Hybrid Bermudagrass and Tall Fescue Turfgrass Irrigation in Central California: I. Assessment of Visual Quality, Soil Moisture and Performance of an ET-Based Smart Controller

Abstract

Research-based information regarding the accuracy and reliability of smart irrigation controllers for autonomous landscape irrigation water conservation is limited in central California. A two-year irrigation research trial (2018–2019) was conducted in Parlier, California, to study the response of hybrid bermudagrass and tall fescue to varying irrigation scenarios (irrigation levels and irrigation frequency) autonomously applied using a Weathermatic ET-based smart controller. The response of turfgrass species to the irrigation treatments was visually assessed and rated. In addition, turfgrass water response functions (TWRFs) were developed to estimate the impact of irrigation scenarios on the turfgrass species based on long-term mean reference evapotranspiration (ETo) data. The Weathermatic controller overestimated ETo between 5% and 7% in 2018 and between 5% and 8% in 2019 compared with California Irrigation Management Information System values. The controller closely followed programmed watering-days restrictions across treatments in 2018 and 2019 and adjusted the watering-days based on ETo demand when no restriction was applied. The low half distribution uniformity and precipitation rate of the irrigation system were 0.78 and 28 mm h−1, respectively. The catch-cans method substantially underestimated the precipitation rate of the irrigation system and caused over-irrigation by the smart controller. No water-saving and turfgrass quality improvement was observed owing to restricting irrigation frequency (watering days). For the hybrid bermudagrass, the visual rating (VR) for 101% ETo treatment stayed above the minimum acceptable value of six during the trial. For tall fescue, the 108% ETo level with 3 d wk−1 frequency kept the VR values in the acceptable range in 2018 except for a short period in mid-trial. The TWRF provided a good fit to experimental data with r values of 0.79 and 0.75 for tall fescue and hybrid bermudagrass, respectively. The estimated VR values by TWRF suggested 70–80% ETo as the minimum irrigation application to maintain the acceptable hybrid bermudagrass quality in central California during the high water demand months (i.e., May to August) based on long-term mean ETo data. The TWRF estimations suggest that 100% ETo would be sufficient to maintain the tall fescue quality for only 55 days. This might be an overestimation impacted by the relatively small tall fescue VR data in 2019 owing to minimal fertilizer applications and should be further investigated in the future.

Response of Landscape Groundcovers to Deficit Irrigation: An Assessment Based on Normalized Difference Vegetation Index and Visual Quality Rating

“…Performance of the smart irrigation controller. The overestimate of ETo by the Weathermatic SL4800 was similar to the 5% to 8% and 3% to 12% overestimation that we observed in two turfgrass irrigation trials in central and southern California, respectively (Haghverdi et al 2021a(Haghverdi et al , 2021c. A higher range of ET o overestimation (9% to 33%) was reported in a study done in Gainesville and Wimauma, FL (Rutland and Dukes 2014), which could be attributed to their different climatic conditions.…”

“…However, few studies evaluated their performance for landscape groundcovers (Shober et al 2009; US Bureau of Reclamation 2008), particularly in arid and semiarid regions such as inland Southern California, where keeping plants alive with minimum water application is often required (Haghverdi et al 2021c;Serena et al 2020). Efficient irrigation scheduling using ET-based controllers depends on the availability of science-based plant factor information for each landscape species and the accuracy of the ET o estimations by the irrigation controller (Haghverdi et al 2021a). Hence, the objectives of this study were to 1) evaluate the effect of irrigation rates on VR and NDVI of 10 landscape groundcovers; 2) examine the strength of linear relationships between VR and NDVI for each groundcover species, 3) estimate the response of groundcover species to multiple irrigation regimes under extremely low, high, and mean atmospheric evaporative demand using GCWRFs; and 4) determine the reliability of the Weathermatic smart ET-based controller for autonomous irrigation scheduling.…”

Pertinent Water-Saving Management Strategies for Sustainable Turfgrass in the Desert U.S. Southwest

“…In general, ET increases with aridity which is a commonplace in U. S. southwest. A deficit irrigation study in Central California showed that 70-80% reference evapotranspiration (ET o ) replacement irrigation is required to maintain an acceptable hybrid bermudagrass turf quality during the summer months when the ET demand is high [19]. Drought stress accompanied by high temperature affects turfgrass growth rate, aesthetic quality, and ET [17].…”

Appraisal of Groundwater Contamination from Surface Spills of Fluids Associated with Hydraulic Fracturing Operations

“…Very little precipitation occurs along the west side of the basin. Annual precipitation is often 237 to 1367 mm per year (Haghverdi et al, 2021). The rain mostly occurs during the winter months, while high rates of evaporation dominate during the summer months, as temperatures often exceed 37 °C (United States Department of Agriculture, 2009).…”