Nitrogen Fertilizer Residual Effect And Its Fate In Winter Wheat-Summer Maize Rotations In North China Plain

In North China, we often ignore the residual N from last stubble and lack quantify parameter that estimated soil-fertilizer nitrogen behavior in situ field. In this study, we made winter wheat and summer maize rotation system study target in China North Plain. This research established the field ¹⁵N-micropolt experiments, we could explicit the after-effects and fate of nitrogen fertilizer in winter wheat and summer maize rotations. Furthermore, we investigated and surveyed correlation literature, recognized and accounted the original dates which related to the research of ¹⁵N-microplot experiments, analysed the relationships of fertilizer N, plant N, and soil N, explored and built the quantify parameters of fertilizer N in winter wheat and summer maize rotations of China North Plain. This could increase fertilizer N utilization efficiency in winter wheat and summer maize rotations, decrease the environmental pollution of fertilizer N, and provide reasonable evidence of fertilizer N use in agriculture. The main results were as follows:(1) The after three crops all up-took the ¹⁵N-labeled fertilizer that was residued from the first winter wheat. Following ¹⁵N-labeled fertilizer application rates increasing, the ¹⁵N was up-taken by the after three crops increased significantly, but following increasing of crops for rotation, absorption amounts and absorption rate decreased significantly. Overlying N utilization efficiency of four crops was significantly higher than the N utilization efficiency of the right winter wheat. The overlying N utilization efficiency of N75, N150, N225 and N300 treatments accounted for 53.8%,58.7%,58.6% and 55.8% ( the right crop season was HN822); 60.0%,61.3%,60.9% and 55.2%, respectively( the right crop season was KN9204).(2) In the first winter wheat and summer maize rotation system and two rotations system, the fate of ¹⁵N all displayed crops uptake>soil residue>fertilizer loss. There was different from the fist winter wheat season. By growing four plants, after the fourth summer maize harvest, the range of soil residue in profile was 22.3⁹6.2kgN/hm², the ratio of soil residue was from 22.1% to 33.5%. The range of total loss was 9.3⁵5.3kgN/hm², and the loss ratio was 8.9% to 18.4%.(3) After every crop harvest , there was a lot of nitrate in soil profile. Two rotation systems finished, there was residual ¹⁵N in 0²00cm soil profile. Following nitrogen fertilizer application rates increasing, the nitrate and residual ¹⁵N amount increased, Following increasing of crops growth, the moving trend of nitrate and residual ¹⁵N was downward in vertical direction.(4) In North China Plain, Following nitrogen fertilizer application rates increasing, the yield of winter wheat and summer maize were increased first and then decreased. Gain N uptake of winter wheat was higher than straw, while summer maize was opposite. The three fates of nitrogen fertilizer all increased with the increasing of nitrogen fertilizer rates. There were differences between different areas.(5) With the nitrogen application rates increase, the soil nitrogen balance from wane to surplus. In the condition of 50% straw returning to field, when the soil nitrogen to balance, the winter wheat and summer maize nitrogen fertilizer rate were 194kgN/hm² and 198kgN/hm², and In the condition of 100% straw returning to field, the nitrogen fertilizer rate were 164 kgN/hm² and 126 kgN/hm².(6) In North China Plain, between the nitrogen fertilizer fate and nitrogen application rates(winter wheat season:75³75 kgN/hm²; summer maize season:40³60kgN/hm²) presented a significant liner relation within a certain range in winter wheat and summer maize. The recovery rate of every nitrogen fertilizer fate and fertilizer rate presented bad liner relationship(R2=0.024⁰.210), except total N rccovery rate and grain use rate of winter wheat and summer maize, and loss rate of winter wheat.