Influence of non-edible oil-cakes and their composts on growth, yield and Alternaria leaf spot disease in chilli

Purpose Raw and composted oilcakes of neem, madhuca and simarouba were evaluated for their effect on plant growth, yield, and management of Alternaria tenuissima leaf spot disease, and rhizosphere microorganisms in chilli crop.Method The oilcakes were composted in simple pits containing a mixture (6:1:1) of individual oilcake, soil and rice straw. Growth promotion and disease incidence were assessed in plants grown in soil amended with raw or composted oilcakes of neem, madhuca and simarouba in pot and field. Rhizosphere microflora was also determined in all treatments.Result Raw oilcakes and their composts increased plant growth and yield and considerably decreased disease incidence and severity of A. tenuissima leaf spot in chilli grown in pot and field. The composted oilcakes of simarouba were most effective in improving plant growth and yield and decreasing leaf spot disease in chilli, followed by madhuca and neem oilcake compost. Fruit yield and vitamin C content were also high in simarouba compost. All composted oilcakes increased beneficial microbial population in the rhizosphere, including phosphate solubilizers, freeliving N2 fixers and Trichoderma species. The compost amendment decreased A. tenuissima population in the soil at the same time.Conclusion The growth promotion, yield increase and disease reduction in chilli were attributed to chemical compounds in oilcakes and stimulation of beneficial microbes in the rhizosphere by raw or composted oilcakes. This study demonstrated that composted nonedible oilcakes could be used for soil amendment in place of agrochemicals to increase productivity, manage soilborne diseases and improve soil health.