Implications of Temperature and Rainfall Variability on Wheat Vegetative Health and Grain Yield in Narok County of Kenya

This study investigated the implications of temperature and rainfall on wheat vegetative health and grain yield in Narok County, Kenya, using Normalized Difference Vegetation Index (NDVI) and annual grain yield data as dynamic indicators of crop performance. Meteorological data were sourced from the Narok Meteorological Station in the form of monthly averages for temperature and rainfall for the period 1975 – 2022. Data analysis tools included correlation and regression techniques. May rainfall and minimum temperatures in April and June were found to significantly affect NDVI, while September minimum temperature, June maximum temperature, and March–May rainfall significantly influenced grain yield. Quantile regression revealed that rainfall in May consistently increased NDVI across 25th, 50th, and 75th percentiles, whereas June’s minimum temperature had a varied influence depending on the crop’s canopy density. Similarly, grain yield was positively associated with September minimum temperature and March-April-May rainfall, especially at low and high yield levels, while an increase in June’s maximum temperature significantly contributed to reduced yields across years. The findings reject the null hypothesis while confirming that wheat NDVI and grain yield are significantly influenced by climatic variables, particularly at distributional extremes. By integrating NDVI into the analysis, this research bridges a methodological gap, offering a more comprehensive assessment of climate impacts on crop performance beyond final yields. The study underscores the need for tailored agronomic and climate adaptation strategies that consider intra-seasonal climate variability and its differential effects on wheat health and productivity