砂质农业土壤养分积累和迁移特点的研究

Accumulation and Transport of Nutrients in Agricultural Sandy Soils

研究表明,砂质土壤开垦农用后,土壤有机质和保肥性(CEC)明显下降。除大棚蔬菜地外,施用的氮和钾肥不易在土壤中积累,很容易在短时间内沿剖面迁移至地下水,或随地表径流迁移至周围水体。但磷可以活性较高的可提取态形式积累在砂质土壤剖面中,并可逐渐随水进入地下水或迁至地表水,对环境造成危害。长期施用化肥的砂质农地地下水中磷、氮浓度可达到较高的水平。田间观测和模拟淋洗试验表明,砂土中养分极易随水迁移,高浓度的养分流失常发生在施肥后的降雨过程中。因此在砂质土壤上应避免高量施肥,肥料宜少量多次施用,不宜在雨前施用肥料。

Organic matter and cation exchangeable capacity of sandy soils tended to decline following the conversion of forestland to agricultural uses. Nitrogen and potassium induced by fertilization were not significantly accumulated in the topsoils, they could be rapidly transported to groundwater or runoff to surface waters. However, phosphorus could be significantly accumulated in sandy soils as extractable forms that were active and could be gradually released into groundwater and surface waters. Long-term application of fertilizers to the sandy soils influenced significantly groundwater with increased concentrations of P and N. As compared with other soils, nutrients in the sandy soils could be easily transported with water. Significant runoff of N and P was often noted in the fertilized fields during heavy rainfall. It was recommended that application of high rate of fertilizers should be avoided, and any fertilizers should be avoided to apply in the sandy soils before the rain.