Maximum Yield USA September 2018 | Page 44

Which type retains the most water? My initial answer is stone wool, but I would love to see a trial between the choices. While water holding capacity is important, I think a good adaptive zone and attentive irrigation strategy is more vital. Oxygen getting to the roots is crucial to healthy plants. Coco coir or stone wool are great at providing a good balance of air and water to the root zone. As with any of the medium choices, I think it comes down to choosing the right distribution systems for the crop with appropriately sized containers. Which type retains the least water? Would this be the best choice for growers in carefully controlled indoor settings? It’s hard to say which of the media hold the least water due to the different shapes and particle sizes we can get nowadays. More surface area in the medium typically means more water holding capacity. Container size also has a lot to do with how much water it holds. That said, in a carefully controlled environment, I tend to not want a big water holding capacity simply due to how easily you can overwater plants, which stresses the root zone. How does water retention in soilless media affect nutrient uptake for plants? Too much retention (due to poor choices concerning media, containers, and irrigation) leads to waterlogged containers and root damage. Maintaining aerobic conditions is critical to a healthy root system for optimal nutrient uptake. 44 Maximum Yield “ MORE surface area in the medium typically means more water holding capacity.”