Impacts of applying corn-straw compost on microorganisms and enzyme activities in pot soil cultivated with mustard

A pot experiment planted with mustard was conducted for investigating impacts of compost of corn straw on soil microbial community and enzyme (urease, sucrase, catalase and cellulase) activities. Results show that the compost application could increase the biomass of mustard and numbers of bacteria, fungi and actinomycetes which are higher than those of the control and inorganic fertilizer treatments. Numbers of these three group microorganisms are highest during the harvest stage of mustard in all treatments. Activities of soil enzymes (urease, sucrase, catalase and cellulase) are significantly increased in the compost treatments compared with the control or inorganic fertilizer treatments. However, the change trends of the activities are different at the growth stages of mustard. The maximum value of urease activity occurs during the harvest stage, while the value of sucrase is lowest at this stage except the compost and inorganic mixed fertilizer treatment. The catalase activity is stable before the harvest stage and then is declined obviously after the stage. The maximum value of cellulase activity appears at the bloom stage, while lower at the seedling and harvest stages. Significant positive correlations are found among part of the soil enzyme activities. Furthermore, there are significant positive correlations between part of the soil enzyme activities and numbers of microorganisms, and these results indicate that soil enzyme activities and microorganisms could be considered as good indicators of soil fertility level.