Effects of Coir Dust Mulch on Evapotranspiration of PH4 Maize in Coastal Region of Kenya

摘要

Although the Coastal region of Kenya is awash with abundance of moisture bearing South Easterly monsoons, (and therefore tropical rainfall) from the adjacent vast Indian Ocean, heat stress, high velocity wind regimes are major factors limiting crop productivity in the region. Occurrence of these abiotic factors tend to occasion cloud free conditions, high atmospheric demand and vapor pressure deficit that results in increased soil moisture deficit, which more often coincides with critical stages of maize growth resulting in poor maize yields. A 2x3 randomized complete block design experiment was set in 2007 and 2008 seasons at Pwani university farm using PH4 maize variety and coir dust mulch treatments at two levels, with and without mulch, to evaluate effects of coir dust mulch in ameliorating the effects of high temperatures and high velocity wind regimes on soil moisture status. The results showed that PH4 maize evapotranspired at an average rate of 157.5 mm and 151.3 mm per phasic growth stage in non-mulched and coir mulched maize crops, respectively during the relatively wetter season I; and by 156.3 mm and 151.0 mm in non-mulched and coir mulched maize crops, respectively during the relatively drier season II. Coir mulching reduced the average rates of water use per phasic growth stage by 3.9% and 3.4% during the relatively wetter and drier seasons I and II, respectively. The results showed that during the relatively wetter season I, between 534-549.6 mm of soil moisture had to be expended as basal evaporation before any tangible dry matter yields could be obtained, while during the relatively drier season, 167.7-190.1 mm had to be expended. This basal evaporation values represented 48.2% and 17.0% of long rain’s total precipitation during seasons’ I and II, respectively, indicating that much of the received precipitation was not effectively used for grain production, but mainly lost as non-productive component of seasonal evapotranspiration. The results also indicated coir mulching resulted in decreased seasonal evapotranspiration but significantly increased conserved 100 cm-profile soil moisture early in the season, when compared to non-mulched control treatments. This conserved moisture was available later in the season for increased dry matter and grain yields. Coir mulching increased WUE by 8.4%. The study showed that adoption of a simple agronomic practice of applying a 10 cm thick layer of coir dust mulch could increase maize productivity by 10.4% and help improve livelihoods of people in Coastal region.