多年定位试验条件下不同施磷水平对土壤无机磷分级的影响

通过对小麦/玉米轮作不同施磷水平7年14季定位试验土壤养分状况的分析与评价,探讨石灰性潮土有效磷耗竭和积累状况下土壤全磷、无机磷分级形态的变化规律,并运用通径分析和逐步回归分析,研究Olsen法、Mehlich3法、树脂交换法测定的土壤有效磷与各无机磷形态的关系。结果表明:(1)与初始土壤相比,N0P0K0、N2P0K2处理全磷总量分别降低了15.2%,29.7%,无机磷总量降低了13.5%,11.8%,N2P2K2、N2P3K2处理全磷总量分别增加了8.2%,27.2%,无机磷总量增加了11.1%,27.8%。供试土壤无机磷含量以Ca_(10)-P、Ca_8-P为主,施用磷肥可提高Ca_2-P、Ca_8-P、Al-P、Fe-P占无机磷总量的相对比例。(2)磷耗竭状态下,植物利用的无机磷来源于缓效磷源(Ca_8-P、Al-P、Fe-P;75%)、无效磷源Ca_(10)-P(11.5%~14.0%)、速效磷源Ca_2-P(7.5%~8.9%);无机磷盈余状态下,积累的无机磷主要转化为Ca_8-P(50%~70%)、Al/Fe-P(10%~23%)、O-P(8%)、Ca_2-P(0.2%~1.8%)。(3)Ca_2-P、AlP对3种方法测得的有效磷均具有正向作用且贡献率较大。Olsen法测定的无机磷主要是Ca_2-P、Ca_8-P,Mehlich3法主要是Ca_2-P、Ca_8-P、Al-P,阴离子交换树脂法主要是Ca_2-P、Fe-P。(4)Olsen法、Mehlich3法、树脂交换法均适于评价土壤有效磷水平,Olsen法最优。

Effects of Different Phosphorus Application Levels on the Inorganic Phosphorus Fraction Under Multi-year Location Experiment

Through the evaluation of the soil nutrient in a 7-year long-term fertilization experiment of wheat-maize rotation with different phosphorus application levels, the inorganic phosphorus fractions under the phosphorus depletion or accumulation in calcareous fluvo-aquic soils were studied. Path analysis and multiple regression analysis were performed to investigate the relationships among various soil available phosphorus determined by three methods, so did phosphorus fractions. The results showed that: (1) Compared with the initial soil, the total phosphorus under N0P0K0 and N2P0K2 were decreased by 15.2% and 29.7%, respectively, and the total inorganic phosphorus decreased by 13.5% and 11.8%. The total phosphorus under N2P2K2 and N2P3K2 were increased by 8.2% and 27.2% respectively, while the total inorganic phosphorus increased by 11.1% and 27.8%. The formations of inorganic phosphorus in the tested soil were mainly Ca₁₀-P and Ca₈-P. The application of phosphorus fertilizer could increase the relative proportions of Ca₂-P, Ca₈-P, Al-P and Fe-P. (2) In the depletion state of phosphorus, the inorganic phosphorus used by plants mainly came from slow-release phosphorus sources (Ca₈-P, Al-P, Fe-P; 75%), un-available phosphorus sources Ca₁₀-P (11.5%~14.0%), and available phosphorus sources Ca₂-P (7.5%~8.9%). At inorganic phosphorus surplus condition, excess inorganic phosphorus mainly converted to Ca₈-P (50%~70%), Al/Fe-P (10%~23%), O-P (8%), and Ca₂-P (0.2%~1.8%). (3) Ca₂-P and Al-P had positive effects on available phosphorus extracted by three methods with the greater contributions. Ca₂-P and Ca₈-P could be effectively extracted by the Olsen method. While, the Mehlich3 method mainly extracted Ca₂-P, Ca₈-P and Al-P, and the main extraction of AEM were soil Ca₂-P and Fe-P. (4) All the three methods were feasible for determining soil available phosphorus contents, and the Olsen method was the best.