We at ECHO are sometimes asked what we recommend for a germination medium in situations where seeds or seedlings need to be started in pots or plastic sacks before going out to the field. This past summer, we conducted a trial at ECHO to make and evaluate potting mixes that could serve as effective substitutes for purchased potting mediums, since ready-made potting mixes are typically unavailable, impractical or expensive in many developing countries. Nurseries usually resort to developing some ratio of topsoil, sand, and organic material (e.g. animal manure and/or compost) to serve as a potting medium. For our trial, we sought to use ingredients that would be accessible in many areas of the developing world. Based on some common potting mix recipes, we developed a series of recipes using the following components: sand, cow manure, compost, and both charred and un-charred rice hulls.
The trial was conducted in the ECHO greenhouse, where seedlings could be monitored and watered regularly. Using maize (Zea mays) as an indicator crop, our goal was to identify one or more potting mediums that would prove suitable for a healthy, uniform population of seedlings for use as transplants.