Evaluating soybean stand
As soybean planting wraps up, it’s time to consider evaluating soybean stands. Planting conditions were not always ideal this year. Soil conditions were a little wet when planting started and now have turned fairly dry in most areas. Here are some points to keep in mind when evaluating soybean stand.
1.) Uneven stand. I evaluated a soybean stand last week in west central Ohio. Similar to last year, soybean emergence is a little uneven. Last year, we observed soybeans at the VE stage (emergence) and the VC stage (unifoliates open) while some soybean plants were not yet emerged (but the seed was viable). Initially, this was not a pretty stand, but more plants emerged, the stand evened out, and yields were good. Keep in mind soybean plants may be at different stages, but if the seed is viable (i.e., not damaged from disease or insects), the field should be fine.
2.) Reduced stand. Dig around in areas where there are no plants. If you find seed that is healthy and germinated but not broken through the soil, a little moisture should help the plants emerge. (Soils were dry in many areas late last week.) In 2012, it took six weeks before plants received enough moisture to germinate. If you find dead seedlings (disease) or no seed or seedlings (insects), then take a stand count.
3.) Stand counts. I briefly discussed how to take a stand count in last week’s article. If you missed it, you can find it here toward the end of the article: http://corn.osu.edu/newsletters/2014/2014-15-1/early-season-soybean-damage-frost-ppo-or-disease
4.) Replanting. Replanting decisions should be made very carefully and only after conducting a stand count. If all plants in a field are lost, it is beneficial to replant because there is still adequate time left in the growing season. (I have seen a field that lost all plants due to a flooding river that was flowing through a field.) If only areas of fields were affected, replant the affected areas while leaving the rest of the field as is.
If the entire stand is reduced, the field can be inter-planted to fill in the reduced stand. Keep in mind, however, we estimate a soybean yield reduction of 0.5 bushel/day when planting later than mid-May. Additionally, previous research conducted by the AgCrops Team indicates that a stand of approximately 50,000 plants/acre (at harvest) results in a 15% yield reduction compared to 116,000 plants/acre (when planting in May).