低分子量有机酸对不同肥力土壤磷素的活化作用

Activation of organic acids on phosphorus of soil with different fertility

针对石灰性土壤磷素固定累积问题,采用化学浸提方法,探讨低分子有机酸对不同肥力水平土壤磷素的活化作用,提高磷素的有效性。结果表明,对于低肥力和中肥力土壤,相同浓度下有机酸活化土壤磷的能力表现为草酸>柠檬酸>苹果酸;对于高肥力土壤,相同浓度下有机酸活化土壤磷的能力为柠檬酸>草酸>苹果酸。低浓度时有机酸对土壤磷的活化有抑制作用,在速效磷含量较低的低肥力、中肥力土壤上抑制作用较为明显,而苹果酸的抑制作用最为显著。有机酸能显著降低土壤浸提液pH值,柠檬酸的降低作用最强。对同一种有机酸而言,土壤磷的活化量随pH值的升高而降低。

To solve the problem of soil phosphorus accumulation and fixation in calcareous soil,extraction experiments were conducted to investigate the effect of organic acids with low molecular weight（LMW） on phosphorus activity in different fertile calcareous soils.The results showed that the organic acids could significantly stimulate the mobilization of soil phosphorus in all three soils tested.When in the same concentration,the three organic acids followed an order of oxalic acidcitric acidmalic acid in the capability of activating soil phosphorus in the low fertility and moderate fertility soil;In the high fertility soil,the three followed the order of citric acidoxalic acidmalic acid.Low concentration of organic acids（≤2 mmol/L） could significantly restrained soil phosphorus activity in low and moderate fertility soil,especially for the malic acid.LMW organic acids could decline the pH of soil extract significantly,and the citric acid showed the strongest declining capacity. Meanwhile,for the same kind of organic acid,the extent of phosphorus activating decreased with the increasing of soil pH.