Influence of Integrated Nutrient Management on Red Leaf Index of Cotton and Incidence of Insect Pest and Disease in Cotton and Soybean Intercropping System

A field experiment was conducted at All India Coordinated Research Project on Soybean, Main Agricultural Research Station, University of Agricultural Sciences, Dharwad, Karnataka, India to study the integrated nutrient management practices on red leaf index, insect pests and diseases in cotton and soybean intercropping system in 1:2 row proportion during kharif 2015. The study was undertaken to evaluate the sources of nutrients to red leaf index and incidence of insect pests and diseases. The field experiment was laid out in a randomised complete block design with three replications and twenty treatments. Treatment comprised of organic and inorganic sources of nutrients used in different combinations. Soybean introduced as intercrop in cotton with 40 x 10 cm spacing for soybean and 120 x 60 cm for cotton. There were no visual symptoms of leaf reddening at October 1st, and lowest red leaf index was observed in treatment receiving 100% RDF (recommended dose of fertiliser) for cotton and soybean + Vermicompost 1.25 t ha-1 + Gliricidia 2.5 t ha-1. At 40 DAS, lower incidence of Spodoptera larvae was observed in treatment receiving 100% RDF for cotton and soybean + Gliricidia 2.5 t ha-1 + Pongamia 2.5 t ha-1, 100% RDF for cotton and soybean + Vermicompost 1.25 t ha-1 + Gliricidia 2.5 t ha-1 and 100% RDF for cotton and soybean + Vermicompost 1.25 t ha-1 + Pongamia 2.5 t ha-1. At 85 DAS, lowest pod borer incidence was observed in treatment receiving 100% RDF for cotton and soybean + Vermicompost 1.25 t ha-1 + Pongamia 2.5 t ha-1compared to other treatments. Lower percent disease incidence of angular leaf spot of cotton was observed in 100% RDF for cotton and soybean + Vermicompost 1.25 t ha-1 + Pongamia 2.5 t ha-1 than other treatments. At 65 DAS lower percent disease incidence of Alternaria leaf blight of cotton was observed in treatment receiving 100% RDF for cotton and soybean + Gliricidia 2.5 t ha-1 + Pongamia 2.5 t ha-1, 100% RDF for cotton and soybean + vermicompost 1.25 t ha-1 + Gliricidia 2.5 t ha-1 and 100% RDF for cotton and soybean + vermicompost 1.25 t h-1 + Pongamia 2.5 t ha-1 compared to other treatments. It could be concluded that application of 100% RDF for cotton and soybean + Gliricidia 2.5 t ha-1 + Pongamia t ha-1 in cotton and soybean intercropping systems reduced the red leaf index and provide resistance to crop against insect pests and disease.