by Eric Soderholm, Organic Production Coordinator
The following builds on the tips provided in the September 2014 eNews entitled “On-farm Variety Trial Design Considerations, Part 1.”
When planning a variety trial, the key traits you need to observe and measure and the protocol you use to evaluate them deserve considerable forethought. Once the trial is laid out, planted and maintained for several weeks or months, you won’t get a second chance to collect comparative data once a crop reaches and passes prime maturity. Don’t let your efforts in developing a uniformly treated, replicated trial go to waste; think ahead about what is important to your operation. Spend some time drafting a list of what you value in a particular crop. Do you favor kale varieties that produce vigorous seedlings and can compete with germinating weeds? Perhaps you want pea varieties that have long harvest windows for your CSA and farmers’ market sales. Crop evaluation traits will fall into one of two categories: qualitative or quantitative. Qualitative traits—like fruit shape, flavor, and uniformity— are often evaluated using a standardized rating scale that is developed ahead of time. Quantitative traits can be measured in an appropriate unit (lbs, inches, etc…) or by rating, which would include yield, fruit diameter, or days to maturity.
Be careful not to overcommit yourself when deciding how and what to evaluate in a trial. Time can be a precious commodity during the growing season—let this be a guiding principle when establishing your evaluation protocol. Taking measurements of each individual plant in a plot may be unnecessarily burdensome. If the population planted for the trial is too large to evaluate in its entirety, it may be best to choose a portion of each plot at random to evaluate. Rating even the qualitative traits may increase your efficiency. Remember that you are looking for a big picture view of the performance of the variety and the quality of the data you collect is just as important as the quantity. In addition to taking specific measurements or making ratings, it is also important to keep accompanying notes about each of the plots that capture information that might be otherwise lost. For example, if there is a variety that has a high yield, but has a growth habitat that slows harvest speed, it is worth noting as a factor to consider. In addition to specific traits, it can be helpful to assign each variety an overall rating at the end of your evaluation.
For an extremely informative description of designing, conducting, and evaluating on-farm variety trials, check out this publication from the Organic Seed Alliance:
On-farm Variety Trials: A Guide for Organic Vegetable, Herb and Flower Producers
https://seedalliance.org/publications#publication_category_title_13