Influence of cropping sequences on soil suppressive/conduciveness against Sclerotium rolfsii in different agro-climatic zones of West Bengal, India

Aim: To study the influence of different cropping sequences (CSs) on soil suppressive or conduciveness towards Sclerotium rolfsii in different agro-climatic zones (ACZs) of West Bengal, India. Methodology: Farmer’s field surveys were conducted to explore the suppressive activity of various crop rhizosphere during each winter, October to January (2016-2019). The survey was done in 14 districts of five ACZs in West Bengal (India), and the total surveyed sample size was 511. The S. rolfsii disease incidence (DI%) data of Rabi crop in surveyed areas and sclerotial population, soil suppressive index, FDA hydrolysis, dehydrogenase activity and culturable microbial assay were performed. Results: In this data set (n=511), the foremost soils belonged to no suppressive category (74.47%), followed by slight suppressive category (20.74%). Negligible number of soils belonged to moderate (0.39%) and strong suppressive (0.39%) category. The population of Pseudomonads was higher in both strong and moderate suppressive soil rather than slight and no suppressive soils. Culturable population of soil Pseudomonads, Bacillus and Actinomycetes varied in five different ACZs. Interpretation: Paddy-brassica vegetables, paddy-maize and paddy-cucurbits vegetable-based CSs exhibited relatively high soil uppressiveness whereas paddy-legumes, jute-paddy-legume vegetables and pulses based CSs showed high soil conduciveness towards S. rolfsii. Soil microbial influences on crop rhizosphere along with “crop rotation effect” was the key reason for the disease suppressive activity. Key words: Agro-climatic zones, Crop rotation, FDA hydrolysis, Rhizosphere, S. rolfsii, Suppressive soil