不同种类小分子有机酸对砖红壤磷素形态转化的影响

【目的】明确有机酸的作用机制,为提高酸性红壤累积态磷素(P)可利用率提供科学依据。【方法】采用室内模拟试验研究了草酸、柠檬酸、苹果酸为代表的小分子有机酸对砖红壤磷素形态的影响。【结果】柠檬酸处理抑制了树脂交换P(P1)的解吸,而水(对照)、草酸和苹果酸处理促进了P1的解吸;在培养前期,3种有机酸抑制了NaHC_O3提取态无机P(P2)的活化,柠檬酸抑制作用最强,草酸抑制作用最弱;3种有机酸处理在整个培养时期均表现为活化NaHC_O3提取态有机P(P3)的作用,其中草酸活化能力最强;3种有机酸促进了NaOH提取态无机P(P4)的活化,其中草酸活化作用最强;3种有机酸抑制NaOH提取态有机P(P5)的活化;在整个培养时期,3种有机酸都表现为抑制稀盐酸提取态P(P6)、浓盐酸提取态无机P(P7)、浓盐酸提取态有机P(P8)和残留态P(P9)活化的作用。【结论】3种有机酸在不同培养时期对土壤磷形态的作用不同,草酸活化能力最强,其次是苹果酸,最后是柠檬酸。

Effects of various low-molecular-weight organic acids on phosphorus transformation in lateritic soil

[Objective] To reveal the action mechanisms of organic acids, and provide a scientific basis for raising the utilization rate of accumulative phosphorus(P) in acidic red soil.[Method] Laboratory simulation experiments were conducted to study the effects of low-molecular-weight organic acids, represented by oxalic acid, citric acid and malic acid, on P form in lateritic soil.[Result] SDuring the whole incubation period, citric acid inhibited resin-P(P₁) desorption, while water (control), oxalic acid and malic acid enhanced resin-P(P₁) desorption. At the earlier stage of incubation, all three organic acids inhibited the activation of NaHCO₃-extractable inorganic P(P₂), with citric acid having the highest inhibition effect and oxalic acid having the lowest. Three organic acids activated NaHCO₃-extractable organic P(P₃) during the whole incubation period, and oxalic acid showed the strongest activating effect. Three organic acids enhanced the activation of NaOH-extractable inorganic P(P₄) and oxalic acid displayed the strongest activating effect. Three organic acids inhibited the activation of NaOH-extractable organic P(P₅). During the whole incubation period, three organic acids inhibited the activation of dilute HCl-extractable P(P₆), dense HCl-extractable inorganic P(P₇), dense HCl-extractable organic P(P₈) and residual-P(P₉).[Conclusion] Three organic acids showed different effects on soil P forms at different times of incubation. Oxalic acid showed the strongest activating effects, followed by malic acid and then citric acid.