How to size up replant options
You took your best shot and planted when soil conditions were right. Weather and perhaps insects conspired to leave you with a ratty stand. What now?
Most agronomists will tell you it boils down to three options: Leave the stand alone and take what comes; tear up the stand and replant; or tear up patches.
Here’s an example. Suppose you count population in a dozen spots at random. Population ranges from 6,000 to 31,000 plants per acre. The average is 19,500 plants per acre. The corn was planted April 25. It’s now June 1.
• Push the pencil before bringing disk to the field.
• Make replant decision on facts and probabilities, not emotions.
• Factor in replanting costs, other side effects of replanting before deciding.
“It’s always tough to know the best course of action for a problem field,” says Betsy Bower, agronomist with Ceres Solutions, Terre Haute, and an Indiana Certified Crops Adviser.
“First, it depends on the time of year when you make the decision. Compare estimated yield of current stand to estimated yield of a full stand planted at the current date.”
You can get insight using the Purdue University Corn and Soybean Field Guide published by the Purdue Diagnostic Training Clinic. Purdue’s AY-264-W, “Estimating yield and dollar returns from corn replanting,” is also a great resource to determine cost estimates for replanting. Both contain tables comparing expected yield in relation to stand and planting date. Find the bulletin at www.agry.purdue.edu/ext/pubs/AY-264-W.pdf.
From the table in AY-264-W, you determine that if you planted April 25 and now have 19,500 plants per acre, you can expect 91% of optimal yield.
However, if you plant June 1 and obtain 32,000 plants per acre, you’re only looking at 80% of optimum yield.
Put in terms of bushels, if you expected 200 bushels per acre, with a stand of 19,500 planted April 25, you could still possibly harvest 182 bushels per acre. With a perfect stand on June 1, you would only expect 160 bushels per acre. The 2009 season was an exception.
Naturally, the decision isn’t quite that easy. If the existing stand isn’t even, subtract off from the expected total. If some plants within rows are smaller than others, they may act like weeds. You will also need to worry about weed control where the canopy won’t close.
If the thin spots of 6,000 plants are in a large enough area and accessible, replanting them might be an option. However, calculate replanting costs and the risks of late planting, Bower says.
This article published in the June, 2010 edition of INDIANA PRAIRIE FARMER.