Allelopathic effects of root and leaf leachates of coconut on selected beneficial microorganisms from coconut rhizosphere

摘要

Coconut is a major perennial oil seed crop in India and its each part is used in agriculture, food, fibre, fuel, medicine and industry. Its productive life lasts for 70-80 years, hence, it needs continuous supply of nutrients from its rhizospheric region. Coconut fanners are predominantly marginal; hence, seldom apply fertilizers due to financial constraints. Under such circumstances, many agriculturally beneficial microbes [diazotrophs (10,20), phosphate solubilizers (22) and plant growth promotingrhizobacteria] provide the minimal nutrition to palms. However, their population and activities are affected by tannins and phenols released from biomass, leachates and root exudates. In coconut gardens, the allelochemicals are added to soil through (i)incorporation of 11.2 tonnes of biomass per year (leaf, inflorescence, husk) (3), (ii) stem and leaf leachates during rainy season (June-October) (i) and (iii) root exudates in 2.0 m diameter of each palm (6). The leachates influence the rhizosphere microflora in coconut based cropping system (ii). Therefore, a preliminary in vitro study was conducted to determine the effects of different concentrations of leaf and root leachates of adult coconut palm on growth of 10 selected beneficial microorganisms isolated from coconut rhizosphere.