长期不同施肥对潮土磷素吸附特征的影响

Effects of Long-term Fertilization on Phosphorus Adsorption Characteristics of Fluvo-aquic Soils

土壤磷素是限制潮土生产力提高的重要营养元素。研究不同施肥处理磷素的吸附特征及其与土壤理化性质的关系,可以为提高潮土磷素有效性和合理施肥提供科学依据。本研究基于封丘长期定位施肥试验,选用七种处理:不施肥(CK)、氮钾施肥(NK)、氮磷施肥(NP)、磷钾施肥(PK)、氮磷钾施肥(NPK)、1/2有机肥+1/2氮磷钾(1/2OM)和有机肥(OM),通过测定土壤理化性质和磷素吸附量,利用Langmuir和Freundlich等温吸附模型拟合了吸附曲线,并结合方程计算了最大吸附量(Qm)、亲和力常数(K)、最大缓冲能力(MBC)、吸附饱和强度(DPS)、Freundlich吸附常数(a)和吸附指数(b);运用相关分析和冗余分析(RDA)探讨了影响土壤磷素吸附特征变化的主要因素。结果表明:随着平衡溶液磷浓度的增加,不同施肥处理的磷素吸附量均表现出先快速增加,后缓慢增加的趋势。与CK和NK处理相比,NP、PK和NPK处理的磷素吸附能力增强,Qm和MBC分别增加了15.62%~23.60%和2.94%~23.46%;而1/2OM和OM处理的磷素吸附能力下降,K和MBC分别降低了39.60%~49.57%和36.09%~56.15%。相关分析和RDA结果表明:有机质(SOM)、pH、游离氧化铝(Ald)和C/P是影响潮土磷素吸附特征的主要因素。此外,1/2OM处理的DPS值相较于OM处理降低了30.92%。长期有机无机肥料配施可以增加有机质含量,降低磷素吸附能力,且相较于单施有机肥可以减少磷素流失风险。

【Objective】The availability of soil phosphorus(P)usually limits the productivity of fluvo-aquic soil.In order to provide a scientific basis for improving P use efficiency and rational fertilization in fluvo-aquic soils,the adsorption characteristics of P and its relationship with soil properties under long-term fertilization were studied.【Method】We selected seven treatments:no fertilizer(CK),no P fertilizer(NK),no potassium fertilizer(NP),no nitrogen fertilizer(PK),mineral fertilizer NPK(NPK),half compost plus half mineral fertilizer NPK(1/2OM)and compost alone(OM)in a long-term fertilization experiment at Fengqiu,to determine soil properties and P adsorption capacity.The Langmuir and Freundlich equations were used to fit the isothermal adsorption curves.Furthermore,the maximum adsorption capacity(Qm),adsorption constant(K),maximum buffer capacity(MBC),P adsorption saturation(DPS),Freundlich adsorption constant(a)and adsorption index(b)were calculated.Correlation analysis and redundancy analysis(RDA)were used to explore the vital factors affecting the soil P adsorption characteristics.【Result】The results showed that P adsorption in fluvo-aquic soil fitted both the Langmuir(R2≥0.80)and Freundlich(R2≥0.89)isotherms.With the increase of P concentration in the equilibrium solution,P adsorption capacity rapidly increased at first and then slowly afterwards.Compared with CK and NK,Qm and MBC of NP,PK and NPK increased by 15.62%–23.60%and 2.94%–23.46%,respectively,however,K and MBC of 1/2OM and OM reduced by 39.60%–49.57%and 36.09%–56.15%,respectively.Correlation analysis and RDA results showed that organic matter(SOM),pH,free Al oxides(Ald)and C/P were the main factors affecting P adsorption characteristics of fluvo-aquic soil.In addition,the DPS of 1/2OM was 30.92%lower than that of OM.【Conclusion】Long-term combined NPK fertilizer with compost can increase the content of SOM,reduce P adsorption capacity and reduce the risk of P loss compared with OM.