干旱半干旱地区农田土壤NO_3-N深层积累及其影响因素

ACCUMULATION OF NO_3-N IN DEEP LAYERS OF DRY FARMLAND AND ITS AFFECTING FACTORS IN ARID AND SEMI-ARID AREAS

以长期试验资料为基础,着重分析了干旱半干旱地区农田系统中施肥、作物、降水、耕作措施以及土壤类型和特性对产生土壤NO3 N深层积累的影响。分析发现,氮肥的过量施用和400～800mm降水量偏低是导致干旱半干旱地区土壤NO3 N积累在100～300cm土层的主要因素。随着氮肥用量的增加,NO3 N深层积累显著增加;氮磷配施有助于降低其积累量。不同作物对氮素的吸收利用效率也是影响NO3 N深层积累的因素,作物之间的轮作方式会有效降低NO3 N深层积累;休闲期种植合理植物可有效降低NO3 N深层积累。NO3 N深层积累主要产生在质地较重的土壤上,带正电荷粘土矿物对NO3 N吸附是导致热带土壤中NO3 N积累的主要因素。深入研究深层积累NO3 N的生物有效性、迁移变化机理、与作物根系之间的关系以及对土壤性状和环境的影响具有重要意义。

Accumulation of NO3N in deep layers is the unique of N cycle in rained farmland in the arid and semiarid areas. Based on the longterm experiment, the effects of fertilization, crop, rainfall, tillage systems, rotation, and soil properties on the NO3N accumulation were reviewed. The over application of nitrogen fertilizer and the precipitation of 400～800 mm mainly contributed to the NO3N accumulation in the 100～300 cm depth. The NO3N accumulation in the 100～300 cm depth was increased with the increase of N rates, fertilizer N incorporation with phosphate fertilizer could reduce the NO3N accumulation. The nitrogen usage efficiency also affect NO3N accumulation due to N uptake by crops, crop rotation and fallow crop could reduce the NO3N accumulation. NO3N accumulation was mainly developed in the soils with heavy texture. The clay mineral with large positive charge mainly contributes to NO3N accumulation in the tropical soils. The further research emphases about the NO3N accumulation in the deep depth were put forward as follows: bioavailability, transport in soil profile under rain fed or irrigation, the relation to crop root distribution and growth, and the effect of the NO3N accumulation on soil properties and soil gas.