Abstract
A field experiment on nutrient omission plot technique (NOPT) on Bt cotton-wheat cropping system was conducted at research farm of the Division of Agronomy Indian Agricultural Research Institute, New Delhi during rainy season of 2010 and 2011. The experiment had 10 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-1 N-P-K-S-Zn). Same nutrient omission treatments were tested on wheat keeping the plots fixed. Yield was estimated in terms of seed cotton, lint, seed and oil yield. The uptake of nutrients in omission plots gave an estimate of the indigenous soil nutrient supply and nutrient use efficiencies. Results showed that N was the most limiting factor 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. The corresponding figures for the year 2011 were 26.5, 15.5 and 12.4%, respectively. N continued to be the most limiting nutrient followed by P and K during the year 2011. P omission led to the higher yield reduction during the second year of experimentation which proves that P supplies fast depleted in the cotton-wheat cropping than the K supply. Lint yield followed similar trends. The yield reduction due to S and Zn omission ranged from 2.0 to 5.0% which was statistically at par with the plots under balanced fertilization both the years. Key words: Seed cotton yield, lint yield, nutrient omissions, nutrient concentration, nutrient uptake, nutrient use efficiency.
Highlights
Cotton is the most important commercial crop of India, often referred as the ‘White Gold’ providing employment to about 60 million people, is cultivated on an area of 11.1 m ha and out of which the area under Bt cotton has already crossed 90% (CICR, 2011)
Results showed that N was the most limiting factor 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
It considerably reduced the yield attributes which was reflected in lower stalk, seed cotton, lint and oil yield
Summary
Cotton is the most important commercial crop of India, often referred as the ‘White Gold’ providing employment to about 60 million people, is cultivated on an area of 11.1 m ha and out of which the area under Bt cotton has already crossed 90% (CICR, 2011). The American boll worms alone cause a yield reduction of 40 to 70% under severe infestation. An alternate strategy to circumvent this problem was followed by cloning and transferring the genes encoding the toxic crystal δ-endo toxin protein from the soil bacterium Bacillus thuringiensis to cotton. The Bt transgenic cotton (Bollgard of Monsanto) was developed successfully in USA, having the ability to control the bollworms during crop growth effectively. In India, cotton wheat cropping system is followed on 1.40 m ha and on 2.62 m ha in Pakistan. The total area under cotton-wheat cropping system comes to about 4.0 m ha in the north-western plains of India and Pakistan.
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