# Estimating Sunflower Yield (8/16/12)

The sunflower yield for oil sunflower can be calculated by the number of plants per acre, the head diameter, the seed size, the number of filled seeds per head, and observing how much of the center of the head is filled.

The yield is calculated by multiplying 2,450 by the “multipliers” from the charts below.

First estimate the plant population from a number of locations within a field, away from the head lands.

The value of the multiplier can be calculated for plant population numbers in between listed values in Table 1. The next measurement is the sunflower head diameter. Measure a number of heads in the field, and take the average. Plants with more space tend to have larger heads so it is important to take a representative field sample.

The next multiplier is related to the seed size. Remove several seeds approximately one to two inches from the edge of the head and compare to the seed outlines in Table 3.

To obtain a percentage of good seed, cut a slice out of the sunflower head, hand remove the seeds, and estimate the percent filled seeds.  For instance, when observing 100 seeds of which 9 seeds are either not filled or severely damaged due to insects, the multiplier will be 0.91 (= 91% filled seeds).

The last measurement is to observe the center seed set. If there is no seed set in the center one inch of the head, multiply by 0.975; if no seeds are set in the center two inches of the head, multiply by 0.95; if there is a hole in the center of the head, multiply by 0.9.

Yield calculation

Yield is calculated by multiplying 2,450 by the multipliers from the charts above. For example in a sunflower field with a stand of 21,000 plants per acre, a head size of 7 inches, a medium seed size with good seed count of 91 percent, and no seed in the center one inch, you would do the following.

Multipliers used: 2,450 x plant population x head size x seed size x seed count x center seed set = lbs/acre.

Yield calculations for this field would therefore be: 2,450 x 1.05 x 0.82 x 1 x 0.91 x 0.975 = 1,871 lbs/acre. If bird damage is visible an estimate of the percent damage (and therefore percent seeds left in the head) can be used to adjust the yield estimate. With 2% of the seeds removed by birds the yield estimate in the example would be 1,871 x 0.98 = 1,834 lb per acre.

Hans Kandel