By: Jerrold Tesmer, Extension Educator, Fillmore & Houston Counties
Due to the late planting dates and a cooler than normal growing season this year, many corn fields will probably be harvested for silage. There is 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 immature corn? Typical calculation methods for pricing normal corn silage include:
Relative feed value of known forage market.
Silage ($/T) = ¼ to ½ value of hay
Silage ($/T = 8 times the price of a bushel of corn. If already harvested, then 10 times.
Feed replacement or substitution costs
Use market prices for energy, protein, and digestibility (NE of corn, soybean meal, hay)
Contracted price above the cost of production (280 - 320 $/A).
If the corn is immature a quality adjustment factor for maturity might be necessary. Some University of Wisconsin work suggests: Pre-tassel = 90%; Silk = 80%; Soft dough = 85%; Early dent = 90%; ½ kernel milk line = 100%; and Black layer = 90%
Two "quick and dirty" ways to estimate corn silage yield are:
Based on Grain Yield...for stressed corn, about one ton of silage per acre can be obtained from each 5 bushels of grain per acre. For example, if you expect a grain yield of 50 bushels grain per acre, you will get about 10 ton/acre of 30 percent dry matter silage. For corn yielding more than 100 bushels per acre, about one ton of silage per acre can be expected for each 7 to 8 bushels per acre.
Based on Plant Height...if little or no grain is expected, a rough pre-harvest estimate of yield can be made by assuming that one ton of 30 percent dry matter silage can be obtained for each foot of plant height (excluding the tassel. On this basis, "waist-high" corn 3-4 feet tall will yield about 3 to 4 tons per acre of silage at 30 percent dry matter.
Sample Weight Method...A more accurate way to estimate yields is to weigh the corn plants from a portion of an acre (1/100th) in several spots of the field. To do this, determine row width, then cut corn plants in one row for a certain length according to row width in the following table:
Row Length Row Width
32.50 ft. 30"
28.75 ft. 36"
27.50 ft. 38"
26.25 ft. 40"
Next, weigh the amount of whole corn plant material cut in pounds. Divide the pounds harvested by 4. That's the estimated tons produced per acre. Follow this method for several areas and average the results.
In order to obtain actual tons harvested, weigh each wagon load or count how many feet of silage went into a silo after settling. If you know the silo size, how many feet of silage was put up and what the moisture was, silo charts can be used to calculate tons stored. Dividing stored tons by acres harvested will give you the yield per acre.
The information above was obtained from work done by University of Wisconsin Corn Agronomist Joe Lauer, and UW-Extension Agriculture Agent Greg Blonde.