If April’s wet soil conditions continue into May and June, compaction and/or inadequate seed-to-soil contact during planting may cause yield reductions for soybean farmers, says Bill Wiebold, University of Missouri (MU) Extension agronomist.
Mark Hanna, an Iowa State University (ISU) Extension engineer, agrees that during a wet year, soybean growers need to pay close attention to the machinery they use to avoid compaction problems and still obtain good soil closure over seeds.
To help farmers overcome 2009’s potential soybean planting challenges and ensure optimal returns, Wiebold and Hanna provide the following top-5 tips:
1. Practice no-till. “For soybeans, I would advise tilling as little as possible,” says Wiebold. “Even a disk or field cultivator can compact the soil enough to prevent the tap root from being able to grow through the compacted zone.”
No-till planting should also help boost the bottom line, points out Hanna. “Number one, soybeans don’t see much yield response from tillage,” says Hanna. “Number two, you can really lower your input costs by going no-till.”
However, when planting soybeans into formerly flooded corn fields, some tillage may be necessary, he adds. In this situation, growers should first scout the field for problems, remove any debris and then use a field cultivator or disk to mix the soil if sand and clay deposits have accumulated or to level off rills prior to planting, says Hanna.
2. Pay Attention to planting depth. Soybean seeds are more sensitive to planting depth than corn seeds are, cautions Wiebold. “You’ll need to plant soybeans deep enough to reach soil moisture, but not too deep that seeds won’t have enough energy to emerge,” he explains.
“Row units typically have better depth control than drills and in many cases better slot closure than other planting mechanisms,” adds Wiebold. “If your planter can help ensure good emergence, then you can save money on seed costs.”
The appropriate seed depth can vary slightly depending on soil moisture, soil type, soil temperature and planting date, points out Hanna. For example, late-planted seed in drier or sandier soils can be planted deeper than early planted, wetter soils that tend to crust. However, for most situations, seed depth should be between 1¼ and 1½ in, he adds.
3. Keep an eye on down pressure. “If soils are on the dry side, I’d put a little more pressure on the closing wheels to ensure good seed-to-soil contact,” says Hanna. “If your soils are on the wet side at planting, I’d ease off the down pressure. Too much down pressure in wet soils would overly compact the soils and make it difficult for seedlings to emerge.”
On the other hand, finding the right down pressure for wet soils can be tricky without also causing compaction problems, warns Wiebold. In some cases, it may be better to wait for drier soil conditions to develop than to risk “mudding in” the crop, he advises.
4. Stop soil crusting. “Soybeans are very susceptible to soil surface crusting, which could break off or strip the emerging plant leaves,” says Wiebold. “Leaving ample residue on the soil surface helps intercept raindrops and prevents crusting.”
Hanna agrees. “Unlike corn, there is generally less yield response from clearing away crop residue ahead of the planter than when planting soybeans,” he says. “It’s actually good to keep some residue on the soil surface when planting beans to prevent soils from crusting and causing poor emergence. If you don’t have access to a rotary hoe and your soils tend to crust, then this can be important.”
5. Monitor seed delivery problems. “Seed size doesn’t seem to be much of an issue this year compared to some years,” says Hanna. “However, with an air-type planter, you’ll still need to make sure that the air pressure is set appropriately for the seed size. Also, check the gasket seals around the seed metering system for cracks that could cause air leaks and seed delivery problems.”