Effects of Different Dosages of Biogas Fertilizer on Wheat-Soybean Crop Rotation Production and Soil Environment

Biogas fertilizer is a high-quality, efficient input widely used in agriculture. However, its optimal dosage and effects on soil nutrients, yield, crop traits, and pollution risk in wheat–soybean rotation need to be clarified. This study was conducted at an ecological recycling agricultural base in Xiangcheng County, Henan Province, China. Five treatment groups were established: CK (no fertilization), T1 (low biogas fertilizer, 105 kg/20 m²), T2 (medium biogas fertilizer, 120 kg/20 m²), T3 (high biogas fertilizer, 135 kg/20 m²), and T4 (conventional fertilizer, 1.3 kg/20 m²). Results showed that biogas fertilizer had little impact on soil pH and did not significantly increase soil or product pollutants. Meanwhile, it significantly improved soil total nitrogen, total phosphorus, available phosphorus, quick-acting potassium, and hydrolyzed nitrogen. Crop crude protein, calcium, phosphorus, potassium, and vitamin C levels also increased. The study concludes that biogas fertilizer effectively enhances crop yield and quality in wheat–soybean rotation, improves soil nutrients, and poses no pollution risk at the tested dosages. T2 (120 kg/20 m²) is recommended as the optimal application rate.