Abstract:

In recent years, nitrogen over fertilization has become an unassailable fact in summer maize-winter wheat cropping system in north China plain, especially in summer maize growing season, resulting in N use efficiency (NUE) rapidly decrease and causing a series of ecological and environmental problems, such as underground water pollution, acid rain, global warming and stratospheric ozone depletion, and so on. The objective of this experiment was to study the effects of three application rates (0, 90 and 180 kg N/ha) of three types of nitrogen fertilizer (common urea, coated urea and compound fertilizer) on N absorption, accumulation, translocation and nitrogen fertilizer (NF) utilization of summer maize cultivars, Zhengdan 958 and ND 108 under condition of lower NF application rate, and to provide some beneficial references for ameliorating the fertilization techniques and increasing NUE of summer maize in this area. The main results showed that N accumulation amount was increased but nitrogen physiological efficiency, nitrogen fertilizer efficiency and NUE descended with the increment of N application rate from 0 to 180 kg N/hm2. Under condition of the same N application rate, NUEs of coated urea and compound fertilizer treatments were bigger than that of common urea treatments, especially in the treatments of 90 kg N/ha for Zhengdan 958 and 180 kg N/ha for ND 108 (Table 2, 5 and 6). Difference existed in N staggered accumulation trends between two cultivars under zero N application, and their alternation under N application showed genotypic difference likewise (Table 2). In N application treatments, N accumulation amount was increased before silking stage, but descended in middle and late filling stage, and this trend was more evident for Zhengdan 958. N absorption of summer maize, especially of Zhengdan 958 in the middle and late filling stage could be restrained if N accumulation amount was too much in the stage of sowing to 21 d after silking. There was a genotypic difference in nitrogen harvest index (NHI), nearly 6% more in Zhengdan 958 than in ND 108. With NF application, NHI of Zhengdan 958 was descended evidently, but that of ND 108 changed unconspicuously. Compared to NHI under common urea application, NHI under coated urea and compound fertilizer application was lower and the difference was significant at 0.05 probability level when N application rate was 90 kg N/ha for Zhengdan 958 and 180 kg N/ha for ND 108 (Table 2). Translocation amount of leaf N and stem-sheath N and their contribution rates to grain N were increased with the increment of N application. Leaf N was translocated to grain mainly from 21 d after silking to maturing stage, but stem–sheath N did mainly from silking to 21 d after silking stage (Table 4). Fertilizer-N played the role mainly before silking, especially from 12–leaf to silking stage, and the difference of N accumulation amount between N application treatments and zero N treatment reached to the maximum around silking stage.

Key words: Summer maize, Type of nitrogen fertilizer, N accumulation, N transshipment, N use efficiency