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CAB Review

Impact of transgenic Bt cotton on soil health.

Abstract

Cotton is an important fibre crop of global and economic significance. For effective control of bollworms, transgenic Bacillus thuringiensis (Bt) cotton was introduced on a commercial scale in 1996, with an aim to reduce pesticide consumption. Presently, transgenic cotton is grown on 24 million hectares, which occupies 14% of global acreage planted to transgenic crops (185.1 million hectares). In recent years, considerable research efforts have been directed towards the study and assessment of the use of transgenic crops. Although transgenic Bt cotton is proven for its benefits in controlling insects, concerns still remain about its ecological impact on soil ecosystem function and biodiversity. This review focuses primarily on the persistence of cry toxin, if any, and impact on soil ecosystem functioning; because sustainable agriculture depends on soil - the basic natural resource. Based on the research from cotton-growing nations, there was no solid substantiation that points out adverse effects on soil health or fertility in terms of soil biology and ecology following cultivation of transgenic cotton. The Cry proteins released through root exudates and plant residues of Bt cotton appears to have no consistent and long-term effects on the soil biology. Some differences between Bt and non-Bt cotton were indicated for soil microbial community structure and their population. However, majority of the studies indicated that these differences were transient in nature and not statistically significant. Therefore, differences observed may not be related to the inserted Bt transgenes.