Double crop soybeans in WI may be worth it
The other option to expedite harvest is physically combine the wheat crop at a greater moisture content that we normally would. If a grower has access to a stripper header, winter wheat can be combined a few points wetter than with a conventional reel type head. Recognize that stripper headers decrease straw quality and if you are intending to sell the straw, then this must be factored into your decision.
The other factor to consider is the drying cost or dockage associated with harvesting and selling wet grain. Based on 2011 data the average dockage for moisture was $0.05 per bushel per point of moisture above 13.5% plus a factor for shrink. Also be aware that some elevators have an upper limit for grain moisture they will accept.
Once we have the wheat harvested we must consider the realistic yield potential of soybean planted in July for WI. An extensive planting date study was conducted in the early 1990s to quantify the effect of planting date and maturity group on soybean yield. Since full season maturity group soybeans were considered unrealistic for this late of planting only early and mid-group soybean cultivars were used.
click image to zoomFigure 1. Planting date effect on grain yield (bu per acre) of early to mid-maturity group soybeans (0.4 to 1.8 RM) in southern WI (Data from early 1990s planting date study). The average yield of a soybean planted on July 5th was 20 bushels per acre with a range of 9 to 33 bushels (Figure 1). The latest planting date in this study was July 12th which yielded 13.6 bu per acre (only one year data). For yield potential and harvestability, (a combine may not be able to pick up the lower pods) a grower should plant a mid-maturity group soybean (no earlier than 0.5 to 1.0 maturity group earlier than your full season soybean) instead of an ultra-early maturity group bean (0.5 or earlier).
To maximize yield potential in late planted soybean, growers should target a stand of 180,000 plants per acre in a drilled system. Wider row spacings and reduced plant stands will lead to reduced yield potential due to decreased canopy development. Planting too few seeds can also lead to a lower physical pod set and harvest issues. To achieve 180,000 plants per acre a grower may have to plant up to 200,000 seeds per acre (assuming 90% germ). It has been difficult to put forward a good “average” seeding cost as the farm gate prices for glyphosate tolerant untreated seed ranges from $30 to near $50 per unit. Add to that the broad range in seed treatment costs (seed treatments are discussed below) and seed costs can approach $60.00 per unit. If we assume 140,000 seeds per bag and 90% germ the input cost range for double crop soybean seed is $42.85 to $85.71. Couple this with the planting cost ($17.70 per acre; 2012 Iowa Custom Rate Guide), herbicide plus application ($12.00 per acre; Conley best guess), complete harvest ($40.15; 2012 Iowa Custom Rate Guide), fertilizer removal and “miscellaneous” costs the profit margin does significantly tighten, but still remains positive if we can hit the 20 bushel mark.