Evaluating capabilities of novel warm-season crops to fill forage deficit periods in the Southern Great Plains
Abstract
Low nutritive value of perennial grasses during mid-late summer limits stocker cattle production in the Southern Great Plains (SGP). Our objectives were to explore annual crop species that might fit as a summer forage, and quantify their forage potentials under the highly variable agro-climatic conditions of the SGP. A field experiment compared the seasonal changes in aboveground dry matter (ADM), leaf-to-stem ratio, and chemical composition of tepary bean (Phaseolus acutifolius) and guar (Cyamopsis tetragonoloba) to soybean (Glycine max). Tepary bean outperformed soybean and guar by producing greater ADM (6.5 Mg ha-1) with a leaf-to-stem ratio of 3.1 at 65 days after planting (DAP), and its chemical composition also remained superior and consistent throughout the growing season. Secondly, ten mothbean (Vigna aconitifolia) lines were evaluated for their forage, grain or green manure potentials. Mothbean lines generated a ADM range of 7.3-18.1 Mg ha-1 with 10.8-14.6% crude protein (CP), 32.0-41.7% neutral detergent fiber (NDF), 20.7-29.6% acid detergent fiber (ADF), and 73-84% in vitro true digestibility (IVTD) at 100 DAP. Third, eleven finger millet (Eleusine coracana) accessions were assessed for their adaptability and forage characterization under the SGP conditions. Finger millet accessions resulted in ADM ranging from 5.0-12.3 Mg ha-1, which contained 10.5-15.6% CP, 59.8-73.4% NDF, 26.8-38.2% ADF, and 59.7-73.0% IVTD at 165 DAP. Finally, a greenhouse study was conducted to compare vegetative growth and physiological responses of mothbean, tepary and guar under four different water regimes. Tepary bean showed the lowest stomatal conductance (gs) and photosynthetic rate (A), but it maintained the highest instantaneous water use efficiency (WUEi) among species under water-stressed treatments. At final harvest (77 DAP), the ADM generated by tepary bean was 38-60% and 41-56% higher than guar and mothbean, respectively, across four water deficits. Tepary bean was identified as the most drought-tolerant and reliable option for SGP among the tested species, considering its higher biomass production, WUEi, leaf-to-stem ratio, and consistent nutritive value when grown as a summer forage. Future research should focus on defining management practices for growing these novel crops in extensive production settings for grazing or hay.
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- OSU Dissertations [11222]