Comparisons of Silage Harvest Methods to Predict Corn Grain Yield Potential.

Multi-peril Crop Insurance (MPCI) is a type of crop insurance that covers many different naturally occurring perils including hail, drought, and excess moisture.  Current policy requires that if corn is insured for grain and the producer wants to put it to another use, ie silage, the producer must have the corn appraised before harvest for silage occurs.  Alternative methods of predicting the grain yield potential of a drought stressed corn crop would be useful for producers who insure a crop for grain and then harvest it for silage.  Experiments were conducted during 2006, 2007, and 2008 at the University of Wisconsin Agricultural Research Stations near Arlington, WI, and the Russell Larson Agricultural Research Farm near State College, PA.  Two hybrids, Pioneer 37R71 (97 day RM) and NK 58-D1 (108 day RM) were planted in all years at each location. In the fall, harvests were made from each main plot at four growth stages ranging from 0.75 milk, to grain harvest at physiological maturity. At each harvest, grain yields were also estimated by trained crop insurance adjusters.  Alternative methods of estimating grain yield were compared. We calculated a starch based yield by estimating the starch dry matter yield and then converting that to grain, assuming that grain is 70% starch and 15.5% moisture.  Estimates of the final potential grain yield based on a silage harvest estimate were usually lower, both with the adjusters method and with the starch based yield estimate. Differences  between the silage grain yield estimates and combine yields tend to decline with advancing milk line. The relationship between the adjusters yield and the starch based yield varies between years and harvest dates. The adjusters estimate of grain yields at the grain yield harvest show good agreement to the combine grain yields.