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

Abstract

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 pest and disease in cotton and soybean intercropping system in 1:2 row proportion during June 2016. The study was undertaken to evaluate the sources of nutrients to red leaf index and incidence of insect pest and diseases. The field experiment was laid out in 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. Results found that there was no visual symptoms of leaf reddening at October 1st and lowest red leaf index was observed in T17 (T1 + Vermicompost 1.25 t ha-1 + Gliricidia 2.5 t ha-1). Lower incidence of Spodoptera larvae (Spodoptera litura Fabricius) was observed in T16 (T1 + Gliricidia 2.5 t ha-1 + Pongamia 2.5 t ha-1), T17 (T1 + Vermicompost 1.25 t ha-1 + Gliricidia 2.5 t ha-1) and T18 (T1 + Vermicompost 1.25 t ha-1 + Pongamia 2.5 t ha-1) at 40 DAS. Lowest pod borer (Cydia ptychora Meyr.) incidence was observed in T18 compared to other treatments. Lower per cent disease incidence of angular leaf spot of cotton was observed in T18 than other treatments at 85 DAS. Lower per cent disease incidence of Alternaria leaf blight of cotton was observed in T16, T17 and T18 compared to other treatments at 65 days after sowing. Integrated nutrient management in cotton and soybean intercropping systems reduced the red leaf index and provide resistance to crop to withstand against insect pest and disease.