DETERIMINATION OF CROP WATER REQUIREMENT AND CROP COEFFICIENT AT DIFFERENT GROWTH STAGES OF LOWLAND BREAD WHEAT (Triticuma estivum L.) AT MELKASSA, OROMIA, ETHIOPIA

Abstract

Accurate estimation of crop water requirements is crucial for better water-use efficiency and better planning of irrigation water resources. A crop water requirement is estimated using 'Kc ETo' approach. However, locally determined Kc information is not available for many crops in Ethiopia. In view of this, an experiment was conducted to determine the crop water requirement and crop coefficient of wheat during cool cropping season from lysimeter study. The study was carried out at Melkassa agriculture research center which is located in semi-arid climate zone of Ethiopia. Two drainage type of lysimeter were used to measure the daily ETc of wheat Gambo variety. Water balance equation was applied to calculate ETc. The ETo was determined from daily weather parameters (minimum and maximum temperatures, wind speed, relative humidity and sunshine hours) obtained from agro-meteorological observatory of MARC using the FAO CROPWAT 8.0 software. The Kc was obtained from the ratio of measured ETc to ETo. The average seasonal ETc for wheat crop was found to be 501.8mm. The mean measured ETc for initial, development, mid-season and late-season was 54.9, 140.8, 218.8 and 87.3mm period,-1respectively. The average Kc values were 0.57, 0.92, 1.19 and 0.7 for initial, development, mid and late seasons, respectively growth stage. The Kc values found in this experiment differed slightly from the average of FAO estimation. This indicates that there is a need to develop Kc values for given local climate condition and varieties. The yield and average number grains per spike obtained were 7.15 t ha -1and 68, respectively. Also the maximum plant and spike height was obtained 103 and 12 cm, respectively.