Determination of Local Barley (Hordeum Vulgare) Crop Coefficient and Comparative Assessment of Water Productivity for Crops Grown Under the Present Pond Water in Tigray, Northern Ethiopia

Abstract

An experiment was carried out in 2010 at Mekelle, in northern Ethiopia, to measure the evapotranspiration, to estimate barley crop coefficient (kc), and to evaluate the water productivity taking into account the major crops grown under the present pond irrigation system. Four locally made lysimters were installed in the middle of barley field to measure barley evapotranspiration. The single crop coefficient approach was used to estimate barley crop coefficient. The average seasonal evapotranspiration of barley was 375 mm which is similar to many other cereal crops in the region. The single crop coefficient values for early, vegetative, mid and late crop stages were 0.6 – 0.8, 0.6 – 1.0; 1.0 – 1.05 and 0.3 - 0.4 respectively. The result showed that these crop coefficient values obtained in this experiment were similar to the crop coefficient values obtained in the past except for kc initial. Therefore, the assumption that local barley crop coefficient values differ from that of the documented values was incorrect. Furthermore, the major reason for mismanagement of irrigation water in barley fields was not due to use of wrong crop coefficient values but could be due to inadequate irrigation technical skill and knowledge of the farmer. The average economic water productivity (EWP) of barley for the very wet, wet, normal, dry and very dry seasons scenario were 0.99, 0.7, 0.65, 0.57, and 0.44 USD m-3, respectively, whereas the corresponding crop water productivity (CWP) values for grain were 1.53, 1.08, 1.0, 0.88 and 0.68 kg m-3, respectively. The EWP and CWP of barley were compared with onion and tomato
under pond water irrigation at the five climatic scenarios. The crop water productivity for tomato and onion were 85 – 87% and 76 – 78% higher than that of barley, respectively. The
corresponding economic water productivity for tomato and onion were 87 – 89% and 81 – 82% higher than that of barley, respectively. We concluded that growing tomato and onion would bring more income or yield per m3 of pond water supplied than growing barley. The implication is that as supply and demand determines the price of products, farmers and extension workers need to balance the crop area coverage per irrigation scheme so that undesirable price falls and rises could be avoided. Evaluation of crops based on their water productivity would improve the productivity of irrigation schemes and ultimately improve food security in the arid and semi-arid areas where water scarcity is critical problem and irrigation is a necessity for crop production.

Key Words: Barley, Evapotranspiration, Crop coefficient, Water productivity.