Methods of cotton (Gossypium hirsutum) establishment and zinc fortification in cotton-based cropping systems: Direct and residual effect on onion (Allium cepa) and system productivity of cottononion cropping system

Abstract

A field experiment was conducted during rainy (kharif) and winter (rabi) seasons of 201314 and 201415 at New Delhi, to evaluate the effect of 2 methods of cotton establishment (direct sowing and transplanting) and 5 zinc-levels (control, 2.5, 5.0, 7.5 kg Zn/ha and 0.5% zinc sulphate foliar spray at 60 and 90 days after planting ) on cotton (Gossypium hirsutum L.) and their residual and direct effect of 5.0 kg Zn/ha in place of foliar treatment on the succeeding wheat [Triticum aestivum (L.) emend. Fiori & Paol.] and onion (Allium cepa L.) crop. In this re- search paper residual effect of treatments applied to cotton and direct effect of Zn on onion has been presented along with system productivity and resource-use efficiency. Productivity of cotton and onion was higher during 201314 than 201415. Onion recorded significantly higher economic parameters and nutrient uptake after trans- planted cotton than direct sown. Onion produced statistically similar growth and yield attributes, bulb yield, gross and net returns and nutrient uptake, due to direct application of 5.0 kg Zn/ha and residual effect of 5.0 and 7.5 kg Zn/ha to cotton, which were significantly superior to control and residual effect of 2.5 kg Zn/ha. Based on 2 years average, gain in net returns was 40,350, 43,200 and 47,950/ha due to residual effect of 5.0/7.5 kg Zn/ha and direct effect of 5.0 kg Zn/ha over control. Both residual and direct effect of Zn found to enhance the quality of bulb in terms of Zn enrichment and on an average 32.0, 31.8% and 36.2% increase in Zn uptake was recorded due to residual effect of 5.0/7.5 kg Zn/ha and direct effect of 5.0 kg Zn/ha respectively. Based on 2-years average, sys- tem productivity in terms of seed cotton equivalent yield (9.45 t/ha), production efficiency (27.0 kg/ha/day), eco- nomic efficiency (736.9 /ha/day) and irrigation water productivity (1.16 kg/m3) of transplanted cottononion crop- ping system was significantly greater than the direct sown cottononion system. Successive increase in Zn-levels caused significant increase in system productivity, production efficiency, economic efficiency and irrigation water productivity up to application of 5.0 kg Zn/ha. So based on the study it is concluded that in Bt cottononion crop- ping systems 5.0 kg Zn/ha to Bt cotton is sufficient to meet the zinc requirement of both the crop and transplanted cotton is better than direct sown cotton.