Effect of wheat straw and cellulose degrading fungi of genus Trichoderma on soil respiration and cellulase, betaglucosidase and soil carbon content

D. Draganova*, I. Valcheva, Y. Kuzmanova, M. Naydenov

Department of Microbiology and Ecological Biotechnologies, Faculty of Plant Protection and Agroecology, Agricultural University, 12 Mendeleev, 4000 Plovdiv, Bulgaria

(Manuscript received 12 June 2018; accepted for publication 31 August 2018)

Abstract. Due to the intensive soil exploitation and increased mineral fertilization, the degradation of plant residues in the soil is becoming more difficult and slower over the years. This disturbs the structure of the soil and the nutritional balance and leads to a reduction in soil fertility. To solve the problem, microorganisms capable of degrading plant residues in the soil can be used. The purpose of this study was to investigate the effect of fungi of genus Trichoderma on the biodegradation of wheat straw in the soil by observation of the change in cellulase enzyme activity in the soil and the increase in soil biological activity. The highest basal soil respiration was noted at T2TUR (65.76 μgCO2) and T6 (53.69 μgCO2). During the entire straw degradation period, the highest endoglucanase activity was observed at T4 (285.0 μgGlu) and T6 (275.56 μgGlu), whereas the highest β-glucosidase was noted at T6 (5220.3 μgPNP/g/h) and T1UKR (5020.0 μgPNP/g/h). The presence of cellulose-degrading fungi positively affected the increase in the total amount of microbial biomass at the end of the study period, whereas the amount of Corg was increased in all straw amended variants. At the beginning of the process, CMCase correlated with the microbial carbon (r=0.896 for Cmic) and β-glucosidase activity was closely connected with both soil organic carbon and microbial carbon (r=0.819 for Corg and r=0.866 for Cmic). At the end of the investigated period a stronger correlation with Corg was observed.