The best time to inspect corn or soybeans for stand counts as well as to identify problems from planting, insects, and/or diseases, is shortly after seedlings emerge. Of the three most common methods for taking stand counts, the most accurate method for corn and wide-row soybeans is the wheel method. Some farmers prefer the 1/1000th acre method. The hoop method is the best choice for drilled soybeans.
You should count only plants that have a good chance of surviving. Remember that soybean plants are often able to compensate for low plant populations, while corn plant populations are more directly related to yield potential.
Count 150 plants and measure the distance from start to finish with a measuring wheel. Divide the number of feet traveled into the appropriate factor in Table 1 to determine plant population. For example, if you walked 94 feet while counting 150 plants in 30-inch rows, the population is 2,613,600 ÷ 94 = 27,804 plants per acre. You may repeat the count several times and average the results.
|Stand count evaluation factors of measuring the distance when counting 150 plants|
|Row width (inches)||Factor|
Count the number of plants in a length of row equal to 1/1000th of an acre based on row width (Table 2). Multiply the number of plants by 1,000 to get plants per acre. Repeat the process in several locations in the field for an accurate estimate.
This method should be considered for drilled soybeans. Measure the diameter of the hoop, toss it in the field, and count the number of plants inside the hoop. Do this in at least 5 locations in the field. Multiply the average number of plants by the appropriate factor listed in Table 3 to get the number of plants per acre. Notice that having a diameter of 28 ¼” allows you to simply multiply by 10,000 to obtain the number of plants per acre. You can make a hoop this size by cutting anhydrous tubing to 88 ¾” and joining it to form a circle.
As you evaluate a crop stand for potential replanting, you should also consider if the field is irrigated or dryland, the plant population, plant spacing, the date of potential replanting, and crop insurance guidelines.
|Stand count evaluation factors, by hoop diameter, for determining soybean plant populations using the hoop method|
|Diameter of Hoop (inches)||Factor|
Illinois agronomy handbook. 23rd Edition. University of Illinois Extension. Purdue corn & soybean field guide. Purdue University. 2007.
Lee, D. A guide to corn production in Georgia 2013. University of Georgia.
Wiebold, W. and Massey, R. Corn and soybean replant decisions. April 2012. University of Missouri. G4091.