Early High Moisture Wheat Harvest Improves Wheat and Double-Crop Soybean Yield and Quality.

Soybean [Glycine max (L.) Merr.] following winter wheat (Triticum aestivum L.) is the most prevalent double-cropping system in the United States. Double-cropping may increase profit, spread out cash flow, ensure global food security by increasing food production, and provide environmental benefits via continuous land cover. However, soybean yields less in double-cropping than full-season production systems due to delayed planting. Harvesting wheat at high moisture (e.g., 20%) may allow 7 to 10 d early soybean planting without affecting wheat yield and quality. We evaluated the effect of early high moisture wheat harvest on wheat and double-crop soybean yield and quality across five Mid-Atlantic states including Pennsylvania, Maryland, Delaware, Virginia, and North Carolina in 2015 and 2016. At each location, wheat was harvested five times at 4 to 7 d intervals beginning when grain moisture approached 20% and immediately planted six soybean cultivars of three relative maturities. Wheat grain moisture tended to decrease with time, depending on weather. Wheat harvesting dates explained 77% of the variation of wheat relative yield for 2015 and 2016, which decreased quadratically with delaying harvesting. Wheat test weight decreased linearly and falling number decreased curvilinearly with delayed harvesting. Double-crop soybean yield decreased quadratically as planting was delayed from early June to late July. However, the degree of yield loss due to late planting varied with locations. Cultivar yield differences were more dependent on environment than relative maturity. Normalized difference vegetation index (NDVI) usually peaked between R4 and R5 stages with the maximum value of 0.90. At the R2 stage, NDVI was highly correlated with relative soybean yield and explained 60% of the variation of relative soybean yield. The research is continuing in 2017. Results to date suggest that harvesting wheat at high moisture can increase wheat yield by reducing test weight loss as well as double-crop soybean yield by allowing early planting; hence, increase overall double-crop enterprise income.