Agricultural land use regulates the fate of soil phosphorus fractions following the reclamation of wetlands

Over half of the Earth's wetlands have been reclaimed for agriculture, leading to significant soil P destabilization and leaching risks. To evaluate the effects of agricultural land use on soil P stability, we used sequential P extraction to in-vestigate the long-term effects of wetland cultivation for rice and soybean on soil P fractions, including labile and mod-erately labile inorganic/organic P (LPi, LPo, MPi, and MPo), and stable P in Northeast China. The results showed that soybean cultivation decreased the total P by 35.9 degrees A degrees, whereas rice cultivation did not influence the total P content (p < 0.05). Both the soybean and rice cultivations significantly increased LPi (p < 0.05). Soybean cultivation significantly decreased the LPo and MPo compared to rice cultivation, and the latter increased MPi by 309.28 degrees A degrees compared with the reference wetlands (p < 0.05). Redundancy analysis indicated that pH, poorly crystalline Fe (Feca), crystalline Fe (Fec), and total organic carbon (TOC) explained similar variations in P fractions during soybean and rice cultivation (54.9 degrees A degrees and 49.7 degrees A degrees, respectively). Similarly, during soybean or rice cultivation, pH negatively influenced LPo and MPo, while Feca positively influenced MPi and LPi. Furthermore, TOC showed a positive role in LPo, and MPo, but a negative effect on LPi and MPi during rice cultivation. Hence, we concluded that the cultivation of soybean or rice create contrasting modifications to wetland soil P fractionation by altering TOC, Feca, Fec, and pH. Our study indicates that agricultural land use can regulate the fate of wetland soil P fractionation, with potential benefits to both i) P risk management in cultivated wetlands and ii) potential approaches for future wetland restoration.

Automated summary

More than half of the Earth's wetlands have been converted for agriculture, resulting in instability and leaching risks of soil phosphorus (P). This study evaluated the effects of agricultural land use on soil P stability by investigating the long-term impacts of wetland cultivation for rice and soybean in Northeast China. The results showed that soybean cultivation decreased total P content, while rice cultivation did not have a significant impact. Both soybean and rice cultivations increased labile and moderately labile inorganic/organic P fractions. Various factors, such as pH, Fe minerals, and organic carbon, were found to influence P fractions during soybean and rice cultivation.