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.

As an essential mineral element for plant growth, Magnesium (Mg) is involved in photosynthesis and influences nutrient availability in soil. However, its impact on Phosphorus (P) availability in apple rhizosphere soil and the underlying microbial regulatory mechanism remain unclear. To investigate whether and how Mg enhances soil P availability, this study integrated metagenomics and bioinformatics to assess the effects of Mg on apple plant growth, P accumulation, P availability, microbial community, and phosphorus-cycling genes (PCGs). The results show that Mg significantly increased soil P availability, particularly the labile and moderately labile Pi fractions. Mg-treated groups showed higher diversity and richness of P-cycling microorganisms and distinct microbial community structures. Metagenomic sequencing revealed a greater enrichment of functional genes involved in organic P mineralization (phoD and opd), inorganic P solubilization (gcd), and P transport and regulation (ugpABCE) in Mg-treated groups. Significant positive correlations were observed between soil labile P, moderately labile P, and the abundance of PCGs, as well as between soil exchangeable Mg and P-cycling pathways. These findings suggest that Mg enhances P availability by modulating the P-cycling microbial community. Thus, this study proposes that Mg can serve as a rhizosphere prebiotic to reduce the use of phosphate fertilizer in apple production.

Nitrogen (N) and magnesium (Mg) deficiencies involve distinct underlying damage mechanisms and recovery responses. In this study, the physiological and biochemical responses of hydroponically grown cucumber plants to N or Mg deficiency and their recovery after nutrient resupply were evaluated. Considering that these deficiencies induce oxidative stress, we evaluated alterations in the antioxidant system and the accumulation of hydrogen peroxide (H₂O₂). The results revealed that both N deficiency and Mg deficiency inhibited cucumber growth and biomass production, with more pronounced adverse effects observed in leaves under Mg-deficient conditions. N resupply effectively restored leaf morphology, gas exchange parameters, and photosynthetic efficiency. In contrast, Mg resupply resulted in only partial recovery. This limited recovery can be attributed to irreversible damage to the photosynthetic system caused by the inability of antioxidant enzymes to effectively scavenge excessive amounts of reactive oxygen species (ROS), indicating that Mg deficiency triggers H₂O₂-induced cellular damage. Furthermore, the application of the H₂O₂ scavenger DMTU (N,N'-dimethylthiourea) significantly reduced H₂O₂ levels under both deficiency conditions, particularly under Mg-deficient conditions. These findings demonstrate that N deficiency and Mg deficiency have distinct effects on antioxidant responses and underscore the pivotal role of H₂O₂ in plant responses to nutrient deficiency stress and subsequent recovery. These findings suggest that targeted modulation of H₂O₂ levels may serve as a promising strategy to increase crop resilience, offering a clear direction for future research.

Soil exchangeable magnesium (ex-Mg) deficiency is increasingly recognized as a critical limitation for crop production in subtropical regions. This study focused on Fujian Province, a representative subtropical region in China, to identify the key determinants of soil ex-Mg using a large-scale survey of 6833 soil samples. Field experiments were also conducted to evaluate the effects of Mg fertilizer application on eight crops, including cauliflower, sweet potato, peanut, soybean, citrus, tea, potato, and sweet corn. Results showed that the average soil ex-Mg concentration across Fujian was 83.8 mg·kg^–1, with 81.5% of samples below the established sufficiency threshold of 120 mg·kg^–1. A clear spatial pattern was observed, with higher ex-Mg levels in downstream plains and substantially lower concentrations in upstream mountainous areas. Random forest analysis revealed that soil exchangeable Ca, precipitation, and soil pH were the primary factors influencing soil ex-Mg concentration. Field experiments demonstrated that supplementary Mg fertilization increased crop yields by 5.3%–22.2%, nitrogen uptake efficiency by 5.6%–10.8%, and quality indicators by 8.4%–28.3%. These findings highlight the importance of incorporating Mg into regional nutrient management strategies to mitigate widespread Mg deficiency and enhance sustainable crop production in subtropical regions.