Weed dynamics, silage yield and nutritive value of spring maize under different maize-based crop rotations

The growth of the livestock industry in the northwestern Indo-Gangetic plains is constrained by a persistent deficit in the sustainable supply of high-quality fodder. Silage production offers a viable solution to this challenge, with maize (Zea mays L.) being an ideal crop due to its rapid growth and high palatable biomass. However, weed competition and silage yield of spring maize (sown in February) can vary across different crop rotations. To identify a suitable crop rotation that minimizes crop–weed competition in subtropical conditions, the performance of spring maize was evaluated under both weedy and herbicide-treated (atrazine at 0.892 lb acre⁻¹) conditions across three crop rotations: summer maize–oat (Avena sativa L.)–spring maize (M-O-SpM), summer maize–turnip rape (Brassica rapa ssp. oleifera)–spring maize (M-T-SpM), and summer maize–rapeseed (Brassica napus L.)–spring maize (M-RS-SpM) during 2020–2021 and 2021–2022. In these rotations, summer maize was cultivated for grain, while spring maize was grown for silage production following the harvest of the respective winter crops. Among the rotations, M-RS-SpM exhibited greater weed competition in spring maize compared to M-T-SpM and M-O-SpM rotations. Under herbicide-treated conditions, spring maize silage yield was 23.4% and 21.9% higher in M-T-SpM and M-O-SpM, respectively, than in M-RS-SpM. Additionally, silage quality, assessed in terms of nutritive value, fermentation characteristics and digestibility, was superior in M-T-SpM and M-O-SpM rotations. These rotations also recorded 6.2%–6.9% higher maize equivalent yield and11.2%–14.4% greater net returns under herbicide-treated conditions. Therefore, the maize–turnip rape–spring maize and maize–oat–spring maize rotations, when combined with chemical weed control in spring maize, are recommended for enhancing silage productivity and profitability in dairy farming systems of north-western India.