Increasing yield and mitigating environmental emissions by applying suitable magnesium fertilizer in forage production

The scarcity of high-quality forage remains a major constraint to sustainable ruminant production in China. The effectiveness of different magnesium fertilizers under varying soil conditions has not been fully investigated in forage production. This study evaluated the agronomic and environmental effects of rapid-release fertilizer of kieserite (MgSO4·H2O), slow-release fertilizer of calcined magnesite (MgO) and Mg blended formulations (kieserite:MgO 1:1, K1M1; and kieserite:MgO 2:1, K2M1) on forage yield, Mg release dynamics and leaching characteristics in strongly acidic Mg-deficient soils, slightly acidic Mg-moderate soils and alkaline Mg-enriched soils. This investigation was conducted as pot experiments, soil incubation trials and soil column leaching simulations. Mg fertilizer application increased forage yield by 41%–946% and Mg uptake by 22%–5407% than the CK, with the most substantial improvements occurring in strongly acidic Mg-deficient soils. Mg blended formulations had relatively better performance in forage production than kieserite or MgO. These have characteristics of solubility in water, release, and leaching for various Mg fertilizers. Kieserite has a rapid release rate and the highest exchangeable Mg2+ accumulation, simultaneously with the highest leaching rate (16%–30%). In contrast, MgO has a slow-release rate and the lowest leaching rate (–2.4% to 3.8%). K1M1 and K2M1 have moderate release rate to support forage growth, a low magnesium leaching rate and mitigate soil acidification in acidic soils. Also, Mg application reduced greenhouse gas emissions per unit of forage by 14%–90%. Optimized Mg fertilizer application has the potential to increase annual perennial ryegrass production by 4.64 Tg in China. This research provides a scientific foundation for optimizing Mg fertilizer types for forage production in various soils to achieve green agricultural development.