Research Project: Increasing the Utility of Turf in Urban Environments of the Southwest U.S.

Location: Water Management and Conservation Research

2023 Annual Report

Objectives
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.

Approach
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 assessed 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.

Progress Report
This report documents progress in fiscal year (FY) 2023 for project 2020-13210-001-000D, “Increasing the Utility of Turf in Urban Environments of the Southwest U.S.”, which began in May 2020. To accomplish Objective 1 and its associated sub-objectives, visual assessment data on establishment, spring green up, turf color and quality, as well as spectral data using unmanned aerial vehicle (UAV) were collected every other week on bermudagrass, zoysiagrass, and native grass field experiments by ARS researchers in Maricopa, Arizona. Deficit irrigation treatment of 80, 60, and 40% historical evapotranspiration replacement (crop coefficient factored) was started for bermudagrass and native grasses on May 1, 2022. The preliminary data analysis reveals variation among bermudagrass genotypes for drought stress tolerance. Zoysigrass field experiment, comprising four species, each with a different number of genotypes was transplanted in May 2022, and deficit irrigation treatment was started on May 1, 2022. In addition to reflectance data, image data are being collected on all field experiments. In support of Sub-objective 2B, ARS researchers in Maricopa, Arizona, conducted two studies to evaluate the impact of water chemistry on hybrid bermudagrass varieties (TifTuf, Tifway, and Midiron) evapotranspiration, growth, and quality. Three water sources (RO, local well, and recycled) each supplied at full irrigation levels (1.0 × ETa) over two, eight-week study periods. It was found that irrigation water quality influences critical factors for hybrid bermudagrass growth and variability exists among three commercially available varieties for ET rates, quality, and shoot growth.

Accomplishments
1. Interaction of genotypes and irrigation water source affects turfgrass quality and ecosystem services. ARS researchers in Maricopa, Arizona, studied turfgrass performance of three hybrid bermudagrass varieties (TifTuf, Tifway, and Midiron) using three irrigation water sources (reverse osmosis, local well, and recycled) each supplied at full irrigation levels (1.0 × ETa) over two, eight-week study periods. Irrigation with recycled water reduced evapo-transpiration rate but had non-negative effect on water use efficiency and visual turfgrass quality in the short-term. A long-term effect on soil health and a broader range of commonly used turfgrasses requires further study.

Review Publications
Serba, D.D., Hejl, R.W., Burayu, W., Umeda, K., Bushman, B.S., Williams, C.F. 2022. Pertinent water-saving management strategies for sustainable turfgrass in the desert U.S. southwest. Sustainability. 14(19). Article 12722. https://doi.org/10.3390/su141912722.
Straw, C., Bolton, C., Young, J., Hejl, R.W., Friell, J., Watkins, E. 2022. Soil moisture variability on golf course fairways across the United States: An opportunity for water conservation with precision irrigation. Agrosystems, Geosciences & Environment. 5(4). Article e20323. https://doi.org/10.1002/agg2.20323.
Maulana, F., Perumal, R., Serba, D.D., Tesso, T. 2023. Genomic prediction of hybrid performance in grain sorghum (Sorghum bicolor L.). Frontiers in Plant Science. 14. Article 1139896. https://doi.org/10.3389/fpls.2023.1139896.
Fall, S.T., Kanfany, G., Diack, O., Serba, D.D., Diao, Y., Sy, O., Fofana, A., Morris, G.P., Kane, N.A. 2022. Genetic improvement of pearl millet in Senegal: Past, present, and future prospects. In: Kane, N.A., Fonceka, D., Dalton, T.J. Crop Adaptation and Improvement for Drought-Prone Environments. Manhattan, KS: New Prairie Press. p. 465-495.