Root Exploration, Initial Moisture Conditions, and Irrigation Scheduling Influence Hydration of Stratified and Non-Stratified Substrates

Abstract

Soilless substrate stratification (i.e., layering unique substrates within a single container) is an emerging substrate management strategy that may provide opportunities to augment nursery resource use. As such, this research aimed to analyze water movement through containers during hydration events under different initial moisture conditions. The results indicated substrate stratification had minimal influence on water movement compared to non-stratified systems (uniformly filled nursery containers). Cyclic irrigation significantly increased the stratified substrates’ ability to retain water when irrigated at 20% volumetric water content (p < 0.0001) and significantly decreased the total volume leached (p < 0.0001). Moreover, irrigating the substrate profile with shallow and more frequent irrigations facilitated stratified substrates ty reach effective container capacity conditions (p < 0.0001n compared to non-stratified systems. The stratified systems took longer to leach all gravitational pores (p = 0.0266). In dry moisture conditions, non-stratified substrates were more hydrated when cyclic irrigation applications were applied compared to single applications (p = 0.0492). This study demonstrated that cyclic irrigation scheduling enhanced water retention in both non-stratified and stratified profiles under different initial moisture conditions and can be used as an irrigation strategy when dry substrate conditions prevail.

Stratified substrates enhance water storage and distribution between irrigation events

“…Once plant root establishment took place, there were visually similar observed patterns to that of fallow profiles, yet fluctuations were more extreme (Figure 6). Plant roots have been shown to have large effects on water movement (Criscione, Fields, & Owen, 2022; Hoskins et al., 2014) and moisture content distributions (Bauerle et al., 2013) in soilless substrate systems. Pustjarvi and Robertson (1975) stated that in most soilless substrates, matric tensions are likely to range between −10 and −100 hPa.…”

“…Increasing the tortious pathways for water movement slows down infiltration rates, and as a result, more thorough wettings are typically achieved (Bilderback & Jones, 2001). Criscione, Fields, and Owen (2022) reported that water infiltrated (entry‐to‐exit) more slowly through the entire container profile in stratified substrates compared to non‐stratified systems. Therefore, infiltrating water velocities were likely slower in the top half (with regard to traditional systems; Hoskins et al., 2014), equaling a more laterally distributed wetting front ( r = 0.8038).…”

“…Spatially positioning desired hydraulic properties through engineered substrates may improve water efficiency in container production. Some preceding stratified research has evaluated fine bark particles atop of coarse bark in the substrate profile, thereby reducing saturated capillary fringe occurring at the bottom of container, while increasing water retention in the top portion of the container profile (Criscione Fields, & Owen, 2022). Stratifying soilless substrates is a synergistic approach, where the combined effect's goal (i.e., layering two substrates) is to improve the entire hydraulics of the system.…”

“…However, few have explored water movement and distribution in the stratified profile. Criscione, Fields, and Owen (2022) reported that applied water generally moved slower through stratified versus non‐stratified profiles.…”

Stratified Substrates Can Reduce Peat Use and Improve Root Productivity in Container Crop Production

“…The potential use of stratified substrates has been shown to improve natural resource efficiency by modifying the physical nature of the container-substrate profile (Fields et al 2021b). Preceding stratified research has layered fine-textured substrates (e.g., to enhance water and mineral nutrient retention) in the upper container proportions, whereas in the lower proportions, coarse substrates were used to encourage drainage and reduce deleterious water table effects (Criscione et al 2022a(Criscione et al , 2022bFields et al 2021b). Promising results have demonstrated that substrate stratification may support possibilities for nursery growers to reduce water and fertilizer inputs by 25% and 20%, respectively, and continue producing equivalent or better crops than traditionally used nursery production methods (Criscione et al 2022a;Fields et al 2021b).…”