Effects of Different Mixing Rates of Controlled-Release Urea and Common Urea on Grain Yield and Nitrogen Use Efficiency of Summer Maize

Abstract

Using controlled-release urea (CRU) with releasing period of 60 d and conventional urea (U) as experimental materials, the effects of different mixing rates of CRU (0, 10%, 30%, 50%, 100%) and U with the equality of nitrogen fertilization every treatment on photosynthetic efficiency, grain filling rate, grain yield, economic profits and nitrogen use efficiency of summer maize were studied. Results were as follows: (1) Net photosynthetic rates, chlorophyll contents and nitrate reductase activity in ear leaves of treatments with different ratio of CRU were always higher , the grain filling was started-up faster and grain active filling duration was longer than those of U treatment. (2) With the increase of proportion of CRU, the grain yield was increased firstly and then gradually decreased. Compared with U treatment, the increase of grain yield in CRU+U treatments was 2.90%, 7.91%, 9.48%, and 5.68% in turn and the increase of economic profits was 397.34, 1 077.65, 1 263.94, and 611.3 yuan ha?1 in turn. (3) In all treatments, nitrogen agronomy efficiency was 8.31, 10.55, 11.81, 12.5, and 9.46 kg kg?1 in turn, among them, CRU treatments showed 1.15–4.19% more than U treatment; nitrogen use efficiency was 29.71%, 31.83%, 38.49%, 40.72%, and 44.63% in turn, among them CRU treatments showed 2.12–14.92% more than U treatment. (4) Applying CRU with a mixing ratio of 50% was most beneficial to increase the yield of summer maize.