Comprehensive effects of nitrogen fertilizer management on yield, economic performance and nitrogen use efficiency of spring maize in Loess Plateau, China

Objectives The comprehensive effects of fertilizer sources, rates, fertilization times and fertilization places on the yield, economic performance and nitrogen use efficiency (NUE) were studied in rain-fed farmland, aiming to provide a scientific reference for reducing nitrogen rate and simplifying practices in the production of spring maize in Loess Plateau area.

Methods Two experiments were conducted in Changwu County, the south of the Loess Plateau. The tested maize cultivar was ‘Xianyu 335’, and the planting row was alternating with plastic film mulched row. 1) Fertilizer effect experiment in 2017–2018. The treatments included no N application (N0); conventional fertilization (N225, split application between film-mulched row); conventional reduced application (N180, split application between film-mulched row); a single basal application of urea in reduced rate (B-N180, application between film-mulched row); a single basal application with sulfur coated urea in reduced rate between film-mulched row (B-SCU) and under film (B-SCUi); a single basal application with reduced matrix-based slow-release urea between film-mulched row (B-MU) and under film (B-MUi). The soil mineral nitrogen (MN) content and plant N contents were measured during the growth period of spring maize. The yield and residual MN in the 0–200 cm soil profiles were quantified when harvest. 2) The fertilizer nitrogen release trial was conducted during growth season without maize in 2018. The 6 treatments included: common urea applied between film rows (U) and under film (Ui); sulfur coated urea applied between film rows (SCU) and under film (SCUi); matrix-based slow-release urea applied between film rows (MU) and under film (MUi). The content of MN in soil pedon (5 cm × 6 cm × 100 cm) under fertilizer bags was quantified, and the MN increment during trial was regarded as the N released by the fertilizers tested.

Results The N sources, N rates and fertilization time and place markedly affected the yield, N uptake and accumulation in plant and N use efficiency, and the rainfall amount and distribution in growth seasons also influenced the distribution of fertilizer N in soil profile and the N uptake and N use efficiency of maize significantly. The application of N 180–225 kg/hm² increased grain yield by 49.5%–84.7% in two years. Compared with N225, the yields in B-MU, B-MUi and B-N180 did not varied obviously, but the NUE increased by 4.41%–23.61%, the economic incomes increased by 346–1586 yuan/hm², and the N residuals in soil also declined. Nevertheless, the yield, N accumulation, N use efficiency and economic benefit of B-SCUi declined. Although there was no yield loss of N180 in 2017, the yield and net profit loss were of 23.31% and 5623 yuan/hm² respectively in 2018 compared to N225. The effects of yield increase were better in treatment of applying fertilizer between film rows than those under film. The N release of matrix-based slow-release urea was matched with the local hydrothermal conditions and synchronized their N release pattern with crop N uptake rates.

Conclusions A single basal application of nitrogen fertilizer between the film-mulched rows could increase yield, fertilizer efficiency and profit of maize production as a results of providing sufficient N before the bell stage of spring maize, reducing the N loss after topdressing and avoiding the difficult topdressing in dry season in the Loess Plateau area. The nitrogen release of matrix-based slow-release urea matches well with N uptake and root development of spring maize, and could maintain the yield stability with reduced 20% of fertilizer input, so it could be used in simplification practice. Sulfur-coated urea is not suitable for the technology as too slow nitrogen release in the early stage of maize growth.