Guidelines for Public Yield Trials
March 2007
Plot Selection and Preparation
Plot selection should be based on uniformity of soil, both type of soil and surface. Consultation with the owner or branch (experiment) station should take place before assignment of land. Low spots for standing water or known soil type problems should be avoided.

Seedbed preparation is of utmost importance, with land worked with minimal soil compaction by tires, usually at angle, with previous crop refuse distributed evenly. Turns of equipment should be outside the plot area, reducing tire compaction concerns. At least four soil samples should be taken per replication area to determine variability within the whole plot, and these samples should be utilized for applying N, P, and K to reach realistic yield goals of that particular production area.
Seed Preparation
All seed of every hybrid should be treated similarly, with both fungicide and insecticide application considered. Size 2, 3, or 4 should be planted for oilseed hybrids. Confection seed should be tested for blanks to be sure each seed has the capability of producing a plant. Confection seed should also be small enough to fall down the tubes of the experimental cone planters and not get caught in any mechanism.
The design of the field should try to make each replication as square as possible. Three replications should be the minimum, but previous experience may indicate four replications may be needed to lower CV%.
Plot Size
The minimum plot length should be 25', but up to 50' can be considered. Plots can be four rows wide, with the middle two rows harvested for yield, or two rows wide with both rows harvested for yield. A minimum between row width of 30 inches should be used. Plots should be planted east-west (see harvest below).
Number of Seeds Planted
To lower CV%, the number of seeds per row planted should be between 60 and 75 for a 25' row length. The planting depth should be carefully calibrated to be sure seeds are placed in soil with moisture and covered completely.
Rabbit Control
If rabbits are a concern, an electric fence should be erected. The electricity can be powered by battery or by a HOL-DEM solar activated electric fence controller.
This is probably one of the most critical operations of a sunflower test trial. Depending on the intended plant population, the number of plants thinned per row should be extremely uniform. If the workers are inexperienced, the supervisor should use 25' sticks with marks where plants should remain. Doubles, or two plants germinating in the same place, should be carefully separated and one plant saved without disturbing the remaining plant. At the beginning and end of each row, a plant in excellent condition should be selected.
Weed Control
Treflan or Sonalan should be applied and incorporated in the fall or early spring if possible. If not possible, Spartan can be utilized along with Prowl. For a grassy weed problem, Poast, Select, or Assure II can be sprayed. Cultivation should be done with extreme care, not too late or plants may be broken by axel or tool bars.
Insecticide Application
The plot should be monitored each week. Timely insecticide applications should be applied for insects such as cutworms, sunflower beetle, stem weevil, banded sunflower moth, seed weevil, and sunflower moth.
Bird Control
A local farmer or responsible person should be hired to go through the plot at least twice each day to shoot birds. Boomers should be utilized, with timers, so that the explosions will scare birds during the daylight hours. If birds are a severe problem, a net can be purchased which can be placed over plots and removed just before harvest.
A desiccant should be applied in the northern regions to uniformly dry down hybrids after the last hybrid has reached physiological maturity. When moisture percentage of the latest hybrids has reached 16%, harvest should begin. Harvest by combine should travel from east to west to assure that all heads of each plot enter the combine. Enough time should be allowed to make sure all seed of a plot has gone through the combine and has been measured or collected. 
Yield results with a CV greater than 20% should not be published with yields. Yield information can be distributed to individual seed companies with their individual results only. This will greatly minimize the misuse of information. Results with other agronomic information can be published, however. It is the policy of the National Sunflower Association that only yield trials with a CV less than 20 percent will be published in its publications or website.
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