Impact of N-fertilization and peanut shell biochar on soil microbial community structure and enzyme activities in a Typic Haplustoll under different management practices

Abstract

The application of biochar with N-fertilizer is one of the most attractive practices for increasing soil quality and fertility. However, few studies have examined the combined effects of peanut biochar and urea on soil microbial community structure and function. Phospholipid fatty acid (PLFA) analysis and various enzyme activities were used to monitor microbial community structure and function in a 20-week incubation experiment. Different rates of biochar (0, 1, and 3% dry wt. soil) and N-fertilizers (with or without urea addition at 0.2 g kg−1) were applied to a Typic Haplustoll under conventional (CV) and conservation (CS) land management practices. A pristine forest soil (CK) was also included as control. Overall, the lowest microbial activity and abundance of microbial PLFA bioindicators were recorded under CV, confirming that conservation management may improve soil quality. Our study also indicated that the effect of biochar and management practices on the microbial community structure was more significant than that of urea. Particularly under both CS and CK, biochar tended to increase glucosidase, glucuronidase, and phosphomonoesterase activities, being on average 65%, 43%, and 85% significantly higher in biochar 3% than in the control treatment, respectively. Thus, we found a strong correlation between soil macronutrients and enzymes such as glucosidase and urease. Although total PLFA content was poorly affected, biochar addition increased some individual PLFA biomarkers, suggesting that both the biochar rates (1% and 3%) may increase Gram-negative bacteria and fungal populations. Regardless of biochar addition, urea application significantly increased urease activity. We also found a positive correlation between fungal PLFAs (VAM and total fungi) and urease activity, indicating that biochar tended to increase fungal biomass. The combined application of biochar and urea to soil under appropriate management may thus be a feasible and effective strategy for improving soil microbial quality.