|Zobeck, Teddy - Ted|
Submitted to: Trade Journal Publication
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/29/2011
Publication Date: 8/8/2011
Citation: Zobeck, T.M., Allen, V.G., Cox, J.J., Philipp, D. 2011. Variation of soil and plant characteristics among old world bluestem species. Agricultural Sciences. 2(3): 347-356. Interpretive Summary: Old world bluestems (Bothriochloa spp.) have been successfully introduced as grasses for livestock forage in the semiarid Texas High Plains. However, questions remain on effects of these grasses on soils. In this study we evaluate how three different species of old world bluestem (Caucasian, WW Spar, and WW-B Dahl) affect soil properties. We measured the soil texture, the ability of the soils to hold together during rainfall, the soil density, soil strength, soil root content, and types of carbon and nitrogen. The grasses differed in the amount of above-ground plant mass and below-ground root mass. The Caucasian and WW-B Dahl had about twice the above-ground plant mass with about one-quarter fewer roots than WW Spar. Soil where Caucasian was grown had the highest density and WW Spar had the lowest density. The greater root mass of WW Spar produced a lower soil density. However, although the WW Spar had the lower density, it had the highest soil strength, greatest root mass, organic matter content, and had the greatest ability to withstand rainfall without breaking apart. WW-B Dahl often had soil properties that were similar to both other species. WW_B Dahl has been shown to be higher in forage quality, animal performance, and carrying capacity than WW Spar and is perhaps the best choice among these three species to optimize both animal performance and desirable soil properties.
Technical Abstract: Old world bluestems (Bothriochloa spp.) have been successfully introduced as grasses for livestock forage in the semiarid Texas High Plains. Questions remain, however, on effects of these grasses on soil resources. We tested the hypothesis that differences in grass species produce differences in soil properties important to crop growth and useful in selecting the optimum species for the Southern High Plains of Texas. Three old world bluestem (Bothriochloa) species [C.E. Hubbard ‘Caucasian’, B. caucasica (Trin.); ‘WW Spar’, B. ischaemum (L.) Keng.var ischaemum (Hack.); and S.T. Blake ‘WW-B Dahl’, B. bladhii (Retz)] were grown in a randomized complete block design, with three replications, for nine years on a clay loam soil near Lubbock, Texas. Soil samples were collected in the ninth year to determine soil texture, wet aggregate stability, bulk density (BD), soil organic carbon (SOC), particulate organic carbon (POC), and soil strength as measured by the cone pentrometer. The grass species differed in their above-ground biomass and below-ground root production. In the ninth year of production, Bothriochloa caucasica and B. bladhii produced about twice the above-ground biomass with about 25 % fewer roots than B. ischaemum. Soils where B. caucasica was grown had the highest BD (1.36 Mg m-3) and B. ischaemum had the lowest (1.31 Mg m-3). The soil in which B. ischaemum was growing had a lower BD, greatest root biomass, organic matter content, and aggregate stability suggesting superior soil quality for agricultural production. The species B. bladhii, however, often exhibited soil properties that were similar to both other species tested. Since Bothriochloa bladhii had superior or similar soil properties for plant growth among the species tested and has been shown to be higher in forage quality, animal performance, and carrying capacity than the other species, it appears to be the best choice among these three species to optimize both animal performance and desirable soil properties.