Organic carbon and iron and aluminum oxides are the main phenolic substances formed by soil aggregates. Because of the competition between P and SOC for the binding sites on the surfaces of Fe/Al oxides, soil aggregation is inhibited, thus affecting the distribution of SOC in aggregates and aggregate stability. However, the effects of additions of P on aggregate stability and distribution of SOC in different land-use types (upland and paddy soils) remain unclear.

Based on long-term fertilization experiments in typical red soil uplands and paddy soils in southern China, this study uncovers the differences in mechanisms of organic carbon distribution and soil aggregate stability in response to long-term phosphorus addition. The results indicate that P addition significantly decreased the proportions of macro aggregates in non-P limited conditions. In upland soil in the P-limited category, P addition increased the proportion of macro aggregates, while the effect of P addition was not significant in paddy soil. P addition increased SOC of >2-mm fraction in P-limited conditions in upland soil and decreased SOC of >2-mm fraction in paddy soil regardless of P status. The addition of phosphorus not only has a direct effect on the stability of aggregates, but also has an indirect effect on stability by affecting the transformation between the forms of Fe/Al oxides and affecting SOC cycling. The effect of P on aggregate stability is strongly influenced by P limitation status and land-use type. The results provide an important theoretical basis for in-depth interpretation of the effects of long-term phosphorus application on soil organic carbon and aggregate stability.

The above research results were published in the journal Soil and Tillage Research (IF= 5.374) under the title Organic Carbon Distribution and Soil Aggregate Stability in Response to Long-term Phosphorus Addition in Different Land-use Types. Doctoral student Du Jiangxue and Dr Liu Kailou (currently an associate research fellow of the Jiangxi Institute of Red Soil, Jiangxi Province, China) from the Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, are the co-first authors, and research fellow Zhang Huimin is the corresponding author. The research was funded by the National Natural Science Foundation of China, the National Key Research and Development Program of China, the Basic Research Fund of the Central Public-Interest Scientific Institution, and the Jiangxi Provincial Doctoral Research Fund.

https://doi.org/10.1016/j.still.2021.105195

Diagram of P addition effects on aggregate stability through SOC, microbial mining, iron, and aluminum oxides.

Blue and red arrows indicate positive and negative effects, respectively. Dashed arrows represent insignificant effects (P > 0.05).