长期施无机磷肥对黄泥土稻田土壤磷库的影响

Effects of long-term application of inorganic phosphate fertilizer to soil phosphorus pools in yellow-mud soil paddy fields

本研究选取太湖流域黄泥土长期定位试验田作为研究对象,明确40 a长期施磷对水稻土土壤磷库、磷形态及有效性的影响。结果表明:长期施磷(NPK)处理的土壤总磷和有效磷含量高达589.58 mg·kg^(-1)和51.67 mg·kg^(-1),比不施磷(NK)处理显著增加126.61%和216.41%。两处理无机磷均以Fe-P和Ca-P为主,约占无机磷的69.53%~79.86%,有机磷以活性和中活性有机磷为主。长期施磷使稻田无机磷含量在3个生育期均极显著增加,增幅为170%以上,其中Al-P和Fe-P的含量及相对占比显著提升,Ca-P含量增加但相对含量明显降低,O-P含量变化较小而相对含量降低。长期施磷处理下有机磷含量仅在分蘖期增幅显著(33%),主要表现为活性和中活性有机磷含量显著增加。与分蘖期相比,抽穗期长期施磷处理的Al-P、Fe-P以及高稳定有机磷的相对含量明显下降,Ca-P和中活性有机磷的相对含量上升,而长期不施磷处理表现为Fe-P、O-P以及高稳定有机磷的相对含量下降,Ca-P和中活性有机磷的相对含量上升。Al-P、Fe-P、Ca-P、O-P和中活性有机磷均与有效磷(AP)显著正相关。研究发现:Al-P、Fe-P和Ca-P是黄泥土稻田最主要的有效磷源,土壤缺磷时土壤磷酸酶等对有机磷的活化也是重要的有效磷来源之一;长期施用无机磷肥导致稻田土壤无机磷库累积明显,磷流失风险增加,因此应在保证稻麦高产的前提下合理降低磷肥施入量,充分活化利用土壤中固存的难溶态磷来提高土壤磷素利用率。

In this study,a long-term positioning field in the Taihu Lake basin was selected to study the effects of long-term chemical phosphorus(P)fertilizer application on soil P content,form,and availability(yellow-mud soil).The results showed that the soil total P and available P contents in NPK treatment were as high as 589.58 mg·kg^(-1)and 51.67 mg·kg^(-1),which were significantly increased by 126.61%and 216.41%over the no P(NK)treatment.The inorganic P in the two treatments was mainly Fe-P and Ca-P,which accounted for approximately 69.53%–79.86%of inorganic P.Organic P was mainly active and medium active organic P.Long-term P application significantly increased the inorganic P content by more than 170%in the three growth stages of the yellow-mud soil field in comparison with the NK treatment.The content and relative proportion of Al-P and Fe-P increased significantly,the Ca-P content increased while the relative proportion was significantly reduced.In addition,the O-P content remained stable,but the relative proportion decreased.Organic P content,especially active and moderately active organic P content,increased significantly only at the tillering stage(33%).Compared with the tillering stage,the relative proportions of Al-P,Fe-P,and highly stable organic P in the NPK treatment decreased,while the Fe-P,O-P,and highly stable organic P in the NK treatment decreased at the heading stage,while Ca-P and medium active organic P increased.Al-P,Fe-P,Ca-P,O-P,and moderately active organic P in yellow-mud soil were significantly positively correlated with available P(AP).The results indicated that Al-P,Fe-P,and Ca-P were the main effective P sources in yellow-mud soil paddy fields,and the activation of organic P by soil phosphatase was an important source of available P when the soil is short of P.Long-term application of inorganic P fertilizer resulted in the obvious accumulation of inorganic P pools in paddy soil and increased the risk of P loss.Therefore,the amount of P fertilizer should be reasonably reduced through organic P substitution to promote the activation of soil insoluble P to ensure a high yield of rice and wheat and reduce the risk of P loss.