Diversified crop rotation: Synergistically enhancing peanut yield and soil organic carbon stability

Abstract

Diversified crop rotations are acknowledged for their capacity to improve soil fertility and increase crop productivity through increasing plant carbon inputs. However, the microbial mechanisms involved in soil organic carbon (SOC) dynamics remain elusive, especially in the high-nitrogen peanut field. This study aimed to investigate the effects of crop rotation on peanut yield, SOC mineralization (K_c), its temperature sensitivity (Q₁₀), and the main drivers in the rhizosphere and bulk soils. A 6-year field experiment was conducted including three cropping regimes: peanut continuous monocropping (P), peanut-Orychophragmus violaceus rotation (PO), and peanut-winter wheat-summer maize rotation (PWM). Microbial alpha diversity, community composition, and occurrence networks were characterized using 16S rRNA and fungal ITS region sequencing. Compared to P, PO increased the rhizosphere nitrate nitrogen, which suppressed root biomass and reduced the rhizosphere SOC and Q₁₀. In the bulk soil, incorporation of labile and nitrogen-rich residue under PO increased soil mineral nitrogen, which stimulated K-strategists and reduced K_c through intensifying microbial carbon limitation. Finally, PO exhibited the lowest SOC accumulation across treatments through promoting the primed soil carbon loss. Compared to P, PWM increased the rhizosphere total nitrogen, stimulated root biomass, and enhanced the rhizosphere K_c. In the bulk soil, the low-quality residues input may alleviate the microbial carbon limitation, which not only promoted SOC stability by facilitating the microbial preferential utilization of labile carbon but also reduced Q₁₀ through decreasing microbial biomass and increasing activities of carbon-cycling enzymes. The significant increases in microbial diversity in both rhizosphere and bulk soils of the PWM treatment also contributed to the greater SOC accumulation relative to PO. However, the theoretical increase in SOC content was offset by soil carbon loss associated with straw removal of maize at harvest. PO enhanced peanut yield by increasing the rhizosphere pH and optimizing soil microbial communities. PWM showed advantage in increasing yield over PO (51.8 % vs. 20.7 %) due to its promotion of root development, a more balanced composition of soil nutrient, and additional enhancement of microbial diversity and enzyme activities. Therefore, PWM achieved a synergistic benefit for both crop productivity and SOC stability, thus contributing to agricultural green development. This study underscores the need for properly accounting for the crop residue quality and soil initial nutrient status in devising sustainable planting model.