Effect of continuously appling controlled-release fertilizers on nitrogen balance and utilization in winter wheat-summer maize cropping system

Abstract: Currently, the research about the controlled-release fertilizer affecting crop yield and nitrogen loss is extensive, but it's lacking about the soil nitrogen balance after long-term applying controlled-release fertilizer with different managing practices. This study determined ammonia volatilization, nitrogen uptake by crop and nitrite accumulation in soil with applying controlled-release fertilizer for 3 years continuously in winter wheat/summer maize cropping system in North China Plain (NCP). There were 5 treatments: no nitrogen fertilizer (CK), conventional dosage of urea (CU), optimum dosage of urea (75% of the conventional dosage, OU), conventional and optimum dosage of controlled-release fertilizer (CC and OC), respectively. The CK treatment was chosen from a long-term experiment without nitrogen lasting for 15 years, and the CU treatment was 505 kg/(hm2·a) (nitrogen amount) based on the average of the survey at the local farmlands. The results showed that ammonia volatilization was lower after the controlled-release fertilizer was applied in the 3 periods (base fertilizer for wheat, top dressing for wheat and base fertilizer for maize) in the whole growth season in a year, due to the prevention of the hydrolysis of urea by adding the inhibitor in controlled-release fertilizer, especially in the warmer condition of base fertilizer for maize. At the end of the three-year experiments, the accumulation of nitrate in soil for the OU treatment was lower significantly than the CU treatment in the whole profile (0-180 cm); while for the OC treatment the accumulation reduced only in the deep layers (below 100 cm). There were no significant differences in the yield of wheat or maize among the 4 treatments of nitrogen applied in the first year, due to the excessive fertilization in the past years. The yield of maize for OC treatment was significantly higher than that for the OU in the second year, but for wheat both in the second and the third year. In contrast, for the CC treatment, the yield of maize only in the second year was higher than the CU treatment. As for the average yield of wheat and maize in 3 years, the OU treatment was significantly lower than other 3 treatments (OC, CC and CU treatments). The average of nitrogen apparent efficiency in 3 years was the maximum for the OC treatment, followed by the CC and the CU treatments; and the CU treatment was the minimum. This study shows that the use of controlled-release fertilizer can't increase the yield of the crop with conventional dosage applied, but can significantly improve the nitrogen apparent efficiency with reducing fertilizer input by 25%, and also can maintain the long-term soil nitrogen balance.