Effect of sowing time Nitrogen and irrigation levels on yield fibre quality and cry protein concentration in Bt Cotton

Abstract

To find out the nitrogen requirement, schedule of nitrogen application, feasibility of newlinedetopping, irrigation level and date of planting for Bt-cotton and to assess their effects on newlinegrowth, yield, cry protein concentration and fibre quality parameters, two field experiments newlineand two pot culture studies were undertaken at Agriculture Research Station, Dharwad for newlinetwo years (2005-06 and 2006-07) under irrigated conditions. Mean of two years results newlineindicated that increasing level of N from 80 to 120 and further to 160 kg/ha significantly newlineimproved seed cotton yield by 12 and 18.6 per cent, respectively. Application of N with newlinerecommended practice of three splits as well as N applied in seven splits at 15days interval newlineproduced on par yields. However, more number of split application was beneficial at higher newlinedoses of N. Detopping of Bt-cotton at 80 DAS had no significant influence on seed cotton newlineyield. N fertilization significantly affected the cry protein levels at various stages. At 60 DAS, newlineincrease in level of N from 80 to 120 kg increased cry protein by 9.3 per cent and further newlineincrease in N application to 160 kg /ha improved the cry protein by 14.8 per cent. Leaf newlinenitrogen concentration and spad readings were followed same pattern as that of cry protein newlineconcentration. N levels and management techniques have little influence on quality newlineparameters. Fibre length improved with N application up to 120 kg per ha. Economic analysis newlineof Bt-cotton production indicated that N up to 120 kg per hectare applied with present newlinerecommended practice without detopping recorded significantly highest net returns. newlineResponse of Bt-cotton to date of sowing indicated that yield reduction to the extent of newline18.8 and 54.9 per cent was noticed when sowing was delayed from June to July and further newlineto August, respectively. Irrigation at 0.8 IW/CPE ratio produced significantly more seed cotton newlineyield (1807 kg/ha) as compared to unirrigated and 0.4 IW/CPE ratio. However, it was on par newlinewith 0.6 IW/CPE ratio. Early sowing in June with irrigation at 0.6 IW