不同施肥条件下农田硝态氮迁移的试验研究

NO^-₃-N的淋失是旱地农田氮素损失的重要途径之一，也是引起地下水污染的一个主要原因。在黄土高原地区，夏玉米生长正逢雨季，是NO^-₃-N淋失的主要时期。该研究基于阻水层理论和黄土高原地区传统的垄作习惯，在手工模拟机具成垄压实施肥的基础上研究了该施肥法与传统的平地施肥、垄沟施肥(成垄不压实)条件下土壤NO^-₃-N的迁移动态，结果表明，在供水量相同条件下，由于平地和垄沟条件下水分分布的差异，导致平地土壤中的NO^-₃-N较垄沟耕作易于迁移。在生育前期，由于作物根系对NO^-₃-N的吸收和拦截，成垄压实与成垄不压实施肥对阻止NO^-₃-N随水下移差异不大；生育后期，当作物需肥量减小时，成垄压实施肥能够阻止NO^-₃-N向深层土壤迁移累积。玉米收获后，3种施肥方式下土壤NO^-₃-N迁移深度为平地(>60 cm)>垄沟施肥(>45 cm)>成垄压实施肥(＜35 cm)。

Experimental Study on Nitrate Transport for Different Fertilization Methods

Nitrate leaching to groundwater is one of the major nitrogen losing ways in dryland farming system. The major season of nitrate leaching is rainy season in summer as corn growing, with strong intensity of rainfall (from July to September) in the Loess Plateau region. Localized compaction ridge fertilization method is a nitrogen fertilizer application that has theoretical basis on the water flow barrier and local ridge tillage, and it is assumed that less fertilizer leaching would occur. In this paper, the nitrate transports under localized compaction ridge (which made by hand), ridge without compaction and plate fertilization method are studied. Results of the experiment show that under the same amount of supply water, nitrate of plate fertilization method is easier to move than that of ridge fertilization method as water distribution difference. In prophase of growth period, there is no notable difference in nitrate movement among localized compaction, ridge and ridge without compaction fertilization method for roots of plant absorbing and/or holding up the nitrate. In the later stage, the corn needs little fertilizer, nitrate can be held up in the upper soil with localized compaction ridge fertilization methods. At the corn harvested season, depth of nitrate leaching under plate fertilization method is the largest(>60 cm), while that under ridge without compaction fertilization method is mediate(>45 cm), and that under localized compaction and ridge is the smallest(<35 cm)