Soil moisture variability on golf course fairways across the United States: an opportunity for water conservation with precision irrigation

Authors: STRAW, CHASE - Texas A&M University; BOLTON, CONNOR - Texas A&M University; YOUNG, JOEY - Texas Tech University; Hejl, Reagan; FRIELL, JOSH - Toro Company; WATKINS, ERIC - University Of Minnesota

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2022
Publication Date: 12/7/2022
Citation: 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. Article number 4. https://doi.org/10.1002/agg2.20323.
DOI: https://doi.org/10.1002/agg2.20323

Interpretive Summary: Fairways are intensely managed areas present on all golf courses and represent a large proportion of the irrigated area within a course. The commonly relied upon approach to schedule irrigation on fairways has been a combination of visual observations of the turfgrass and short-term forecasts. This approach often leads to all fairway areas across the course receiving the same amount of irrigation, regardless of specific area needs. Precision irrigation is a strategy which attempts to reduce water consumption by only applying irrigation where, when, and in the amount needed. A useful component of precision irrigation is to generate soil moisture variability maps, which can be developed by using soil moisture sensors equipped with Global navigation Satellite System (GNSS) technology. Previous research has noted excessive variability within golf course fairways, however this research has been limited to only a few states and a few fairways per course. To encourage repeatable, uniform, and large-scale data collections, a protocol was developed at the University of Minnesota in 2019 which outlines standard procedures to collect georeferenced soil moisture data using a GNSS-equipped, handheld soil moisture meter. The objective of this case study was to report fairway soil moisture variability findings from nine golf courses (four public and five private) in eight states (AZ, CA, CO, FL, KS, MN, NH, and TX) that completed the protocol during 2019-2022. Approximately 80-315 georeferenced soil moisture data points were collected per fairway using either a FieldScout TDR 300 with an external GNSS receiver or FieldScout TDR 350 with an internal GNSS receiver. For each course, data was collected on the same day and 7 to 14 fairways were considered. Soil moisture variability was present regardless of climate region and course characteristics, indicating soil moisture variability may be inevitable at large scales. These findings suggest that advancing irrigation practices and technologies to conserve water resources through precision irrigation is needed.

Technical Abstract: Annual median water use per hectare on fairways is between ~2,800,000 and 14,000,000 liters, depending on the region. Conventional fairway irrigation relies on visual observation of the turfgrass, followed by secondary considerations of short-term weather forecasts, which oftentimes lead to “blanket” applications to the entire area. The concept of precision irrigation is a strategy to achieve water use reductions by making applications only where, when, and in the amount needed. The use of technology, such as soil moisture sensors and valve-in-head sprinkler control systems, can further enhance its application. Fairways have the most promise for water conservation through precision irrigation on golf courses due to their more intense management compared to roughs and larger area compared to greens and tees. Soil moisture sensors equipped with GNSS can obtain georeferenced point data for creating soil moisture maps to identify variability, which may be useful for fairway precision irrigation. Previous research conducted in FL and MN has created soil moisture maps to demonstrate that variability within fairways can be excessive, but findings are limited to a few golf courses in these states, and only 1 to 2 fairways per course. To further investigate soil moisture variability at larger scales, a golf course fairway soil moisture mapping protocol was developed at the University of Minnesota in 2019. The protocol outlines standard procedures for golf course superintendents to collect georeferenced soil moisture data (% volumetric water content; VWC) with a commercially available, GNSS-equipped, handheld soil moisture meter. The objective of this case study was to report fairway soil moisture variability findings from nine golf courses (four public and five private) in eight states (AZ, CA, CO, FL, KS, MN, NH, and TX) that completed the protocol during 2019-2022. The courses exhibited varying course types (i.e., public versus private), turfgrass species, soil types, irrigation system ages and control, and irrigation philosophies. Approximately 80-315 georeferenced soil moisture data points were collected per fairway using either a FieldScout TDR 300 with an external GNSS receiver or FieldScout TDR 350 with an internal GNSS receiver. All data at an individual course were collected the same day, and 7 to 14 fairways were considered depending on course. Cumulative rainfall and irrigation 7 days prior to data collections were recorded. Soil moisture variability was determined through summary statistics, box and whisker plots, and ordinary kriging to create spatial maps. The mean, range, and coefficient of variation of soil moisture on fairways across courses were from 22.4 to 42.8% VWC, 27.6 to 43.7% VWC, and 7.5 to 39.4%, respectively. Box and whisker plots and spatial maps of soil moisture aided in visualizing the variability within and between fairways at all courses. Results suggest that soil moisture variability at large scales may be inevitable in fairways, regardless of climatic region and course characteristics, which further reiterates the need for advanced irrigation practices and technologies for water conservation via precision irrigation.