Evaluation of microbial and enzymatic communities in soil and rizosphere from soybean plants

Abstract

Understanding the biological and biochemical soil properties, as well as its enzymatic activity is important in designing an efficient alternative to demonstrate desired modifications in the soil. Such modifications are related to crop systems, cultivation practices or other human activities. The objective of this study was to evaluate the diversity of some microorganisms (Bacillus, Pseudomonas, Trichoderma and Fusarium) and enzymatic activity in soil from soybean crops with different yields. Soil sampling was determined according to the productivity yields of the property, which were divided into high, medium, and low yield. Microorganisms were evaluated by counting populations of fungi and bacteria through serial dilutions of total bacteria, Bacillus, Pseudomonas, Trichoderma and Fusarium. The b-glucosidase, acid phosphatase and arylsulphatase activities were determined by spectrophotometry after one hour of incubation at 37 oC, with the specific substrate p-nitrophenol-b-D-glucopyranoside, p-nitrophenol-phosphate and p-nitrophenyl sulphate, respectively, for each studied enzyme. Urease was determined by the ammonium release method, after incubating the soil with urea for two hours, at 37 oC. Soil samples from the high-yield plot had higher concentrations of Bacillus and total bacteria. The low-yield soil showed a higher level of colonies of the genus Fusarium. The studied enzyme activities (b-glycosidase, arylsulphatase and urea) were found at lower values in soil samples from the high-yield field and differed statistically from the low-yield field. However, in the rhizosphere samples, these enzymes had a higher activity in the high-yield field. In view of these results, it is possible that the yield of soybean plants influences the number of microorganisms and the enzymatic activity of the soil microbiota.

Key words:  Bacillus, p-nitrophenol-b-D-glucopyranoside, Pseudomonas, Trichoderma and Fusarium