Evaluation of Sprinkler Irrigation Evaporation Losses in Ilaro, Ogun State, South Western Nigeria

Abstract

Under the prevailing climate change the world is currently facing, efficient irrigation water management is essential to ensure food security, especially in countries with similar climate to Nigeria. Hence, this study was undertaken at the Research Farm of Federal Polytechnic, Ilaro, Ogun State, Nigeria to evaluate evaporation losses during sprinkler irrigation between March and July 2019. Experiments were performed using 360 rotating sprinkler and single nozzle of diameter 3 mm, while due cognizance was taken of the prevailing climatic conditions. Three operating pressures, namely, 50 kPa, 100 kPa and 150 kPa, representing low pressure, medium pressure and high pressure, respectively, were used. The results showed that operating pressures influence droplet sizes, droplet heights and flow rate during the experiment. In addition, it was observed that at operating pressures of 50 kPa, 100 kPa and 150 kPa, mean percentage of evaporation losses were 8.88%, 13.21% and 16.46%, respectively, indicating that evaporation losses increased with increasing operating pressure. Further analysis showed that percentage evaporation losses increased at higher relative humidity, thereby emphasizing the predominance of air temperature and wind velocity as climatic variable influencing sprinkler evaporation losses. The relationship between wind velocity (Vw ) and air temperature (Ta) and to predict evaporation losses (E ) was a function of E = 7.968Vw + 0.393Ta – 19.977. Therefore, it was concluded that, both climatic factors and operating pressures influence the rate of evaporation losses during sprinkler irrigation, adequate attention should be paid to variation of climatic variables since sprinklers are sold with their specified operating pressures.