ABSTRACT

Climate change and variability is a global issue that needs to be given proper attention because of its impacts on the agriculture and other aspects of socio-economies. Annual rainfall and temperature data of four decades (1971-2010) for Zaria Local Government Area of Kaduna State located within Latitude 11o081N and Longitude 07o411E were obtained from Nigerian Meteorological Agency (NIMET), Zaria, and analysed in order to establish climate variability in the area. Three methods were used to study the climate variability namely: statistical differences between the two equal-length time scales of 1971-2000 and 1981-2010, respectively, coefficient of variability (CV); and the Anomaly approach. However, trend analysis using t test, Sen’s estimator slope and Mann Kendall were also carried out in order to determine the trend in the climatic variables. On other hand, multiple non linear regression analysis was performed for the annual maize, millet and sorghum yields on the climatic variables using Sigma plot 11.0. The three models of the crops developed were evaluated using statistical error measurement. The result revealed that the differences between the two means of the equal-length time scales revealed variability of: 7mm, 0.50oC, 0.30oC and 0.40oC for rainfall, maximum, minimum and mean temperatures, respectively. Similarly, the CVs of rainfall, maximum, minimum and mean temperatures were: 0.145, 0.026, 0.036 and 0.025, respectively indicating low variability. However, the anomaly results revealed that 21 years (52.5%) recorded dry; while 19 years (47.5%) recorded wet; 1983 having the highest dry of 323mm; and 1972 has the lowest dry of 15mm. On the other hand, the highest wet of 340mm occurred in 1978; while the lowest wet of 9mm was recorded in 1971. Moreover, 24 years (60.0%) were warmer than normal; 13 years (32.5%) less warm than normal; while 3 years (7.5%) had normal mean temperature. The Sen’s estimator slope revealed downward trend of 94mm/yr in 1971-1980 decades; while it recorded upward trends of :90mm/yr, 30mm/yr and 118mm/yr, respectively during 1981-1990, 1991-2000 and 2001-2010 decades, but they are not statistically significant. However, the mean temperature recorded upward trends of 0.2oC/yr, 0.2oC/yr,0.1oC/yr and 0.2oC/yr, respectively in 1971-1980, 1981-1990, 1991-2000 and 2001-2010 decades. The regression analysis revealed that only 28.9%, 45.2% and 24.2%, respectively for maize, millet and sorghum yields variation can be accounted for by the rainfall and mean temperature. However, out of the three developed models, the millet model was the most fitted and valid as it recorded the lowest total and mean square errors of: 0.335 and 0.030, respectively. It was followed by the sorghum m

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