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Early assessment of corn and soybean stands can help identify potential crop concerns early in the season. Three common methods for taking stand counts are the 1/1000th acre method, the wheel method, and the hoop method.
When evaluating a corn or soybean stand, only count plants that have a good chance of survival. Keep in mind that while corn plant populations are a critical component of yield, soybean plants are better able to compensate for low plant populations. A significant soybean stand reduction does not automatically translate into a significant loss of yield potential and sometimes it may be more economical to leave a soybean stand with adequate population and distribution.
Count the number of plants in a length of row equal to 1/1000th of an acre based on row width (Table 1). 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.
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 2 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 should repeat the count several times and average the results.
This method should be used 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 five locations in the field. Multiply the average number of plants by the appropriate factor listed in Table 3 to determine the number of plants per acre. Notice that having a diameter of 28 ¼ inches allows you to simply multiply by 10,000 to obtain the number of plants per acre. This size of hoop can be made by cutting anhydrous tubing to 88 ¾ inches and joining it to form a circle.
Illinois agronomy handbook. 2002. 23rd Edition. University of Illinois Extension. Pg. 31. Purdue corn & soybean field guide. 2014. Purdue University. Lee, R.D. 2013. A guide to corn production in Georgia 2013. University of Georgia. http://www.caes.uga.edu/. Wiebold, W. and Massey, R. 2012. Corn and soybean replant decisions. University of Missouri. G4091. http://extension.missouri.edu/p/G4091. Web sources verified 3/25/16. 160326095029