Estimating Yields in Sunflower Fields

Sunflower yields can be estimated using the tried and true method that is used during the annual sunflower survey. Typically, September is an ideal month to estimate yields. Sunflowers should be at R7 stage of growth.

Components needed to estimate yield are: harvestable plant population per acre, average head diameter, seed size, percent good seed set in heads, and center seed fill. Each of the measured yield components are assigned multipliers from the charts below. These are multiplied by 2450 to give estimated yield goal.

Sampling Method

1. Pick an area away from the edge of the field.
2. Measure 25 feet between two rows
3. Count plants in both rows. Do not include plants that will not produce seed. Take this total and divide by the area (25 ft x 2 x row width (ft)= area measured) multiply by 43560 ft2. This is referred to as the harvestable plant population per acre. Once population is determined, the multiplier for plant population can be selected from the table below.
4. With a flexible tape measure, measure the diameter of five consecutive (harvestable) heads. Add the diameters and divide total by five. This is the average head diameter. This number is plugged into the chart below to determine the multiplier for head diameter.
5. Cut a wedge out of a typical head. Thresh seed and put in a small container. These can be measured for seed size by comparing the seed to the outlines in table below.
6. Take 100 seeds from seed sample and determine percent filled seeds. The percent of filled seeds is the multiplier for seed set.
7. To measure center seed set determine the width of area that has no seed fill in the center of the head. If there is no seed fill in center inch of head the multiplier is 0.975. If there is no seed in the center 2 inches of the head multiply by 0.95.

Yield estimate in lbs per acre is determined by taking the multipliers for plant population x multiplier for head diam. x multiplier for seed size x percent good seed set x multiplier for center seed set x 2450. So for example to determine the estimated yield for a field that has a plant population of 17000, average head diameter of 8.0 inches, seed size “medium-heavy”, 98 % seed fill and no seed in the center inch, the formula would be as follows; 2450 x 0.85 x 1.00 x 1.1 x 0.98 x 0.975=2188 lbs/acre. Estimating yield in 3 to 4 spots per field and averaging the results will result in a better estimate.

Source: iGrow