河西绿洲灌区膜下滴灌水稻氮素平衡及氮肥投入阈值研究

Research on nitrogen equilibrium and nitrogen fertilizer input threshold in rice soil with drip irrigation in the Hexi Oasis irrigation area

为确定河西绿洲灌区膜下滴灌条件下基于产量及环境安全的水稻氮肥投入阈值,于2020、2021年在张掖节水农业试验站开展水稻膜下滴灌栽培田间试验,研究不同施氮水平(纯氮0、135、225、315、405 kg·hm^(-2))对水稻产量、土壤矿质氮累积及土壤氮素平衡的影响。结果表明,水稻产量与施氮量呈显著的二次抛物线关系,最佳经济效益氮肥用量为222 kg·hm^(-2),对应水稻产量为5684 kg·hm^(-2)(最高产量的99.7%)。土壤矿质氮累积量与施氮量呈显著的指数相关关系,施氮量为225 kg·hm^(-2)时,矿质氮累积量为119 kg·hm^(-2),与135 kg·hm^(-2)施氮量处理差异不显著,施氮量达到315 kg·hm^(-2)时,矿质氮累积量显著增加,并且出现由浅层向深层迁移的趋势;氮表观平衡值与施氮量呈显著线性正相关,土壤氮素达到表观平衡时,对应的施氮量为171 kg·hm^(-2)。综合考虑产量、矿质氮累积量、土壤氮盈余与施氮量的关系,得出河西绿洲灌区膜下滴灌水稻合理氮肥投入阈值为171~222 kg·hm^(-2)。该施氮量比最高产量氮肥用量降低10.8%~31.3%,既保证了水稻高产稳产,又有效降低了氮素在土壤中的盈余与淋失风险,为该区域水稻减氮高产高效栽培提供了理论依据。

In order to determine the nitrogen fertilizer input threshold of rice based on yield and environmental safety under drip irrigation in the Hexi Oasis irrigation area,field tests on rice drip irrigation were conducted at the Zhangye Water-Saving Agricultural Pilot Station in 2020 and 2021.Five nitrogen application levels of 0,135,225,315 kg·hm^(-2),and 405 kg·hm^(-2) were set and labeled as N0,N1,N2,N3,and N4,respectively.Then,the impacts of the nitrogen application levels on the rice yield,accumulative mineral nitrogen,and nitrogen balance in soil were studied.The results showed that nitrogen application significantly increased the rice yield and formed a significant quadratic parabolic curve together with the rice yield and the amount of nitrogen applied.The rice yield reached the value of 5684 kg·hm^(-2)(99.7%of the maxium yield)when 222 kg·hm^(-2) of nitrogen was applied.There was a significant exponential correlation between the cumulative amount of mineral nitrogen in soil and the amount of nitrogen applied.When the amount of nitrogen applied was 315 kg·hm^(-2),the cumulative amount of mineral nitrogen was 151 kg·hm^(-2),which was significantly higher than the levels of 119 kg·hm^(-2) when the amount of nitrogen applied was 225 kg·hm^(-2).Additionally,when the amount of nitrogen applied reached 315 kg·hm^(-2),the mineral nitrogen moved from the shallow to deep layers,following a trend of aggregation.There was a significant linear correlation between the nitrogen apparent balance value and the amount of nitrogen applied.The amount of nitrogen applied was 171 kg·hm^(-2) when the nitrogen apparent balance value of nitrogen was 0.When the amount of nitrogen applied ranged from 171 to 222 kg·hm^(-2),the rice yield was 5551 to 5684 kg·hm^(-2),the cumulative amount of mineral nitrogen in soil was 104 kg·hm^(-2) to 118 kg·hm^(-2),and the nitrogen balance value was 0 kg·hm^(-2) to 44 kg·hm^(-2).By considering the relationship among the yield,accumulative amount of mineral nitrogen,soil nitrogen surplus,and the amount of nitrogen applied,the proposed rational nitrogen fertilizer input threshold for rice under drip irrigation in the Hexi Oasis irrigation area is 171 kg·hm^(-2) to 222 kg·hm^(-2).Under this nitrogen application condition,the rice yield is high,the input and output of nitrogen in soil reach equilibrium,and the cumulative amount of mineral nitrogen is low,ensuring a high and stable rice yield and reducing environmental risks.