Effects of one-time application of controlled-release urea combinated with solid granular urea on grain yield and nitrogen utilization of spring maize in dryland

Objectives A two-year on-farm experiment was conducted to evaluate the effects of nitrogen (N) application rate and fertilization method on spring maize yield, economic income, dry matter accumulation, N accumulation and utilization, and soil inorganic N residues in dryland.

Methods The experiment had a split-plot design with three fertilization methods (solid granular urea one-time fertilization (OF), solid granular urea basal and top-dress fertilization (TF), and one-time application of a mixture of controlled-release urea and solid granular urea (MF)) as the main factors and six different N application rates of 0, 60, 120, 180, 240, 300 kg/hm² (expressed as N0, N60, N120, N180, N240, N300, respectively) as the sub-factors. For the assessment of biomass and total N contents, maize samples were collected at stage of 10 expanded leaves (V10), silking stage (R1), milking ripening stage (R3) and harvest stage (R6).

Results 1) Yield did not increase when N application rate reached 240 kg/hm² in the three fertilization methods. Yield under MF method was 5.0% and 4.2% higher than those under OF and TF methods, respectively. Economic income under MF method was 7.9% and 25.7% higher than those under OF and TF methods, respectively. 2) Dry matter accumulation increased significantly with increase of N application rate in the three fertilization methods. Dry matter accumulation at silking and harvest stages under MF method were significantly higher (19.5% and 12.5% at 240 kg/hm², respectively) than those under OF method. 3) Periodical N accumulation at silking and harvest stages increased significantly with N application rate. Total N accumulation due to application of MF method at 240 kg/hm² rate (N240) was 32.7% and 20.9% higher than those of OF and TF methods, respectively. 4) N content of stem, leaf and grain at harvest stage and N translocation amount from stem and leave to grain increased significantly with N application rate. Average stem, leaf and grain N contents, and N translocation amount were higher in MF method than those in TF and OF methods. 5) MF method significantly increased the partial factor productivity, agronomic efficiency and apparent recovery rate of N and decreased soil mineral N content at harvest stage and apparent N loss, compared with those of OF and TF methods.

Conclusions MF method significantly increased yield, economic income, nitrogen accumulation and utilization, but reduced soil N_min at harvest when N application rate was 240 kg/hm².