Enabling Wheat and Soybean Double Cropping Systems in Pennsylvania.

Double-cropping soybean following winter small grains is often a profitable cropping system that can also help have environmental benefits. One strategy for improving double crop soybean yields and profitability is to plant soybeans as early as possible. Earlier planting can be facilitated by harvesting winter wheat earlier or planting other crops such as winter barley. To better understand the yield response of soybean to planting date and the potential to improve profits with earlier planting, we conducted two studies to evaluate the double-crop soybean planting date response in PA. Six soybean varieties from relative maturity groups (RM) ranging from 3.3 to 3.9 were planted after wheat (June 27, July 6, 12 and 19) at Landisville, PA, and after barley (July 1, 7 and 13) at Rock Springs, PA in 2016. At Landisville, we also assessed the impact of harvesting wheat early at higher grain moisture levels. Predictions of soybean yield response to planting date using a 36-year weather data was done in Landisville with the cropping systems simulation model CYCLES. The results indicated a decline in wheat test weight and yield with delayed harvest, albeit at a lower cost for drying the grain. Harvesting wheat with ≈ 20% grain moisture allowed planting soybean nine-days earlier compared with traditional harvest at 14% moisture. Delaying soybean planting reduced yield in this year, but at a lesser rate than the long term simulated yield. Observed and simulated soybean yield agreed well at Landisville (R²=0.76). The lower soybean yield decline in 2016 as opposed to longer term simulations could be due to greater water stresses in the earlier planting in 2016 demonstrated by the model simulations. Soybean RM did not affect grain yield at Rock Springs. However, RM 3.9 cultivars appeared to be a good strategy to improve yields at late planting in Landisville. These results demonstrate the importance of early harvest in wheat that can facilitate early planting of double crop soybeans and improve the profitability of the system due to higher wheat and soybean yields. Simulation models can help explain yearly weather effects on yield and help strategically plan the expansion of double cropping systems.