A marginal but steady decline has been observed in Bt cotton yield per acre in India during the last few years.
When the Bacillus thuringiensis (Bt) variety of cotton was introduced in India, it caused a revolution and resulted in huge increase in productivity and brought prosperity to Indian farmers.
According to the statistics of the Cotton Advisory Board (CAB), under the Union Ministry of Textiles, the average cotton productivity during the pre-Bt cotton period of 1993-2001 was around 300 kg/ha.
The next four to five years saw a remarkable increase in cotton productivity due to adoption of Bt technology by Indian farmers and 2007-08 saw a peak yield of 554.39 kg/ha.
However, since then the yield has slowly but steadily declined to 524.13 kg/ha in 2008-09, 513.1 kg/ha in 2010-11 and 492.77 kg/ha in 2011-12.
The yield per hectare is estimated to fall further in the current cotton season October 2012-September 2013 to 488.89 kg/ha.
Experts attribute the gradual decline in productivity of Bt cotton to newer pest attacks that emanate from changes in climatic conditions.
Some analysts also attribute the decline in average Bt cotton yield to sowing the seeds in non-optimal fields categorized on the basis of several factors like soil fertility, availability of water, weed management, etc.