Effect of Rainfall and Temperature Variability on Green Gram Yield in Tharaka South Sub County, Tharaka Nithi County, Kenya

Globally, green gram is a significant legume particularly in Arid and Semiarid Lands (ASALs), as a source of food, income, and soil enhancement. Despite this importance, green gram yield in Tharaka South Sub County is still too low at 560 kg/ha far below the crop’s estimated national potential of 1500 kg/ha and compares unfavorably with the global and national average of 730 kg/ha and 670 kg/ha, respectively. Green gram production is primarily rain-fed and variability in rainfall and temperature affects the ideal conditions favourable for the crop growth. This study aimed at quantifying the effect of rainfall and temperature variability, separately and jointly on green gram yield in Tharaka South Sub County, Tharaka Nithi County, Kenya for the period 2002-2021. Secondary data on seasonal rainfall, temperature, and green gram yield was collected from the Meteorological Services and County Department of Agriculture. Data was analysed using qualitative and quantitative methods by use of coefficient of determination, Analysis of Variance (ANOVA), correlation, and regression analysis. The study found that rainfall variability explained 30.4% of the variables affecting green gram yield. The findings of the model showed that a 1% increase in rainfall in March-April- May (MAM) season increased yield of green gram by 49.3% but no effect was observed in OND (October-November-December) season. Temperature variability explained 28.5% of the variables affecting green gram yield. Further, the model findings revealed that a 1% increase in temperature in OND season decreased yield of green gram by 48.5% and no effect was observed in MAM season. A combination of rainfall and temperature variability explained 34.2% of the variables affecting green gram yield.  The model coefficients showed that a 1% increase in rainfall and temperature during the OND season increased yield of green gram by 16.2%. In addition, it was noted that a 1% rise in temperature and rainfall during MAM season reduced the output of green gram by 13.2%. The study concluded that rainfall and temperature had an effect on green gram yield and recommended that green gram farmers need to adapt to the changing climate to lessen the effects of climate change and for sustainable green gram production.