Effects of partially replacement of inorganic N with organicmaterials on nitrogen efficiency of spring maize and soil inorganic nitrogen content under the same N input

【Objectives】 Study on the effect of proper ratio of organic N replacing chemical N on the N use efficiency and soil N content in the long run will provide base support for the efficient fertilization and sustainable soil fertility. 【Methods】 The long-term experiment on black soil fertility and fertilizer efficiency (Gongzhuling City, Jilin Province) was used, and spring maize cultivar, Zhengdan958 was selected. Plant and soil samples were collected from five treatments: no fertilization (CK), fertilizer N (N), fertilizer NPK (NPK), NPK plus pig manure (MNPK) and NPK with straw (SNPK).The nitrogen accumulation, translocation of maize and N use efficiency were studied at six growing stages of maize, seedling, jointing, belling, tasseling, blister and maturity, under the long-term experiment condition. 【Results】 The nitrogen accumulation of maize is increased from the jointing to belling, and the highest daily accumulation is in the belling stage. In MNPK treatment, the value is 86.44 kg/ha, significantly higher than in NPK and SNPK treatments. The total amounts of N transferred from leaves and straw-sheath to grains were 99.0, 79.7 and 87.2 kg/hm2 in MNPK, SNPK and NPK treatments, respectively, with the corresponding contribution to grain N of 51.0%, 47.7% and 47.2% respectively. MNPK shows the significantly higher N translocation and contribution than SNPK and NPK treatments. The partial factor productivity of applied N is over 60 kg/kg in the MNPK treatment. Compared to the NPK treatment, SNPK treatment has no obvious differences on PFPs and N harvest index (NHIs). Soil inorganic nitrogen of the MNPK treatment is higher than that of NPK treatment in the whole growing stage, which reaches the highest amount of 60.83 kg/kg at the belling stage. 【Conclusions】 Replacing chemical N with organic N could improve the accumulation and translocation of inputted nitrogen, improve N use efficiency and increase the capacity of soil N supply in the long-run. Replacing 70% of the N 165 kg/ha input with manure fertilizer N or 30% with maize straw N is proved to be a feasible way in nutrient management of spring maize at black soil region in Jilin.