北方干旱区降解膜覆盖农田玉米生长和氮素利用模拟及优化

为了明确干旱区降解地膜覆盖下作物生长及氮肥利用特征,在内蒙古河套灌区进行两年的降解膜覆盖农田施肥试验。在降解膜覆盖下设4个施氮水平:0(BN0)、216(BN1:追施氮160)、276(BN2:追施氮220)、336(BN3:追施氮280)kg/hm2,另设高氮塑料地膜覆盖(PN3)与高氮无膜覆盖(NN3)处理作为对照。率定和验证了不同类型地膜覆盖条件的DNDC模型(denitrification-decompositionmodel,脱氮-分解作用模型),模拟并研究了不同类型地膜覆盖及不同施氮量对玉米生长、氮素吸收及利用效率的影响,并基于线性+平台模型优化了施肥模式。结果表明:在灌浆期降解地膜与塑料地膜覆盖下玉米生长无明显差异,干物质累积量2a平均仅降低了2.41%(P>0.05),但比无膜处理分别提高了9.65%(P<0.05);在收获期降解地膜与塑料地膜覆盖处理之间差异增大但仍未达显著水平,仅降低了3.07%(P>0.05),且作物的日吸氮量、产量、氮肥利用率和氮素吸收效率也无显著差异,2 a平均分别仅降低1.09%、3.97%、3.08%和2.22%(P>0.05),但比无膜覆盖处理分别提高了7.04%、13.67%、12.90%和8.90%(P<0.05)。随着施氮量增加干物质累积量的增大趋势趋于平缓甚至出现负值,施氮量为336 kg/hm2(BN3)处理较276 kg/hm2(BN2)处理降低了1.06%,日吸氮量、累积吸氮量和产量仅提高了0.35%、0.78%和0.34%(P>0.05),而比216 kg/hm2(BN1)处理分别提高了6.41%、8.38%、23.58%和35.37%(P<0.05)。通过DNDC模型不同情景模拟及线性+平台模型寻优,得到降解地膜覆盖农田施氮肥252.94 kg/hm2时,继续增加氮肥对产量无明显促进作用,为该地区降解地膜覆盖下较优的施肥模式。

Simulation and optimization of maize growth and nitrogen utilization under degradation film mulching in arid areas of North China

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.