Cropping rotation improved the bacterial diversity and N-cycling genes in tobacco fields through a 19-year long-term experiment

Abstract

Soil microorganisms play crucial roles in various processes within the soil ecosystem, such as nutrient cycling, organic matter decomposition, and maintenance of soil structure. However, their responses to fertilization and different cropping systems in tobacco soils remain poorly understood. In this study, we conducted a 19-year-long field experiment on rice-tobacco rotation cropping (R) and continuous tobacco cropping (C), with three fertilization treatments: no fertilizer (NF), chemical NPK fertilizer (NPK), and composted pig manure (OM). The composition, co-occurrence patterns, N-cycling genes (nifH, AOA-amoA, AOB-amoA, nirS, nirK, and nosZ) of the bacterial communities as well as the soil properties were analyzed in the soils after tobacco was harvested. The pH and available potassium (AK) in the rotation cropping soil were significantly lower than those in continuous cropping soil, while the α-diversity index, and the abundance of nifH, nirS, nirK, and nosZ genes were opposite. The phyla Chloroflexi, Desulfobacterota, MBNT15, and Nitrospinota, as well as number of low-abundance genera, were significantly enriched in rice-tobacco rotation cropping. Partial least squares path model (PLSPM) indicated that cropping systems had a greater influence on the variations in bacterial communities compared to fertilization practices. These findings enhance our understanding of the significance of land management and fertilization in shaping the soil bacteria of tobacco. The rice-tobacco rotation cropping system demonstrated greater benefits to soil microorganisms and N-cycling genes compared to continuous cropping system.