Where soybean stands have been devastated by hailstorms, drowning, or some other factor, producers may be thinking about replanting, said Kraig Roozeboom, K-State Research and Extension crop production specialist.

With later-than-optimal planting dates, should producers make any changes in management strategies? Should a shorter-season variety be substituted as we move into late-June planting dates?

“As planting is delayed, the situation begins to resemble double-crop soybean production,” Roozeboom said. “The soybean crop following wheat is usually planted two to six weeks later than the optimum date for highest yields. Since planting is delayed, often until the end of June or early July, producers might be tempted to switch to a shorter-season variety to ensure the crop will mature before frost. This would be a mistake, however.”

While planting a variety that is too late in maturity will increase the likelihood of frost damage, switching to a substantially earlier maturing variety should be resisted for a couple of reasons, he said.

• First, early-maturing varieties planted late in the season will usually have limited vegetative development, short stature, and low yield potential.
• Second, any given variety will have fewer days to flowering, pod development, and maturity when planted late compared to earlier planting dates.

“The highest yields in a late-planted or double-cropped system are often achieved by using the same variety or one only slightly shorter in maturity as what is used in full-season production,” Roozeboom said.

Other management practices can be affected by late planting, however, he added.

“When soybeans are planted late, the period for vegetative growth is shorter and this reduces canopy development. As a result, increasing the seeding rate alone or in combination with narrow row spacing can help the crop compensate by providing the opportunity to produce more pods in the canopy,” the agronomist said.

Seeding rates can be increased by 30 to 50 percent in high-rainfall environments if planting is delayed until late June or July. Although past research has demonstrated no consistent benefit for narrow row spacing (less than 30 inches) in Kansas, narrow rows may have an advantage in late plantings in the eastern half of the state, Roozeboom said.

More information about soybean production is available at K-State Research and Extension county and district offices and in the Soybean Production Handbook and search for C-449.