The purpose of the present study was to simplify the previous experiments by utilizing the same substrate (peat:perlite), the same additions (low rates of limestone), the same greenhouse, and the same pest management practice (biological control with Encarsia) for all treatments. We also wanted to try several recently-OMRI certified materials which would potentially be easier to formulate, less expensive, and easier to apply with the drip system. Although two were recommended by their manufacturers as complete fertilizers, as far as we are aware, neither had previously been tested on tomatoes either in the field or in containers. By simplifying the comparisons, we hoped to determine the best way to overcome problems with high salts and pH and otherwise optimize a container system for organic greenhouse tomato production. Another objective in using these two fertilizers was to compare plant performance both with the fertilizers previously used and with a new formulation made in-house with a combination of commercial and generic ingredients that potentially could be made inexpensively on-farm as well. All the ingredients in this in-house formulation would be allowable in the new national standards.
