Study On Different Nitrogen Application Levels On Nitrogen Transport,Conversion And Effects Of Utilization Rate In Sandy Farmland

The experimental area of this study is located in Nanitan Village,Bulanghe Township,Yuyang District,Yulin City,Shaanxi Province.The subjects were spring maize grown locally for two years,from 2017 to 2018.Based on the analysis of soil moisture content,crop growth index and soil nitrogen under different nitrogen application treatments during the experiment,the applicability of RZWQM2 model in the experimental area was validated by two-year field test data.The spring maize variety planted in the study area was “Woyu No.3”,and the corn growth index and nitrogen application rate were positively correlated to some extent.Similarly,the change of nitrate nitrogen in the soil of the study area is mostly 0~40cm,and the accumulation of nitrate nitrogen provided by the deep soil layer accounts for more than 67.4% of the accumulation of nitrate nitrogen in the 0~70cm of the whole soil layer.During the experiment in 2018,the nitrogen uptake of T100~T400 different nitrogen treatment crops was 230.20 to 360.05kg/ha,and the nitrogen uptake of T300~T400 nitrogen treatment crops was not significant(p>0.05),while there was significant difference between the T300~T400 nitrogen treatment and the T100 and CK nitrogen treatment(p<0.05).It indicates that the increase of nitrogen application rate would affect the nitrogen uptake of crops.However,when the nitrogen application rate exceeds a certain value,increasing the nitrogen application rate would not significantly increase the nitrogen uptake of crops.During the 2018 experimental period,the loss of nitrogen in the nitrogen treatment of T100~T400 increased with the increase of soil nitrogen application.The losses of nitrogen in the four different treatments were 41.88kg/ha,96.19kg/ha,96.57kg/ha and 195.07kg/ha,respectively.The apparent nitrogen loss of T100~T300 was not significantly different(p>0.05),and the apparent nitrogen loss of these three treatments was significantly different from that of T400(p<0.05).This shows that excessive application of nitrogen can cause nitrogen loss and waste.The nitrogen agronomic efficiency of nitrogen use efficiency in 2018 ranged from 12.95 to 20.69 kg/kg with an average of 17.5 kg/kg.The nitrogen use efficiency of CK~T400 treated with different nitrogen treatments was 72.21 to 102.26kg/kg.The physiological efficiency of nitrogen fertilizer varied from 49.39 to 66.30kg/kg in the different nitrogen treatments from T100 to T400,with an average of 54.35kg/kg.The partial productivity of nitrogen fertilizer was 39.41 to 104.87kg/kg under the different nitrogen treatments,and the average value was 63.72kg/kg.The difference of nitrogen fertilizer productivity between T300 and T400 treatment was not significant(p>0.05),T100 treatment,The difference in nitrogen fertilizer productivity between T200 treatment and T300 and T400 treatment was significant(p<0.05).The RZWQM2 model was calibrated with field data in 2017 and validated with field data in 2018.The results show that the soil moisture content and soil nitrogen simulation effect of 10~60cm soil layer is better than the surface layer 0~10cm.Comprehensive analysis shows that the model can well simulate of the experimental area.