By Sara Bauder
Figure 1. Water stands in a pasture with an unplanted soybean field in the background in Bon Homme County on 6/21/18.
With the longest day of the year in the rearview mirror, some soybean producers in the southern part of the state find themselves in an uncomfortable situation. Although some sources report that South Dakota soybeans are 100% planted, areas in Bon Homme, Hutchinson, Douglas, and Charles Mix counties and the surrounding region are still struggling to get a soybean crop planted due to frequent rain events. With the heavy rains that occurred this past week in many areas of southeast South Dakota, many producers also face waterlogged soils and dying crops. While some farmers with minimal or no soybeans planted may have already elected to take
Prevented Planting on their soybean crop, others may still be weighing their options. If a producer is determined to plant soybeans and/or has already purchased seed, there are still considerations that may help maintain soybean yields.
Soybeans are photoperiod sensitive; this simply means that they adjust their growth rate prior to flowering with day length. Soybean yield is determined by photosynthesis products that are supplied to the plant during reproduction. In an ideal situation, we want soybeans canopied as soon as reasonably possible to increase sunlight interception and yield potential. This correlates to why yield increases are often observed in earlier versus later planted soybeans because they flower sooner, and have a longer growing period for reproductive stages. In fact, in a long-term soybean planting date study at the Southeast Research Farm near Beresford, SD from 1986-2001 there was a 0.4-0.5 bu/acre loss per delayed planting day on average from early to mid-June.
Late Planted Soybean Considerations
With many producers still considering planting or replanting beans in late June, there are a few components to help compensate for potential yield loss due to shortening of the growing season.
- Seeding rates are an important first consideration; ideally, rates should be increased by 10-15% to help compensate for lost nodes and pods.
- Narrowing row spacing or drilling can also assist with yield increases; this helps with faster canopy closure and helps increase photosynthesis and pod height in conjunction with increased seeding rates.
- Maturity rating is another important factor to consider. If a producer still has the option to find an earlier maturity, it would be best to find a bean that is about 1.0 RM earlier than your typical maturity rating on a ‘normal’ year. This can help maximize yield potential and plant height. SDSU Extension Soybean Variety Trial Results may be helpful in comparing maturity groups in your area as well.
- Replanting soybeans can bring several additional questions to consider. See Replanting Soybeans: A Clouded Decision for more information on replanting considerations.
Other Planting Options
In some areas where water is now standing in unplanted fields or crop insurance has been filed, farmers need to turn to new options. If this is the case, check with your crop insurance agent before making further decisions on planting a crop other than originally intended. Some producers may plan to wait until the fall and plant winter wheat or other fall planted crops; however, keeping your soil covered throughout the summer can be very beneficial.
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