Low nutritive value of perennial warm‐season grasses often causes limitation to stocker cattle production in the U.S. southern Great Plains (SGP). Exploration of novel legumes capable of generating nutritious summer forage is required to fill forage deficit periods. This 2‐yr field experiment compared the seasonal changes in forage biomass, leaf/stem ratio, and chemical composition of three varieties each of tepary bean [Phaseolus acutifolius (A.) Gray] and guar [Cyamopsis tetragonoloba (L.) Taub.] to soybean [Glycine max (L.) Merr.]. Tepary bean cultivar Black outperformed soybean and guar varieties by producing 18–48% greater aboveground dry matter (ADM) amounts (6537 kg ha⁻¹) with a leaf/stem ratio of 3.1 at 65 days after planting (DAP). The ADM and leaf nutritive value of soybean were not surpassed by the other five tested legumes, but had the least digestible stems with an in vitro true digestibility (IVTD) of 529–581 g kg⁻¹ in both years. Guar varieties maintained a lower leaf/stem ratio (1.3–1.5 kg kg⁻¹) throughout the growing season, which could limit its value for grazing compared to other legumes. We concluded tepary bean could serve as an alternate forage option to soybean for producers in the SGP. Tepary bean possessed the greatest capabilities for producing adequate biomass yields with superior and consistent nutritive value when grown as a summer forage. Future research should focus on defining management practices for growing tepary bean in extensive production settings for grazing or hay.

中文翻译：

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大平原南部的三生豆和瓜尔豆的夏季觅食能力

多年生暖季草的营养价值低，通常会限制美国南部大平原（SGP）的牲畜饲养量。为了填补草料短缺时期，需要探索能够产生营养夏季草料的新型豆类。这项为期2年的田间试验比较了三生豆（菜豆（Phaseolus acutifolius（A.）Grey）和瓜尔豆（Cyamopsis tetragonoloba（L.）Taub ）的三个品种的牧草生物量，叶/茎比和化学组成的季节性变化。大豆[ Glycine max（L.）Merr。]。三元豆栽培品种黑土的表现优于大豆和瓜尔豆品种，产生的地上干物质（ADM）量（6537 kg ha ^-1）增加了18–48％），在种植后65天时叶/茎比为3.1（DAP）。大豆的ADM和叶片营养价值没有被其他五种豆科植物超越，但其茎的可消化性最低，两年的体外真实消化率（IVTD）为529–581 g kg ^-1。瓜尔豆品种的叶/茎比保持较低（1.3–1.5 kg kg ^-1）在整个生长季节，与其他豆类相比，这可能会限制其放牧价值。我们认为小豆可以作为SGP生产者的大豆替代草料选择。当夏季饲草种植时，三生豆具有最大的能力来产生充足的生物量，并具有优异的营养价值。未来的研究应侧重于确定在广泛的放牧或干草生产环境中种植三元豆的管理方法。