By Jeffrey Graybill, Penn State Extension
Here are some things to consider when thinking about replanting a poor stand of soybeans.
Soybean acreage has been growing in recent years as well as the trend to plant soybeans much earlier than was traditionally done. These two factors can team up with unfavorable weather and soil conditions to result in reduced and/or uneven stands. Modern seed treatments which incorporate both fungicides and insecticides can sometimes help when planting into challenging conditions. However, seed treatments will never be a replacement for sound agronomic practices including well maintained equipment, planting into appropriate soil conditions, and with an eye on the weather forecast.
Maybe you tried to do everything correctly, but when scouting your fields you find reduced and variable stands. Before you tear up the field and replant, here are some things to keep in mind:
- First, determine the cause. If the same conditions persist, you can easily have poor stands a second time. Was it seed quality? Inaccurate planter calibration? Seeding too deep or too shallow? Soil crusting? Herbicide injury? I nsect feeding? Disease? Early planting with slowed emergence and growth can also be a culprit.
- Second, determine stand density. You need an accurate assessment of the field before you can make decisions. There are several techniques available to make population counting accurate and simple.
- Third, estimate your yield potential. Did you know that a fairly uniform low stand of 60,000 ppa has over 90% of the yield potential of a stand with 160,000 ppa. However, a full stand re-planted June 10th only has 88% of the yield potential of that planted May 10th. There are tables available which you can use to evaluate the costs and benefits of replanting or allowing a thin stand to remain. Remember, soybeans have an amazing ability to compensate for low stands.
Decide to replant, fill-in or leave the field alone. Most data shows that filling in or thickening up a stand rarely adds yield. Later planted soybeans cannot compete well if they are established several weeks after the initial planting. If you have some very thin spots, then that portion of the field may be a candidate for this practice, however this can affect harvest maturity and create a nuisance when you want to follow with a small grain or cover crop.
The 2013-14 Penn State Agronomy Guide (p 83) has tables of information to walk you through this important decision.
Another excellent fact sheet has been produced by Purdue Extension.