| Abstract
| - The effect storage had on the microbial biomass in two soils (Trevino and Fargo) was compared tothe effect storage had on each soil's capacity to degrade metsulfuron-methyl. Soils were collectedfrom the field and used fresh (<3 weeks old) or stored at 20 and 4 °C for 3 or 6 months. Thephospholipid fatty acid content of the soils was used to monitor changes in the microbial biomassduring storage and incubation in a flow-through apparatus. In both soils, [phenyl-U-14C]metsulfuron-methyl was used to monitor changes in the route and rate of degradation along with 14CO2 evolution(mineralization). Total microbial biomasses in both soils were significantly reduced for soils incubatedin the flow-through apparatus, whereas only the Trevino soil's microbial biomass was significantlyreduced as a result of storage. The microbial communities of both soils were significantly different asa result of storage as shown by discriminant analysis. In both soils, degradation rate, pathway ofdegradation, and mineralization of metsulfuron-methyl were significantly affected by storage comparedto fresh soil. The half-life of metsulfuron-methyl increased significantly (P< 0.05) in the Trevino soilfrom 45 days (fresh) to 63 days (stored soil), whereas in the Fargo soil half-lives increased significantly(P< 0.05) from 23 days (fresh) to 29 days (soils stored for 6 months). In both soils, mineralizationof [14C]metsulfuron-methyl was significantly (P< 0.05) higher in fresh soils compared to stored soils.The degradation pathways of metsulfuron-methyl changed with storage as evidenced by the loss offormation of one biologically derived metabolite (degradate) in stored soils compared to fresh soils. Keywords: Storage; biomass; microbial community; pesticide; metsulfuron-methyl; half-life; degradation pathway
|
