长期定位施肥对水稻土磷素形态的影响

本文通过长期定位施肥试验研究了21年不同施肥处理水稻土中磷素形态及其含量的变化。结果表明，长期不施肥的土壤无论是有机磷还是无机磷中有效磷含量均呈下降趋势，而有机-无机肥配施的有机磷含量不仅高于无肥处理而且还高于单施化肥的处理，并且有利于活性和中度活性有机磷含量的提高。对无机磷的影响，有机-无机肥配施不仅有利于提高Ca-P、Al-P和Fe-P的含量，而且对促进闭蓄态磷的活化效果明显。可见有机-无机肥配施可提高土壤有机磷含量和增加土壤无机磷有效形态的含量。另从土壤有效磷对水稻产量的影响分析可知:当红壤稻田土壤有效磷含量在20mg/kg左右时，增施磷肥对水稻增产效果不明显。

Influence of long-term localized fertilization on phosphorus forms in paddy soil

An experiment was carried out to study the change of the content and forms of phosphorous (P) in a red paddy soil under 21 years—localized fertilization. The result showed: both organic P and available P content decreased without fertilization. The content of organic P under combining application of organic and inorganic fertilizer was higher than those under no fertilization and solo chemical fertilizer application. Combining application of organ-inorganic fertilizer not only could increase the content of Al-P, Fe-P and Ca-P in red paddy soil, but also significantly improve the activation of O-P, indicating that combining application of organic - inorganic fertilizer could enhance the content of both soil organic P and available P. Furthermore，our results showed that applying additional P had negligible effect on rice yield when the content of the available phosphorus in the red paddy soil was around 20mg/kg.