IMPACT OF CLIMATE VARIABILITY AND CHANGE ON SORGHUM PRODUCTION IN SUDAN – SAVANNAH AGROCLIMATIC ZONE OF NIGERIA.

Abstract

Temperature, rainfall and solar radiation have effects on the crops at all the stages of production. These effects are felt majorly by cereal crops because of their constant need of considerable amount of weather parameters at every stage of growth, and Sorghum happens to be one of such. Sorghum (Sorghum bicolor (L.) Moench ssp.), is a drought resistant crop, able to withstand periods of high temperature and even waterlogging, thereby making it a good staple food in food – insecure regions in the world. This study evaluates the potential impact of climate variability and change on sorghum production in the semi-arid region of Nigeria. Sorghum yield data collected from the archives of the Institute of Agricultural Research, Ahmadu Bello University Zaria for 30 – year were correlated with climate parameters from the same source. The data were analysed to show the impact of weather parameter: Temperature (maximum and Minimum), Relative humidity (morning and afternoon) and Rainfall on Sorghum yield in Samaru, Zaria, Nigeria. The variability and trends of climate parameters on sorghum yields were determined using coefficient of variation, linear regression and Mann-Kendall test. The result from the regression analysis shows that rainfall is decreasing at the rate of 0.77mm/year in the study area and more drought period were observed between 1982 and 2001. The pattern of rainfall in the study area is unimodal, an implication of only one rainfall peak. This is of importance to the production of Sorghum because of its adaptive nature to both drought and waterlogging. There is an increasing yield as rainfall decreases. However, between 2010 and 2013, yield increases as rainfall increases. The trend of other climatic parameters were also considered. The results showed insignificant trend for the intra seasonal rainfall characteristics. There is however, positive significant trend for maximum and minimum temperature at annual scales. The correlation coefficient was observed to be 0.82. The result showed that there were excellent agreement between the simulated and the observed values which indicated the performance of the CERES-Sorghum model in DSSAT to simulate yield of sorghum. The baseline period (1976 to 2006) indicated a decreasing trend in simulated sorghum yield. The result indicated that sorghum yield was decreasing annually by 48 kg/ha. This decrease in yield seen in the baseline period coincide with decreasing maximum temperature as observed during the period under study. Field experiments were also conducted for 2017 and 2018 to determine the input of different cultivars, weather parameters, fertilizer application and planting management on the yield of sorghum in a changing climate. The experiment were laid out in a randomized complete block design with two replication over two seasons. The result indicated that sorghum yield was decreasing annually in all the cultivars by 48 kg/ha, 41 kg/ha and 29 kg/ha. This decrease in yield seen in the baseline period coincide with decreasing maximum temperature as observed during this period. The projected yield under IPCC 8.5 scenario (increase Carbon emission and anthropogenic activities), sorghum was projected to increase by 28 kg/ha per annual under SAMSORG-17 variety, 33 kg/ha per annual under SAMSORG-43 variety and 34 kg/ha per annual under SAMSORG-44 variety. To explain this increase in sorghum yield in the cultivars variety, we further investigated the trend of weather conditions (rainfall, minimum temperature, maximum temperature and rainfall) associated during this projected period (2006 to 2030) using the Mann-kendal test. The results from the analysis state clearly the need to put into measure practices that will make cultivars more adaptive to climate changes. The statistical significance of the trends suggest that the p-value derived from the test, serves as a criterion to define the class boundary. The change in trend is considered significant when the obtained p ≤0.05 at 95% significant level, otherwise it is not significant. Maximum and minimum temperature were significantly increasing under IPCC 8.5 scenario as suggested from their p-values which was less than 0.05, the result indicates point out that high temperature could affect crops by speeding up their development and growth stages and reducing their life cycle. As a result short maturing cultivars could be most affected by the higher temperature effect on their growth and development stages as compared to long maturing cultivars. The study concludes that climate change will bring about a change in air temperature and rainfall amount which will invariably affect agricultural production system either directly or indirectly. The agricultural production is a whole lot of process that needs weather at one point or the other, from land preparation to harvesting. There are specifications of variables for each process which will be altered when the climate changes. The results from the two climate scenario further stated that the increase in temperature will lead to increase in yield, if other phenological processes are held constant.