Estimation of Water Requirements of Early and Late Season Maize (Zea mays) in Uyo, Akwa Ibom State, Nigeria using Penmann Equation

Abstract

This study estimated the water requirements of early and late season maize (Zea mays) cultivation in Uyo, Akwa Ibom State, Nigeria, using 20 years (2004-2023) of meteorological data from the University of Uyo. The Penman equation was employed to calculate reference evapotranspiration (Eto), while crop coefficient (Kc) values were used to estimate crop evapotranspiration (ETcrop) for both seasons. The data were analyzed using descriptive analysis. Result showed that the calculated seasonal crop evapotranspiration values 536.64 mm for early season and 493.14 mm for late season fall within the known range for optimal maize growth (500-800 mm), confirming the crop’s moderate to high water demand. The effective rainfall surpassed the estimated water requirements (ER of 615.85 mm and 623.93 mm for early and late seasons respectively). This indicates that Uyo’s climatic conditions are conducive for rain-fed maize cultivation, especially during the early season. However, moisture deficit of 74.15 mm was observed in May for the early season and a deficit of 69.10 mm and 12.87 mm was observed in October and November during the late season cropping. These periods correspond to the reproductive and maturity stages of the crop, which are highly sensitive to water stress. The moisture shortfall in the late season maturity stage justifies the recommendation for supplementary irrigation (91.45 mm) to sustain yield and physiological functions. Given that rainfall often exceeds the crops water requirement, intercropping maize with compatible species could enhance water use efficiency and reduce the risk of excess moisture affecting plant health or soil structure.