A study on earthworm population and microbial activity in their casts in long-term tillage and residue management practices.

Abstract

Earthworms are very important organisms in improving the soil biophysical properties by their action of burrowing and cast production (Lavelle 2001). Therefore, the present study was carried out to study the effects of varying tillage practices [Permanent bed (PB), Zero tillage (ZT) and Conventional tillage (CT)] and cropping systems [Maize - wheat - Mungbean (MWMb), Maize - Chickpea - sesbania (MCS),Maize - Mustard Mungbean(MMuMb) and Maize - Maize - Sesbania (MMS)] on earthworm population and fertility of earthworm casts (EC). This study was undertaken in a long term experiment going on at fixed site since 2008. The number of earthworm was observed in kharif season 2019 after digging soil 20x 20 x20 cm and number of EC was observed using a square meter quadrant at three random sites per replications at flowering stage. Number of earthworm is higher in zero tillage system and best system irrespective of the tillage was MWMb. The above observations were also reflected in EC counts. Fertility of EC indicated by its biological activity in terms of assays viz., fluorescein diacetate (FDA) hydrolysis, urease and alkaline phosphatase (APA) which were found to be significantly higher in EC than the bulk soil taken from 0 - 15 cm depth, while the beta glycosidase activity was observed to be non significant between soil and EC. The EC has 2.1 times FDA (15.49 μg Florescein g−1 h−1), 1.33 times APA (174.14 U / gram of dry soil) and 1.09times urease activity (141.85 μg NH4 - 1N - g - 1 dwt 2h - 1) than surrounding soils. Furtherthere was no significant difference between the fertility of EC from the different tillage and cropping systems. Since fertility of EC remains constant irrespective of the environment, the variation in number of casts/earthworms in tillage system plays the major role in soil fertility.