BIOLOGICAL ACTIVITY OF ENERGY CROPS SOIL

Abstract

Introduction. Renewable energy development strategy assumes a significant increasing of the area under energy crops. The energy crops creation and maintenance should not lead to the soil depletion. Investigation of this problem requires the study of the microbiota as an important soil component. The purpose was to investigate the characteristics of microbial communities and their biological activity in the root zone of energy plants.

Methods. The five energy crops soil biological activity were investigated in field conditions. The objects of research were culture of Mickantus x giganteus, Alnus glutinosa (L.) Gaertn., Salix viminalis L., hybrid willows of M.M. Gryshko National Botanical Gardens NAS breeding Salix viminalis x S. caprea and Salix viminalis x S. acutifolia. The allelopathic activity was analyzed by bioassays method. Microbiological investigations were carried out by conventional methods – seeding of certain dilutions of soil suspension on selective cultural medium. The processes of organic matter development were observed.

Results and discussion. It was shown that the root secretion of test plants had a small allelopathic activity. The microbiological processes intensity depends on the season, environmental conditions, the plant metabolites physiological and biochemical characteristics. The soil micromycetes number dynamics of seasonal variations differed depending on the culture and data was higher than control variant as a result of studies. The actinomycetes number dynamics corresponded to the common regularities - its quantity gradual reduction in summer and the same gradual increase in autumn. The soil ammonifiers number under investigated plants was about the same level at the beginning and the end of the vegetation period. Significant differences were observed only in the dynamics of this data.  Their number was the maximum in the soil under the hybrid willows, but it was minimal in other samples in the summer. The largest number of ammonifiers was in A. glutinosa root zone, and the lowest – in the M. x giganteus.

The soil nitrogen consumption microorganisms dynamics increased gradually its number in summer and also decreased in autumn. Significant decrease of their number was noted only in soil under A. glutinosa.

We observed that the processes of organic matter transformation were fairly balanced, especially in the root zone of hybrid willows.

The number of cellulolytic microorganisms was higher in the soil under the experimental crops than the control at the beginning of the vegetation period. Cellulolytic microorganisms content was also significantly higher comparative to control samples in all research plant at the end of vegetation. The fairly high soil cellulolytic activity in all studied energy crops except A. glutinosa was noted.

Conclusions. The soil microbiological and mycological investigations under different energy crops indicate the plants root secretions provide favorable conditions for microorganisms activity. The cultivation of hybrids S. viminalis x S. caprea and S. viminalis x S. acutifolia provides positive impact on soil microbial coenosis and enriches its ammonifiers and cellulolytic organisms. It was found that hybrid willows crops mainly contribute the accumulation of organic matter in soil (evidenced by the mineralization coefficient and cellulose decomposition). Root soil M. x giganteus and S. viminalis marked reverse trend. The A. glutinosa microbiota was different from the other variants on all parameters. We consider that further studies will establish more common regularities of processes in soil under energy crops.