连续6年施磷肥对土壤磷素积累、形态转化及有效性的影响

长期施磷肥对土壤磷素积累、形态转化以及有效性的影响是国内外土壤化学研究的热点之一。本研究利用从2008年开始在京南地区进行的紫花苜蓿连续6年施用磷肥定位试验,研究不同施肥处理对紫花苜蓿田土壤磷素积累、形态转化及其有效性的影响。试验地土壤为褐潮土,试验开始前耕层(0~20 cm)土壤有机质为11.2 g/kg,全磷为0.77 g/kg,速效磷为5.66 mg/kg,pH为8.3。结果表明,连续不施磷肥土壤的全磷、速效磷、无机磷各组分含量较连续施磷肥处理均明显降低,说明连续施用磷肥可显著扩大土壤中的有效磷库;不施磷肥处理耕层(0~20 cm)土壤全磷下降了6.94%,速效磷下降了16.3%,施用磷肥处理耕层土壤全磷增加1.3%~13%,速效磷增加164.7%~335.9%;不同的施磷肥处理对Ca₂-P含量的影响最大,不施磷肥的土壤Ca₂-P几乎耗竭,而施磷处理的Ca₂-P增加幅度可达19~36倍;此外,施用磷肥也使土壤Ca₈-P、Ca₁₀-P、Al-P、Fe-P、O-P有不同程度的提高。通过2013年的停施磷肥试验可知继续施磷肥的处理(F₂)与停施磷肥的处理(F₂')在土壤磷素水平、苜蓿产量及养分含量上均没有显著差异,表明磷肥存在明显的后效作用,之前积累在土壤中的磷素具有生物有效性。

P fertilization effects on the accumulation,transformation and availability of soil phosphorus

The effects of phosphorus (P)fertilization on the accumulation,transformation and availability of P in soil chemistry have drawn much attention in recent years.This paper reports on a six-year fertilization ex-periment (beginning in 2008)with alfalfa grown in the south region of Beijing.The soil type in the study area is fluvo-aquic.Before the experiment was performed,soil organic matter was 11.2 g/kg,total P was 0.77 g/kg,available P was 5.66 mg/kg and soil pH was 8.3 in the topsoil (0-20 cm).The results showed that the contents of total P,available P and inorganic P in various forms decreased markedly without P fertilization and increased significantly when P fertilizer was applied.Total P and available P in soils without fertilization de-creased by 6.94% and 16.3% respectively,while in soil treated with six years fertilization they increased by 1.3%-13.0% and 164.7%-335.9% respectively.The effects of different P fertilizer treatments on Ca2-P
content were significant.Ca2-P content was almost depleted in the non-fertilization treatment,while levels in the fertilization treatment increased 19-36 times.P fertilization also increased the soil content of Ca8-P,Ca10-P,Al-P,Fe-P,O-P.When fertilization was stopped in 2013 it was found that no significant differences existed in soil P level,alfalfa yield and nutrient content between the treatments of continued fertilization (F2 )and ceased fertilization (F2′).The results indicate that long term P fertilization has significant and continuous effects.The accumulation of P in soil contents should also enhance future biological performance.