Productivity and profitability of Bt cotton (Gossypium hirsutum)–wheat (Triticum aestivum) cropping system as affected by nutrient omissions

A field experiment on nutrient omission plot technique (NOPT) in Bt cotton (Gossypium hirsutum L.)-wheat {Triticum aestivum (L.) emend. Fiori & Paol} cropping system was conducted at New Delhi during 2010–11 and 2011–12. The experiment had 20 treatments, laid out in randomized block design with three replications in fixed plots. Treatments comprised omission of N, P, K, S and Zn, 50% omission of N, P, and K, absolute control (no nutrient applied) and optimum plane of nutrition (150-26.4 -50-15-3 kg/ha N-P-K-S-Zn). Each of the 10 treatments was duplicated and randomized so that there were 20 plots within each replication for cotton. Same nutrient omission treatments were tested on wheat in 50% of plots and uniform N was applied in the remaining 50% of the plots. Yield in cotton was estimated in terms of seed cotton, and stalk yield. Nitrogen proved to be most limiting nutrient and there was a reduction in the seed cotton yield to the tune of 28%, 6.5% and 14.5% due to N, P and K omissions during the year 2010. N continued to be the most limiting nutrient followed by P and K during the year 2011. The corresponding figures for the year 2011 were 26.5%, 15.5% and 12.4% respectively. The yield reduction in seed cotton yield due to S and Zn omission ranged from 2.0–5.0%, which was statistically at par with optimum nutrition treatment during both the years The reduction in the grain yield of wheat due to N, P and K omission was 35%, 9.5% and 2%, respectively during the year 2010–2011 and the corresponding figures for the year 201112 were 48.5%, 11.1% and 7.7%, respectively. The reduction in grain yield due to S and Zn omission was marginal and ranged from 2.0–2.5% during both the years. Highest net profit of 1,33,340 and 1,58,340 was earned from cotton-wheat cropping system during the years 2010–11 and 2011–12, respectively, in the optimum nutrition plots.