The phrase “Desert Durum” has been trademarked with the United States (U.S.) patent office under the ownership of the Arizona Grain Research and Promotion Council and the California Wheat Commission. Only Durum wheat produced in the desert region of Arizona and southern California qualify for this trademark. Between 250,000 to 450,000 metric tons of desert durum are produced annually in Arizona. Desert Durum is prized for its high quality by national and international pasta industries.

Durum wheat is generally grown in the Desert during the winter-spring period in rotation with fall and fall-winter vegetable crops. This crop is established (germinated) by either planting into the soil moisture (shortly after a pre-irrigation), sprinkler irrigation after seeding, or by basin surface irrigation after seeding. The remainder of the season it is generally irrigated by surface basin irrigation. However, on a few sites in the state it is irrigated by pivots or linear-move sprinkler systems.

We have measured seasonal ETc ranging from 565 mm (1.9 AF) to 691 mm (2.3 AF), with an average of 630 mm (2 AF) (Figure 1). Interestingly, this is close to the value of 648 mm estimated by Erie for common wheat. In-season irrigation application efficiencies for Durum wheat production typically approach 90% in the Yuma area but are generally less in other regions of Arizona due to higher water infiltration rates on coarser textured soils and longer irrigation runs. The required leaching to maintain salt balance suitable for Durum wheat grown in rotation with lettuce and irrigated with Colorado River water would be 138 mm (0.45 AF) (Figure 2). Thus, the total water required for sustainability is approximately 768 mm (2.5 AF). If wheat is the most salt sensitive crop in the rotation, the total water required for sustainability is 653 mm (2.1 AF). If a portion of the required leaching is deferred to a pre-irrigation off season, the leaching fraction deficit would be added to the pre-irrigation total. It should be noted that irrigation with water with higher salinity than the Colorado River would have a higher leaching requirement that can be calculated using criteria outlined previously. More details of the wheat evaluation can be found in French et al., 2020. The calculated Kc values by growth period are shown below.