长期轮作与施肥对农田土壤磷素形态和吸持特性的影响

通过对黄土旱塬地区长期定位施肥(26a)条件下的不同轮作系统的土壤磷素形态和吸持参数的测定，研究了轮作和施肥对土壤磷素吸持特性和磷素形态的影响，以及土壤磷素吸持参数与磷素形态之间的关系。结果表明，长期轮作与施肥都可以减低土壤磷素的最大吸附量（Qm），相对于其它轮作和连作，在氮磷（NP）施肥下，小麦-玉米-豌豆轮作可以减低土壤的Qm，在氮磷有机肥（NPM）施肥下，小麦-玉米轮作可以减低土壤的Qm。在施肥相同的条件下，小麦-玉米轮作和小麦-豌豆轮作可以显著增加土壤中各形态无机磷的含量，长期轮作比连作可以增加土壤中的有效磷养分，尤其对Ca2-P的提高效果更为显著。相关分析表明，Qm和磷吸持指数（PSI）与全磷（T-P）、Olsen-P、CaCl2-P、Ca2-P、Ca8-P、Fe-P、Ca10-P和有机磷呈极显著负相关（p＜0.01），与闭蓄态磷（O-P）呈显著负相关（p＜0.05），与Al-P关系不显著。土壤有机质（SOM）与Qm、PSI和磷最大缓冲能力（MBC）之间存在极显著负相关关系，与磷吸持饱和度（DPSS）存在显著正相关。通径系数和逐步回归分析表明，在石灰性黑垆土土壤的无机磷形态中，Ca2-P对Olsen-P的贡献最大。

Forms of soil phosphorus and P adsorption in soils under long-term crop rotation and fertilization systems

Forms of P and P sorption parameters in soils under different crop rotation systems in a 26a long-term fertilization field experiment in an arid loess plateau were determined for study of effects of crop rotation and fertilization on forms and adsorption of the phosphorus in the soil and relationships between soil phosphorus adsorption parameters and phosphorus forms. Results show that both long-term crop rotation and long-term fertilization reduced the maximum P adsorption capacity(Qm) of the soil; relative to other crop rotation and continuous cropping systems, the application of nitrogen and phosphorus fertilizer (NP) reduced Qm of the soil under the Wheat-Corn-Pea crop rotation system, and the application of NP plus organic manure (NPM) had a similar effect on Qm of the soil under the Wheat-Corn crop rotation system. The same in fertilization, the Wheat-Corn rotation and Wheat-Pea rotation systems significantly increased the contents of various forms of inorganic phosphorus, and the soils were higher in available P under long-term crop rotation than under continuous cropping, especially in Ca2-P. Correlation analysis shows that Qm and phosphorus sorption index (PSI) were significantly negatively related to total phosphorus (T-P), Olsen-P, CaCl2-P, Ca2-P, Ca8-P, Fe-P, Ca10-P and organic phosphorus(P<0.01), and to occluded phosphorus(O-P, P<0.05), too, but insignificantly to Al-P. Soil organic matter(SOM) was found to be in extremely significant negative relations to Qm, PSI and maximum buffer capacity(MBC), but in positive one related to the degree of P sorption saturation(DPSS). Path analysis and stepwise regression analysis show that among the inorganic phosphorus fractions in calcareous Heilu soil, Ca2-P contributed the most to Olsen-P.