Effects of different biogas slurry application patterns on nitrogen and phosphorus losses in a paddy field

Biogas slurry, as a substitute for chemical fertilizers, is usually applied according to the needs of biogas slurry to be consumed at onetime. This poses a great risk of short-term nutrient overload in soils, resulting in high losses of nitrogen (N) and phosphorus (P) from farmland. Therefore, a field experiment was conducted to identify the optimal irrigation pattern for biogas slurry in paddy field by monitoring N and P losses via surface runoff, leaching, NH₃ volatilization, and denitrification as well as rice yield and soil residue with five fertilizer application patterns: no fertilizer application, conventional chemical fertilizer, and three biogas slurry irrigation patterns including the current irrigation pattern of three times (BS1), irrigation pattern of five times (BS2), and 20% reduction of N input with five irrigations (BS3). BS2 treatment significantly increased the yield of rice by 13.91 and 23.37% compared to the CF and BS1 treatments, respectively. But the BS2 treatment promoted NH₃ volatilization loss by 70% compared with the BS1 treatment. The BS3 treatment decreased the total N loss and P loss by 14.33 and 21.95%, respectively, compared to the BS1 treatment, along with a 10.26% increase in yield. Therefore, increasing the irrigation frequency of the biogas slurry to five times and reducing the fertilizer application rate by 20% was the optimal irrigation pattern in paddy field with the best agricultural and environmental benefits.