Substrate stratification: layering unique substrates within a container increases resource efficiency without impacting growth of shrub rose

Authors: FIELDS, JEB - LOUISIANA STATE UNIVERSITY; Owen Jr, James - Jim; Altland, James

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2021
Publication Date: 7/22/2021
Citation: Fields, J., Owen Jr, J.S., Altland, J.E. 2021. Substrate stratification: layering unique substrates within a container increases resource efficiency without impacting growth of shrub rose. Agronomy. 11(8). Article 1454. https://doi.org/10.3390/agronomy11081454.
DOI: https://doi.org/10.3390/agronomy11081454

Interpretive Summary: Container plant production requires the use of relatively high amounts of fertilizer and agrichemicals. The soilless substrate components utilized by the industry hold relatively little water with low chemical retention or exchange capacity as compared to mineral soils, resulting in need for more frequent water and fertilizer application compared to most field grown crops. Substrate stratification refers to layering different substrates or different textures of the same substrate within a single container. Stratifying substrates allows for more precise fertilizer placement by applying fertilizer to the top of the container to reduce nutrient loss during plant establishment. Stratifying the substrate might also be used to create a more optimal air and water gradient for establishment and growth. The goal of this research was to assess the water dynamics/gradient throughout stratified container substrates and determine if stratified substrates could be used to produce plants with reduced water and fertilizer in a nursery setting. Substrate stratification within the container caused no deleterious effects on crop growth and development. Equal quality and size crops were produced with 20% reduction in fertilizer. Moreover, reduction of daily water did not adversely affect the crops grown in stratified systems when compared to the control. Stratified systems present a considerable opportunity to increase or maintain containerized crop productivity while mitigating resource wasting through excessive leaching or application.

Technical Abstract: Nurseries rely on soilless substrates to provide a suitable growing media for container grown crops. These soilless substrates have been developed to readily drain water to prevent issues with waterlogging and associated soil-borne disease. A negative consequence of high porosity and subsequent drainage throughout the container profile requires high or frequent irrigation rates with poor retention of applied nutrients. Placing a substrate having a relatively high moisture and nutrient retention atop a coarse and freely draining substrate could further optimize water and nutrient retention while allowing for needed gas exchange for plant establishment and growth. Containerized Red Drift® rose (Rosa ‘Meigalpio’ PP17877) were grown under 16 mm or 12 mm daily irrigation utilizing a traditional pine bark substrate or stratified substrates with either a conventional bark, bark fines, or a bark:peat mixture atop of a coarse bark within a container. The stratified substrates received 20% less fertilizer. During the first growing phase or season, plants grown in stratified substrates outperformed those grown in conventional, non-stratified bark substrates under normal irrigation. The stratified substrates did not reduce growth under reduced irrigation regimes. Overall, crop growth was equal or superior with stratified substrates when compared to the non-stratified controls, even with a 20% reduction of fertilizer. This research suggests that stratified substrate systems can be used to reduce fertilizer and irrigation rates while producing a crop of similar or superior quality to conventionally grown containerized crops.