Effects of Mixed Application of Controlled-Release N Fertilizer and Common Urea on Grain Yield, N Uptake and Soil N Balance in Continuous Spring Maize Production
Objective]The mixed application of CRN and common urea was considered as a good alternative technique for single basal fertilizer application. This study aimed to evaluate the effects of mixed application of CRN and urea on grain yield, N uptake, N balance in a soil-crop system, and to provide reference to scientific N management techniques for spring maize.[Method]A two-year fixed plot experiment was conducted in the major maize production area in the central Jilin province from 2010 to 2011, including five fertilization treatments, including Treatment I (No N fertilizer, N0), Treatment II (100% urea, CRN0%), Treatment III (15% CRN+85% urea, CRN15%), Treatment IV (30% CRN+70% urea, CRN30%), and Treatment V (45% CRN+55% urea, CRN45%). In this study, grain yield, N uptake, N efficiency of spring maize, soil inorganic N accumulation and mineralization, and N balance in soil-crop system were investigated, and the appropriate mixed ratio of CRN was determined by considering comprehensive performances.[Result]The results showed that mixed application of CRN and urea increased significantly aboveground dry matter and grain yield of spring maize, compared with single basal application of urea, while no differences were found between the various mixed ratios. On an average of two growing seasons, the highest grain yield of 9.39 t·hm-2 was obtained in the CRN30% treatment, which was 9.0% (0.77 t·hm-2) higher than that in the CRN0% treatment. Application of N fertilizer was a major way of N input in soil-crop system, which accounted for 63.5% of the total N input, while the contributions of soil inorganic N prior to sowing and N mineralization were 19.2% and 17.3%, respectively. The net N mineralization during maize growing season was 34.4 kg·hm-2 in 2010 and 66.1 kg·hm-2 in 2011, while that was in the range of 15.2-26.4 kg·hm-2 among treatments during the overwintering stage between two growing seasons. Cropped N uptake by maize plants was a major way of N output and its contribution ranged from 68.1% to 99.5% with an average of 80.7%. With increasing mixed ratio of CRN, both N uptake in plant and residual inorganic N in soil showed continuous increased trends and reached the highest values of 234.2 and 108.1 kg·hm-2 in the CRN30% and CRN45% treatments, respectively, which were 18.0% and 45.1% higher than those in the CRN0% treatment, respectively. Nevertheless, apparent N loss decreased with increasing mixed ratio of CRN, and therefore led to reduced apparent N surplus. The lowest apparent N surplus was 114.4 kg·hm-2 in the CRN30% treatment, which was reduced by 38.4% compared with the CRN0% treatment. In the treatments with mixed application of CRN, inorganic N contents were higher significantly in topsoil (0-30 cm) but lower in subsoil (60-90 cm) than that in the CRN0% treatment, indicating that less N was leaching down when mixed CRN was applied. The average results throughout two growing seasons showed that: Apparent N recovery rate increased significantly from 50.1% in the CRN0% treatment to 69.4% in the CRN30% treatment, and apparent N residual rate increased significantly with mixed application of CRN, while apparent N loss rate decreased significantly from 37.3% in the CRN0% treatment to 6.0% in the CRN45% treatment.[Conclusion] The mixed application CRN and urea is not only conducive to improve grain yield and N uptake of spring maize, but also to maintain a higher soil inorganic N content and reduce N loss, therefore resulting in increased N fertilizer use efficiency. Under the current condition, the appropriate mixed ratio of CRN for spring maize production in Northeast China is around 30% when 185 kg N·hm-2 is applied.
spring maizecontrolled-release N fertilizermixed applicationgrain yieldN uptakeN balance
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