Advanced Study on Variability in Length of Rainy Season for Selected Crops Production in Coastal and Upland Areas of Akwa Ibom State, Nigeria

This study assessed variability of rainfall in coastal and upland areas of Akwa Ibom State, as a guide for cultivation of maize, tomato, yam, cassava, oil palm and cocoa in the areas. Rainfall variability is the degree to which onset, length of growing season, cessation, amount and distribution of rainfall varies across an area due to climatic influence. The study was done in four different locations – coastal areas (Eket and Oron) and upland areas (Uyo and Ikot Ekpene). Daily rainfall data were obtained from Nigeria Meteorological Agency (NiMet), Abuja, for a period of 30 years (1989 – 2018). The amount of annual rainfall was determined using descriptive statistics; percentage of rainfall distribution was determined using precipitation concentration index equation; and onset, cessation and length of growing season were determined using Instat+ 3.36 software. The annual rainfall shows high variability between coastal and upland areas. Coastal areas experienced high amount of rainfall with average annual rainfall of 3282.50 mm (Eket) and 3094.87 mm (Oron); while the average rainfall for upland areas were 2272.24 mm (Uyo) and 2007.49 mm (Ikot Ekpene). All the areas experienced moderate precipitation distribution with coastal areas – Eket (11.31%) and Oron (11.67%); upland areas – Uyo (12.67%) and Ikot Ekpene (13.70%). Coastal areas (Eket and Oron) recorded early onset, late cessation and long length of growing season than upland areas (Uyo and Ikot Ekpene). The mean onset for Eket and Oron were 19th and 21st February; cessation 4th and 1st December and length of growing season 289.0 and 283.5 days respectively. The mean onset for Uyo and Ikot Ekpene were 8th and 17th March; cessation 16th November and 12th November and length of growing season 265.2 and 255.3 days respectively. The study shows that only upland areas can support sustainable production of yam and cassava, while both upland and coastal areas can support sustainable production of oil palm and cocoa. Also, sustainable production of tomato and maize production may not be achieved in both areas. Climate variability is a serious environmental issue that possess great threat to sustainable development and food security. Therefore, to avert the risks of crops failure, poor yield and economic loss, the use of seasonal climate outlook is recommended for adjusting farm operations and farming system decisions.