Conducting On-Farm Variety Trials
Micaela Colley, OSA and Dr. Hector Valenzuela, Vegetable Specialist, UH CTAHR
Valenzuela: When I first came here, the university was looking for band-aids to control plant diseases and insects, but I wanted to return to the source. I wanted to figure out what kind of seeds to plant that would be resistant to these problems. That’s how I got started with variety trials. I cannot overemphasize the value of visiting your plants and of walking into the fields. Every time you walk into the field, you learn something. Valuable observations are gathered over time, and farmers know this language. Farmers speak a different language than researchers—they know what is happening on the ground.
Variety trials are useful because they show you which varieties make it on their own with little inputs. Growers tend to narrow down their choices to what grows well in their plot without a battle to keep their crops going. I test different varieties to evaluate seeds from around the world to see what does well here without a struggle. Different varieties are attractive to different markets.
Colley: OSA teaches growers how to conduct trials on your own farm. Trials help farmers evaluate seed sources, expand market potential, assess crop stresses on-site at their farm, and assess seed growing potential on-site. They help to determine how a crop will respond in a particular location to particular environmental stresses, such as wind, rain, etc.
The first step in planning your trial is to identify what you are trying to learn. Are you looking for a drought resistant variety or for varieties to fit various rainfall belts? Next, identify seed sources by perusing catalogs to identify seeds that fit different niches. Omri.org has a listing of organically available seeds. The National Public Genebank Service is another source of materials deposited by farmers. Small amounts of material are available to farmers with a reciprocal agreement to send in material. Include a check variety to compare with the trial—either something you’ve already planted or the most common variety in the area.
Once you are ready to conduct your trial, you have a few choices. Observational trials involve a single planting. They provide a snapshot of how different crops look, grow, and taste, and they serve as a process of elimination to narrow down various contenders. Replicated trials involve two or more plots on your farm. They provide much greater assurance that the results you see are due to genetic differences between varieties rather than due to differences in environmental conditions in the landscape.
To minimize environmental variability, set out three different blocks within a similar environment. Within each block plant multiple plants so that you have enough plants to give you a good idea of how the variety responds. Randomize the order of planting different varieties within the plots to minimize the effects of plot-to-plot interactions, for example, to minimize the chance of a taller variety shading out a shorter variety. This is called randomization and will give you the best idea about how the variety performs.
The on-farm variety trial guide from OSA includes guidelines for how many plants to plant for different species. Start with enough plants so that you have enough individual plants to collect seed and maintain genetic variability within the population. Start with the best seed you can find so that you have best genetic material available—this minimizes the work you have to do to improve plants on your farm.
Ensure that you give your plots consistent treatment in terms of irrigation, cultivation of weeds, fertilization, and harvesting. Use your normal planting practices to ensure that the space between rows and the amount of irrigation replicates the way things will be when you actually produce the crop.
Mark and map the trial so you can easily identify the plots. I recommend using wooden stakes with sharpies.
With two replications, it is feasible to evaluate results. For statistically significant results, however, you will need three replications.
When you evaluate your results at the end of the trial, consider your top five goals. For evaluation purposes, we often use scoring versus measuring. At the end of the season, lay out plants and evaluate quickly which bulbs are biggest. For example, score the smallest as “1,” with “9” representing the most desirable result for that particular trait. Use only odd numbers 1-3-5-7-9. This allows you to easily pick 1 – the worst in the plot, 9 – the best in the plot, and 5 – the plant in the middle. Remember that 9 is the best plant on your farm during this year, not the best plant you ever saw in your life.
When evaluating your results, look for vigor (how fast does this variety sprout and grow?), pest tolerance, weed competition, fertility utilization (does the variety have a good strong root system that taps into nutrients?), and flavor.
A variety trial evaluation sheet is downloadable on the OSA Web site. This tool will help you make sense out of the data and decide which variety to plant again.
The online Farmer Tool from Oregon State University will create statistics for you from your data. This tool assigns a letter ranking to let you know which varieties performed about the same and which were not as good.
Next, compare your data for different traits so that you can assess overall performance. Average the traits or give more weight to vigor, flavor, or appearance—you can individualize how you weigh the various traits.
I envision a Hawai‘i Trial Network. There is so much potential for developing island by island trials. With so many microclimates, Hawai‘i could create a network that captures performance under varying climate conditions.