2018 ASHS Annual Conference

In aridland cropping systems salts are most effectively managed by leaching. When irrigation efficiencies are poor, the leaching requirements (LR) of salts for agricultural sustainability are often incidental to these inefficiencies. However, as irrigation efficiencies are improved, caution must be exercised so that the seasonal leaching fraction (LF) achieved is not less than the leaching required for continued sustainability. This presentation evaluates the multiple cropping systems in the lower Colorado River region. Water application efficiencies for the salt sensitive vegetable crops (fall-winter-spring) widely produced in the region have improved dramatically over the past two decades. In fact, many field irrigation operations in the vegetable cropping system, while providing for the crop’s water requirement, are net salt loading events (LF<LR). In contrast to the vegetable systems that are furrow irrigated, the spring-summer rotational field cropping systems are irrigated in basins, and due to slower irrigation advance resulting from increased soil and crop friction, net irrigation efficiencies are sometimes poor relative to crop consumptive use. Data we have collected suggests that these water application inefficiencies associated with the rotational crops, and associated leaching fractions, may sometimes be key to sustainability in the entire annual cropping system. Furthermore, pre-irrigation in the late summer before vegetables are planted is also important. Existing challenges to further improvements in irrigation efficiencies for the annual multi-cropping systems, in the context of salt management, will be discussed.