定位施肥对紫色菜园土磷素状况的影响

基于紫色菜园土壤莴笋-白菜轮作3a的12季连续定位施肥试验,研究施肥对土壤磷素状况的影响。结果表明,在紫色土上以化肥为基础增施有机肥(泥炭或菜籽粕)既提高土壤磷含量,又增加无机磷组分中有效磷源和缓效磷源的比例,且不会增加磷素淋失的风险,是所有处理中最优者;增磷、增钾处理虽然提高了土壤磷含量,但未能提高速效磷源与缓效磷源的比例;增氮、增硼及常规施肥降低土壤磷含量和提高无效磷源的比例;无肥处理磷含量最低,无效磷源比例最高。紫色菜园土无机磷约为有机磷的4—6倍,无机磷各组分以钙磷为主,占I-P总量的60.89%—67.92%,显示紫色土风化程度较低。各形态磷素呈Ca10-P>Ca8-P>Fe-P≈Al-P≈OC-P>Ca2-P序列变化,其中Ca2-P和Al-P总共仅占无机磷总量的11.47%—19.43%,表明紫色土中对植物最有效的磷源不足;而Ca10-P和OC-P共占无机磷总量的42.48%—59.55%,意味着紫色土无机磷有一半左右是以作物不可利用的形态存在的。紫色土全磷与无机磷、有机磷、Ca2-P、Ca8-P、Al-P、Fe-P、OC-P及Ca10-P呈显著正相关;无机磷与多种形态磷呈显著正相关(除有机磷、Ca2-P、有效磷外);有机磷与全磷、Ca2-P显著正相关;有效磷与全磷、Ca2-P、Al-P、Fe-P显著正相关;无机磷组分间也都存在显著正相关关系(OC-P与Ca10-P间有极显著正相关,但它们与其它无机磷组分无相关性)。表明在土壤磷的整个循环系统中,不同组分无机磷与有机磷之间处于一个动态平衡中,它们之间存在着相互影响和制约。土壤pH与各形态磷关系密切。对土壤有效磷与无机磷组分间的关系进行系统分析,简单相关分析结果土壤有效磷与Ca2-P、Fe-P呈极显著正相关,与Al-P呈显著正相关,与Ca8-P、OC-P、Ca10-P正相关但不显著;通径分析结果对土壤有效磷直接影响较大的无机磷组分是Al-P、Ca8-P与Ca2-P,其中Ca8-P的直接影响为负效应;逐步回归分析结果与通径分析一致。综合分析得出,Ca2-P、Al-P是最有效的磷源,Fe-P、Ca8-P次之,Ca10-P与OC-P是非有效磷源。莴笋和白菜产量与紫色土壤Ca2-P、Ca8-P、Al-P、Fe-P呈显著正相关,与OC-P、Ca10-P无相关性。紫色土各形态无机磷与两种蔬菜产量的相关系数r大小依次为Ca2-P>Fe-P>AL-P>Ca8-P>Ca10-P>OC-P,这与各形态无机磷与有效磷简单相关分析的结果一致。

Effect of site-specific fertilization on soil phosphorus in purple garden soil

A three-year(12 seasons) of experiment was conducted on a purple garden soil under a lettuce-cabbage rotation to investigate effect of site-specific fertilization on soil phosphorus(P).The combined application of organic manure(peat or rapeseed meal) and chemical fertilizers in purple garden soil was the optimal treatment which improved the content of phosphorus as well as the ratio of available to slow-available P in soil inorganic P and did not increase the risk of phosphorus leaching.The addition of P and potassium fertilizers could increase the content of phosphorus but failed to improve the proportion of available and slow-available P in soil inorganic P.The addition of nitrogen and boron fertilizers and conventional fertilization treatments decreased the P concentrations and increased the percentage of unavailable P in soil inorganic P.The no fertilizer treatment displayed lowest contents of P and highest percentage of unavailable P in soil inorganic P.The results showed that the content of inorganic P was 4—6 times higher than that of organic P in the purple garden soil.The main inorganic form of P was calcium phosphate which accounted for 60.89%—67.92% of soil inorganic P indicating a low weathering stage of the soil.The contents of inorganic P were in the order of Ca10-P>Ca8-P>Fe-P ≈ Al-P ≈ OC-P>Ca2-P.The total concentration of Ca2-P and Al-P accounted for 11.47%—19.43% of soil inorganic P suggesting the lack of the most effective phosphate in the purple garden soil.The total amount of Ca10-P and OC-P accounted for 42.48%—59.55% of soil inorganic P indicating about half of inorganic P was unavailable for crop.Soil total phosphorus was significantly correlated with inorganic P,organic P,Ca2-P,Ca8-P,Al-P,Fe-P,OC-P and Ca10-P.Soil inorganic P was significantly correlated with various forms of phosphorus(except for organic P,Ca2-P and available P).Organic P had significant positive correlation with soil total P and Ca2-P.Available P showed significant positive correlation with soil total P,Ca2-P,Al-P and Fe-P.There was significant positive correlation between OC-P and Ca10-P.These results showed that various forms of inorganic P and organic P were in a dynamic balance and interaction in the cycle system of soil phosphorus.Soil pH was highly correlated with the studied forms of soil phosphorus.Correlation analysis,path analysis and stepwise regression analysis methods were applied to examine the relationship between soil available P and inorganic phosphorus compounds.Soil available P was closely correlated with Ca2-P,Fe-P,and Al-P.Path analysis and stepwise regression showed that soil Al-P and Ca2-P had significant positive association with soil available P while Ca8-P had a significant negative association with soil available P.Additionally,yields of lettuce and cabbage were significantly correlation with soil Ca2-P,Ca8-P,Al-P and Fe-P.The correlation coefficients of various forms of soil inorganic P and yields of lettuce and cabbage were in the order of Ca2-P>Fe-P>AL-P> Ca8-P>Ca10-P>OC-P.On the basis of these results,it can be concluded that Ca2-P and Al-P followed by Fe-P and Ca8-P were the most effective forms of phosphorus while Ca10-P and OC-P were ineffective forms of phosphorus in the purple garden soil.