Humic acid rich vermicompost promotes plant growth by improving microbial community structure of soil as well as root nodulation and mycorrhizal colonization in the roots of Pisum sativum

Humic acid rich vermicompost (HARV) was used to impart plant and soil health as compared to chemical fertilizers (CF), and normal vermicompost (NV) involving pea (Pisum sativum cv. Bonneville) as the host plant. The plant growth parameters of the crop were recorded at the time of harvesting and soil microbial structure was studied by using DGGE (Denaturing Gradient Gel Electrophoresis) on a temporal basis (0 day, 12th day, 30th day and 60th day). The growth parameters showed an increase of 34.04%, 50.61% and 33.12% in total height, fresh weight, and dry weight as compared to conventional chemical fertilizers (CF) and 25.53%, 70.13% and 59.49% as compared to control. The DGGE profiles revealed that maximum bacterial and fungal diversity and density occur in soil supplemented with HARV on 12th day (both Shannon's index and Margalef's index showed highest bacterial diversity (2.87) and richness (5.52) and highest fungal diversity (2.76) and richness (4.96)). The lowest values for the indices (Margalef's and Shannon for bacteria 2.51 and 1.78 and Margalef's and Shannon for fungi 2.12 and 1.43 respectively) were observed in CF applied soils on the 60th day where diversity was even lower than in case of control soil indicating the negative impacts of chemical fertilizers on soil microbial diversities. Amendment of soil with organic fertilizers improved root nodulation and AMF colonization; the increment being higher in HARV. External application of AMF and Rhizobium further improved these parameters suggesting that AMF and Rhizobium act synergistically with HARV in improving plant growth and soil health. (C) 2016 Elsevier B.V. All rights reserved.