Abstract
Bt cotton hybrids require large supply of metabolites to support their greater boll load and commonly suffer from premature leaf senescence. A field experiment was conducted to study the nutritional status of Bt cotton leaves during boll development stage and to evaluate the most profitable source of foliar fertilizers. Treatments included basal application of 0 and 60 kg·K2O·ha-1 as muriate of potash (MOP) in main plots and foliar spray treatments viz: 4 & 6 sprays of 2% potassium nitrate (Multi-K, 13-00-45), 4 & 6 sprays of NPK Blend (Polyfed, 19-19-19), 4 sprays of MOP, 4 sprays of MOP + urea (to supply same amount of N & K as in potassium nitrate) and unsprayed control in sub plots. The results revealed that only N and K contents of premature senesced leaves were below the sufficiency range for cotton sufficient levels of P, Fe, Mn, Zn and Cu were observed. Though the concentrations of N and K in both the petiole and leaf blade initially improved with foliar spray, N content declined below the unsprayed control at later stages. Basal application of MOP increased seed cotton yield by 19%. Four foliar sprays of KNO3, NPK, MOP and MOP + urea recorded yield increase in seed cotton yield of 22.8%, 22.4%, 18.5% and 24.5%, respectively over unsprayed control. Six sprays of KNO3 and NPK had no yield advantage over four sprays and rather proved economically less viable.
Highlights
India is the world’s third largest cotton producer, with average production of 2707 TMT
A field experiment was conducted to study the nutritional status of Bt cotton leaves during boll development stage and to evaluate the most profitable source of foliar fertilizers
The results revealed that only N and K contents of premature senesced leaves were below the sufficiency range for cotton sufficient levels of P, Fe, Mn, Zn and Cu were observed
Summary
India is the world’s third largest cotton producer, with average production of 2707 TMT. Under cotton in Punjab, but the crop suffers from premature leaf senescence during boll development. The characteristic rusting and premature senescence of both lower and young cotton leaves at the top of the plant late in the season, resembling potassium deficiency symptoms, have been reported earlier [3,4,5]. Wright [12] reported that cotton plants with premature senescence had twice the fruit loads but lower concentrations of potassium and nitrogen in leaves compared to healthy leaves without symptoms in the same field. Present investigation aimed to 1) investigate the nutrient status of cotton leaves during boll development and 2) compare the effectiveness of different foliar fertilizers on Bt cotton
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