Effect of peanut straw mulching on the soil nitrogen change and functional genes in the Camellia oleifera intercropping system.

Purpose: This study aims to evaluate the impact of peanut straw mulching on the N change and the functional genes in Camellia oleifera intercropping systems. Methods: A field experiment with different types of straw mulch treatments (conventional tillage, whole, and crushed) and timing was (50 d and 150 d) established between 2018–2022; the soil N fractions, N transformation rates, the abundance and dominant species compositions of ammonia-oxidizing archaea (AOA), nirK, and nirS-harboring genes were investigated. Results: The whole peanut straw mulching of 150 d significantly improved (P < 0.05) the content of soil microbial biomass N (MBN), ammonia N (NH₄⁺), and nitrate N (NO₃^-). The soil nitrification and ammonification rates increased by 96.8% and 132% in the 150 d of peanut crushed and whole straw mulching, respectively. Notably, the peanut straw mulching of 50 d mainly affects the diversity and relative abundance of AOA while the soil nirK and nirS-harboring genes were affected by 150 d crushed and whole peanut straw mulching, respectively. Redundancy analysis showed that crushed and whole peanut straw mulching affects nitrate reductase as the primary factor in regulating the soil N cycle via functional genes and soil variables. Conclusions: Long-term whole peanut straw or whole and crushed mixed straw mulching could hence be recommended to dryland farming communities to increase the soil N cycle and crop productivity in the C.oleifera-peanut intercropping system. [ABSTRACT FROM AUTHOR]