Effect of Bt cotton on nutrient dynamics under varied soil type

Abstract

Since transgenic cotton was first grown commercially in India in 1996, the areas cultivated have increased rapidly around the world. Bt cotton is produced by inserting a synthetic version of a gene from the naturally occurring soil bacterium <em>Bacillus thuringiensis</em> into cotton. Bt cotton may affect nutrient dynamics in many ways during its life-span with regard to the temporal-spatial relevance of Bt proteins. Given this, we aimed to evaluate nutrient availability under both Bt and non-Bt systems and varied soil type. The study was conducted during the 2010 wet season (July to December) in a net-house at the Institute of Agricultural Sciences of Banaras Hindu University. It was carried out on three different soil orders i.e. entisol, inceptisol and alfisol. Bt-cotton (<em>cv</em>NCS-138) and its non-transgenic isoline (<em>cv</em>NCS-138) were grown until maturity. A <em>no crop</em> pot was maintained with three replications for all the three soil orders. Study design was a factorial experiment under a completely randomized block design with three replications. The study concludes that available N was reduced by 12-13% under Bt-cotton compared to non-Bt isoline and n<em>o crop</em> treatment whereas it showed a significant increase in available P in the soil under Bt-cotton (7.8% increase) compared to non-Bt isoline and <em>no crop</em> treatment. Furthermore, it has been observed that available K value varied from 82.88 kg ha-1 to 76.88 kg ha-1 in the soil under Bt-cotton and from 90.33 kg hato-1 83.55 kg ha-1 in the non-Bt crops and a significant increase in the Avalaible Zn in the soil under Bt-cotton compared to non-Bt isoline and<em> no crop</em> treatment

Impact ofBt-cotton on soil microbiological and biochemical attributes

“…In Bt-rhizosphere, micronutrient DTPA-Zn and Fe contents were observed higher as compared to non-Bt. Significant increase in the available Zn and Fe in the soil under Bt-cotton over non-Bt cotton was due to higher root biomass-mediated exudation and this might the most important reason for the increase (Beura & Rakshit, 2011). In conclusions, Bt-cotton expressing cry1Ac gene producing Bt-toxin had no detrimental effects on soil microbiological activities such as culturable bacterial population, microbial activity via respiration, dehydrogenase and phosphatase activities.…”

Effects of Bt-cotton on biological properties of Vertisols in central India

“…Cultivation of nutrient exhaustive crops like Bt-cotton may lead to a rapid depletion of soil organic C and other essential nutrients, which might cause soil degradation (Lal 2015). Although intensive cultivation of Bt-cotton might add increased biomass to the soil, a negative C and N balance might occur due to rapid depletion of nutrients in such systems (Sarkar et al 2008;Beura & Rakshit 2011). Further, intensive cultivation under mechanized farming cause rapid changes in native ecosystems that might cause easy oxidation of soil organic C (Awale et al 2017).…”

Studies on correlations between soil chemistry and bacterial population in rhizosphere of Bt and non-Bt cotton and characterization of rhizobacteria

“…Bt crops affect nutrient cycling and change the chemistry of the rhizosphere [17]. Nutrient dynamics are influenced by diverse means during microbial life span based on time and space relevance [18]. The change in soil pH directly influences the microbial activity which leads to a drastic change in enzyme activities in the soil [19].…”