Getting the most out of soybeans might mean planting them sooner

On many farms, getting the corn crop in the ground will be the top priority this spring as planting season gets started. But, more research is suggesting that planting soybeans in April can offer real advantages for that crop as well.

“If you ask most guys when they plant soybeans they will tell you, ‘after corn.’ We think a change needs to be done there,” said Missy Bauer, with B&M Crop Consulting. “With better planters that get seed in the ground more uniformly, and new seed treatments with fungicides and insecticides, we think early planting dates are important. The earlier the planting date the more opportunity we have for sunlight. Sunlight is one of our biggest issues for soybeans. The more we can capture the better off we are.”

Practical Farm Research work from Beck’s Hybrids has consistently shown yield benefits from getting soybeans planted in April compared to May planting dates.

“If we can plant our beans the same time as corn that would be great. The earlier you get the plant established, the more nodes you are going to make,” said Mark Apelt, certified crop advisor for Beck’s Hybrids. “Planting soybeans after corn is an old habit from back before we had seed treatments. Some of the biggest changes in the last 10 to 15 years have been on seed treatments. We have consistently shown higher and more consistent yields the earlier you plant. All of our April planting dates in the long-term studies have shown a yield advantage for 17 or 18 years. March is a little on the early side and the first week of April was only a little bit above average or a little less. But when you get into the second, third and fourth weeks of April, almost all of those yields are 4% to 5% higher.”

In addition to yield, there are other benefits to planting soybeans earlier.

“One of the main things we want to have happen, especially in 15-inch rows, is to have things shaded by the longest day of the year on June 21. The further along we can be with that the better off we are going to be,” he said. “The earlier you plant the sooner you can shade out the weeds that are there.”

There may also be harvest benefits when planting earlier.

“One of the main reasons you run into more green stems at harvest is that you don’t have enough beans on the plant to draw down its extra energy. The plant is just sitting there because it is waiting for someplace to put it and it has no place to go,” Apelt said. “If you plant earlier, you have more pods on the plant and pods are more of a draw and that could reduce the amount of green stems.”

Apelt said there should be no need to adjust the maturity used for planting earlier, but cautions that there could be some stand reduction.

“When you plant earlier you will have a reduced stand. That doesn’t mean you need to plant more, but you will have a reduced stand when compared to planting in the latter half of May,” he said. “As long as the stand is reduced evenly in the field, you will get more branching that goes on and that still means more stems and more nodes. That is the take home message. Even if you are down to 70,000, 80,000 or 90,000 plants, that is still OK. Your plants will branch out more.”

James Specht, an agronomist with the University of Nebraska, pointed out that there are also benefits to water-use efficiency by planting soybeans earlier.

“You want to have your soybean crop transpire a greater fraction of the seasonally available water, simply because there is a linear relationship between the amount of total water transpired by the crop and final crop yield. The seasonally available water includes off-season rainfall that was stored as soil water prior to planting, plus all of the in-season rainfall,” he said. “Crop water use includes water lost via evaporation directly from the soil, as well as water lost as transpiration from the leaves. Crop water use efficiency can be improved by reducing evaporative water loss as this means more water will be available for transpirational water loss.”

Specht said that early planting helps with this because:

• The cooler soil and air temperatures prevailing in late April or early May are much less conducive to soil water evaporation than the temperatures in late May and early June.

• The canopy closes earlier in the season, which reduces the interception of solar radiation by the soil surface, thereby lessening the heating of soil surface that drives soil water evaporation.

• And the higher humidity that often prevails in a closed (versus open) soybean canopy minimizes the degree of evaporative soil water loss.

“In addition to allowing plants to collect more seasonal solar energy for use in photosynthesis, early planting also increases the yield potential by allowing the crop to use more of the seasonally available water for transpiration because less soil water is lost to evaporation,” Specht said.

Of course the yield penalty for planting later and the benefits of planting earlier vary based on the conditions during the growing season, and the planting conditions.

“The yield reward arising from early planting should not be used as a reason to plant seed into seedbeds that are too wet to plant,” Specht said. “Other than trying to plant early, exercise good judgment relative to the other seed planting practices.”


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