Water use efficiency of maize (zea mays ) A dryland area of kenya.

This study was undertaken to investigate the variations of water use efficiency of two varieties of maize (Zea mays L.), viz. makueni and katumani composite B with planting density. and meteorological parameters under rainfed conditions. The study was conducted during the short rains season of 1990 at Kibwezi Dryland Research Station of the University of Nairobi in Machakos district, Kenya. The experimental design comprised two blocks, one for each maize variety, and three treatments characterised by Low (24,000 plants/ha), Medium (36,000 plants/ha) and High (83,000 plants/ha). Planting was done manually on 10th of November 1990. Neither manure nor fertilisers were used. Weeding was also done manually on 1st of December 1990. Dry matter in kg/ha was· obtained on weekly basis by harvesting two plants chosen at random from the centre of each plot. From grain filling stage, the grain dry matter was separated from the total above-ground dry matter. Harvest index was computed as a percentage of grain yield dry matter to total above-ground dry matter. Evapotranspiration was determined weekly by the water balance approach. Water use efficiency in g/mm was computed as a ratio of dry matter to evapotranspiration. Makueni composite gave higher harvest indices than katumani composite for all the plots. Medium planting -xvidensities gave the highest harvest indices. Relative dry matter accumulation rates between makueni and katumani varieties and also planting densities were not significantly different. Makueni composite was superior to katumani composite B in absolute dry matter accumulation rate during grain filling stage. Makueni composite out yielded katumani composite B in grain yield by approximately 23.5% and by 14.1% in total aboveground dry matter. Katumani composite plots showed higher crop water use than the corresponding makueni composite plots under the prevailing meteorological and soil water conditions. Crop water requirement was maximum during silking period for both varieties of maize. Makueni composite exhibited higher water use efficiency than katumani composite B in both grain and total above-ground dry matter production. For both yield components, water use efficiency decreased with increasing plant population. Although long term studies in the literature recommend a planting density of 37,000 plants/ha for maize in dryland areas, this study shows that it is possible to get higher yields with a planting density of 83,000 plants/ha.