Trying to beat the buzzer isn't just for athletes- it is also what greenhouse growers are trying to do everyday in the spring season. As the busiest season, as well as the most economically important one, taking the time to work ahead is welcome whenever the opportunity presents itself. One way to save time and expedite planting (or sticking cuttings or seeding plug trays) is to prefill containers with substrate. When the planting, sticking, or seeding line gets going, filling containers won't slow it down.
While prefilling containers can be a big time-saver, it can also cause problems during production if done incorrectly. First and foremost, when containers and trays are prefilled with substrate, they need to be stacked correctly; and when I say "stacked correctly", it is to avoid "nesting" of trays and containers on top of each other. While the ability of containers and trays to nest within each other is a huge space-saving benefit for shipping and storage, it can cause problems with prefilled containers.
When prefilled containers nest on top of each other, it changes the physical properties of soilless substrates. For those containers under compression- which is all of them except those on the top layer- stacking with nesting is going to end up reducing the air space in substrate, as well as the bulk density. This effect is going to be magnified once the substrate is irrigated in thoroughly after transplanting into containers and trays. The water holding capacity is also going to be greater once the substrate is watered in. With reduced air space and increased water holding capacity, this compression is going to cause the substrate to hold more water and prolong the time it takes for the substrate to dry down.
Read more at e-Gro