Effect of the blending ratio of controlled-release urea and conventional urea on yield and nitrogen utilization efficiency of sweet corn

ObjectivesEffects of different blending rates of controlled-release urea (CRU) and conventional urea (U) at different N amounts on growth, grain yield, nitrogen uptake and nitrogen efficiency of sweet corn were studied to provide reference for the application and dissemination of CRU in sweet corn production.

MethodsField experiments of sweet corn were carried out using sweet corn cultivars of Huazhen and Yuetian 9 as tested materials in Boluo County and Huiyang County of Guangdong Province simultaneously in 2015. Conventional urea and controlled-release urea were mixed in different ratio and total N input in different rate. No nitrogen fertilizer as CK, urea N 360 kg/hm² (U1), 252 kg/hm² (U2), N 252 kg/hm² with 40% CRU (40% CRU1), N 180 kg/hm² with 40% CRU (40% CRU2), N 252 kg/hm² with 60% CRU (60% CRU1), and N 180 kg/hm² with 60% CRU (60% CRU2). All treatments were fertilized with P₂O₅ 157 kg/hm² and K₂O 360 kg/hm². Straw and ear of sweet corn were collected at maturity period for the N analysis. The yield and yield components were also recorded after the harvest.

ResultsThe ear yields of sweet corn were increased significantly due to the nitrogen applications (P < 0.05), and increased as more nitrogen was applied. The highest ear yield of sweet corn was achieved under the U1, and the second highest yield was obtained under the 60% CRU1, but that of the 40% CRU2 decreased significantly. No significant differences between the U1 and the 60% CRU1 were observed. On the basis of the uniform N rate, the yields of different treatments at the two sites were all in order: 60% CRU > 40% CRU > U. The application of N fertilizers mainly increased the ear yield through increasing the ear length and diameter and kernel number per row. The accumulative amounts of dry matter and N uptake of sweet corn were increased significantly by applying N fertilizers, the average increases of dry matter and N uptake in straw and kernel were 55.1% and 24.2%, and 95.0% and 43.4%, and the increases in the straw were greater. The accumulative amounts of dry matter and N uptake of sweet corn were increased due to more N applied. And on the basis of the same N rate, accumulative amounts of dry matter and N uptake of sweet corn under different treatments at the two sites were in order: 60% CRU > 40% CRU > U. On the basis of the same N rate, the agronomic N use efficiencies, partial factor productivities of N fertilizer and N recovery efficiencies of different treatments at the two sites were all in order: 60% CRU > 40% CRU > U. But no significant differences in the physiology efficiencies of nitrogen and nitrogen harvest indices among different treatments were observed. There were no significant differences in Vc and soluble sugar contents of sweet corn among different treatments.

ConclusionsThe yield, dry matter and N uptake of sweet corn were increased due to the blending application of controlled-release urea and urea, and increased more with controlled-release urea addition of 60%. The blending application of controlled-release urea and urea could benefit to the nitrogen utilization efficiency of sweet corn, and be potential way to decrease the total N fertilizer input.