Effects of crops on the humus accumulation process in the grey forest soils of Priangarye.

The influence of a number of agricultural plants in the crop rotation on the grey forest soils in the Irkutsk Region upon the intensity of the humification process was investigated by means of microbiological and biochemical tests. The synthesis, decomposition, and the accumulation ratio of humus were concluded from the phenoloxidase activity. The cellulose-decomposing microflora and algaeflora were taken into consideration as well. The humus synthesis processes were most active in the wheat and lucerne plots, they were less effective in the fallow and virgin soils. The lack of organic matter in the permanent fallow soil cuts down the humus accumulation ratio and the counts of microorganisms. The soil cultivation intensifies the humus synthesis processes and changes the composition of microorganisms in the soil. Algae which are mainly represented by green and blue-green species are an additional source of organic substance in the soil. Decomposition of organic substances in the soil proceeds with an active participation of cellulose decomposers which are mainly represented by fungal and bacterial flora. In rare cases actinomycetes can be found. Application of mineral fertilizers intensifies the humus accumulation process and improves the qualitative and quantitative composition of microflora in all the plots under investigation.