Abstract
It is great meaningful to optimize the fertilization system under degradable film mulching for alleviating environmental pollution. In order to capture the effects of degradable film mulching on crop growth and nitrogen fertilizer utilization under in arid area, a two-year experiment (2016-2017) was carried out at the Muleitan water-saving experimental station in Hetao Irrigation District, Inner Mongolia of China. Four nitrogen application levels were set under degradable film mulching: 0 (BN0), 216 (BN1: 160 for topdressing), 276 (BN2: 220 for topdressing) and 336 (BN3: 280 for topdressing) kg/ha, and high nitrogen with plastic film mulching (PN3) and high nitrogen with no mulching (NN3) treatment as a control. The effects of different types of film mulching and different nitrogen application rates on maize growth, nitrogen uptake and utilization efficiency were studied, and the DNDC (denitrification-decomposition) models for different types of film mulching were calibrated and verified, and fertilizer pattern was optimized under degradable film mulching based on the linear and platform model. The results showed that simulated data of the DNDC model on the nitrogen uptake, dry matter accumulation and yield of crops are in good agreement with the measured results, EF and R2 were all greater than 0.93, RMSE was 0.10-0.16, 1181.52-1236.68 and 723.94-761.3 kg/ha, NRMSE 7.85%-13.34%, 9.18%-9.73% and 7.52%-8.28%, respectively. There were no significant differences for maize growth between degradable film mulching and plastic film mulching during maize filling stage, the dry matter accumulation for degradable film mulching treatment decreased by 2.41% (P>0.05) compared with the plastic film mulching treatment, and increased by 9.65% (P<0.05) compared with no film mulching treatment. In maize harvest period, the difference of maize growth between plastic film mulching and degradable film mulching increased butdid not reach significant level, only 3.07% (P>0.05), and increased by 9.69% (P<0.05) compared with no film mulching treatment. There were no significant differences in nitrogen uptake, yield, nitrogen use efficiency and daily nitrogen uptake efficiency between the degradable film mulching and plastic film mulching, only decreased by 1.09%, 3.97%, 3.08% and 2.22% (P>0.05), but increased significantly by 7.04%, 13.67%, 12.90% and 8.90% compared with no mulching treatment (P<0.05), respectively. The growth rate of dry matter accumulation was decreased by 1.06%, daily nitrogen uptake, accumulation nitrogen uptake and yield only increased by 0.35%, 0.78 and 0.34% with the increase of nitrogen application rate for BN3 compared with BN2, respectively (P>0.05), while increased by 6.41%, 8.38%, 23.58%, and 35.37% (P<0.05) compared with BN1, so the BN2 treatment with the topdressing nitrogen content of 220 kg/ha showed the best growth and nitrogen utilization. Additionally, the optimal nitrogen rate was 252.94 kg/ha that was obtained by different scenario simulation of DNDC model and optimization of linear and platform model under the degradable film mulching, and there was high nitrogen utilization efficiency, and the yield-increasing effect would not appear if nitrogen fertilizer was continued to increase. So, there was similar effects of degradable film mulching on maize growth and nitrogen utilization compared with plastic film mulching, and the optimal nitrogen application was 252.94 kg/ha, and the maize yield could reach 11 357.37 kg/ha under degradable film mulching in arid area.
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