Research at the Qiyang Red Soil Experimental Station of the Chinese Academy of Agricultural Sciences revealed the effects of adding phosphorus to nitrogen mineralization and nitrification in red soil with different fertilization over a long period of time, providing a theoretical basis for guiding the management of nitrogen and phosphorus in dryland red soil. The research results were published in the internationally renowned journal Soil & Tillage Research.

The phosphorus addition caused changes in soil microorganisms and nitrogen cycle-related enzyme activities, which in turn affected nitrogen transformation. The soil nitrogen content was different after long-term fertilization, and the responses of nitrogen mineralization and nitrification to exogenous phosphorus were different. However, the effects of phosphorus addition on the long-term nitrogen mineralization and nitrification of different fertilized soils, and the appropriate phosphorus application rate under different soil nitrogen levels, are still unclear.

Based on the long-term fertilization positioning experiment of typical dryland red soil in southern China, combined with the indoor phosphorus addition culture experiment, this study revealed the response mechanism of nitrogen dynamics in high-nitrogen and low-nitrogen soils to exogenous phosphorus, and clarified the appropriate amount of phosphorus application.

The results showed that phosphorus addition only significantly promoted the nitrogen mineralization rate of high-nitrogen soils; and that with the increase of the nitrogen mineralization rate and NH₄⁺-N, the nitrification rate also increased. However, the addition of phosphorus in low-nitrogen soils aggravated the nitrogen limitation of microorganisms, which was not conducive to improving soil nitrogen availability. Regression analysis showed that the soil nitrogen mineralization rate was the highest at the phosphorus addition level of 60 kg ha^-1 (calculated as P₂O₅), and the soil microbial activity was strong, so that that level was appropriate for phosphorus application, was beneficial to crop growth and reduced the risk of phosphorus pollution.

Sehrish Ali, a Pakistani doctoral student from the Institute of Agricultural Resources and Agricultural Regional Planning of the Chinese Academy of Agricultural Sciences, and Liu Kailou, a graduated doctoral student (now an associate researcher at the Jiangxi Institute of Red Soil and Germplasm Resources), are the co-first authors, and researcher Zhang Huimin is the corresponding author.

This research was supported by the National Natural Science Foundation of China, the Innovation Project of the Chinese Academy of Agricultural Sciences and the "Double Thousand Plan" project of Jiangxi Province.

Paper link: https://doi.org/10.1016/j.still.2023.105710