Nitrogen Loss from Cotton (Gossyium spp.) Plants Grown on Rainfed Vertisols

Abstract

Low recovery efficiency of nitrogen (N) is mainly attributed to the various losses from the soil after application. N loss from the plants could be substantial probably contributing to the low and inefficient use of N by the cotton cultivars belonging to the different species. However, there is limited information on the recovery efficiency, especially for the transgenic Bt cotton hybrids grown in India with surplus fertilization. In an on-going field experiment, we estimated N uptake and determined the recovery efficiency of cotton grown on a rainfed Vertisol. A difference in N uptake at peak boll formation and at final harvest was considered as the N volatilized from the cotton plant. The transgenic hybrid, ‘Ajeet-155 BGII’, had the highest N uptake followed by Upland cotton cultivar ‘Suraj’ and an Asiatic cotton cultivar ‘Phule Dhanwantary’. However, the recovery efficiency was the least with ‘Ajeet-155 BGII’ hybrid (27.2%) that also had the highest N loss from the plant (32.3-63.9 kg N/ha). Proportion of fertilizer-N lost in the transgenic cotton was >18.0% as compared to 3.6% for ‘Phule Dhanwantary’ and 10.5% for the cultivar Suraj. Among the species, Asiatic cotton (G. arboreum) had higher recovery efficiency of N and lower N loss from cotton plants than the Upland cotton (G. hirsutum) cultivar (Suraj) and transgenic Bt hybrid (Ajeet- 155 BGII). Growing Asiatic cotton would have the potential to reduce environmental damage and contribute to a cleaner cotton-based production system. Taking into account the plant N loss from plants could be used as one of the important criteria for improving use efficiency and also to calculate an accurate N balance sheet.