Stand Assessment and Replant Evaluations for Corn and Soybean

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.

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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.

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1/1000th Acre Method

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Table 1  
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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.

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Wheel Method

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Table 2  
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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.

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Hoop Method

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Table 3  
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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.

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Deciding Whether to Replant

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  • Determine what caused the stand loss.
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  • Evaluate the population and uniformity of the remaining stand and estimate the yield potential of the existing stand.
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  • Estimate the full cost of replanting and the yield potential of the replanted crop; remember to consider seed costs, fuel, equipment, and labor costs, pesticide costs, and crop insurance stipulations. Sometimes, even though the predicted yield potential of the replanted stand is greater than the existing stand, the costs of replanting may outweigh the additional yield of the replanted crop.
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  • Evaluate the current and forecasted weather conditions.
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  • If a decision is made to replant, consider using slightly higher seeding rates. This may help to speed canopy closure for better weed control and soil moisture retention.
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  • Determine whether you will use tillage or herbicides to destroy the existing stand. If soil moisture loss is an issue, herbicides may be a better option.
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  • Consider the average killing frost date for your region when determining maturity ratings of the replant crop. Changing to an earlier maturing variety may not be necessary depending upon the replant date.
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  • Scout areas of different planting dates in the same field for pest problems. The difference in planting date may cause a pest to be in one part of the field but not in another.
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  • Reduced stands allow more light to reach the soil surface, increasing the potential for greater weed competition and soil water evaporation. Weed control should be a high priority, but especially in fields with reduced stands.