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.

Many specialty crop growers are transitioning high-value crops from in-ground production to soilless culture due to the diminishing availability of fumigants, increasing pest pressure, extreme weather, and the need for flexible production practices. The objective of this study was to determine the research and educational needs of specialty crop growers who are transitioning to soilless substrates. North American growers were surveyed using an online instrument that incorporated Likert-type statement matrices, open-ended questions, and demographic questions. Additionally, two virtually led focus groups were conducted to further expand upon the quantitative findings with descriptive data. Respondents indicated the most important factors in considering whether to adopt soilless substrates were improving, managing, and reducing overall plant quality, disease management, and crop loss, respectively. The most important research needs were understanding the effects of substrates on crop quality and uniformity, fertilizer management, and economic costs and benefits/return on investment. In both the grower survey and focus groups, crop quality and uniformity were among the highest-scored responses. Food safety, disease and pest management, consumer perception, substrate disposal-related issues, transportation, and return-on-investment were also identified as important factors when considering soilless substrates.

Background and aims: Containerized soilless substrates are highly porous to ensure adequate air storage to overcome the “container” effect- the lower part of the container nears saturation which can decrease root health and growth. Substrate porosity is dynamic, evolving over time. As roots fill pores, substrate decomposition and in-situ particle movement change the physical structure, shifting its storage properties and performance. Research is sparse in understanding how developing roots change their morphology throughout production (temporally) and while growing throughout the three-dimensional substrate matrix (spatially). Thus, it would be beneficial to understand how root development impacts container moisture characteristics. This study aimed to quantify root morphological development and water storage (θ) spatiotemporally in conventional or engineered soilless substrate systems. Methods: Helianthus annus ‘Rio Carnival’ was grown in 30.5 cm tall PVC columns in a conventional (non-stratified; 100% of the container is filled with a single composite) bark- or peat-based substrates or engineered (stratified; fine-bark atop coarse-bark; peatlite layered over pine bark) systems. Columns were frozen after roots were partially- (22 d) or fully-grown (43 d) and were separated in five vertical sections. Root morphology and θ were measured within each layer. Results: The results showed that stratified systems overall stored less water, especially in coarser sub-stratas. Partially rooted columns generally stored more water and fully rooted columns drained more. Plants grown in stratified systems had greater fine root development than when grown conventionally. Conclusion: Container-grown roots can be engineered to produce more fibrous root systems by spatially manipulating substrate θ.

Soilless substrate characterization often occurs with fallow substrates, which excludes information about how roots influence substrate properties. This study had two primary objectives: (1) investigate how the presence of root systems alters storage and hydraulic properties of a Sphagnum peat substrate; and (2) assess if data collected can be used in computational infiltration models to infer how root presence changes moisture redistribution. Helianthus annus ’Lemon Queen’ seeds were sown into 347.5 cm3 and 250.0 cm3 cores filled with peat moss. Three treatments were applied: (1) fallow, prior to production conditions; (2) fallow, after 42 d of production conditions; and (3) rooted, after 42 d of plant growth. Storage properties were assessed along with relationships between volumetric water content (θ) and matric potential (Ψ). Afterward, data was used in HYDRUS 1-D to model moisture distribution after maximum water storage conditions. The results showed that rooted substrates proportionally increased water-filled pores (+5%) and decreased air-filled pores (-7%), reduced overall substrate solids by 60%, and occluded 6-10% of the container volume. Rooted systems contained greater θ with declining Ψ than fallow substrates, accompanied by shifts from macropores (i.e., pores with effective diameters >416 µm) to mesopores (i.e., pores between 10 and 416 µm). Moisture redistribution models simulated a reduced moisture differential from the top-to-bottom of the profile after 24 h comparing pre-production fallow (67%) to rooted substrates (26%). These results highlight that root presence alters substrate properties, such that characterization done on fallow media may not adequately reflect actual growing conditions.