Soil microbial community structure and microbial activities in the root zone of nothapodytes nimmoniana

Abstract

Camptothecin (CPT) is a bioactive secondary metabolite of Nothapodytes nimmoniana (Graham) Mablerley and has strong antitumor activity due to its ability to inhibit DNA topoisomerase I. In this study the changes of soil chemical and microbiological properties in the root zone of N. nimmoniana under application of two different nitrogen (N) fertilizers with different rates were investigated. There were seven treatments consisting of four rates of chemical N fertilizer, two rates of organic fertilizer, and a control where there was no fertilization and planting. Two-year-old N. nimmoniana plants were used in the study. Ten months later the plants were harvested and the soils were collected for analyses of chemical properties, microbial carbon (MBC), microbial nitrogen (MBN), respiration rate (basal respiration), phospholipid fatty acids of microorganisms, and six soil enzyme activities. Results showed that higher rates of N fertilizer resulted in greater dry matter yield of N. nimmoniana, while N rates had no significant effect on the CPT concentrations of roots and the whole plants except for lower CPT concentration in the N4 (applying 10.0 g N per pot in total) treatment. There was no difference in chemical properties, MBC, MBN, respiration rate, and N mineralization rate of soils among chemical N fertilizer treatments. N. nimmoniana decreased the soil microbial communities as compared with the control. Compared with bacteria and actinomyctes, fungi were more affected by N. nimmoniana cultivation. In contrast, N. nimmoniana had no effect on the activities of soil enzymes. Different rates of chemical N fertilizer had the same effect on the microbial communities. However, the application of organic fertilizer demonstrated a significant amelioration on the adverse effect of the soil microbial communities resulting from the cultivation of N. nimmoniana. © 2012 Japanese Society of Soil Science and Plant Nutrition.