Effects of Climate Variability on Maize Yield in Nakuru County, Kenya
Koimbori, Jackson Kinyanjui
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The current climate in East Africa is characterised by large variability in rainfall and temperature with occurrence of extreme events such as prolonged and severe droughts that have led to increased cases of crop failure, hunger and destruction of habitats. This study analyzed the effects of climate variability on maize yield among farm holders in Bahati Sub- County, Kenya for the period 1985 to 2015. The specific objectives of this study were: to establish climate variability trends in rainfall and temperature experienced by farm holders in Bahati Sub-County, to analyze the effects of climate variability on maize yield in Bahati Sub- County and to identify and evaluate the existing climate variability adaptation strategies practised by farmers in Bahati Sub-County, Kenya. The climate parameters used included rainfall onset, rainfall cessations, seasonal rain, annual rainfall, annual mean temperature, maximum and minimum temperature. A descriptive case study was used relying on both primary and secondary data. Stratified random sampling technique was used to select 394 households from Dundori, Kabatini, Kiamaina and Bahati wards based on Yamane (1967) formula. Primary data was collected through household surveys and secondary data on rainfall and temperature for the past 30 years (1985 to 2015) was purposively sampled and collected from Nakuru Meteorological Station. Maize yield data for Bahati Sub-County was collected from the MOA, Tegemeo Institute and Nakuru County Agricultural Office for the period 1985 to 2015. The data collected on rainfall, temperature and maize yields was analyzed using Microsoft Office Excel 2010 and SPSS software version 23 to generate frequency tables, pie charts, graphs and moving averages. The findings were that annual rainfall and maize yield have shown a decreasing trend, while the average annual, maximum and minimum temperature have shown an increasing trend from 1985 to 2015. Rainfall has shown a decreasing trend during the long rain season and an increasing trend during short rain season. Rainfall variability is significant in both seasonal and annual trends with the highest annual rainfall variation below average occurred in 2000 with a variation of 350.40mm and highest annual variation above average occurred in 2010 with a variation of 475.80mm. The long rain season recorded the highest rainfall variation below average in 2000 with a variation of 253.17mm and the highest rainfall variation above average in 2010 with a variation of 263. 53mm.The Short rain season recorded the highest rainfall variation below average in 1985 with a variation of 111.08mm and the highest rainfall variation above average in 1997 with a variation of 247.31mm. Annual average temperature has shown an increasing trend ranging from 17.7°C in 1989 to 19.7°C in 2009. Maximum temperature trend has shown a slightly gradual increase of 0.008°C annually. Minimum temperature trend has shown a slightly gradual increase of 0.075°C annually. Annual maize yield variability has shown a decreasing trend ranging from +11,913 Tonnes in 2000 to +62,615 Tonnes in 1988 above average. The findings revealed that there is a significant, positive and strong relationship between rainfall trend and maize yield (r= 0.741, p = 0.000). The study also revealed that there is a significant, moderate and negative linear relationship between maximum temperature and maize yield (r= -0.510, p= 0.03). However, the study findings also revealed that the relationship between minimum temperature and maize yield had an insignificant, weak and negative relationship (r= -0.166, p= 0.372). Eighty-six-point three percent of the respondents from the opinion findings strongly agreed that climate variability has influenced their annual maize yield levels in Bahati Sub-County. Sixty-four-point five percent of the respondents disagreed that the adaptation strategies implemented have improved maize yields in the area. The study suggested for further research to be done on maize varieties that are tolerant to climate variability and on the best adaptation strategies of reducing maize farmer’s vulnerability to climate variability. Also, Nakuru meteorological station should provide forecast prediction to the farmers on the onset and cessation of the growing season so as to help maize farmers plant and harvest on time.