Seasonal changes of microbial population in maize and soybean rhizosphere under conventional and organic growing systems

Abstract

The aim of this study was to compare abundance of microorganisms in the rhizosphere of maize and soybean grown under conventional and organic management. The trial was set up on the chernozem soil at the experimental field of Bački Petrovac, Institute of Field and Vegetable Crops, Novi Sad. Rhizosphere samples were collected in two sampling terms during 2014 (July 7 and August 14) and analysed by the indirect dilution method followed by plating of soil suspension on selective nutritive mediums: soil agar for the total number of microorganisms, meat peptone agar for the number of ammonifiers, Waksman-Carey medium for the number of cellulolytic microorganisms, synthetic medium for the number of actinomycetes, Czapek Dox agar for the number of fungi, and N-free medium for the number of azotobacters and free N-fixers. The results showed significant differences in microbial abundance between plant species, growing systems and sampling terms. Significantly higher number of microorganisms was found in rhizosphere of soybean compared to maize, as well as in organic growing system compared to conventional. Significant differences between sampling terms were recorded for the number of ammonifiers, azotobacters, fungi and actinomycetes, while the number of most tested microbial groups was higher in the second sampling term.