| China is a big producer and consumer of N fertilizer in the world. In recent years, due to unreasonable application of nitrogen fertilizer, the fertilization effect is declined and nitrogen use efficiency reduced and environmental pollution aggravated. Understanding where the nitrogen fertilizers are leached in farmland ecosystemland can help explore the best nitrogen managing approach for coordination of crop yield and environmental protection, which is also the critical requirements to improve nitrogen use efficiency, to reduce N losses, guarantee the food production and to protect the environment. A lot of researches on the whereabouts of the nitrogen have been done at home and abroad. However, different crop systems, different climate, different soil conditions and different fertilization and cultivation management practices all will affect the whereabouts of nitrogen. There were seldom reports on the whereabouts of nitrogen in the mustard-maize rotation systems under diferent management modes. In this paper, we used nutrient leakage-pool facilities to research different nutrient conditions and its effect on crop yield, nitrogen absorption, nitrogen leaching and nitrogen volatile in the mustard-maize rotation systems in Southwest China and explore the effect of different nutrition management modes, nitrogen dosage and organic fertilizer on nitrogen volatile. We hope that would underlie the optimization of nitrogen fertilizer in mustard-maize rotation system in the region. The main results were as follows:Different nutrient managerial models could significantly affected the mustard corn yield and nutrient uptake. Enhancement and suitable organic and inorganic fertilizer treatment significantly improved crop yields and nitrogen-use efficiency; crops applied by organic and inorganic fertilizer have gained the highest yield in two seasons. Compared with conventional fertilization, mustard and corn respectively increased by 42.8% and 21.5%. N-use efficiency is increased by 16 percentage points. Mustard and maize production of the optimal management respectively increased by 3.9% and 13.7% than that of farmers’conventional fertilization. N-use efficiency increased by 6%. Due to the partial NPK ratio imbalance, unreasonable nitrogen fertilizer management, conventional fertilization mode adopted by the farmers results in that crop yield and nitrogen uptake and utilization was low, nitrogen losses were high, environmental risks were large. According to crop requiring fertilizer characteristics and soil fertility to optimize fertilization and organic and inorganic fertilizer,it is the best way to achieve the goal of high production, high nutrient efficiency and environment-friendly.In Mustard-maize rotation system, the total amount of nitrogen leaching was 11.30-136.84 kg-hm"2, the average was 51.14 kg-hm-2. Mustard’s average nitrogen leaching was 14.14 kg-hm-2, and corn’s was 37.19 kg·hm"2. Corn nitrogen loss per season was 2.6 times of the mustard. Nitrogen leaching was mainly affected by fertilization and seasonal rainfall, the amount of nitrogen leaching was a significant positive correlation with the same period rainfall. Optimize fertilization could significantly reduced the nitrogen leaching, compared with conventional fertilization mustard the nitrogen leaching per season decreased by 49.7%, corn decreased by 45.7%. Nitrogen leaching increased with the fertilizer dosage. There was a significant quadratic relationship between nitrogen dosaget (x, kg-hm"2) and nitrogen leaching (y, g-hm-2):y(mustard)=0.2007x2-22.873x+5700.3,r=0.9659**, y(corn)= 1.6438x2-74.016x +5802.9, r=0.9758**.Organic and inorganic fertilizers compound could significantly reduced nitrogen leaching and volatilization losses, improved crop nitrogen uptake and soil nitrogen preservation. Compared with equal inorganic fertilizers, organic and inorganic composition reduced nitrogen leaching and volatilization by 47.3% and 52.0%, crop nitrogen uptake and utilization increased by 14.4%, soil nitrogen content increased by 25.4%. Organic and inorganic fertilizers compound was the important measures to ensure sustained high crop yield, build up soil fertility, reduce nitrogen losses, and increase nitrogen utilization.In mustard-maize rotation system, under the experimental conditions, the average processing nitrogen application rate were 507.5 kg-hm"2, where crops absorption accounted for 41.0%, losses 28.0% (9.3% leaching of nitrogen, volatile loss of nitrogen18.7%), and soil residual nitrogen 31.0%. Different nutrient management mode significantly affected the whereabouts of the nitrogen, the compound of organic and inorganic significantly improved nitrogen utilization and residual of soil nitrogen, and reduced nitrogen losses than the nitrogen fertilizer nitrogen-use efficiency increased by 9.8 percentage points, soil residual rate by 6.8%, and nitrogen loss by 50.3%. Compared with control group, enhancement of crop uptake and soil residual nitrogen increased by 6.4% and 4.0%, nitrogen leaching and volatilization declined by 6.5% and 3.5%. Therefore, fertilization scheme optimization designed by crop requiring fertilizer characteristics and soil fertility was the best nutrient management mode to achieve the goal of high production, high nutrient efficiency and environment-friendly. |
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