Effects of different cultivation patterns and nitrogen fertilization on soil nitrogen supply of in the wheat-maize rotation system

A six year positioning experiment of wheat-maize rotation was used to compare the effects of different cultivation patterns and nitrogen application rates on soil N supplying ability. The results show that compared with the conventional control treatment (CC), the contents of total hydrolysable N (THN), microbial biomass nitrogen (SMBN) and mineralized nitrogen potential (N0) of soil under the straw mulching treatment (SM) are significantly increased, and the fractions of different forms of soil organic nitrogen are enhanced as well. The contents of THN and N0 are increased under the furrow cultivation pattern (FM) and the increased rates are lower than those of the SM pattern, while the content of SMBN is decreased. The contents of THN, N0, amino acid N (AAN), amino sugar N (ASN), ammonium N (AN) are also increased under the nitrogen fertilization, while the content of SMBN is decreased, especially for the N 240 kg/ha rate. The interaction between cultivation pattern and nitrogen application rate on fractions of different forms of organic nitrogen in soil is not statistically significant (P>0.05). The correlation analysis results indicate that there are significantly positive correlations between N0, SMBN, AAN, hydrolysable unidentified N (HUN)(P<0.05), which implies the last three fractions maybe the major contributors to the soil mineralized nitrogen.