Effect of base nitrogen application depth on summer maize yield, nitrogen utilization efficiency and nitrogen residue

【Objectives】 Effects of base nitrogen application depth on summer maize yield, fertilizer nitrogen uptake and fertilizer nitrogen utilization efficiency(NUE) as well as the fertilizer nitrogen residue in soil were studied in Northern China Plain area.【Methods】 This study was carried out through a plot experiment and a simulated experiment using 15N labeled urea. Six treatments were designed for the plot experiment, CK, row-side N application(T-side), N application depth of 8 cm (T-8), 16 cm (T-16), 24 cm (T-24) and all above the depths (T-all) in rows. The doses of N, P2O5 and K2O were 180 kg/hm2, 120 kg/hm2 and 150 kg/hm2respectively. The tracing experiment was conducted in situ and undisturbed soil columns in the field, and three treatments were designed, 15N labeled urea was applied at 8 cm in depth, common urea was applied at 16 cm and 24 cm (N8); 15N labeled urea was applied at 16 cm in depth, common urea was applied at 8 cm and 24 cm (N16); 15N labeled urea was applied at 24 cm in depth, common urea was applied at 8 cm and 16 cm (N24). The nutrition doses are the same as plot experiment. 【Results】The plot experiment results show that the maize yield under T-all is the highest, which is significantly higher than that under T-24. Compared with the T-side treatment, the maize yields of T-all, T-8, and T-16 are increased by 6.65%, 3.29% and 5.43% respectively. The maize yield under the T-24 treatment is the lowest among all fertilizer treatments. The nitrogen uptake under the T-24 treatment is the lowest at the maize growth stages among all fertilizer treatments. Compared with the T-side treatment, the nitrogen uptakes under the T-all treatment are lower at the silking stage and higher at the harvest time. The band fertilization method mainly affects the soil alkali-hydrolyzable nitrogen content in ridge (fertilization position), but little effect between ridges(non-fertilization position) is found. The surface soil alkali-hydrolyzable nitrogen contents in the seed row are significantly increased under the T-side and T-8 treatments, compared with T-16 and T-24. The tracing experiment results show that the NUEs of urea at application depths of 8 cm, 16 cm and 24 cm are 37.24%, 31.33% and 18.75% respectively. After the maize harvest, the N residual in the 0-100 cm soil layer under the N24 treatment is significantly higher than those of the N8 and N16 treatments. The residual N is mostly in 40-80 cm soil layer under the N24 treatment.【Conclusions】 The suitable depth of base application urea is 8-16 cm for the summer maize in the region.