Valentina SANDOR, Roxana VIDICAN, Vlad STOIAN, Mignon SANDOR*
Nowadays, fertilizers demands in agricultural fields disturb many essential processes among which are soil communities’ structures and functions are directly affected. At the basis of all processes in soil stands microbial activity. The entire microbial community is considered the food web controller. Several methods can be applied to measure microbial profile in soil related to their activity. Community respiration rates, biomass dynamics and enzyme activity are commonly used technics to assess functional aspects of soil biologic community. Recently CLPP is widely used for assessing microbial community functional diversity. We hypothesized that community level physiological profile could be influenced by fertilizers (mineral and organic), soil biota (earthworms and collembolans) and soil texture (sandy and loamy). In a greenhouse experiment, 60 microcosms were set up in a 2x2x3 experimental design to observe the pattern of microbial community based on their ability to metabolize a wide range of standardized substrates with a modern profiling technique named MicrorespTM. Correlation analysis showed that the changes in the catabolic profiles of soil microorganisms in both sandy and loamy soil were significant caused by mineral and organic fertilizer applied. In sandy soil earthworms and collembolan presence, together with mineral and organic fertilizers, activates a microbial functional group with the ability to convert α-Ketoglutaric acid. Fructose sugar is representative in catabolic profiles of sandy soil without inoculated biota, independent to the application of fertilizers. Loamy soil treatments promote a microbial biomass, dominant in community structure, capable of metabolizing fructose and malic acid substrate and partly α-Ketoglutaric acid. Based on observed results, application of fertilizers in the presence of soil biota, act to increase the complexity of functional profile. The entire soil communities show a high capacity of turnover due to the application of experimental treatments. Non-rhizospheric experimental setup provides the opportunity to study the overall response of soil community to treatments, even at low values. Mineral fertilizers act toward a reduction of the microbial activity, as an opposite effect visible in organic treated microcosms. Inoculated fauna enhanced a different community level physiological profile, dependent on soil texture - higher in sandy soil. In loamy microcosms it was observed that fertilization produces a powerful constrains on biological community. The most diversified microbial functional profile was observed in soils treated with organic fertilizer.
collembolans, earthworms, manure, MicroResp, NPK
Presentation: oral