Calculating the Value of Normal and Immature Corn Silage

September 5, 1996 3(24):143-144

Joe Lauer, Corn Agronomist

Due to late planting dates and a cooler than normal growing season this year, many corn fields will probably be harvested for silage. There is even great potential for corn in these fields to be too immature for proper corn silage harvest. How should the value of corn silage be adjusted for frosted immature corn? Typical calculation methods for pricing normal corn silage include:

  1. Relative feed value of a known forage market.
    Silage ($/T) = 1/4 to 1/2 value of hay
    Silage ($/T) = 6 to 8 times the price of a bushel of corn. If already harvested, then 10 times.
  2. Feed replacement or substitution costs
  3. Use market prices for energy, protein, and digestibility (NEL of corn, soybean meal, hay)
  4. Contracted price above the cost of production (280-320 $/A).

For most crops, forage quality and value decreases with maturity, that is fiber levels increase and digestible energy decreases. Corn is somewhat unique in that quality increases with maturity. In corn silage most of the digestible energy is in the grain portion. Immature corn will have a lower proportion of grain in the silage. Two approaches to consider for calculating the value of immature corn silage are:

  • Reduce the value of immature corn silage by the cost of buying back grain to bring the grain:stover ratio to a more normal proportion.
  • Use MILK91 to calculate the milk per acre and milk per ton that could potentially be produced from immature corn silage.

Afuakwa and Crookston (1984) described the grain yield impact of frost at different stages of development (see table in adjacent article). A killing frost at the soft dough stage of development would result in a grain yield loss of 55% and at least that much grain would be required to produce normal silage.

The relationship between kernel maturity and silage yield and quality is shown in Table 1. Milk production per acre is 35% less when corn is harvested at the immature soft dough stage compared to the optimum stage at 50% kernel milk. Milk production per ton of immature corn silage (soft dough) was 25% lower than the optimum stage of 50% kernel milk. Thus, the milk production potential would be reduced between 25 and 35% with immature corn harvested for silage. The value of the corn silage should be adjusted accordingly.

Table 1. Relationship between kernel maturity and corn silage yield and quality.
Corn
development
Silage
moisture
Silage
yield
Crude
protein
ADF NDF IVD Milk 
production
  % T/A % % % % lb/A lb/T
Soft dough 76 5.4 10 27 53 77 8600 1600
Early dent 73 5.6 10 24 48 79 10800 1900
50% milk 66 6.3 9 23 45 80 13300 2100
25% milk 63 6.4 9 24 47 80 12600 2000
Black layer 60 6.3 8 24 47 79 12400 1950
derived from Wiersma et al. (1993) and Undersander et al. (1993)

Afuakwa, J.J., and R.K. Crookston. 1984. Using the kernel milk line to visually monitor grain maturity in maize. Crop Sci. 24:687-691.

Undersander, D.J., W.T. Howard, and R.D. Shaver. 1993. Milk per acre spreadsheet for combining yield and quality into a single term. J. Prod. Agric. 6:231-235.

Wiersma, D.W., P.R. Carter, K.A. Albrecht, and J.G. Coors. 1993. Kernel milkline stage and corn forage yield, quality, and dry matter content. J. Prod. Agric. 6: 94-99.


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