水稻肥料定位试验中土壤各形态磷的变化动态研究

Research on soil phosphorus dynamic change under rice fertilization experiments

研究了水稻长期定位肥料试验土壤各形态磷的动态变化及其对水稻生长的影响．长期定位试验设有CK（不施肥）和施NK、NP、NPK4个肥料处理，采用修正的Hedley法对水稻长期定位肥料试验土壤各形态磷进行了研究，结果表明，在集约种稻条件下，土壤活性磷很快发生了变化，从试验第2季开始，不施磷处理（CK、NK）水稻产量明显下降，树脂-P和NaHCO3-Pi均表现出明显的下降趋势，在试验结束时树脂-P含量下降到了其初始含量的30％～60％左右，处于极低的水平状态，而且，随着活性磷的移走，NaOH—Pi、HCl-P和残留-P开始下降补充有效磷．在施磷处理（NP，NPK）中，NaOH—Pi和HCl-P也有下降，而残留-P却有所积累，试验结束时比试验前增加了51％．在水稻的连续种植下，NaHCO3-Po量以每年1～3mg·kg^-1速度下降而NaOH—Po基本上没有变化，表明NaHCO3提取的有机磷比NaOH提取的有机磷对植物更有效．同时也表明，用中等有效磷和稳定性磷来补充活性磷十分有限，在磷肥管理中必需合理增加磷肥的投入来维持土壤磷供应能力从而增加水稻产量。

A four-year field experiment was conducted on a calcareous paddy soil in Zhejiang Province to quantify the dynamics of soil phosphorus （P） pools and their influence on rice grown in an irrigated doublecropping system. Treatments included an unfertilized control （CK） and three different fertilizer treatments （NP, NK and NPK）. A modified Hedley P fractionation method was used to trace the dynamics of soil P pools. Under intensive rice cropping, rapid changes in plant available P fractions occurred depending on the overall P input-output balance. In treatments without P application, significant rice yield losses evolved after the second rice crop and available soil P reserves were drawn down during the subsequent growing seasons. Labile P fractions （Resin-Pi and NaHCO3-Pi） decreased in all treatments and resin-Pi at the end of the experiment was only 30%-60% of the initial level. In no P treatments （CK, NK）, NaOH-Pi, HCl-P, and residue-P contributed to replenishing labile P when soil available P was continuously removed. In treatments with P addition （NP, NPK）, NaOH-Pi and HCl-P were also reduced, while residue-P accumulated , resulting in a 51% increase. The content of NaHCO3-Po decreased by 1-3 mg· kg^-1 . year^-1 under continuous rice cropping, while the content of NaOH-Po remained unchanged, indicating that the Po form extracted by NaHCO3 was more available than the Po form extracted by NaOH. Since replenishment of labile P pools by more recalcitrant P pools is limited, regular P additions are required in intensive cropping systems to maintain the effective soil P supply at levels that are required for high yields.