Assessment of Food Crop Production in Relation to Climate Variation in Osun State Southwestern Nigeria

This study investigated trends in production of nine majorly cultivated food crops between 1992 and 2016 in Osun State, southwestern Nigeria. It also examined the contribution of the State to the total national food production and impact of climate variations on crop yields. It used secondary crop data collected from both the Federal Ministry of Agriculture and Rural Development (FMARD), Abuja and the United Nations Food and Agriculture Organization (FAO) as well as station observation of rainfall, relative humidity, minimum and maximum temperatures. Annual crop productions were estimated and ratio of the State to national crop cultivated area and that of production were computed using both the FMARD and the FAO datasets. The means, standard deviations, interquartile ranges were computed and trend analysis using Mann–Kendall test was done to assess trends and variability in climatic characteristics and basic components of crop production. Multiple regression and synchronization analyses were carried out to investigate the relationship between the crop yield and the climate. Cassava production was found to be the highest with about 0.9 million metric tons per year. The State highest contribution to the national crop production was 3.3 - 5.3% (cocoyam) and the least 0.03-0.04% (cowpea). Rainfall increased annually by 3.5 mm, minimum and maximum temperatures by 0.083 and 0.033°C while relative humidity decreased by 0.32%. Decrease in yam and rice productions was attributed to a combined effect of reduction in yield (due to climate variation) and cultivated area (due to socio-economic factor). Correlations between climate and yields at p < 0.05 differed among the crop types and 48 to 90% of variations in the yields of tomato, yam, cocoyam and cowpea were strongly accounted for by climatic factors. The findings suggest the drive for irrigation to enhance full utilisation of the State’s potential for yam and rice production and propose pragmatic efforts by governments and relevant stakeholders to assist smallholder farmers towards exploiting larger available land area for agricultural production.