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Why Growers Are Turning to Soilless Substrates, and What They Need Next

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  • Why This Matters: 
  • Specialty crop growers across North America face increasing challenges related to water availability, disease pressure, sustainability expectations, and rising substrate costs. 
  • This research highlights how soilless substrates, such as peat, bark, and coir, are already widely used and may become even more essential in the future. 
  • Understanding grower priorities helps guide future research and extension programs so producers receive clear, practical guidance on substrate selection, nutrient management, irrigation, and disposal. 
  • •Insights from this study help growers anticipate coming supply chain, environmental, and regulatory pressures while improving crop consistency, labor efficiency, and overall production quality. 
Background & Research Insights: 
  • The study surveyed 180 North American specialty crop growers and conducted follow-up focus groups with producers in eastern and western regions. It assessed substrate use, production challenges, perceptions, and research needs. 
  • 73.5% of growers already use soilless substrates, and more than two-thirds of them produce over 75% of their crops in these systems. Nearly half of non-users expressed interest in transitioning. 
  • Growers using soilless systems reported improved crop uniformity, reduced disease pressure, greater control of water and fertilizer use, and better food safety, all factors that can drive profitability and product quality. 
  • Key barriers identified include high startup costs, limited reliable information for North America, and disposal challenges, especially for synthetic materials like rockwool. 
  • Because the study is survey-based, results reflect grower perceptions rather than controlled experimental outcomes, but they offer strong direction for future applied research. 
Materials & Inputs Needed: 
  • Through reports from online survey participants and focus group discussions in this study, growers reported using a wide range of soilless substrate components, including peat, composted bark, coir, perlite, vermiculite, and synthetic materials such as rockwool. Substrate blends vary widely by crop type and production system. 
  • Common inputs include wetting agents, fertilizers, lime, and pH-adjusting materials. 
  • Consistency and uniformity were repeatedly cited as essential for successful adoption. 
  • Irrigation systems varied: drip irrigation was commonly paired with larger containers, while overhead systems were typical for smaller pots. 
  • Water quality and nutrient management were central concerns, and growers emphasized the need for practical testing protocols for pH, EC, porosity, and nutrient retention. 
  • Safety considerations include proper handling of fertilizers, managing runoff to meet environmental regulations, and disposing of substrates, especially rockwool, according to local guidelines. 
Step-by-Step Guidelines: 
  • Test before transition: 
    • Evaluate current production challenges and determine whether a partial or full transition to soilless substrates is beneficial. 
    • Start the evaluation with a specific crop block to evaluate feasibility before converting an entire operation. 
    • Growers in the study cited improved uniformity and reduced disease as primary advantages 
  • Match substrate choice with irrigation system: 
    • Substrate water-holding capacity must fit the delivery method. 
    • Drip irrigation pairs well with coarse or mixed substrates, while overhead irrigation may require blends with more consistent moisture distribution. 
  • Check substrate properties: 
    • Assess substrate physical and chemical properties early. 
    • Measure pH, EC, and porosity before planting by conducting regular monitoring throughout the crop cycle to prevent leaching and optimize fertilizer rates. 
    • Many specialty crops require specific pH ranges, as inconsistent materials can result in nutrient deficiencies or waterlogging 
  • Develop a nutrient management plan: 
    • Soilless substrates often require more precise fertilizer regimes compared to field soil. 
    • Minimize nutrient leaching, especially in drought-sensitive regions, by adjusting timing and concentration. 
  • Plan substrate reuse: 
    • Evaluate local disposal options before selecting a substrate.
    • Materials like coir and bark can often be composted or reused, while synthetic substrates such as rockwool pose environmental and cost challenges.
  • Use extension support
    • Use extension resources and research updates when adopting new substrate blends.
    • Stay connected with universities and regional specialists to reduces mistakes and speed up learning curves

    Tips & Pitfalls:

    • Start small when transitioning. Growers noted that switching substrate systems too quickly can lead to irrigation or nutrient mismanagement.
    • Avoid overwatering. Water mismanagement was one of the most frequently mentioned problems, particularly in western regions facing drought and runoff issues.
    • Consider long-term disposal costs. Rockwool and other synthetic materials may be efficient in production but difficult to dispose of legally and affordably.
    • Don’t rely solely on European data. Many growers stated that guidance developed in Europe does not always apply to North American production systems, water quality, or regulations.
    • Invest early in staff training. The learning curve was cited as a major adoption barrier; growers who trained employees early reported smoother transitions.

    Expected Outcomes:

    • Improved crop uniformity, allowing growers to produce more consistent specialty crops with higher market value.
    • Reduced disease and pest pressure, since soilless substrates often provide cleaner starting environments.
    • Better control over water and fertilizer use, resulting in lower waste, reduced runoff, and improved resource efficiency.
    • Enhanced labor efficiency, especially in greenhouse operations where standardized substrate mixes streamline workflows.
    • As growers approach substrate blends with more confidence, they should expect more predictable crop performance and fewer production surprises, though results may vary based on substrate type, irrigation, and crop species.

    AddiIonal Resources:

    Fields, J. S., Owen, J. S., Jr., Lamm, A., Altland, J., Jackson, B., Oki, L., Samtani, J. B., Zheng, Y., & Criscione, K. S. (2023). Surveying North American specialty crop growers’ current use of soilless substrates and future research and education needs. Agriculture, 13(9), 1727. https://doi.org/10.3390/agriculture13091727