Objective 1. Develop drought and heat tolerant turf varieties for use in the U.S. Southwest. Objective 2. Expand opportunities for the sustainable utilization of turf in the urban Southwest by reducing input requirements and maximizing related ecological services. Objective 3. Identify and test innovative management practices to increase water use efficiency and improving irrigation water scheduling technologies for turf.
1. Develop and evaluate drought and heat tolerant turf cultivars for use in the U.S. Southwest. Small plot research will be conducted at the Maricopa Agricultural Center (MAC) in Maricopa, AZ. Focus will be on warm season grasses such as bermudagrass [Cyanodon spp.], but will include other warm- and cool-season turf species suitable to the Southwest U.S. When available, irrigation will be with wastewater from the local water utility. Two levels of irrigation (80 and 50 % of estimated evapotranspiration (ET) replacement) will be examined. Soil water content will be measured weekly using time domain reflectometry in the upper turf root zone (0-0.6 m). Weather data and grass reference evapotranspiration (ETo) is available at the MAC. Plant temperature and turf color and quality will be assesses via weekly remote sensing systems mounted on unmanned aerial vehicles (UAV). Genomic analyses will focus on understanding and characterizing genetic mechanisms association with abiotic stress tolerance. Genomic analysis methods include association studies, high-throughput genotyping, RNAseq and gene expression analyses, genome sequencing and identification, and other forward genetic approaches. 2. Expand opportunities for the sustainable utilization of turf in the urban Southwest by reducing input requirements and maximizing related ecological services. Ecosystem services including carbon sequestration, effects on microclimate and urban habitat will be evaluated at MAC and cooperator sites located in urban Phoenix. Long-term plots irrigated with wastewater will be established at MAC where soil carbon accumulation will be monitored. Soil samples will be collected annually to 2 m and analyzed for carbon, nitrate, and salts. Possible salt buildup and leaching of nitrate to groundwater will be monitored. Effects of turf on the urban microclimate will be evaluated in the urban environment using models, remote sensing and weather station data collected from parks, golf courses and green spaces. Comparisons will be made using matched areas with and without turf. 3. Identify and test innovative management practices to increase water use efficiency and improving irrigation water scheduling technologies for turf. These studies will be conducted in conjunction with those outlined in Objective 1 at MAC. Weekly turf ET will be calculated as the residual of the root zone (0-0.50 m) soil water balance based on changes in measured soil water, measured irrigation and precipitation amounts. Crop coefficients will be determined as the ratio of the soil water balance ET and the ETo from weather data. Water productivity functions will be calculated for biomass yields and quality measures, e.g. color vs. irrigation input and ET. Soil salinity and soil profile nitrate will be monitored with annual soil sampling to 2 m.
To address Objective 1, germplasm of bermudagrass, zoysiagrass, and native grasses have been assembled from various sources in seed and vegetative form. Preparation of the planting materials was conducted in the green house and field experiments were established from plugs. The field experiment was arranged in Split-Block, where the main plots are deficit irrigation treatments and sub-plots are genotypes for all the species. Deficit irrigation treatment was started for bermudagrass and native grasses on May 1, 2022. The irrigation treatments are 100, 75, and 50% historical evapotranspiration replacement. Visual turfgrass quality and color data are being collected every other week. Spectral data is also collected using remote (UAV) and proximal (ACS-211) sensors to capture reflectance data at different wavelengths. Zoysigrass field experiment was transplanted early May 2022 and data on establishment is being collected. Deficit irrigation treatment of the zoysiagrass will start next year. The preliminary data shows variation among the genotypes and some genotypes never stress at 50 ET replacement irrigation.
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