practices designed to maximize biomass yield has shown that multiple harvests of switchgrass may reduce total seasonal yields in some instances and that responses to fertilizer inputs vary with the environment. Seed dormancy often retards rapid establishment of competitive stands of switchgrass. Our research has indicated that seed dormancy can be modified, resulting in increased seed germination and a greater number of switchgrass plants. Research on the physiology of switchgrass has shown that lowland and upland ecotypes differ in photosynthetic rate but not in respiration rate. Findings in each of these areas can contribute to development of switchgrass as a sustainable bioenergy crop. Future research will address molecular biology techniques for exploiting genetic variation, explore canopy architecture and carbon allocation patterns affecting biomass yield, elucidate key factors in successful establishment of switchgrass and provide technology transfer that facilitates scale-up of switchgrass production for commercial energy production.

South Texas Natives: A Collaborative Regional Effort to Meet Restoration Needs in South Texas

South Texas Natives (STN) is an initiative started in 2001 to develop and promote native plants for the restoration and reclamation of public and private lands in south Texas. At the urging of concerned conservationists and private landowners, STN has developed commercially viable sources of native seed and conducted research to discover effective restoration strategies that can be used by private landowners and government agencies to restore native plant communities. STN grew out of a strong partnership among the USDA Natural Resources Conservation Service E “Kika” de la Garza Plant Materials Center, Texas AgriLife Research, Rio Farms Inc, Caesar Kleberg Wildlife Research Institute, and private landowners of south Texas. Plant development efforts center on the release of commercially viable, multiple origin germplasms selected with an awareness of the commercial requirements for production but grounded in genetic and ecosystem function parameters. In addition to plant development efforts, extensive restoration and revegetation research is conducted by STN to develop usable methodology and much-needed guidelines for restoration in south Texas. Current restoration research emphasis centers on providing techniques for the diversification of areas dominated by invasive exotic grasses.

Soil organic carbon pools under switchgrass grown as a bioenergy crop compared to other conventional crops.

Abstract 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.] 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 1900 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.

Plant growth and nutrient uptake characteristics of Fe-deficiency chlorosis susceptible and resistant subclovers

The objective of this study was to evaluate the growth and nutrient-uptake characteristics of Fe-deficiency resistant and susceptible subclover (Trifolium subterraneum L., T. yanninicum Katzn. and Morley, T. brachcalycinum Katzn. and Morley) cultivars on a calcareous soil. Ten subclover cultivars showing varying susceptibilities to Fe-deficiency chlorosis (Karridale, Nangeela, Geraldton, Mt. Barker, Woogenellup, Larisa, Trikkala, Rosedale, Koala and Clare) were grown on a low-Fe, calcareous soil (Petrocalcic Paleustoll) under moist (18% water content, 85% of water holding capacity) and water-saturated conditions using a Cone-tainer® culture system. Chlorosis and its correlation with growth traits and mineral nutrition of the 10 cultivars were examined. The Fe-deficiency susceptibilities of the 10 cultivars decreased in the above order under the moist condition, but in slightly different order under the saturated condition. Shoot and root dry weights, total dry weight, and root-to-shoot ratio were each negatively correlated with chlorosis under both soil-moisture conditions, as was total shoot content of P, Ca, Fe, Mn and Zn. Shoot P and Fe concentrations were each positively correlated with chlorosis under the moist soil condition. Iron and Cu utilization efficiencies (biomass per unit weight of nutrient) in the shoot were each negatively correlated with chlorosis under the moist soil condition. These results suggest that there may be several characteristics of Fe-deficiency chlorosis resistance in subclovers, such as a more effective soil-Fe mobilizing mechanism(s), more balanced nutrition, lower required Fe concentration in the shoot, higher shoot-Fe utilization efficiency, and higher root/shoot ratio under Fe-deficiency stress conditions.

Variation among Trifolium species for resistance to iron‐deficiency chlorosis

Abstract Little information is available regarding the amount of genetic variation among and within Trifolium species for resistance to iron (Fe)‐deficiency chlorosis. A calcareous Parrita sandy clay loam soil (clayey, mixed, hyperthermic, shallow Petrocalcic Paleustoll) that had a history of expression of Fe‐deficiency chlorosis problems in forage sorghum (Sorghum bicolor L. (Moench.)) was used to conduct field studies in 1985–86 and 1986–87. Cultivars of seven Trifolium spp.: arrowleaf (T. vesiculosum Savi.), berseem (T. alexandrinum L.), crimson (T. incarnatum L.), red (T. pratense L.), rose (T. hirtum All.), and subterranean (T. subterraneum L. and T. brachycalycinum Katzn. and Morley) clovers were compared for differences in dry matter production and expression of chlorosis symptoms. Cultivars could be ranked for their adaptability to calcareous soil conditions: ‘Bigbee’ berseem = ‘Kenstar’ red = ‘Kondinin’ rose = ‘Clare’ subterranean > ‘Dixie’ crimson >> ‘Mt. Barker’ subterranean > ‘Yuchi’ and ‘Meec...

Notice of Release of Catarina Blend Bristlegrass: Selected Class of Natural Germplasm

Four selected germplasms of bristlegrass (Setaria vulpiseta (Lam.) Roem. & Schult. and S. leucopila (Scribn. & Merr.) K. Schum. [Poaceae]) have been released for rangeland plantings and wildlife habitat enhancement plantings in the Rio Grande Plain of Texas. Catarina blend bristlegrass is a mix of 4 bristlegrass releases (Kika648 Germplasm, Kika819 Germplasm, Kika820 Germplasm, and Kika677 Germplasm) selected from an extensive evaluation at multiple sites in south Texas. Accessions included in the blend are increased in isolation and blended prior to sale in order to maintain the genetic integrity of each release. These germplasms represent the first commercially available release of bristlegrass that has been tested and is adapted to south Texas.

Notice of Release of Maverick Germplasm pink pappusgrass: selected class of natural germplasm

A selected germplasm of pink pappusgrass (Pappophorum bicolor Fourn. [Poaceae]) has been released for rangeland seeding, highway rights-of-way revegetation, and wildlife habitat restoration plantings in south Texas. Maverick Germplasm pink pappusgrass is a blend of 7 accessions selected from an evaluation at multiple sites in the intended area of use. Selections were made based on multi-year evaluation of plant characteristics and germination tests of seed collected from each location. Following selection, components of the germplasm were increased in isolation and blended following harvest to ensure seed was included from each of the selected accessions. Accessions included in the blend originate from 7 different counties and distinct soil types. This germplasm represents the first commercial release of pink pappusgrass, an important component of native rangeland plant communities in south Texas.

Notice of Release of La Salle Germplasm Arizona Cottontop Selected Class of Natural Germplasm

A selected germplasm of Arizona cottontop (Digitaria californica (Benth.) Henr. [Poaceae]) has been released for rangeland reseeding and wildlife habitat enhancement plantings in the Rio Grande Plain of Texas. La Salle Germplasm Arizona cottontop is a blend of 12 selected accessions from an extensive evaluation at multiple sites in southern Texas. The release comprises accessions that are increased from the original seed collections of native populations to maintain the genetic integrity of each accession. This germplasm represents the first commercially available release of Arizona cottontop that originates from the intended area of use.

Improving Germination in Windmillgrass Ecotypes

Abstract Hooded windmillgrass (Chloris cucullata Bisch.) and shortspike windmillgrass (C. subdolichostachya Muell.) are native perennial grasses with potential for planting on highly erodible sites and on sites where introduced species are not desired. However, in both species, seeds are dormant resulting in poor germination. The objectives of this study were to evaluate effects of lemma and palea removal and caryopsis scarification on seed germination of 8 outstanding ecotypes selected in previous studies for survival and growth characteristics. Seed treatments were 1) whole seed, 2) naked caryopsis, 3) scarified naked caryopsis (30 s), 4) scarified naked caryopsis (50 s), and 5) scarified naked caryopsis (60 s). Germination conditions were 12 h dark 20°C and 12 h light 30°C. Seed lot viability varied from 55% to 62% for shortspike windmillgrass ecotypes and from 71% to 78% for hooded windmillgrass ecotypes. Initial germination index (MIR10) of naked caryopsis for shortspike windmillgrass ecotypes ranged from 16.3 to 21.6, compared to range from 0.2 to 0.6 to whole seed; whereas hooded windmillgrass ecotypes MIR10 ranged from 30.6 to 33.0 to naked caryopsis, compared to range from 5.8 to 8.0 to whole seed. The greatest total germination (P < 0.05) was obtained with naked caryopsis for all ecotypes and the scarification treatments did not have a positive effect on this parameter. As scarification time increased the total germination decreased. Lemma and palea removal improved (P < 0.05) total germination for all studied ecotypes.

A greenhouse technique for screening Trifolium seedlings for iron‐deficiency chlorosis 1

Abstract Susceptible Trifolium plants often exhibit symptoms of iron (Fe)‐deficiency chlorosis when grown on high pH, calcareous soils. A greenhouse method was developed to screen seedlings for Fe‐deficiency chlorosis. ‘Yuchi’ arrowleaf (T. vesiculosum Savi.) and ‘Dixie’ crimson (I. incarnatum L.) clover seedlings were grown in “Super Cell”; Cone‐tainers in six calcareous Texas soils differing in Fe and selected other chemical characteristics. At the fourth trifoliolate leaf stage, chlorosis was induced by saturating the soil for a minimum of 2 weeks. The soils differed in their capacity to induce chlorosis in both clovers. Yuchi was more susceptible than Dixie, showing a higher percentage of chlorosis in five of the six soils. The results indicate that this screening method would be a useful tool for studying Fe‐deficiency chlorosis in Trifolium spp.