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Estimating Plant Density with the Hoop Method (06/02/16)

In the beginning of the growing season it is important to evaluate how many of the seeds actually made it into a growing seedling.

Estimating Plant Density with the Hoop Method

In the beginning of the growing season it is important to evaluate how many of the seeds actually made it into a growing seedling. To estimate established plant densities for solid seeded canola, soybean, and other crops, the hoop or circle method can be used. A “hula hoop” or circle made from plastic or wire may work. The area of the circle is calculated with the formula: Square feet of the circle = [3.14 x (radius in inches)2]/144. For instance if the diameter is 30 inches the radius is 15 inches. [3.14 x 152]/144 = 4.91 square feet (area within the circle). It is important to count plants in various locations in the field. A sample size of 10 observations would give a good estimate of the plant population as long as the counts were done in representative areas of the field. For instance for canola take the average number of plants per hoop (total plants counted divided by 10). If you find 36 plants per hoop divide, for this example, by the area of the hoop 36/4.91 = 7.33 plants per square foot, which equals 7.33 x 43,560 (square feet per acre) = 319,300 plants per acre.

For canola an ideal stand has between 8-12 plants per square foot, but as canola has a good ability to compensate and fill in the gaps, the stand of 7.33 plants per square foot would be adequate.

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A guide for the minimum plant density per crop, regardless of row spacing, is provided in Table 1. However, there are many factors going into a re-planting decision. When considering re-planting, see the extension publication A934; Replanting or Late Planting Crops.

Hans Kandel

Extension Agronomist Broadleaf Crops

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