Impact of reduced tillage and crop rotation on earthworm populations and soil structure

Abstract:

Conventional tillage breaks soil apart; earthworms build it back together. This research measured earthworm population density, species composition, and soil structural parameters under three tillage systems — conventional tillage (CT), reduced tillage (RT), and zero tillage (ZT) — combined with two rotation sequences (rice-wheat and maize-wheat) at Dr. Rajendra Prasad Central Agricultural University, Pusa, Bihar, over two consecutive seasons (2020-21 and 2021-22). ZT supported the highest earthworm density (187 individuals/m²), 2.4 times greater than CT (78/m²). RT occupied an intermediate position (143/m²). Species diversity was also higher under ZT, with the Shannon-Wiener index reaching 1.48 compared with 0.94 under CT. Maize-wheat rotation harboured 22% more earthworms than rice-wheat, likely because of better residue quality and absence of prolonged waterlogging. Soil aggregate stability (mean weight diameter) was 37% higher and bulk density 8.6% lower under ZT than CT. Earthworm density correlated positively with water-stable aggregates (r = 0.83) and infiltration rate (r = 0.79). These findings show that shifting from conventional to reduced or zero tillage, paired with maize-wheat rotation, can rebuild earthworm communities and improve soil physical health in the Indo-Gangetic plains.