Elevation of earthworm biomass by organic cultivation practices Long-term evidence from tea soils

Abstract

Agrochemicals used in conventional agriculture affect soil fauna and flora while organic managementi.e. organic matter incorporation, mulching and avoid of synthetic chemicals etc. favor natural soilinhabitants. Amongst them, earthworms are the most effective bio-indicators which signify structural,microclirnatic, nutritive properties and health of agricultural soils. Data were generated from soils ofthe on going 'TRI-ORCON' trial set up at St. Coombs estate of the Tea Research Institute of SriLanka, Talawakelle. Using standard size quadrates, the number and weight of earthworm eggs andearthworms from 0 - 15 and 15 - 30 ern soil depths were determined at 10 years after exposure toorganic and conventional systems with tea waste, neem oil cake and compost applications and syntheticagro-chernicals respectively. The earthworm biomass was significantly (p<0.05) superior in organicallymaintained soils than that of the conventional. Earthworm activity was significantly diminished due tosynthetic fertil izers and pesticide use; earthworm eggs in the 0-15 ern and 15-30 ern layers were 0 and40 x 10J per ha while compost application exhibited 64.8 x 103 and 200 x 103 per ha respectively.Amongst organic amendments, neem oil cake due to its wormicidal effects and oily and cloggy naturelowered earthworm biomass in the 0 - 15 em layer of which the effect was similar to conventional.The higher aggregate stability in the organically maintained soils with macro pores developed throughearthworm burrows showed strong relationship with the earthworm activity. Therefore, our resultsconfirm the immense potentials of organic management practices in developing biological and physicalparameters through burrowing, loosening of soil, recycling of nutrients and organic matter in deepersoil depths by earthworms and their castings. Resultantly, organic agricultural systems act as analogueforest conditions with activated and conserved native soil biodiversity components assuring long-termsustenance in crop productivity.