2019 ASHS Annual Conference

The Texas High Plains has a semi-arid, windy climate that features high evapotranspiration (ET) demands for crops. Irrigation is essential for vegetable production in the region, but irrigation is constrained by depleting ground water from the Ogallala Aquifer. Therefore, high-tunnel (HT) production systems may reduce irrigation water demand, and protect crops from severe weather events (e.g., hail, high wind, freezing) of the region. The objective of this study was to compare water use efficiency (WUE) of high value vegetables grown in HT versus open fields (OF). We hypothesized that the protection from dry and high winds by HT would reduce water use in peppers and tomatoes. During the 2018 growing season, peppers and tomatoes were transplanted on two HT plots and two identical OF plots. Plastic mulch was used in combination with a surface drip irrigation system. Micrometeorological variables (incoming solar irradiance, air temperature, relative humidity, and wind speed), physiological parameters, and volumetric soil water were measured. Air temperatures were significantly higher during the daytime, and wind speed and light intensity were significantly lower in HT compared with OF. The plants appeared to adapt to larger quantum yield under ~20% less photosynthetically active radiation in HT compared with OF. Larger quantum yield resulted in higher photosynthesis rate during the daytime in HT. A concurrent higher transpiration rate likely benefited the plants in maintaining leaf temperatures under the warmer air temperature by 2.2^oC inside HT during the daytime. The changes in photosynthesis and transpiration of the plants in HT decreased intrinsic and extrinsic WUE at the leaf level. However, at the whole plant level, because of the protection from dry, high winds, the plants in HT required less total water over the growing season compared with OF, resulting in increased WUE. The 2018 data showed that HT production may be economically justified in terms of increased WUE and severe weather risk mitigation for high value vegetable production on the Texas High Plains