Net nutrient balance in soil under different cultivation pattern and nitrogen application rate in semiarid region

A 7-years field experiment was used to study the effects of long-term cultivation pattern and nitrogen application rate on N, P and K nutrient net balances soil under maize-wheat rotation system, and their relationship with nutrient contents in soil was also evaluated. The results showed that the nutrient deficits in soils under the two patterns with straw additions, i.e., mulching and furrow planting, were lower than that of conventional and water-controlling patterns, indicating that straw addition plays an important role in balancing the nutrients in soil. Nitrogen in soil added with 120 kg/ha of nitrogen fertilizer was near balance; when nitrogen fertilizer was increased to 240 kg/ha, nitrogen accumulation in soil increased significantly (averaged at 1471 kg/ha). There were significantly positive relationships between nitrogen balance value in soil and nitrate accumulated in 02 m soil profile, and P and K balance values in soil and Olsen-P and available K in soil. The accumulated nitrate increased about 38.3 kg/ha when N balance in soil was increased at each 100 kg/ha. The deficit of each 100 kg/ha of P and K nutrients in soil, Olsen-P and available K in soils declined about 3.5 mg/kg and 1.0 mg/kg, respectively. It indicates the deficit and accumulation of available nutrients in soils was mainly determined by the nutrient balances in soil.