Micro Analytic Study of Crop Water Use In Relation To Crop Production in Nigerian
The recent variations in climate and their consequences on human affairs particularly on agricultural production call for a closer examination of variations which characterize climate and the effects of such variations on crop production. This thesis applies the concepts of water use and the water balance in examining climate effects on crops. Most of the literatures on crop-climate relationship available in Nigeria are on macro or meso scales in which the effects of climate on agricultural production were based on rainfall obtained outside the immediate environment of crops. Only very few studies discussed the mean annual and mean seasonal variations in water need of crops. In contrast to these studies the present study examines crop-climate relationship on relatively micro scale by using pertinent climatic information obtained from five experimental stations. These stations have a good geographical spread in Nigeria. Specifically, this study identified and examined four main features of rainfall in Nigeria. These include: (a) The mean annual rainfall of which the 1940-85 rainfall data were analysed; (b) the yearly rainfall variations in Nigeria of which the annual values of precipitation for each of the years 1950-85 were computed as percentages of the averages of the period 1940-76 for each of the stations; (c) The locational variations and (d) The application of the concept of seasonality (Oliver, 1980) with respect to mean annual rainfall distribution in Nigeria as well as the year to year variations in the study locations. Similar features of potential evapotranspiration (PE) in the country were discussed. The study also examined the mean water balance in Nigeria in general and the five basic locations in particular and emphasizes the water balance conditions not only within the growing season but during each stage of the growing season. Finally, PE, and P-PE on one hand and crop yields on the other hand were computed In doing these, climatic data were collected from stations other than the five basic stations (fig. 1) for comparative analyses and general discussions on Nigeria. In addition, a review of the literature and past research yielded some data employed in the study. The study shows that completely different patterns of rainfall distribution occur within the same climatic region and stations located relatively close to one another. It also shows that although all parts of Nigeria experience variations in climate, over the past fifteen years, the variations have been more pronounced particularly in the locations in the northern part of Nigeria. These conditions have greatly affected agricultural production over wide areas. The study also confirms previous conclusions that the characteristics of crop, yields are results of a complexity of interacting factors of the physical environment.