Evaluating Stratified Substrates Effect on Containerized Crop Growth under Varied Irrigation Strategies

Abstract

Growers rely on soilless substrates to provide sufficient water and nutrients to containerized crops. Traditional bark-based substrates are engineered to have relatively low water-holding capabilities, which can lead to nonuniform rewetting patterns and inefficient usage of water resources. Engineering substrates to redistribute water dynamics and maximize aeration within the container may improve water resource efficiencies. The goal of this study was to evaluate whether more efficient irrigation schedules can be used when stratifying unique substrates within a container for added crop water and nutrient efficiency. Loropetalum chinense ‘Ruby’ liners were planted and grown in a conventional pine bark substrate or one of three stratified substrate treatments, including a bark:peat, bark:coir, or fine bark layered on top of a coarse bark. The crops were grown under four different irrigation schedules, including single daily application, single application at deficit levels, cyclic application, or cyclic at deficit schedules. Stratified substrates improved crop growth, quality, and yield when compared with plants grown in conventional bark in the single application irrigation treatment. Measured at final harvest, substrates positively influenced plant growth index (P < 0.0001), whereas irrigation scheduling alone had no effect (P = 0.6321). There was a strong interaction between substrate and irrigation schedules on Δ growth index (P = 0.0141). There were strong substrate effects on shoot dry weight (P = 0.0060), root dry weight (P = 0.0342), and growth index (P = 0.0040). The stratified bark:coir treatment outgrew all other substrate treatments. In addition, within all irrigation treatments, plants grown with the stratified bark:coir substrate had the highest survival ratings among the other substrate treatments, whereas the conventional bark had the lowest survival rates. Substrate and irrigation had an effect on nitrogen and potassium leachate concentrations levels (P = 0.0107 and P = 0.0004, respectively). Evaluation of microbial communities showed that substrate (P = 0.0010) and the stratified layer (P = 0.0010) had strong influences on the type of community present and the relative abundance in the treatments used herein this study. Specifically, within cyclic scheduling, bark:peat actinomycete populations were significantly greater than other substrate treatments. Furthermore, under deficit irrigation, stratified substrate systems were able to mitigate crop water stress. The results indicate that when crops such as the Loropetalum are grown in the stratified system, crop growth can be sustained when drought conditions are present. This is possible by providing adequate water availability even under low water inputs until subsequent irrigations during the fragile establishment period, when compared with using traditional bark-based substrates.

Single-screen Bark Particle Separation Can be Used to Engineer Stratified Substrate Systems

“…It involves stacking two unique substrate layers atop one another to reorganize water retention characteristics in the container profile (Fields et al, 2020). This practice has been identified as a possible technique to increase irrigation water efficiency while improving plant growth simultaneously (Criscione et al, 2022). The placement of coarse particles in the lower half of the container promotes drainage where a perched water table is observed (Owen and Altland, 2008), whereas using substrates with high water-holding capacity and increased hydraulic and chemical retention in the upper half may provide more available resources for plant roots and may limit drying from evapotranspiration and gravitational forces.…”

“…To date, Fields et al (2021) and Criscione et al (2022) have identified benefits associated with water and fertilizer management in nursery production using stratified bark substrates. Their work showed that layering fiberamended bark atop coarse bark can increase resource (i.e., fertilizer and water) efficiency while producing similar crops.…”

“…Their work showed that layering fiberamended bark atop coarse bark can increase resource (i.e., fertilizer and water) efficiency while producing similar crops. Criscione et al (2022) also showed that stratified substrates can support quality plant production under irrigation levels that were too low to produce healthy plants grown in traditional pine (Pinus sp.) bark substrates.…”

“…bark substrates. Both Fields et al (2021) and Criscione et al (2022) reduced fertilizer inputs by 20% and produced equal or larger plants in stratified substrates when compared with crops grown in traditional bark substrates.…”

Effect of Substrate Stratification Without Fine Pine Bark Particles on Growth of Common Nursery Weed Species and Container-grown Ornamental Species

“…An additional cultural or nonchemical method that could have potential as a weed management tool is "layering" or stratified substrates (Khamare et al, 2022). This is a new area of research in which multiple substrates, or the same substrate with differing physical properties, are layered within a container to accomplish a production goal, such as decreasing water use or nutrient leaching, or potentially reducing weed growth (Criscione et al, 2022;Fields et al, 2021;Khamare et al, 2022). Because of the inherent moisture gradient in a container filled uniformly with the same substrate, the upper portion dries quickly, which requires more frequent irrigation to provide enough moisture for recently potted plants to establish, especially soon after transplanting and before roots are fully developed (Fields et al, 2020(Fields et al, , 2021Owen and Altland, 2008).…”