Effect of cultivation pattern and nitrogen application rate on soil fertility and nitrate accumulation under maize-wheat rotation system

A field experiment was conducted in Guanzhong of Shaanxi Province to study the effects of long-term cultivation patters and fertilization on organic matter, total soil nitrogen, and the quantity and distribution of nitrate N in soil profile under maize-wheat rotation system. The results indicate that the order of effect of the different cultivation patterns on soil organic matter and total nitrogen contents is: straw mulching > furrow planting > conventional cultivation > water-saving cultivation. Straw mulching has the most significant effect on soil organic matter and total nitrogen contents. Nitrogen application significantly influences soil organic matter and total nitrogen. After 6 years of maize-wheat rotation cropping, the order of residual nitrate N in the 0~200 cm soil profile under different cultivation patterns is: furrow planting > water-saving cultivation > straw mulching > conventional cultivation. There are significant differences in nitrate N accumulation among furrow planting, water-saving cultivation and the conventional cultivation. Nitrate N accumulation in the 0~200 cm soil profile increases with longer cultivation periods and increasing nitrogen application rates. Accumulated nitrate N under 240 kg(N)·hm^{-2 (N240) treatment is significantly higher than that under 120 kg(N)·hm-2 (N120) treatment. The pattern of nitrate N distribution across the soil profiles differs with differing nitrogen application rate. Under N240 treatment, nitrate N content below the 120 cm soil depth increases with soil depth.}