According to the USDA, 66 percent of Michigan soybeans have been planted as of May 26, 2013. Due to the recent rains and the rainy forecast, one-third of the state’s soybean crop will be planted in June.
In general, when soybeans are planted by June 10, management practices do not need to be altered to maximize yield potential. However, when planting becomes delayed past June 10, the following recommendations from Michigan State University Extension should be implemented.
Planting date
Plant as early as soil conditions permit. Planting delays can reduce soybean yields by one-half bushel per acre per day until late June. Also, remember that soybean maturity is delayed by one day for every three to five days that planting is delayed, increasing your risk of frost/freeze injury in the fall.
Soybean variety maturity
Select varieties that are one-half maturity group earlier than adapted, full-season varieties for your area when planting before June 20. After this date, switch to varieties that are up to one full maturity group earlier than adapted, full-season varieties for your area.
Row spacing and planting population
Switch to narrow rows (15 inches or less) and increase planting populations. The combination of narrow rows and higher populations will help the crop canopy cover the soil earlier and capture more of the available sunlight. These conditions produce higher yields by reducing evaporation and increasing photosynthesis. Increase planting populations by 10 percent when planting after June 10 and by 20 percent when planting in late June.
Seed treatments
Fungicide and insecticide seed treatments are less beneficial with late planting as the soil will be warm and germination and emergence should occur rapidly (six days). If you are planting into a field with a history of Phytophthora root rot, select a variety that possesses specific race resistance or select a variety with good field tolerance and treat the seed with mefenoxam at 0.64 fluid ounces per cwt.
Planting depth
Plant into 0.5 inches of uniform moisture if possible, but don’t plant over 1.5 inches deep or less than 1 inch deep with a drill. Depth control is less precise and consistent when planting with a drill and you don’t want to risk leaving soybeans on the surface or placing them too deep.
Soybean aphid management
Scout late-planted fields often and thoroughly. Aphids deposited into soybean fields in the vegetative stages will reproduce more rapidly and reach economic thresholds two weeks sooner than aphids deposited into fields in the early reproductive stages
Source : msu.edu