The Impact Of Nitrogen Fertilization On Wheat, Tomato Yield And Quality And The Dryland Soil Nitrogen Leaching

The conflicts between agricultural resources and agricultural eco-environmental protection is becoming more obvious, with the rapid economic development in China. The problems regarding the effective utilization of nitrogen fertilizer must be solved around the world. The ecological crisis of cultivated land resources in China is serious, and one of the most important factors in agricultural production is the overuse of soil and heavy use of fertilizers. The cost of nitrogen fertilizer is highest in agricultural production. This situation will not change in the nearest future. The amount of nitrogen fertilizer increases year by year, and excessive use of fertilizers has a negative impact on the environment. As a result, the principle and approaches of rational utilization of chemical fertilizer are enhanced under the high output and the reduction of fertilizer. Meanwhile, an incubation experiment was conducted to study the characteristics of N leakage losses and to investigate the behavior of the over-rated nitrogen fertilizer. We study the effects of different amount of nitrogen fertilizer on yield and quality of wheat and tomato. The experiment explored the negative effects on crop physiology and the environment under the conditions of over-rated fertilizer. Soil N losses through leakage process under over-rated nitrogen fertilizer was also simulated. Results showed as followings:(1)The output of wheat increased with the nitrogen levels, the output of wheat had the declining trend after the nitrogen quantity surpassed the certain value. When the nitrogen fertilizer was 184 kg/hm2, the maximum of output was 8.75t/hm2.(2)The grain protein of wheat was improved with nitrogen level's enhancement. When the nitrogen fertilizer was 242kg/hm2, the maximum value of protein content was 16.64%. The grain protein of wheat had the declining trend after the nitrogen quantity surpassed 242kg/hm2. (3)The agronomic use efficiency of nitrogen fertilizer was reduced when the nitrogen level increased. If nitrogenous fertilizer was reduced suitably, farmers may reduce the production investment and increase economic output.(4)With the nitrogen level's enhancement, the output of tomato increased. The output of tomato had the declining trend after the nitrogen quantity surpassed certain value. When the nitrogenous fertilizer was 113kg/hm2, the output was the highest.(5)Theoretical income of tomato increased after suitable nitrogenous fertilizer, and declined after excessive nitrogenous fertilizer was applied. The fertilizer input for optimum theoretical income was between112 kg/hm2 to 140 kg/hm2.(6)The experiment found that NO3--N and NH4+-N in the two kind of soils increased after the straw was incorporated.(7)The slow-release fertilizer (SRF) and urea had the different influences to soil nitrogen losses through leaching: The SRF released nitrogen gradually and slowly, while urea released large-scaled nitrogen in a short time which did not fit the growth pattern of the crops, thus did not favor the crops to absorb nitrogen.(8)NO3--N was different from NH4+-N in leaching process in the soil, NO3--N was easier to loss through leaching than NH4+-N. NO3--N was the dominant form of leaching in garden soil.