Assessment of the Impacts of Climate Variability and Change on Maize Productivity in Narok County, Kenya.

Abstract

Maize is an essential staple food crop in Kenya, including Narok County, whose productivity is often constrained by marked variability in the biophysical and socio-economic factors within the production environment. Climate variability and change threaten the sustainability of smallholder agricultural systems and food security in the county. Thus, strategies that can deliver enhanced and sustainable maize yields and food security are of urgent priority to Kenya and Narok County in particular. This study therefore, aimed to assess the impacts of climate variability and change on maize productivity in Narok county of Kenya. The study used observed daily rainfall, maximum and minimum temperature data for eleven stations in Narok County for the period 1981-2018 obtained from the Kenya Meteorological department, annual maize yield data expressed in MT/ha from the Ministry of Agriculture, Livestock, Fisheries and Cooperatives and CNRM model outputs. Intra-seasonal climate characteristics of onset and cessation dates, number of rainy days, wet spell length, dry spell length, length of the growing season, seasonal total rainfall, maximum temperature, minimum temperature, temperature range and Growing Degree Days (GDD) were analyzed. The double mass curve was used to test for data homogeneity. Time series analysis was employed to determine temporal distribution of the data sets. The Instat Plus statistical package Version 3.36 was used to determine rainfall characteristics at station level. Pearson’s correlation coefficient was used to determine the degree of association between pairs of study variables. The relationship between intra-seasonal climate characteristics and maize yields was determined using the multiple linear regression technique. Rainfall onset dates for most stations indicated an increasing trend, implying late onset of rains in recent years. The cessation dates for the rainy seasons depicted a decreasing trend hence early rainfall cessation in most of the study stations. The length of growing season indicated a decreasing trend, implying shorter/ reduced length of the growing season. The seasonal total rainfall for MAM season decreased over most stations. Dry spell length increased over the study period. Conversely, the intra-seasonal wet spell lengths indicated decreasing trend, signifying shorter lengths of wet spell over the study area. The number of rainy days during MAM season indicated a decreasing trend, implying reduced rainy days within the season. GDD, temperature range, maximum and v

minimum temperatures indicated an increasing trend over the study period 1981-2018 for all the study stations. The results further revealed increased climate variability under future climate (2021-2050) based on both RCP4.5 and RCP8.5 emission scenarios; with more increased climate variability based on RCP8.5 compared to RCP4.5. Both emission scenarios project increased temperature and rainfall during the period 2021-2050. Future climate will more severely impact maize yields under RCP8.5 as compared to RCP4.5. By the year 2050, maize yields are projected to decline by 2.5% based on RCP4.5 and 10.3% based on RCP8.5 emission scenarios. Consequently, effective adaptation strategies to climate variability and change impacts including adoption of drought tolerant early maturation maize varieties and relay cropping in regions with increased lengths of growing season will be key in ensuring increased and sustainable maize productivity and food security in Narok County.