Promoting rice growth can effectively reduce NH₃ volatilization in paddy soil under rice-based cropping system

Reduction of soil ammonia (NH₃) volatilization is very important for improving nitrogen use efficiency and decreasing environmental risks in agricultural production. Two long-term paddy-upland rotations, garlic-rice (GR) and wheat-rice (WR), were conducted to investigate the influence factors and difference of NH₃ volatilization in paddy. Results showed that compared with WR, the loss amount of NH₃ volatilization under GR only decreased by 5.5% when there were no rice plants growing in the soil, but decreased by 26.7% when there were rice plants growing. The decrease of NH₃ volatilization under GR was mainly attributed to the 28.9% and 12.4% reduction in spikelet-developing fertilizer and base fertilizer, respectively. Dry matter accumulation and rice yield under GR was 8.2% and 8.9% higher than that under WR respectively, which leading to a 14.8% increase in nitrogen uptake by rice plants and 15.3–24.7% decrease in the average NH₃ volatilization rate of spikelet-developing fertilizer. NH₃ volatilization of base fertilizer was significant positively correlated with ammoniacal nitrogen concentration in paddy water. The soil C/N ratio increased by 4.2–13.3% under GR, which increased the adsorption capacity of ammoniacal nitrogen and decreased the concentration of ammoniacal nitrogen in paddy water, leading to the average NH₃ volatilization rate of base fertilizer under GR decreased by 12.0–16.4%. In conclusion, NH₃ volatilization was determined by both soil and plant, and the effects of rice plants was more important. To increase soil organic matter content and improve rice growth and nitrogen uptake are promising strategies for decreasing NH₃ volatilization in paddy fields.