EFFECT OF RAINFALL VARIABILITY ON YIELD OF SELECTED CROPS IN BENUE STATE, NIGERIA

Abstract

Crop yield apart from being a source of boost to the economy of a nation, improves the quality of life and aids in the sustenance of human existence. There is therefore the need to investigate the effect of rainfall variability on yield of selected crops in Benue State. Both secondary and primary sources of data collection were employed in the study. CMAP Rainfall data was collected using orbiting satellite image for the period of 30 years from 1988 to 2017 over Benue State. While the crops yield data was collected for 30 years from the archives of Benue State Agricultural and Rural Development Agency (BNARDA). Data from Primary sources were collected with the aid of questionnaire administered to 720 farmers selected through a multi stage sampling technique which saw twelve out of the twenty-three (23) Local Government Areas selected based on the high yield of the crops under study. Each selected LGA was further divided into six (6) extension blocks where the productivity of selected crop yields under study are at maximum, which make a total of 36 extension blocks. Four (4) farming communities were randomly selected from each extension blocks to bring a total of 72 communities. Ten (10) farmers were randomly selected which resulted to a sample size of seven hundred and twenty (720) farmers. That is, 240 questionnaires were being administered from each zone and 60 from each LGA respectively. Descriptive statistics was used to analyse the data and results were presented using frequency tables, charts and figures. Coefficient of variation and Precipitation Variability Index (PVI) were used to determine the rainfall variability. Mann- Kendall test was used to assess the trend of selected crops. Rainfall data from 1988 to 2017 was used to analyse the indices of rainfall (onset, cessation and length of rainy season) and also to determine the effects of onset and cessation on crops yield in Benue. Partial correlation was used to determine the magnitude of zonal rainfall variability. The results of the research show that, precipitation variability index revealed tendency of drought especially the Northern Zone of the State by more than 30% variability followed by the South with variability of 20% to 30% and the East zone with less than 20% variability. Onset of rain begins in the South on the 4th April, followed by the East on the 6th April and on the 9th April for the North. The cessation dates are between 6th October and 17th November across the study areas. The Length of Rainy Season (LRS) is longer in the Eastern Zone (236 days), followed by the Southern Zone (230 days) and then Northern Zone (209 days). It was revealed that the yields of selected crop (cassava, yam, maize, soyabeans and groundnut) show a positive trend while that of rice on the other hand, shows a negative trend over time. In all 73 % of respondents are aware of rainfall variability and have attempted adapting in one way or the other and 69 % affirmed that the method used increased yield. So, it can therefore be concluded based on the findings of the study that, rainfall commences early in the Southern Zone, followed by the Eastern Zone and then the Northern Zone. The onset of rain is similar in all the Zones and crop yields are increasing due to choices for adaptation. The study therefore recommends that other elements of climate such as temperature, relative humidity, and farm management practices should be studied to find the impact of such oncrop yield. There is also need for the intensifying effort towards irrigation farming in order to curtail the uncertainty attached to rain- fed agriculture. Annual sensitization workshops and seminars should be encouraged for farmers, to create awareness among them on climate and its potential impact on crop yield. More extension workers should be deployed in the State owing to their importance to rural farmers. Farmer’s adaptation measures (Changes in planting date and used of improved varieties) to rainfall variability in the State should be harnessed for proper results.