不同降水年型滴灌玉米土壤硝态氮分布、淋失量及氮素吸收利用特征

Soil nitrate-N distribution, leaching loss and nitrogen uptake and utilization of maize under drip irrigation in different precipitation years

  • 摘要: 为寻找满足宁夏地区滴灌条件下不同降水年型的科学施肥模式, 缓解不合理施氮导致的资源浪费、黄河水质下降和地下水污染等问题, 于2018—2020年在宁夏平吉堡农场开展氮梯度试验, 分析不同降水年型下不同施氮处理土壤硝态氮残留和淋溶量以及对滴灌玉米氮素吸收利用和产量的影响。结果表明: 土壤硝态氮含量峰值与降水量密切相关, 丰水年(2018年)硝态氮残留量峰值在40~60 cm土层, 枯水年(2019年和2020年)在20~40 cm土层; 不同降水年型土壤硝态氮残留量和淋失量均随施氮量的增加而增加, 且降水量显著影响硝态氮淋失量; 丰水年由降水因素导致的硝态氮淋失量占总淋失量的50.62%, 枯水年占总淋失量的34.82%。回归分析结果表明, 不同降水年型玉米产量随施氮量呈先上升后下降的趋势, 均在N3处理(施N量为270 kg∙hm−2)下达最高产量, 且N3处理的产量和吸氮量与N4处理(施N量为360 kg∙hm−2)无显著差异; 丰水年N3处理的氮肥利用率、氮肥农学效率和氮肥偏生产力比N4处理分别提升11.38%、6.16 kg∙kg−1和13.85 kg∙kg−1, 枯水年分别提升12.10%、5.06 kg∙kg−1和15.00 kg∙kg−1。综合考量不同降水年型0~100 cm土层硝态氮分布特征和硝态氮淋失量及施氮处理下的产量、氮素吸收利用, 推荐宁夏引黄灌区滴灌玉米不同降水年型下施氮量在270 kg∙hm−2时较适宜, 丰水年施氮最大阈值为275.59 kg∙hm−2 , 枯水年施氮最大阈值为320.20 kg∙hm−2

     

    Abstract: To improve crop yield, excessive nitrogen usage in agricultural production has become increasingly important in recent years. Excessive nitrogen use increases soil nitrate-N accumulation and water pollution, and nitrogen leaching loss varies with precipitation year. It is of great significance to clarify the scientific fertilization model in different precipitation year types under drip irrigation in Ningxia to alleviate the problems of resource waste, water quality decline in the Yellow River, and groundwater pollution caused by unreasonable nitrogen usage. In this study, a 3-year nitrogen gradient experiment was carried out in the Pingjipu Farm, Ningxia Hui Autonomous Region, with five nitrogen application treatments: 360 kg∙hm−2 (N4), 270 kg∙hm−2 (N3), 180 kg∙hm−2 (N2), 90 kg∙hm−2 (N1), and 0 kg∙hm−2 (N0), to analyze the effects of different nitrogen fertilization treatments on soil nitrate-N residues and leaching amounts, as well as on nitrogen uptake, utilization, and yield of maize under drip irrigation in rainy and dry years. The results showed that the peak value of soil nitrate-N content was closely related to precipitation; the peak value of nitrate-N residue was in the 40–60 cm soil layer in the rainy year (2018), and in the 20–40 cm soil layer in the dry years (2019 and 2020). In different precipitation years, soil nitrate-N residues, and leaching increased with the increased nitrogen usage and reached the maximum value under the N4 treatment. Precipitation significantly affected nitrate leaching, and in rainy years, the nitrate-N leaching loss caused by precipitation accounted for 50.62% of the total leaching loss, while in the dry year accounted for 34.82% of the total leaching loss. The regression analysis showed that maize yield initially increased and then decreased by the application rate of nitrogen in different precipitation years. The maximum yield was found under 270 kg∙hm−2 (N3) in different precipitation years, and the yield and nitrogen uptake under the N3 treatment did not differ from 360 kg∙hm−2 (N4). In rainy year, compared with N4, the utilization rate, agronomic utilization rate, and partial nitrogen fertilizer productivity increased by 11.38%, 6.16 kg∙kg−1, and 13.85 kg∙kg−1; and in dry years, they were increased by 12.10%, 5.06 kg∙kg−1, and 15.00 kg∙kg−1, respectively. In summary, when the nitrogen application rate was 270 kg∙hm−2, the yield, nitrogen uptake, and utilization of maize in rainy and dry years were maintained at a high level, and the amount of nitrate leaching was also within an acceptable range. It is recommended that 270 kg∙hm−2 is the appropriate nitrogen application rate for maize under different precipitation patterns in the Ningxia Yellow River irrigation area. The maximum threshold of nitrogen usage in the rainy year is 275.59 kg∙hm−2, and that in the dry year is 320.20 kg∙hm−2. The results from this study can provide a theoretical basis for the decision of scientific nitrogen application in different precipitation years of drip-irrigated maize in the Ningxia Hui Autonomous Region.