How quickly cultivars are replaced indicates how effectively the seeds of new cultivars are supplied and taken up by farmers. Many factors determine the rate of replacement, not least how cultivars are popularised by government agencies, how efficiently seed producers market new cultivars, and how superior the new cultivars are to the ones they should replace. Assessing varietal replacement is not easy, and many indices of varietal replacement have been proposed. In this chapter, data on breeder seed indents is used to calculate weighted average age. For a number of crops, statistics were obtained for certified seed production in Gujarat, Madhya Pradesh and Rajasthan. These data were analysed in the same way as those for breeder seed indents. Information, at the district level, is also available on the uptake of high yielding cultivars (HYVs). These data were used to see the extent of adoption of modern varieties by farmers and whether, as predicted by Byerlee and Heisey, 1990, this is related to the base yields that farmers achieve.
