Synergistic Effects of Rice Straw Return and Nitrogen Fertilizer on Rhizosphere Bacterial Communities and Soil Fertility

Abstract

Returning straw to the field combined with nitrogen (N) fertilizer application is an effective way to enhance soil fertility. While previous studies have focused on soil's physical and chemical properties, the impact of straw returning on the microbial community has been less explored. In this study, we used four treatments including control (CK), nitrogen 150 kg ha−1 (N), straw return 10 tonnes ha−1 (SR), and combined SR and N (SRN= straw return 5 tonnes ha−1 + nitrogen 75 kg ha−1) to understand the effects of N fertilizer application and straw returning on bacterial community structure. Using high-throughput sequencing, we analyzed the bacterial community under different treatments and identified the main factors influencing soil bacterial communities. Results showed that soil properties such as pH, soil organic carbon (SOC), and available phosphorous (AP) were significantly higher in SR+N treatments. While AP, available nitrogen (AN), available potassium (AK), and total nitrogen (TN) were higher in sole N applied treatments.  The results of high-throughput sequencing analyses demonstrated that the main bacteria at the phylum level were Actinobacteria (31-34%), Proteobacteria (25-30%), Acidobacteria (15-21%), and Chloroflexi (13-16%) across the treatments. Furthermore, the SR+N treatment exhibited the highest relative abundances of Dependentiae, Proteobacteria, Chloroflexi, and Bacteroidetes compared to all other treatments. Our results indicated that the combined application of straw return and N fertilizer enhanced soil fertility and increased the abundance of beneficial soil bacteria. Additionally, SOC emerged as the primary factor influencing variations in soil bacterial communities. However, several beneficial bacteria were less abundant in the combined treatment and more prevalent in the sole SR or sole N treatments. Thus, further research is necessary to develop new straw return strategies that optimize agricultural yields while minimizing ecological impacts.