Water Saving Strategies for Leafy Greens in Southwest Texas

The Wintergarden is a semiarid region of southwest Texas known for its intensive irrigated vegetable crops.  However, vegetable production in this region is experiencing an increasing scarcity of water resources and more frequent and severe drought events, which combined are greatly affecting total productivity and the overall economy of the region. At the same time, consumer demand for high-quality, attractive, and locally produced vegetables is rapidly increasing. This study evaluated water use efficiency (WUE) and product quality of high-value leafy vegetables grown under three irrigation systems: low energy precise application (LEPA), subsurface drip irrigation (SDI), and hydroponic-nutrient film technique (NFT), and two  irrigation rates: 70% as deficit and 100%ETc as well-watered control. In spinach, yield and WUE were reduced at 70% ETc under LEPA, while this response was cultivar dependent under the SDI.  In lettuce the overall WUE slightly increased at 70% ETc under LEPA, being also cultivar dependent under the SDI. In kale and collard, 70% ETc caused a slight reduction in yield under SDI.  Lettuce grown under the NFT system had on average a 40% lower head FW than those grown in open field; however, their WUE was 8-fold greater and their growth cycle 40% shorter. Similar trends were measured for kale and collards under the NFT system. This study suggests that the effects of deficit irrigation on yield and WUE of leafy greens grown in this region is highly dependent on the crop species, cultivars and irrigation systems. Water savings in the hydroponic production system were >90% as compared to those under open fields.