Container Substrate Compaction
Roberto G. Lopez, Ph.D., Associate Professor & Floriculture Extension Specialist, Purdue University
If you prefill your propagation or containers for sticking or planting, remember to avoid stacking or “nesting” them on top of each other on pallets or carts (Figure 1 and 2). When containers are filled with substrate and stacked, substrate compaction can occur from the weight of the containers nesting within each other. When the substrate is compacted, air space is decreased or even eliminated, which ultimately means less drainage. Less drainage can lead to overwatering and an increased risk of root diseases.
Trays or containers on the bottom of the pallet or cart can become compacted more than those at the top. Once they are placed on the bench, a grower will notice the vast difference in drainage between the containers that were nested and those that were not.
If you must stack your containers or trays, be sure to offset them (Figure 2) or place a rigid material in between the layers of containers so they do not nest and compact the growing substrate.
Click image to enlarge
Figure 1. Compaction of hanging basket substrate can occur from “nesting” baskets on top of each other. Luckily this grower only has two layers of baskets.
Figure 2. Compaction of container substrate from “nesting” on top of each other.
Figure 3. Plug trays that have been properly stacked to ensure they do not "nest" and cause compaction.