Varietal turn-over and their effect on yield and food security – evidence from 20 years of household surveys in Kenya

The International Maize and Wheat Improvement Centre (CIMMYT), in collaboration with the Kenya Agriculture and Livestock Research Organization (KALRO) (previously the Kenya Agricultural Research Institute or KARI), conducted four nationally representative household surveys in the major maize growing areas during the last 30 years. All surveys used the same two-stage stratified design with maize production zones or agroecological zones (AEZs) as strata, census clusters or sublocations as primary sampling units, and maize-growing households as secondary sampling units. The first survey was conducted in 1992 and covered 79 clusters totaling 1397 farmers. This survey also defined the six AEZs, going from East to West, as the Coastal Lowlands, the Dry Mid-Altitude zone, the Dry Transitional zone, the Moist Transitional zone, the High Tropics, and the Moist-Mid Altitude zone. The second survey, conducted in 2002, covered 185 sublocations based on the 1999 census, with 1652 households. The third survey, of 2010, covered 120 sublocations with 1341 households while the fourth survey, of 2012, interviewed the same farmers with a replacement of 20% of randomly sampled households.