Monitoring Soil Microbial Activities in Different Cropping Systems Using Combined Methods

Cropping activities may affect soil microbial activities and biomass, which would affect C and N cycling in soil and thus the crop yields and quality. In the present study, a combination of microcalorimetric, enzyme activity (sucrase, urease, catalase, and fluorescein diacetate hydrolysis), and real-time polymerase chain reaction (RT-PCR) analyses was used to investigate microbial status of farmland soils, collected from 5 different sites in Huazhong Agriculture University, China. Our results showed that among the 5 sites, both positive and negative impacts of cropping activities on soil microbial activity were observed. Enzyme activity analysis showed that cropping activities reduced soil sucrase and urease activities, which would influence the C and N cycles in soil. Much more attentions should be given to microbial status affected by cropping activities in future. According to the correlation analysis, fluorescein diacetate hydrolysis showed a significantly (P < 0.05) negative correlation with the time to reach the maximum power output (R = −0.898), but a significantly (P < 0.05) positive correlation with bacterial gene copy number (R = 0.817). Soil catalase activity also showed a significantly (P < 0.05) positive correlation with bacterial gene copy number (R = 0.965). Using combined methods would provide virtual information of soil microbial status.