长期不同灌溉对保护地土壤供氮能力的影响

Effect of different Irrigation Methods on Nitrogen Supplying Capacity in Protected Field

采用Stanford和Smith提出的长期间隙淋洗通气培养法,对连续7年采用渗灌、滴灌和沟灌灌溉的保护地土壤有机氮的矿化特性进行研究,并结合土壤起始矿质氮含量,探讨了不同灌溉方法条件下保护地土壤供氮能力的差异。结果表明,保护地土壤硝态氮表现出强烈的表聚特点,表聚程度以渗灌>沟灌>滴灌。长期采用不同灌溉方法显著影响保护地土壤氮矿化势及矿化速率。N0值大小的排列顺序为:滴灌>沟灌>渗灌,k值大小的排列顺序与N0恰好相反,为:渗灌>沟灌>滴灌。与渗灌和沟灌处理相比,长期采用滴灌有利于改善保护地土壤有机氮的品质。土壤供氮能力表现为渗灌>沟灌>滴灌。评价保护地土壤供氮能力时,不仅要考虑土壤有机氮累积矿化氮量的大小,同时也要考虑土壤初始矿质氮的含量。从农业节水和提高氮肥利用率及保护生态环境的角度考虑,建议在本试验措施条件下,渗灌和沟灌处理应比滴灌处理适当减少氮肥用量,且无机氮肥也要尽量晚施;在此基础上渗灌处理氮肥还要尽量深施,以减少表层硝态氮的积累,达到既节水又省肥的目的。

Characteristics of nitrogen mineralization and initial mineral nitrogen were studied in a seven-year-old protected tomato field irrigated by three ways,Subsurface irrigation,drip irrigation and furrow irrigation,using the long-term intermittent leaching aerobic incubation method（Stanford and Smith）.Difference of Nitrogen supplying capacity in protected field irrigated in three ways were studied.Results showed that soil nitrate-N accumulation was serious in 0-30 cm layers.The amount of soil nitrate-N accumulation was most by subsurface irrigation,followed by furrow irrigation and drip irrigation smallest.Nitrogen mineralization potential and mineralization rate were affected significantly by different irrigation method.The order of N0 value was drip irrigation〉 furrow irrigation 〉subsurface irrigation,the order of k value was opposite with N0.Compared with subsurface irrigation and furrow irrigation,long-term drip irrigation was more conducive to improving quality of soil organic nitrogen in protected fields.The order of nitrogen supplying capacity was subsurface irrigation〉furrow irrigation〉drip irrigation.Evaluation of soil nitrogen supplying capacity,should not only consider the accumulative mineralization amount of soil organic nitrogen,but also take into account the content of initial soil mineral nitrogen.More attention should be paid to preventing salt accumulation,and reduce the amount of applying nitrogen fertilizer under long-term subsurface irrigation.Compared with drip irrigation,subsurface irrigation and furrow irrigation should apply nitrogen fertilizer later and deeper in order to save water,improve nitrogen use efficiency and protect the ecological environment.