Strategies for enhancing irrigation efficiency on turfgrass areas

Turfgrass systems are a vital component of urban green infrastructure, providing functional, ecological, and aesthetic services in recreational, sporting, and public landscapes. However, maintaining high-quality turfgrass requires substantial water, which has become increasingly problematic in the context of global water scarcity, climate change, and environmental regulations. Efficient water use has become a priority in sustainable turfgrass management. Unlike traditional agricultural systems, turfgrass areas prioritize usability, plant growth, and aesthetics. Standards for sports turf construction focus on soil properties, drainage, and moisture retention, but increasing drought and water scarcity demand innovative irrigation strategies to maintain functionality. Traditional irrigation systems, particularly sprinkler-based methods, often result in inefficient water use due to wind drift, evaporation loss, and technically induced distribution inaccuracies. Conversely, subsurface drip irrigation offers targeted and potentially more efficient water delivery, though it poses challenges in adequately wetting the turfgrass rootzone. Irrigation delivery systems interact with soil physical properties and rootzone construction methods, thereby affecting water distribution, retention, and turfgrass quality. Efficient irrigation strategies require a nuanced understanding of soil–water dynamics, including the impact of rootzone construction methods and irrigation delivery systems on water retention characteristics and soil moisture distribution. This cumulative dissertation addresses the pressing need to enhance irrigation efficiency in turfgrass areas by systematically investigating the impact of rootzone construction methods on irrigation water distribution, retention, and turfgrass performance. This investigation focuses on using traditional and commonly used sprinkler irrigation (SPR) or subsurface drip irrigation (SDI). Moreover, the study aims to assess the application of numerical simulation models, specifically HYDRUS-2D, to predict and optimize irrigation efficiency under various rootzone–irrigation configurations, with the overarching objective of evaluating strategies to enhance irrigation efficiency in turfgrass areas. To achieve this objective, trials were conducted over several years, encompassing three complementary studies: empirical (field and controlled environment) and modeling-based. The research systematically explores how rootzone construction influences irrigation water distribution, retention, and turfgrass quality, particularly when paired with either SPR-irrigation or SDI. Furthermore, the study evaluates the application of numerical simulation models, specifically HYDRUS-2D, to predict and optimize irrigation efficiency under varying soil–irrigation configurations. The experiments were conducted under both controlled greenhouse and open field conditions. The first study was conducted under greenhouse conditions using controlled irrigation cycles and bare soil profiles (without grass cover) to isolate and analyze water distribution in response to irrigation delivery system type and rootzone construction methods. Three rootzone constructions, two two-layered (analogous to the national standard) and one three-layered, were evaluated under both SPR-irrigation and SDI. The volumetric water content (VWC) was monitored at multiple depths and time intervals following irrigation events. The second study investigated turfgrass quality and water storage in a two-year field trial (2023 and 2024) under deficit irrigation conditions, specifically 60% reference evapotranspiration (ETO). Turfgrass plots featuring perennial ryegrass (Lolium perenne L.) and employing the same three rootzone construction methods used in the greenhouse condition were irrigated using either SPR or SDI. Key performance indicators included turfgrass quality (TQ), rootzone water storage (RWS), and soil water tension (SWT). In the third study, the HYDRUS-2D finite element model was employed to simulate water dynamics within the rootzones and associated irrigation delivery systems (SPR and SDI) based on the observed greenhouse data. The model incorporated soil hydraulic parameters, determined through laboratory analysis, for each material employed in this study. The calibration and validation of the model were conducted with a focus on optimizing model quality and minimizing the discrepancies between observed and simulated outputs, particularly in relation to volumetric water content. The results of the investigations showed that the greenhouse trials revealed distinct patterns of soil moisture distribution across irrigation systems and rootzone designs. SPR-irrigated plots exhibited rapid volumetric water content (VWC) increases at shallow depths (3 cm) followed by substantial decreases within 72 hours, particularly under two-layered designs. Three-layered SDI plots showed a pronounced capillary rise in irrigation water combined with sustained irrigation water retention in the soil matrix, highlighting the system’s efficiency. The field trials demonstrated significant differences in RWS and SWT across rootzone constructions. Two-layered designs under SDI experienced high SWT values (>120 kPa), indicating insufficient moisture retention. In contrast, three-layered designs maintained lower SWT (