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

This study aims to evaluate the impact of peanut straw mulching on the N change and the functional genes in Camellia oleifera intercropping systems.

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.

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.

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.