Purpose

The present study was performed to investigate the effects of the interaction of fulvic acid (FA) with different amounts of nitrogen fertilizer (N) on soil phosphorus availability and transformation in a salt-affected soil and to obtain the direct and indirect relationships between inorganic phosphorus (Pi) fractions and Olsen-P.

Materials and methods

An incubation experiment was conducted to evaluate the effects of nitrogen addition (215, 183, and 151 mg kg^-1, referred as N100, N85, and N70), fulvic acid addition (30 and 60 mg kg^-1, referred as F1 and F2), and their interactions on phosphorus availability (based on soil Olsen-P and inorganic P fractions).

Results and discussion

The results indicated that the application of N100 significantly reduced the release and availability of phosphorus (P). However, the phosphorus recovery (PR) as Olsen-P was significantly enhanced in the N100F1 and N100F2 treatments. The P kinetics was best described by the power function model. Moreover, labile Ca₂-P and Ca₈-P contents decreased as N application rate increased. Combined application of FA and fertilizer N increased the percentage of Ca₂-P and decreased the percentage of Ca₁₀-P at the end of the incubation period. According to the correlation analysis and path analysis, the direct effects of Ca₂-P, Fe-P, and O-P on Olsen-P were significant after 112 days of incubation (P<0.05). The indirect effects of Ca₂-P (R₂₁P_y1 = 0.57) and Fe-P (R₂₄P_y4 = 0.19) were essential contributors to the correlation between Ca₈-P and Olsen-P. Additionally, the indirect effect of Ca₈-P (R₄₁P_y1 = 0.53) contributed significantly to the correlation between Fe-P and Olsen-P.

Conclusions

In conclusion, our results show that the availability of phosphorus can be improved by reducing the amount of nitrogen fertilizer applied in salt-affected soils. Integrating FA and inorganic N fertilizer enhances the release and availability of phosphorus, when excessive amounts of N fertilizers are applied to salt-affected soils.

中文翻译：

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阐明富里酸和氮肥施用对盐渍土磷有效性的影响和相互作用机制

目的

本研究旨在研究富里酸 (FA) 与不同量氮肥 (N) 的相互作用对盐渍土壤中土壤磷有效性和转化的影响，并获得无机磷之间的直接和间接关系。 (Pi) 分数和 Olsen-P。

材料和方法

进行孵育实验以评估添加氮（215、183 和 151 mg kg ^-1，称为 N100、N85 和 N70）、添加富里酸（30 和 60 mg kg ^-1，称为 F1 和F2)，以及它们对磷有效性的相互作用（基于土壤 Olsen-P 和无机 P 部分）。

结果和讨论

结果表明，N100 的施用显着降低了磷（P）的释放和有效性。然而，在 N100F1 和 N100F2 处理中，作为 Olsen-P 的磷回收率 (PR) 显着提高。P 动力学最好由幂函数模型描述。此外，随着施氮量的增加，不稳定的Ca ₂ -P 和Ca ₈ -P 含量降低。在孵化期结束时，FA和氮肥的复合施用增加了Ca ₂ -P的百分比并降低了Ca ₁₀ -P的百分比。根据相关分析和通径分析，Ca ₂ -P、Fe-P和OP对Olsen-P的直接影响在培养112天后显着（P<0.05）。Ca ₂ -P (R ₂₁ P _y1 = 0.57) 和Fe-P (R ₂₄ P _y4 = 0.19)的间接影响是Ca ₈ -P 和Olsen-P之间相关性的重要贡献者。此外，Ca ₈ -P (R ₄₁ P _y1 = 0.53)的间接影响对Fe-P 和 Olsen-P 之间的相关性有显着影响。

结论

总之，我们的结果表明，可以通过减少盐渍土壤中氮肥的施用量来提高磷的有效性。将过量的氮肥施用于受盐分影响的土壤时，结合 FA 和无机氮肥可增强磷的释放和有效性。