Location: Water Management and Conservation Research
Project Number: 2020-13660-009-037-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jun 1, 2026
End Date: Nov 30, 2027
Objective:
1) To measure consumptive water use of sesbania, iceberg lettuce, broccoli, and evaporative water loss from a fallow field.
2) To determine yield and quality responses of 24 drought tolerant cotton genotypes to deficit irrigation.
Approach:
The Yuma area of the Lower Colorado River Region produces over 90% of the leafy greens for the U.S. market during the winter growing season. All vegetable crops commercially grown in the area require irrigation, but the availability of irrigation water from the Colorado River has seen increased decline due to more frequent drought and early snow melt in the upper reaches of the River Basin. Reduced water availability also hinders production of other major economic crops such as cotton. In this project, we will deploy eddy covariance tower systems to measure crop consumptive water use at the University of Arizona Yuma Agricultural Center and evaluate cotton yield and quality responses to deficit irrigation regimes at the University of Arizona Maricopa Agricultural Center. For field trials at the Yuma Ag Center, three eddy covariance systems will be installed in three 9 to 18- acre fields. Two of the fields will be planted with sesbania from June to September as a summer green manure cover crop and the third field will be left fallow mimicking grower practice to save water. Sesbania is a fast-growing high-biomass legume that can potentially improve soil health and productivity. This is especially beneficial to Arizona agriculture where the soils are low in organic content and high in pH, limiting crop growth and nutrient update. In this study, sesbania plants will be chopped and incorporated in the soil as an amendment in September before setting seeds. Soil and plant samples will be taken to determine soil texture, organic matter and nitrogen content, total biomass and carbon content. From October to April, iceberg lettuce will be planted in the fallow field and one of the sesbania fields to compare for beneficial effect from sesbania on nitrogen and soil improvement. Broccoli will be planted in the second sesbania field and yield evaluated at harvest. For field trials at the Maricopa Ag Center, three irrigation rates will be used to assess yield and fiber quality responses of 24 drought tolerant cotton genotypes. Six sensor stations will be installed to quantify soil moisture, salinity, and canopy temperature for determination of plant water stress index. Weekly measurements of leaf stomatal conductance and photosynthesis will also be conducted during the experiment. Field experiments at both Yuma and Maricopa will be repeated in 2027.