Brian Schulker

Graduate Research Asst

Thesis: Substrate Conditioning Influences Hydration Efficiency Through Ebb and Flood Subirriation

The horticulture industry is rapidly expanding container crop production, and substrates are the main component in this change. The componentry of typical soilless growing media includes peat and perlite in a percentage-based mixture with a moisture content around 50%. Moisture contents in soilless media, or peat moss specifically, optimally should be higher than 45% to be able to regain moisture before water repellency (hydrophobic) properties begin to outweigh wetting properties (hydrophilic). The addition of wetting agents, or surfactants, into peat-based media allows the moisture contents to fall below optimal ranges, reducing the transportation cost of the substrates (by weight). The introduction of perlite as a mix component can improve aeration and drainage capability all while reducing the amount of peat needed. In the last 10 years, the substrate industry has begun to explore the palpability of wood-fiber components used in the place of perlite to reduce cost and increase the use of renewables in the industry. Introducing new, lower-cost products is one thing, but understanding that each new component added into a mix has different hydrophysical properties is another. The sub-irrigation techniques of Ebb and Flood, Flood Floor, and Capillary Mats lost some of their vigors with the introduction of drip irrigation systems into container crops. Some of the benefits of sub-irrigation techniques include water conservation, plant growth uniformity, and lower fertilizer requirements (no leaching). To answer some of the concerns about hydration efficiency and sub-irrigation protocols, I intend to focus my research on understanding how preconditioning substrates through moisture content variations, wetting agent types, and pulsing techniques can affect the hydration efficiency of different substrate materials and formulations. Further assessing how each component (peat, coir, perlite, wood fiber, bark, etc.) effects the wettability characteristics of the substrate and influencing further mix design.

Brian Schulker