Relationship between decision support tools, petiole nitrogen based fertilizer management andyield of irrigated cotton (Gossypium hirsutum)

Abstract

A field experiment was conducted to study the relationship among SPAD(Soil Plant Analysis Development-502chlorophyll meter, Minolta Camera Co. Ltd., Japan) meter, Green Seeker (Portable NDVI Analyzer, Trimble Co., US) andpetiole Nitrogen (N) content and cotton yield using the decision support tools for N management in irrigated cotton inVertisol during 2017-18 at Raichur, Karnataka. Treatments consisted of N supplementation at SPAD thresholds of 40,60 throughout, 40 up to 60 DAS- later 50, and 50 up to 60 DAS- later 40, Green Seeker (GS) thresholds of  0.6and  0.8; petiole N of  2 and  3% throughout along with regional recommended fertilizers. It was found that spectralproperties of leaves can be used to precisely establish need based fertilizer N management strategy using SPAD meter andGreen Seeker during boll opening and peak flowering stages, respectively. Strong relationship existed between SPADreadings and petiole N concentration (r2= 0.66 to 0.8) and seed cotton yield (r2= 0.45 to 0.69). Green Seeker-NDVI basedN management is a new practice and requires further study.