Phosphorus (P) is essential for plant growth and crop production and quality.Much information is available on the effects of plant residue quality on rates of decomposition and N mineralization,but fewer studies have evaluated the relationship between residue quality and P release during decomposition.It has been suggested that plant residues may play an important role in this effect due to the P added to soil by residues.However,little is known about the changes in P pools during legume residue decomposition.Residues from Vicia faba L.and Brassica campestris L.with varying P concentrations were added to two kinds of soil with low available P concentration,and the concentration of various soil P pools were assessed by soil P fractionation on days 0,14,28,and 56.In this study,P speciation was determined using solution 31P nuclear magnetic resonance (NMR) spectroscopy to understand the potential fate of residue P in soils.The results showed that residue addition significantly increased cumulative respiration.The size of the P pools changed over time and was affected by both residue P concentration and soil type.For all plant samples,orthophosphate produced the most intense resonance in each spectrum and was the most abundant P species detected in shoot residue,which appeared to be related to their total P concentrations.For crop residues with higher total P concentrations,the greatest proportion was present as orthophosphate.More than 90％ of the phosphorus detected in the plant residue was found to be orthophosphate and phosphate monoester.However,increasing plant concentration of total P did not affect pyrophosphate concentration.Olsen-phosphorus was highest when the experiment began (day 0) but decreased as the experiment progressed.The increase in residual P found in all residues indicated that part of the mineralized P was converted into stable organic and inorganic P,which occurred mainly in the initial phase.These changes were generally more pronounced in high-and medium-P residues than in low-P residues.More Resin-P,NaHCO3-Pt,and cumulative respiration was detected in the acid purple soil than in the neutral purple soil,which may be attributed to the high Ca2+ concentration in the neutral purple soil.This study demonstrated that changes and transformations in soil P pools over time depend on residue P concentration and soil type,and that they have the potential to be delivered to soil in a form readily available to plants and soil microorganisms.%植株残体降解可直接或间接地影响土壤磷素的有效性,为探讨不同磷浓度植株残体降解对紫色土磷分级体系的影响,结合31P核磁共振分析技术,选取了3种磷浓度不同的植物残体与两种紫色土进行室内模拟培养试验,得出了以下研究结论:(1)添加植株残体显著增强了紫色土呼吸强度,且紫色土分级体系中的活性磷含量均高于对照处理(2)31P-NMR分析结果得知,植株残体的正磷酸盐、磷酸单酯占浓缩液全磷比例的90％以上,高磷植株的正磷酸盐和磷酸单酯含量显著高于中磷和低磷植株,土壤磷素有效性的变化与植株残体的正磷酸盐和磷酸单酯含量有关;(3)紫色土分级体系中的活性磷在0d含量最高,随着培养周期的延长,土壤磷素有效性会出现降低的趋势;酸性紫色土的累积呼吸强度、分级体系中活性磷(Resin-P、NaHCO3-Pt)所占比例均高于中性紫色土,与土壤钙含量有关.综上所述,植株残体的磷浓度越高,更有利于提高土壤磷素的有效性,本研究结果为农业生产中秸秆还田技术提供了理论参考.
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