Evaluation of dry spells during sensitive growth stages for maize crop in Western Kenya

Abstract

Evaluation of dry spells during the growing season of maize crop is done for the Lake Victoria basin in Kenya. The evaluation is based on suitable criteria for daily rainfall threshold (DRT) values that link the dry spells to the growing season. Three criteria: a) 1 mm DRT adopted from the Kenya Meteorological Department (KMD)-a storm of 1 mm is considered a wet day; b) 5 mm DRT that approximates to the mean reference evapotranspiration (ETo) of the region over the growing season; c) 10 mm DRT adopted from the region’s rainfall onset criteria of 40 mm in 4 days, were tested by varying the durations of the dry spells between 7 to 30 days for the region. Dry spell analysis results obtained were interpolated in ArcGIS 10 using ordinary kriging, with or without anisotropy, and severity zones for agricultural planning mapped. The results presented through both temporal and spatial techniques indicate that probability of dry spells occurrence increases with increase in dry conditions. Results for the 5 mm DRT with durations of 7 days and 10 days are presented spatially to capture the severity of dry spells during germination and flowering stages of maize crop. The dry spells severity during germination stage is highest towards the northern part of Lake Victoria Basin (Kenya) and around the Lake shores with values ranging from (0-65%) and (0-59%) for the 7 and 10 days durations respectively. For flowering, the probability of dry spells range from (0-73%) and (0-65%) for the 7 and 10 days durations respectively with the highest severity occurring along Lake Victoria shores and the lowest around microclimatic (forests and topographic) features. These results indicate that point- specific analysis of agroclimatic parameters is crucial for agricultural planning since variations occur over short distances. The greater values fall within zones that produce a lot of maize hence the need for mitigation measures.