Characteristics of nitrogen mineralization and residual in the soil and nitrogen balance in the continuous spring maize cultivation system in Northeast China

A two-year field experiment was conducted to understand the characters of nitrogen(N)mineralization, residue in the soil and N balance in the continuous spring maize cultivation system in northeast China at two locations with three N fertilization levels N0: no N; N1: moderate N; N2: high N. The effect of different maize hybrids on N mineralization and N loss was also evaluated. The results indicated that accumulated mineralized N during the two years was 203 kg/ha in the fertile soil at Dehui, which was as twice as in the infertile soil at Xinlicheng. The residual N across the two sites was 103-112 kg/ha with N1 treatment within two years, which should be safe for the environment. Under the N2 treatment, however, the residual N at Xinlicheng was 174 kg/ha and it had a risk to be leached out. The residual N was only 107 kg/ha in the fertile soil at Dehui. Crop N uptake did not increase with increasing N input, leading to high N surplus at N2 level. At Xinlicheng, The contribution of residual Nmin was 34.0%-88.4% to N surplus in the soil. At Dehui, the proportion of N mineralization was 28.3% and 36.5% for N1 and N2, respectively. The apparent N loss in Dehui was 54.3%-70.8% with an average of 65.5%, much higher than that in Xinlicheng. It was supposed that the apparent N loss at both sites reflected the transfer of fertilizer N to soil N by the way of biological immobilization. Maize cultivars had an effect on N mineralization and apparent recovery, and therefore, should be taken into consideration to optimize N application.