交替根区滴灌施肥（氮）对蔬菜生长以及氮素利用与迁移的影响

Both alternate partial rootzone irrigation and drip irrigation has great potential in saving irrigation water, stabilizing yield and improving quality of vegetable. Alternate partial rootzone drip irrigation (APRDI), combined by the two water-saving irrigation technologies should be theoretically more efficient in saving water than anyone of these two technologies independently. However, there lack systematic researches on the APRDI. Furthermore, little information is available about how to apply fertilizer simultaneously with irrigation, forming alternate partial rootzone drip fertigation (APRDF). The coupling effects of different water and fertilizer supply under APRDF is also absent. Nitrogen fertilizer is one of the most frequently applied fertilizers in agriculture production. In this research, the suitable soil water conditions for the alteration of irrigation event under the APRDI will be examined, the coupling effects of water and fertilizer (nitrogen fertilizer) supply under APRDF and its mechanisms will be explored. The utilization, movement and distribution in soil profile of fertilized nitrogen or residual nitrate accumulated in different soil layers under APRDF will be observed by 15N label technology under three successive cultivations. The outcome of this research will reveal the soil water condition for controlling the alteration of fertigation under APRDF, explore the water- and fertilizer-saving effects, and elucidate the mechanisms for improvement of yield and quality under APRDF. All these results will provide theoretical support and new fertigation model for efficient use of irrigation water and fertilizer and thus reducing environmental risks in agricultural practice.

交替根区灌溉具有较大的节水、稳产、调质效应；滴灌也具有很大的节水增产作用。两种技术结合形成交替根区滴灌，理论上应该更加具有节水效果。但目前对于交替根区滴灌缺乏系统深入的研究，对这种具有较大节水潜力的灌溉方式下如何进行水肥耦合（形成交替根区滴灌施肥）及其耦合效应与机理缺乏报道。氮肥是农业生产中施用量最大的肥料之一。本项目研究滴灌下根区交替灌溉进行的土壤水分控制条件、交替根区滴灌施肥水氮耦合效应与作用机理，以及利用15N标记、通过多茬种植的方法研究交替根区滴灌施肥下蔬菜对肥料氮、土壤剖面中不同层次累积硝态氮的累积吸收利用率以及标记氮在土壤剖面中长期迁移行为的影响，以期明确交替根区滴灌施肥的控制条件，探讨交替根区滴灌施肥的节水节肥效果，阐明其增产调质作用机制，为农业水肥资源高效利用及降低环境风险提供理论指导和新的灌溉施肥模式。

交替根区滴灌(APRDI)是滴灌技术和分根区交替灌溉技术相结合的一种创新的灌溉施肥方式，具有较大的节水潜力。然而，目前对APRDI缺乏系统深入的研究。本项目研究APRDI进行的土壤水分控制条件、水氮(APRDF)耦合效应，以及利用15N标记技术研究APRDF下多茬作物对肥料氮、土壤剖面中硝态氮的吸收利用与迁移行为的影响。结果发现APRDI在亏缺灌溉量下具有明显的节水增产效应，其中以在70%θf（田间持水量）下进行交替滴灌为最佳，该处理下能促进光合作用，提高保护酶及硝酸还原酶活性，调节体内激素含量；促进根系生长，有利于氮素在耕层的积累和利用；亏缺灌溉下控制土壤水分70%θf的APRDI滴灌处理可以比常规滴灌节水32.1%，比漫灌节水45.0%，但对产量没有显著影响，水分利用效率比常规滴灌提高了46.6%。.与常规滴灌相比，在产量不降低的情况下APRDF可使番茄节约水氮33.3%，西瓜节水40%、氮肥节约50%,并提高了品质。在有机肥氮替代下APRDF处理下西瓜产量增幅从22.5%（无有机肥）下降到12.0%（70%有机肥氮），交替滴灌促进了土壤脲酶、过氧化氢酶、磷酸酶、蔗糖酶活性，以70%有机肥氮替代下APRDF处理最佳。.APRDF有利于降低肥料氮在土壤中的淋溶。第一茬作物种植后肥料氮的利用率比常规滴灌平均提高了10.3%，损失率降低了25.3%；三茬后15N总利用率达到64.6%，比常规滴灌增加了19.2%，损失率平均为26.2%，比常规滴灌降低了29.4%。APRDF下对土壤中30-40cm层次累积的硝态氮当季作物利用率在12.7-19.9%之间，损失率在5.8-11.7%，三茬作物后总利用率为24.1-30.9%，损失率为11.7-23.0%，在低水条件下，损失率和利用率都较低。.因此，交替根区滴灌施氮具有较好的节水、稳产、提质和良好的环境效应。