Early drought and low nitrogen tolerant double top cross maize hybrids for the dry midaltitude ecology of Kenya

摘要

Low soil fertility and frequent drought are the most important constraints to maize (Zea mays L.) production in the dry midaltitude ecologies of Eastern Africa. In Kenya's dry midaltitude zone, the existing maize varieties (Katumani composite B and dryland composite) are not very productive under conditions of moisture stress and low soil fertility (KARI, 1992). With increasing settlement in the marginal areas, increased maize production will require better varieties—probably non-conventional hybrids, like double top cross hybrids—to meet the food demand of a growing population in an environment characterized by declining soil fertility and land holding size. Heterosis, as expressed in a double top cross hybrid, has been responsible for much of annual yield gains in maize (Duvick, 1997). Double top cross hybrid seed will be less expensive to produce. Furthermore, in instances when farmers recycle seed from the previous season, the yield loss will not be very drastic, as this will be, in effect, an open pollinated variety. Therefore, availability of early stress tolerant double top cross hybrids will enhance the ability and the scope of farmers to increase maize production in the dry midaltitude zone of Kenya.