The relationship between reference evapotranspiration, crop yield, and water use efficiency for alfalfa crop under different irrigation treatments in an arid climate

Abstract EN

The relation between the applied irrigation water, plant water consumption and plant yield production are having the interest of most investigators especially in arid regions such as the Kingdom of Saudi Arabia, where water resources are limited.

In this study, field experiments were made to study the relationship between the applied irrigation water, alfalfa plant (Hassawi cultivar) water consumption by evapotranspiration (ET), alfalfa yield production (fresh and dry), and water use efficiency during two successive seasons, summer 1997 and winter 1998.

Four irrigation treatments were considered based on four different soil moisture depletion ratios 9, 18, 36, and 55%, respectively.

The irrigation scheduling was designed for these four treatments where, the different irrigation frequencies (1, 2, 4, and 6 days) and the corresponding water application rates were calculated.

A total of seventeen plant cutting was followed during the different plant seasons, where these cuttings were illustrated as affecting factor in crop ET and yield.

The statistical analysis was made by considering the irrigation treatments and plant cutting number as main effects whereas the studying variables were plant ET, plant yield (fresh and dry), and water use efficiency.

The mathematical functions that fit for the dry yield production (Yd) obtained during the summer with the amount of applied irrigation water were linearism whereas, the function during winter was linearism but relatively low.

The function of fresh yield production (Yf) with the amount of irrigation water during summer was linearism but relatively low, and the function of fresh yield and the amount of water applied during winter season was a second-degree polynomial.

The results showed that during summer season, cut number has a significance effect on evapotranspiration,the amount of irrigation water (W) and the Irrigation Water Use Efficiency (IWUE).

On the other hand, during winter season cut number has a significant effect on all variables while irrigation treatment has only significant effect on plant ET and the water use efficiency (WUE).