Food crop production in Nigeria. I. Present effects of climate variability

Climate and crop productivity are both characterised by inter-annual variability. The common understanding is that the co-variation is indicative of a simple cause and effect relationship. However, the relationship analysed in this paper is that of crops with complex phases of growth and development responding to a climate that is multivariate, dynamic and heterogeneous. Bivariate correlation, multiple correlation and regression analyses were employed to demonstrate the relationship between crop yield and climate. The crops studied were cowpeas, groundnut, millet, maize, sorghum and rice during the period 1983 to 1999 in the Nigerian Arid Zone. The predictive models generated for cowpeas, groundnut, millet and sorghum were statistically significant with 0.05. Among the more powerful determinants of crop yield were rainfall at the onset and at the cessation months of the growing season. Inter-annual changes in the yield of maize and rice were less sensitive to rainfall variability. In general, the linear models failed to incorporate the separation of crop yield variability from rainfall at higher levels of precipitation. During the long periods with normal and above normal rainfall, crop yield sensitivity tends to be weak. However, during the years with unusually low precipitation, crop yield sensitivity becomes more pronounced. For purposes of developing the appropriate adaptation strategies, it is suggested that a distinction be made between drought with its associated disasters and the less hazardous but more frequent inter-annual climate or rainfall variability.