Replanting or Supplementing Soybean Stands

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Growers continue to replant, spot plant or supplement soybean stands this month. In west TN this is due to too much rain, causing surface packing or seed and seedling rots. Dry weather in central TN is creating additional headaches, where wetter spots free of cover crop residue may germinate well, while other parts of fields have seeds germinating over many days as rains fall too late to wet soil profile deep enough. It looks like we will also have a considerable amount of ‘full season’ June planted beans due to either excess or inadequate soil moisture, depending on location.

Since we are in June, I would consider keeping a low but uniform soybean stand.  Low meaning 70-90 thousand plants per acre — especially if beans are planted on narrow rows.  Fields with extremely poor stands or complete bare areas should be replanted or spot replanted to fill in the holes in stand. Timely weed control will be important in fields with thinner stands that tend to canopy late. Where only spot replanting is needed, do it early while the existing crop is small.  That second planting will catch up much quicker if the original stand is not more than one or maybe two trifoliates. Use the same variety or at least a similar maturity bean for a more uniform crop later in the season.

Supplementing thin stands is something folks have tried with varying degrees of success. This involves planting a low population of the same variety back into a field with a too-low stand. If you split row middles some of the original rows will be run down in the process leaving more skips for weeds to grow. Our skip row research suggests that skips don’t necessarily cause yield losses as nearby rows can compensate their pod load, however skips leave wide open spaces for weeds to grow. Driving diagonally across the old rows (think of an angled checkerboard) to increase the plants per square foot in the field can work fairly well as long as you are careful to not over plant, plus entire rows are not flattened in the process. Always use a determinate bean to supplement a determinate thin stand.

The best maturity group choice for June planted soybeans is a MG 4 or 5. Unless you can irrigate, put away the Group 3’s and work with fuller season options. TN collaborated with other states in a USB funded planting date/maturity group study and found that MG 4 varieties tend to have the best yield return as a late plant option over both MG 3 and even MG 5 varieties. Narrow rows will canopy faster. I would not plant much thicker than normal to ‘force’ height yet, but if we get into July we may need to do so.



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