Evaluation of microbial biomass C and N content of the soils cultivated with vetch (Vicia sativa L.) and alfalfa (Medicago sativa L.)


JOURNAL OF THE FACULTY OF FORESTRY-ISTANBUL UNIVERSITY, vol.66, no.1, pp.244-255, 2016 (ESCI) identifier


Legume forage crops have the ability of retaining free nitrogen in the air through symbiotic Rhizobium bacteria found in their roots. Additionally, microbial biomass (MB)-an essential living component of soil and a significant factor influencing plant nutrient dynamics-is considered to be accurate indicator of soil's biological condition. Given the aforementioned aspects, soil MB C (C-mic) and MB N (N-mic) of different legume forage crops were investigated in this study. Soil samples were taken in order to identify certain physical and chemical characteristics of the soil using volume cylinders (0 - 6.5 cm depth) from Vicia sativa L. (VSP) and Medicago sativa L. planted (MSP) areas. To determine the C-mic and N-mic contents, topsoil samples were also taken from 0 - 6.5 cm depth. C-mic and N-mic contents were identified using chloroform - fumigation - extraction method. There was no statistical significance for particle density, bulk density, electrical conductivity, CaCO3 %, and decomposition ratio (C-org/ N-total) of the VSP and MSP soil (P > 0.05). However, some other soil characteristics such as temperature, porosity, sand, silt and clay contents, pH, organic C and total N differed significantly (P < 0.05). Compared to VSP soil, the C-mic contents were determined to be 27 % higher (P < 0.05) in MSP soil. In VSP soil, the soil N-mic content ranged from 83.38 mu g g(-1) to 124.67 mu g g(-1), while it ranged from 91.62 mu g g(-1) to 187.07 mu g g(-1) in MSP soil. The N-mic content of the MSP soil was observed to be approximately 35 % higher than VSP soil, and a statistically significant difference (P < 0.05) was noticed between the two. Moreover, a significant positive correlation was found not only between the C-mic and organic C contents (r = 0.667; P < 0.05) but also between the N-mic and total N contents of MSP and VSP soil (r = 0.881; P < 0.01). The results of the study revealed that soil C-mic and N-mic values differ as the types of planted legume forage crops change. Furthermore, the obtained soil C-mic and N-mic results indicate that soil MSP soil is more fertile than VSP soil.