The Journal of Agricultural Science

Crops and Soils

Reductions in insecticide use from adoption of Bt cotton in South Africa: impacts on economic performance and toxic load to the environment

R. BENNETT a1, Y. ISMAEL a1, S. MORSE a2c1 and B. SHANKAR a1
a1 Department of Agricultural and Food Economics, The University of Reading, PO Box 237, Reading RG6 6AR, UK
a2 Department of Geography, School of Human and Environmental Sciences, The University of Reading, PO Box 227, Reading RG6 6AB, UK

Article author query
bennett r   [PubMed][Google Scholar] 
ismael y   [PubMed][Google Scholar] 
morse s   [PubMed][Google Scholar] 
shankar b   [PubMed][Google Scholar] 


The study reported presents the findings relating to commercial growing of genetically-modified Bt cotton in South Africa by a large sample of smallholder farmers over three seasons (1998/99, 1999/2000, 2000/01) following adoption. The analysis presents constructs and compares groupwise differences for key variables in Bt v. non-Bt technology and uses regressions to further analyse the production and profit impacts of Bt adoption. Analysis of the distribution of benefits between farmers due to the technology is also presented. In parallel with these socio-economic measures, the toxic loads being presented to the environment following the introduction of Bt cotton are monitored in terms of insecticide active ingredient (ai) and the Biocide Index. The latter adjusts ai to allow for differing persistence and toxicity of insecticides.

Results show substantial and significant financial benefits to smallholder cotton growers of adopting Bt cotton over three seasons in terms of increased yields, lower insecticide spray costs and higher gross margins. This includes one particularly wet, poor growing season. In addition, those with the smaller holdings appeared to benefit proportionately more from the technology (in terms of higher gross margins) than those with larger holdings. Analysis using the Gini-coefficient suggests that the Bt technology has helped to reduce inequality amongst smallholder cotton growers in Makhathini compared to what may have been the position if they had grown conventional cotton. However, while Bt growers applied lower amounts of insecticide and had lower Biocide Indices (per ha) than growers of non-Bt cotton, some of this advantage was due to a reduction in non-bollworm insecticide. Indeed, the Biocide Index for all farmers in the population actually increased with the introduction of Bt cotton.

The results indicate the complexity of such studies on the socio-economic and environmental impacts of GM varieties in the developing world.

(Received November 8 2004)

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