长期不同施肥处理水稻土磷素在剖面的分布与移动

稻麦轮作黄泥土施肥试验始于1980年,共布置不施肥、纯化肥、有机肥(猪粪或菜籽饼)、化肥加有机肥、氮肥加秸秆、氮肥加有机肥加秸秆等14种处理。2003年11月麦季取土壤样品分析结果表明:(1)与无肥处理相比,施磷处理和有机肥处理耕层土壤全磷(TP)含量皆有显著增加,并且表现出向下迁移的迹象,有机肥配施NPK化肥处理土壤磷的迁移可达30 cm深度,其余施磷处理均至25 cm。(2)大部分施磷处理在表层0~25 cm内无机磷(I-P)总量发生显著性变化,Ca2-P由于其溶解性强可迁移到30 cm以下,Al-P、Fe-P、Oc-P(闭蓄态磷)的迁移可达25 cm,Ca8-P至20 cm;Ca10-P含量只在有化肥P输入的6个处理的0~15 cm耕层土壤中有显著性增加。(3)土壤有机磷(O-P)含量的变化小于无机磷的变化,只有无机磷配施有机肥的3个处理和仅施PK化肥的处理,其耕层土壤有机磷发生显著性增加。

ACCUMULATION AND DOWNWARD TRANSPORT OF PHOSPHORUS IN PADDY SOIL IN LONG-TERM FERTILIZATION EXPERIMENTS

Objectives of the study were to explore forms, quantities and distribution of soil phophorus in profile of paddy soil as affected by different fertilization patterns in a long-term experiment under a rice wheat (or rape) cropping system, and to evaluate potential effects of transformat ion and downward transport of phosphorus on environment.The experiment that has been carrying on since 1980 on a permeable paddy soil (huang ni tu), is designed to have 14 treatments with 3 replicates.Soil samples were collected from the top soil (0~15 cm) and then layers 5 cm apart till 1 m in depth in November 2002.Significant P accumulation was found at the depth of 25 cm for all P treatments but Treatment M_NPK (Manure+fertilizer N+fertilizer P+fertil izer K) where it was detected at the depth of 30 cm.Inorganic P (I-P) concentrations increased significantly in the soil layer of 0~25 cm for most P treatments.Ca₂-P moved beneath 30 cm in soil depth, Al-P, Fe-P and Occluded-P (Oc-P) to 25 cm in depth, and Ca₈-P to 20 cm in depth.Ca₁₀-P contents increased significantly only in treatments with fert ilizer P application, showing manure P keeps available longer than fertilizer P.Changes in O-P were smaller than I-P in range.Merely in the plots with manure plus fert ilizer P or with fert ilizer P and K, the organic P (O-P) concentration in the top soils (0~15 cm) increased significantly.Long term of P application exceeding P removal by crops were not economical because more inactive Oc-P and Ca₁₀-P accumulated, and led to P accumulation in the top soil and hence the potential of P loss via surface runoff and leaching that would threaten the quality of surface water and groundwater.