Abstract:
Adverse soil moisture deficit as a result of high ambient temperatures and high velocity June
winds at critical stages of maize growth had been singled out as the most important factor
limiting maize yield in Coastal Kenya during long rain season. This study was carried out to
study the effect of foliar applied kaolin and coir dust mulch on evapotranspiration and yield of
Pwani hybrid 4 maize. A 2x2x4x3 split-split plot design experiment, replicated thrice was set at
Pwani University Farm, in 2007 and 2008 seasons, with coir dust mulch as the main plot
treatments; irrigation as the sub-plot treatments, and kaolin at sub-subplot levels. Parameters
measured included plant height, periodic above ground biomass and grain yield, soil moisture
content, soil and air temperatures, % relative humidity and wind run at 31, 49, 66, 83 and 100
days after sowing. Energy and water balance equations were used to determine crop
evapotranspiration. Genstat 14th Edition was used in data analysis and the means obtained used
to develop ET-Yield production functions for predicting Pwani hybrid 4 maize yield in Coastal
Kenya. Coir mulching resulted in reduced evapotranspiration early in the seasons, contributed to
highest (9-15 %) soil moisture conservation, availing it at later stages of growth, up to 49th DAS.
Beyond this period irrigation provided superior soil moisture conditions, especially at critical
stages of maize growth. Coir mulching early in the season could substitute supplementary
irrigation without significant losses in grain yield. Coir mulching was more beneficial in biomass
and grain production during the relatively drier season II than during wetter season I. Coir mulch
alone treatment resulted in highest grain yield (p < 0.05) in both seasons, of 6.7 and 4.9 tons ha-1.
Interactions of coir mulch and irrigation offered the best option in ameliorating June winds
effects. Although irrigation resulted in highest biomass, it did not result in highest grain yield.
Application of kaolin alone depressed final biomass and grain yield. However, its interactions
with coir mulch and irrigation resulted in increased yield during a wetter season except when
applied at floral stages, while its application during a relatively drier season resulted in depressed
yield. Its application during wetter conditions in coir mulched or irrigated maize crop resulted in
significant (p < 0.05) increases in biomass and grain yield of 20-31 % and 41.9 % respectively.
Kaolin had ―short and long term‖ effect on levels of soil moisture, seasonal evapotranspiration
and biomass. The response of Pwani hybrid 4 maize yield to kaolin was highest at floral stages,
and under stress conditions. Multiple linear regressions indicated that coir mulching was the
most important factor in determining the level of grain yield.
