Introducing grazeable cover crops to the winter wheat systems in Oklahoma

Abstract

Fields are typically kept fallow after winter wheat (Triticum aestivum L.) grain harvest in the U.S. southern Great Plains (SGP). Introducing summer cover crops to the system could increase soil conservation and farm profitability if grazed. The objective of this research was to evaluate cover crops' forage yield, residue cover potential, weed suppression, and effect on wheat production. Monocultures and grass-legume mixtures of cover crops were established in mid-June of 2016 and 2017 near Chickasha and Perkins, OK. At 6 weeks after planting (WAP), three cutting regimes based on stubble height were used: severe (2.5 cm), recommended (legumes: 7.5 cm, grasses and mixtures: 15 cm), and no cutting. Cover crops regrowth was chemically terminated at 14 WAP; winter wheat was no-till seeded in mid-October; then harvested in early-June 2017 and 2018. Cultivar Triple Treat sorghum−sudangrass [Sorghum bicolor (L.) Moench × S. bicolor var. sudanese] and grass−legume mixtures showed the greatest available forage dry matter. Grasses and grass−legume mixtures had greater forage dry matter residue and weed suppression than legumes. Results indicated that exceeding 6.4 ± 1.2 Mg ha −1 of total dry matter (TDM) produced during the summer, a wheat grain yield penalty of −50.1 ± 15.8 kg ha −1 resulted for each increment of 1.0 Mg ha −1 of TDM produced. Also, a wheat protein content penalty of −1.9 ± 0.5 kg ha −1 resulted in each increment of 1.0 Mg ha −1 of TDM produced when exceeding to 5.7 ± 1.0 Mg ha −1 TDM threshold. Findings suggest N uptake by high-biomass grasses and mixtures might result in deficient water and N availability for wheat production.

Evaluating cover crops forage nutritive value in Oklahoma winter wheat systems

“…Conversely, PM+MB mixture had no N-deficient pearl millet plants in Perkins, 2016(Horn et al, 2020. This superior CP concentration in Perkins' PM+MB mixture reinforced Horn et al (2020) assumption that N fixation by mung beans enhanced soil N availability for pearl millet development in N-deficient soils (like Perkins). Other studies also reported that planting legumes with pearl millet improved grass crop development in N-limiting environments in Africa (Gbèhounou & Adango, 2003;Aliyu & Emechebe, 2006).…”

“…However, in Perkins, solely planted pearl millet exhibited N-deficiency symptoms, including plant stunting and yellow leaves. Conversely, PM+MB mixture had no N-deficient pearl millet plants in Perkins, 2016(Horn et al, 2020. This superior CP concentration in Perkins' PM+MB mixture reinforced Horn et al (2020) assumption that N fixation by mung beans enhanced soil N availability for pearl millet development in N-deficient soils (like Perkins).…”

“…However, a slightly higher mung bean incidence (12.3%) in PM+MB conferred 63% higher forage yields (Horn et al., 2020) and 20% higher CP concentration than in solely planted pearl millet in Perkins, 2016. The Perkins site had limited soil N content, while the Chickasha site had sufficient soil N content for pearl millet growth (Horn et al., 2020). Thus, pearl millet outcompeted weeds and mung bean in Chickasha.…”

“…However, in Perkins, solely planted pearl millet exhibited N‐deficiency symptoms, including plant stunting and yellow leaves. Conversely, PM+MB mixture had no N‐deficient pearl millet plants in Perkins, 2016 (Horn et al., 2020). This superior CP concentration in Perkins’ PM+MB mixture reinforced Horn et al.…”

“…Details of the sites, establishment, and management of cover crops were presented by Horn et al. (2020). As an overview, both sites had been cropped with winter wheat the previous year.…”