Cover crop forage potential and subsequent sorghum silage yield and nutritive value

Abstract

Achieving high forage production—quantity and quality—could be challenging, specifically in water-limited areas. Intensifying cropping systems with cover crops can provide agronomic and ecosystem service benefits. However, the impacts of cover crops on forage production have not been well studied. This study evaluated the effects of cover crops (grasses + brassicas + legumes [GBL], grasses + brassicas [GB], grasses + legumes [GL], and no cover crop [NCC] control) on sorghum silage [Sorghum bicolor (L.) Moench] yield and nutritive value over 3 years in a semiarid irrigated condition. Cover crops produced 2.1–6.0 Mg ha−1 of annual average harvestable biomass with similar forage nutritive value among treatments. In 2018–2019, sorghum silage yield was 38%–43% greater with all cover crops than with NCC. However, in 2019–2020, only GB had a 23% greater sorghum silage yield than NCC. The neutral detergent fiber content in sorghum silage was 4.8%–5.1% greater with all cover crops, and crude protein was 3%–8% lower with GL and GBL compared to NCC. Therefore, total digestible nutrients, relative forage quality, and milk production potential of sorghum silage were 5%–8%, 11%–19%, and 8%–16% greater, respectively, with NCC than with cover crops. This study demonstrates that replacing fallow with winter cover crops in irrigated silage production systems could provide good quality forage from cover crops without a decrease in subsequent sorghum silage yield. Sorghum silage quality slightly decreased with cover cropping. Nevertheless, cover crop integrated systems could be an alternative for farmers facing declining water availability for irrigated crop production.