Abstract: The experimental purpose is through investigating the effects of combined application of urea on dry matter, nitrogen accumulation, transport and yield of maize, to provide a theoretical basis for mining a reasonable nitrogen fertilizer for high yield of maize. The field experiment was conducted in 2016 and 2018 with a single factor randomized block design. Five treatments were set in the southern mountainous area of Ningxia. CK has no nitrogen application during whole growth season of maize. T1 was applied with 150kg·ha⁻¹ conventional urea base and 75kg·ha⁻¹ conventional urea topdressing in large bell stage. T2 was based on 75kg·ha⁻¹ conventional urea and 75kg·ha⁻¹ controlled-release urea and 75kg·ha⁻¹conventional urea in large bell stage. T3 consists of 75kg·ha⁻¹ conventional urea based and 150kg·ha⁻¹ controlled-release urea based, T4 is a basal application of controlled release urea of 225kg·ha⁻¹. The results showed that the combined application of conventional urea and controlled-release urea could significantly increase the yield compared with CK. Under T3 treatment, the 2-year average yield was higher than that of single application of conventional or controlled-release urea, and reached the maximum in each treatment. Combined application increased the growth rate of leaf area index (LAI) and leaf area index (LAI) in early growth period, but slowed down the decline rate of LAI in late growth period. Compared with CK and T1, controlled release urea treatment significantly increased dry matter accumulation and grain nitrogen accumulation at mature stage. The dry matter transfer before anthesis was low in the treatment with controlled release urea, but it mainly increased the dry matter accumulation after anthesis and the contribution rate of dry matter accumulation after anthesis to the dry matter accumulation of grain, and it increased first and then decreased with the increase of controlled release urea content. Compared with single application of conventional urea, controlled release urea treatment increased nitrogen utilization rate(REN), nitrogen agronomic utilization rate(AEN), nitrogen partial productivity(PFPN) and fertilizer contribution rate(FCR), and T3 had the highest increase. Based on two years experiment results, applying controlled release urea to conventional urea at a ratio of 2:1 may save labor and increase maize yield.

Key words: Corn, Dry matter accumulation, Nitrogen accumulation, Production