Management of sub-soil sodicity for sustainable banana production in sodic soil – An approach

At present about 20 per cent of the world’s irrigated land is salt-affected and 60 per cent of salt-affected soils are sodic. These soils are ameliorated using soluble calcium (Ca2+), which replaces sodium (Na+) at the cation exchange sites of the soil. The displaced Na+ is then leached from the root zone through flushing (excess irrigation) a process that requires adequate flows of water through the soil. Also, most of the reclamation activities are being restricted to the top 0-15 cm which lead to development of secondary salinization and decreases the economic productivity of the soils due to reduced bilological activity in the rhizosphere. Therefore, the purpose of this study was to develop sub soil sodicity management technologies for commercial banana cultivation (cv Pisang Awak) under pits in sodic soils having pH 9.0 (surface) to 9.47 (sub-surface) by using biological ameliorants in integration with reduced level of chemical ameliorants and to study the mechanism underlying alleviation of salt stress by the plant. Application of 25 GRgypsum in the pits along with CSR-B-3 strain of Bacillus thurigenesis a native rhizospheric bacteria of sodic soil reclaimed the rhizosphere soils up to 60 cm. Their combination with vermicompost alleviated the salt stress in the rhizosphere of the crop which resulted in higher bunch weight of 22.7 kg /plant due to the integrated approach of bio and chemical ameliorant. The pH, bicarbonate, carbonate and sodium adsorption ratio (SAR) of soil was reduced due to the synergistic activity of ameliorants. The concentration of potassium (K) and other micronutrients increased in the leaves while Na content decreased, resulting in lower Na/K ratio.