Was thickening soybean stand right call?
Soybean Corner: Now is the time to determine if filling in the stand was beneficial — at harvest will be too late.
Aug 03, 2022
We replanted patches in two soybean fields, and thickened stands by planting more seed next to thin rows in other fields. Should we walk those fields now?
The Indiana certified crop adviser panelists answering this question include Shaun Casteel, Purdue Extension soybean specialist, West Lafayette; Steve Gauck, regional agronomy manager for Beck’s, Greensburg; Andy Like, agronomist with the Evansville AgriSelect LLC, Vincennes; and Dan Ritter, central region agronomist for Dairyland Seed, based near Rensselaer.
Casteel: Stand assessment is critical for early-season decisions like overseeding, patching or replanting. Know stand counts as you go back to those areas now. Variation in plant-to-plant development will depend on when you overseeded and time for establishment. A decision to replant when the original stand was at VC vs. V2 will have drastically different effects on the size and contribution of replanted soybeans to overall yield. Replanted or delayed soybean plants will contribute less to overall yield as difference between growth stage widens.
Assume plant population was 50,000 plants per acre. Then replanted soybeans might develop about 25% of the pod load if planted when the original stand was VC vs. about 10% if the original stand was V2.
Why does this happen? Original soybeans already decided to branch and produce pods on those branches with the subpar plant stand. Replanted soybeans produce less yield because they’re shaded and competing with more advanced plants.
As you walk patches that were replanted, count plants that are still actively growing. Some replanted soybeans get shaded and die. Observe actual pod contributions based on replanted field conditions. These observations should help you decide if it’s worth replanting or overseeding in the future. Walking these areas also helps you define what is really a thin stand.
Gauck: Every time you step into a field, you learn. Look and compare first-crop and replant plants. Did you need to spot seed in? Have first-planted beans branched out and compensated for thinner stands? Look at growth stage differences. Will replant delay harvest? Is replant adding to yield or just helping shade the ground for weed control? Was replanting straight or across original rows? Which worked better? Walking and assessing now will help you deal with emotions of a thin stand next time you have to make this decision.
Like: The first concern would be standability where soybeans are too thick. Look at differences in growth stages between two planting dates and replant strategies. Filling in can affect timing for fungicides since two planting dates will likely arrive at R3 at different times. Additionally, maturity at harvest could be different, creating wet and dry beans in the same field.
Ritter: Pick up what you can. Will thickened stands actually contribute yield? In our Product and Agronomy Research plots at Dairyland Seed, we found adding additional population to a thin stand, 70,000 filled in to 140,000, did little to increase yield over leaving 70,000.
Find the “fill in” beans and evaluate pod and seed development. Look at replanted beans vs. fill in beans vs. a thin area where you did nothing. If you can collect yield data from these separate areas, that would certainly be of value. Use that data in combination with what you observed walking, plus information from trusted advisers, to assist decision-making in the future.