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Title: Biomass production and quality of indian-origin forage Guar in Southern Great Plains

item Rao, Srinivas
item Northup, Brian

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2012
Publication Date: 7/2/2013
Citation: Rao, S.C., Northup, B.K. 2013. Biomass production and quality of indian-origin forage Guar in Southern Great Plains. Agronomy Journal. 105:945-950.

Interpretive Summary: Yearling stocker cattle are a key part of agriculture in the southern Great Plains (SGP), where they graze different forages to gain weight before entering feedlots for finishing. Stockers grazing warm season grasses during late summer have available forages with low protein contents, which limits their growth, so they require protein supplements to improve weight gains. The commercial protein supplements that have been traditionally used can cost three to four times the value of farm-grown supplements. There is a need to explore legumes not normally grown in the SGP that could serve as protein supplements for grazing cattle. Guar is one warm-season annual multi-purpose legume that could serve as high-protein forage. It is grown in semi-arid regions of the world, and is used in India as a vegetable, grain, forage, and cover crop. In the U.S., guar but has largely been used as a grain crop, and no forage cultivars exist for the southern Plains. We conducted a study to describe the seasonal patterns of biomass production, and quality of forage and grain, of 3 Indian-origin lines of forage guar, and compared responses to the locally used cultivar “Kinman”. Our results showed the Indian-origin lines produced less forage and grain than the locally used cultivar. The amount and quality of guar forage and grain was affected more by year and time of year than by plant genetics. These responses were most likely related to the total amount (and timing) of rainfall received during the growing seasons of the study. Additional plant breeding will be needed to develop reliable and productive forage cultivars of guar for the SGP.

Technical Abstract: Guar [Cyamopsis tetragonoloba (L.) Taub.] is a warm-season annual pulse grown in semi-arid regions of the world as a multi-purpose vegetable, forage, cover or fodder crop. Guar could provide late summer forage in the southern Great Plains (SGP), but has largely been used as a grain crop, and no functional forage cultivars exist for the region. We evaluated seasonal forage production and grain yield of 3 Indian-origin lines of forage guar in Oklahoma during 2009-2011. Three replicate sets of 4 plots (3x10 m) were disked, fertilized (26 kg P/ha), and sown (25 kg seed/ha; 60 cm rows; late-May to early-June) with Bundel 1, Bundel 2, and Bundel 3 forage lines, or the grain cultivar Kinman (control). Aboveground biomass was sampled at early and late vegetative stages, and physiological maturity (grain set). Samples collected at maturity were separated into grain, chaff, and non-grain vegetative biomass. Nitrogen (N) and in vitro digestible dry matter (IVDDM) concentrations were determined on all biomass components. Data were analyzed using mixed models with guar lines and growth stage as main effects, and years as a longitudinal (repeated) element. The Indian-origin lines produced significantly less (p<0.05) forage, grain and chaff biomass than the locally adapted cultivar (Kinman). Growing seasons and time within growing seasons had significant (p<0.05) overall effects on biomass produced, N and IVDDM concentrations of forage, chaff, and grain. The lower levels of biomass produced by the experimental Indian lines indicate additional genetic selection will be required to produce forage-type cultivars that are reliable and productive in the variable environments of the SGP.