The relationship between corn grain yield and silage yield is important for determining Loan Deficiency Payments. The current method for calculating this relationship first appeared in 1972 (Table 1). Much progress has been made in breeding adapted high yielding hybrids that are more resistant to biotic and abiotic stresses. Does the old relationship between grain and silage yield still hold?

To describe the relationship between grain and silage yield, data were used where plots had been split with half of the plot harvested for silage yield and the other half harvested later for grain yield. Treatments applied to these plots included various plant density, planting date and row spacing factors. Numerous locations, hybrids and yield levels were obtained over the 1997 and 1998 growing seasons (n = 253).

The relationship between grain and silage yield for current hybrids is described in Figure 1. Grain equivalents at two silage moistures are shown in Table 2. Current hybrids produce grain yield equivalents greater than that of 1972 levels, by 1.0 to 2.0 bushels of grain per ton of silage at 65% moisture. Using the relationship developed in 1972 would under estimate grain yields for calculating Loan Deficiency Payments using modern day hybrids. Further investigation is required to properly describe this relationship.

Table 1. Approximate bushels of dry grain (15.5 percent moisture) contained in a ton of corn silage (62 to 68 percent moisture).
Yield of corn grain	Bushels of dry grain equivalent/Ton of Silage
Bu/A	Bu/T
Less than 90	5.0
90-110	5.5
110-130	6.0
130-150	6.5
Over 150	7.0
Derived from "Corn silage for Wisconsin cattle" - A1178 by Jorgensen and Crowly, 1972

Table 2. Approximate bushels of grain contained in a ton of corn silage during 1997 and 1998.
Grain Yield at 15.5% moisture	Silage at 65% moisture		Silage at 0% moisture
Grain Yield at 15.5% moisture	Silage yield	Grain equivalent per Ton of silage	Silage yield	Grain equivalent per Ton of silage
Bu/A	T/A	Bu/T	T/A	Bu/T
25	7.1	3.5	2.5	10.0
50	9.0	5.5	3.2	15.8
75	11.1	6.8	3.9	19.2
100	13.4	7.5	4.7	21.3
125	15.9	7.9	5.6	22.4
150	18.7	8.0	6.6	22.8
175	22.2	7.9	7.8	22.4