Effects of nitrogen application on dry matter accumulation and translocation of different genotypes of summer maize

The experiment was carried out to study the differences of the dry matter accumulation and translocation efficiency of different summer maize cultivars: Shandan16(SD16), Shandan9(SD9), Hudan4(HD4), Shanzi1(SZ1), Yedan19(YD19), Zhongdan2(ZD2),Yuyu22(YY22), Shandan902(SD902), Nongda108(ND108) and Hudan2000 (HD2000), under the low N level (0 kg/ha) and high N level (240 kg/ha) in Hongyou soil of Southern Loess Plateau. The results show that dry matter accumulation and translocation efficiency are affected by genotypes and nitrogen regulation. There are significant differences among the different genotypes in dry matter quantity of each organ under both N application and no N application. Dry matter quantity of each organ is increased remarkably, and the increased rates are significantly different among the cultivars under the N application. Dry matter remobilization quantity, dry matter remobilization rate and remobilization quantity contribution to grain of each organ are different dramatically for the different genotypes and the N application levels. Effects of the N application levels on genotypes are also different. Under no N application, leaf (53.2 g/plant) and stem (28.2 g/plant) dry matter remobilization quantity of HD2000 are the highest, leaf dry matter remobilization quantity of ZD2 and stem dry matter remobilization quantity of SZ1 are the smallest respectively. While under the N application, leaf (54.7 g/plant) dry matter remobilization quantity of YD19 and stem (52.0 g/plant) dry matter remobilization quantity of HD2000 are the highest. More than 50% grain dry matter of all genotypes came from remobilization of accumulated assimilation products before the anthesis stage, except YY22 and SZ1 under no N application; meanwhile, it is true for all genotypes under the N application. Spike (bract and axis) dry matter contribution to grain of the different genotypes is negative for most of the genotypes under no N application, but is positive for all genotypes under the N application. Contribution of leaf dry matter remobilization quantity to grain is the largest, stem’s is the next, and spike’s (bract and axis) is the smallest. Overall, differences of dry matter translocation quantity, dry matter translocation rate and dry matter contribution to grain among different genotypes are more significant than those between the N application levels. Effects of N application on dry matter translocation quantity, rate of dry matter translocation and dry matter contribution to grain of the different genotypes are varied.