Seeding rate for sunflowers depends on sunflower type. Oil-type sunflower populations range from 20,000 – 22,000 plants per acre (0.6 plants per ft2) but confection-type sunflowers should not exceed 18,000 plants per acre (0.4 plants per ft2) to ensure large seed size.
The easiest method to measure plant stand per acre is by doing the following:
1. Determine row width and using the table below, identify the correct distance to measure 1/1,000th acre.
2. Using a measuring tape, lay out the appropriate length for 1/1,000th acre.
3. Count all plants in the length laid out. When there are doubles, consider only counting one of the plants, since only one is likely to be productive.
4. Document plants counted.
5. Repeat steps 2-4 ten times.
6. Average all plant counts to determine and approximate final plant stand.
Another simple way to assess plant stand is to use the table below, developed by Manitoba Agriculture and Resource Development:
Seed Density as a Function of Row Spacing
In years when establishing a healthy and robust sunflower crop seems impossible due to various growing conditions, it is a very difficult decision on whether to terminate or keep a crop. Above are just a couple of ways to accurately determine how many plants are viable, which will help to estimate yield potential and all the costs required to bring sunflowers to maturity.
There is no documented data on the lowest plant population a producer can grow and still make a profit. Good record keeping and market knowledge will help someone in this situation make an educated assessment on whether the crop will be profitable or not.