Enhancement of colonisation of soybean roots by arbuscular mycorrhizal fungi using vermicompost and biochar

Abstract

Pollution and contamination of soil is one of the major concerns in the world today. Excessive use of synthetic fertilisers has caused tremendous harm to the environment and the human population indirectly. Chemical residues accumulated in crops that find their way to into the human food chain have been found to have adverse health effects. Enrichment of lakes with runoff from heavily-fertilised farms has resulted in eutrophication and pollution of water bodies. Application of organic matter and use of mycorrhiza have been recommended as ways of mitigating these problems. The aim of the study was to investigate the effect of organic amendments on colonisation of soybean roots by arbuscular mycorrhizal fungi. The study consisted of a field experiment of seven treatments with 3 replications in a complete randomized block design. The treatments were biochar (B), vermicompost (V), mycorrhiza (M), biochar and vermicompost (BV), biochar and mycorrhiza (BM), biochar, vermicompost and mycorrhiza (BVM), mycorrhiza and vermicompost (MV), and the control block which had no amendments (NT). Before planting of soybeans and application of amendments, soil samples were collected for characterization of soil chemical properties and mycorrhizal spores. Soybean seeds were planted in each plot. At flowering time, roots were screened for percentage mycorrhizal colonisation and dry mass of plants from each plot was taken. At harvest time, soil samples, plants and harvested soybeans from each plot were collected and dry weight taken. There was mean increase of 53.38% in levels of phosphorous and 15.33% of carbon in the soil after application of amendments. Levels of nitrogen decreased in all treatment blocks. There was a significant (P<0.0000) increase in arbuscular mycorrhizal fungi spores after application of treatments. The colonization percentage of arbuscules in roots was highest (14.7%) in the bio char and vermicomposting blocks (BV) while the blocks without any treatment, NT, had the lowest colonization percentage of 1.2%. The highest dry weight of both shoots and roots were recorded in blocks treated with biochar which also had the highest weight of harvested soy bean seeds with a mean of 171.28g. Blocks treated with mycorrhiza had the lowest harvest weight of soybean seeds with a mean of 58.17g. From this study it was concluded that the organic amendments enhanced the activity of the already-present mycorrhizal fungi in the soil, without requiring the introduction of commercial mycorrhizal amendments and biochar enhances microbial activity which stimulates crop productivity.