Late Planting & Replanting Decisions

June 3, 2016

Late Planting & Replanting Decisions
I’m sure there has been, but it’s hard to remember a year when we’ve had so much rain in April and May. This has put many farmers behind on their planting or made replanting necessary. Last week I spoke with one farmer who said he was about finished with replanting and was just getting ready to start on his re-replanting. To say getting a crop in the ground and up this year would be a major understatement.

The latest USDA NASS report (when I wrote this column last week) released on May 31 showed that soybean planting was 73% complete across the state, behind 82% of average. Emergence was also delayed with 36% of the crop emerged compared to an average of 49%. Delayed planting always brings questions on what management changes should be made for the later planting date.

Changing to shorter maturity groups is not needed at this time because late planted soybeans will typically require fewer days to reach maturity than earlier planting dates. Because soybeans are photoperiod sensitive, flowering and development will be triggered by day length, resulting in similar maturity among planting dates, although earlier plantings will have more nodes and yield potential.

Research conducted at the University of Nebraska in 2003 compared planting dates ranging from May 2 to June 16. Even though planting was delayed by 45 days, maturity was only delayed 7 days for several MG 3+ soybean varieties. In 2004, the same study was conducted comparing an April 28 and a June 17 planting date. The mid-June planting delayed maturity by 22 days even though the planting date was 50 days later.

A similar study conducted by South Dakota State University in 2013 comparing shorter season varieties had similar results. Switching from a 2.8 to a 1.8 MG at a later planting date reduced the time to maturity by only five days. Therefore, changing maturity groups will not make a large difference in maturity so keep this in mind if you are considering changing to an earlier maturity group.

If planting is delayed past June 15, you may want to go with the earliest maturity group number recommended for your area, such as reducing your MG number by 0.5-1.0. Frost before maturity becomes a concern with late June or early July plantings, but don't try using a maturity group much shorter than that or you will sacrifice yield potential.

The next consideration is row spacing. With late planting, narrower row spacing is recommended. Because the longest day of the year occurs on June 21, and all days get shorter after that, soybeans need as much sunlight as possible to make pods, seed, and yield. To close the canopy sooner, you may want to consider planting narrower than 30 inch rows. This will help the crop's ability to capture as much incoming sunlight as possible.

Many sources recommend increasing seeding rates by 10% after early June for drilled and planted beans. Research at Iowa State University did not show a yield response with increased seeding rates at later planting dates. Also, given that there is a wide range of seeding rates, a blanket statement of a 10% increase may not be appropriate.

Finally, it is important to be aware of crop insurance considerations and your options. Review your policy or check with your insurance agent. In summary, right now soybean producers should consider:

•   maintaining their current maturity group, or reducing it no more than 0.5-1.0 as we near mid-June,

•   narrowing their row spacing,

•   custom planting to finish planting sooner, and

•   possibly increasing their seeding rates by 10% if they normally plant lower populations.

For more information on delayed planting or replanting, visit the University of Nebraska CropWatch website at or contact your local Nebraska Extension office.