Keeping marginal stand counts might be the best option when measured against costs to replant.

A seven-year Arkansas corn trial study comparing planting dates and stand counts may help growers decide if replanting will lead to greater returns.

Higher yields, fewer in-season inputs, fewer chances for lodging, and earlier harvest support planting corn early. The downside, according to Jason Kelley, wheat and feed grains Extension agronomist, University of Arkansas, Systems Division of Agriculture, is the potential for lower plant populations if conditions worsen after planting. "This could result in having to make the difficult decision to replant," says Kelley, addressing farmers at the 2020 National Conservation Systems Cotton and Rice Conference held recently in Memphis, Tenn.

Data from seven years of Arkansas irrigated corn planting date studies in east central Arkansas indicate optimum yields can be gained when planting from March 15 to the end of April. "After May 1, heat during grain fill generally leads to yield decline," Kelley says. "Planting a week or two later and getting good stands will usually yield more than a field with marginal stands planted early."

Kelley wanted to know if those yields transferred into profit for farmers.

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2019 trial results

The plant population and replant trials included five hybrids planted at seeding rates from 25,000 to 45,000 plants per acre. The first trial was planted early in cold soil temperatures and received 10 inches of rain within 10 days of planting. "That weather gives us real world results. It was clear we weren't going to get adequate stands on many plots," Kelley says. "Planting 34,000 seeds resulted in 24,800 plants with frequent skips. Many growers would consider replanting."

A duplicate trial planted on April 29 when yields would normally begin declining shows comparative data. "With a seeding rate of 34,000 and near ideal post-planting conditions, our stand count was excellent with nearly 34,000 seeds per acre. It yielded 221 bushels per acre, a 15-bushel per-acre increase over the earlier trial," Kelley says. The early trial planted with a 34,000 plants per acre seeding rate resulted in a final stand count of 24,800 and harvested 206 bushels per-acre."

Replanting takes time and increases input costs at an average of $67 per-acre. "We saw quickly the profit from the 15-bushel yield gain was lost in replanting costs," Kelley says. "In this case, the thin stand may have delivered a greater return over replanting and achieving a perfect stand."

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Kelley advises planting in that optimum planting window to avoid yield decline. "If you can't plant in that window, I'm more inclined to keep fields with marginal stand counts, especially when you consider the extra input costs," says Kelley.