稻麦轮作磷肥减施下水稻土磷素生物有效性特征

Characteristic of Soil P Availability in Reduced P-Input Rice-Wheat Cropping Rotation Paddy Soils

土壤磷素化学分级提取方法被广泛应用于磷素状态及特征分析,但相关提取方法缺乏土壤根际过程的表征。基于磷素的根际过程特点,采用一种磷素生物有效性(the biologically-based phosphorus,BBP)分级方法,研究太湖稻麦轮作区磷肥减施定位试验田实施7 a后麦季收获期土壤磷素生物有效性及其影响因素。结果表明:就宜兴试验田而言,稻季不施磷麦季施磷处理(PW)CaCl_2-P含量与稻麦季均施磷处理(PR+W)之间无显著差异,Citrate-P、HCl-P和Enzyme-P含量则差异显著(P<0.05)。就常熟试验田而言,不同磷肥减施方式对各磷组分含量总体无显著影响,仅Pzero处理HCl-P含量与PR+W处理相比明显降低。两块试验田用BBP法提取的4种土壤磷组分含量与有效磷含量之间的决定系数(R^2)不同:宜兴有效磷主要来自Citrate-P(R^2=0.587,P<0.01)、HCl-P(R^2=0.587,P<0.01)和Enzyme-P(R^2=0.531,P<0.01),常熟有效磷主要来自HCl-P(R^2=0.386,P<0.05)和Citrate-P(R^2=0.280,P<0.05)。4种磷组分含量由大到小依次为HCl-P、Citrate-P、Enzyme-P和CaCl_2-P。冗余分析结果表明,土壤pH、碱性磷酸酶(S-ALP)是影响磷组分变化的重要因素,与土壤磷组分间存在一定的正相关关系。认为该研究结果能加深对减磷条件下土壤磷素生物有效性的理解。

Chemical soil phosphorus(P)extraction has been widely used to characterize and understand changes in soil P fractions,however lacking adequately capture rhizosphere processes.Relying on two reduced P-input experimental stations in Taihu rice-wheat cropping rotation area,the biologically-based phosphorus(BBP)grading method was used to evaluate the availability and influencing factors of soil P during wheat-growing stage.The trial of long-term positioning P fertilizer reduction has been conducted for 7 years.The results show that,in Yixing Station,CaCl 2-P in soil treated with P fertilization at wheat season only(PW)had no significant difference with soil treated at both rice and wheat seasons(PR+W),while Citrate-P and HCl-P as well as Enzyme-P under PW treatments were significantly low(P<0.05).As for Changshu Station,no significant differences were shown between three P-reducing treatments and PR+W;only Pzero treatment significantly reduced the concentration of soil HCl-P.Correlation coefficients between four BBP fractions and Olsen-P at two stations were different.Olsen-P was mainly from Citrate-P(R 2=0.587,P<0.01),HCl-P(R 2=0.587,P<0.01)and Enzyme-P(R 2=0.531,P<0.01)in Yixing,while mainly from HCl-P(R 2=0.386,P<0.05)and Citrate-P(R 2=0.280,P<0.05)in Changshu.The concentration of four BBP fractions followed the order of HCl-P>Citrate-P>Enzyme-P>CaCl 2-P.Furthermore,RDA showed that soil alkaline phosphatase(S-ALP)activity and pH were the dominant factors for the changes in soil P,and correlated with soil P fractions positively.These results may be helpful for understanding of the changes in soil P status while P-input was reducing.