Frequently Asked Questions
Estimating Corn Silage Yields
Mark Mayer, Agriculture Agent, UW-Extension-Green County
Requests are often made for pre-harvest methods to estimate corn silage yields. These estimates are needed in making decisions regarding feed inventories and for selling the standing crop. Cash grain producers who are considering the opportunity costs of harvesting drought stressed corn as grain vs selling to neighboring livestock producers as whole plant silage need to assess yield potentials in order to evaluate grain and silage marketing options. Two “quick and dirty” guidelines for estimating yields of corn silage are as follows:
Based on Grain Yield —
For moisture 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 of grain per acre, you will get about 10 ton/acre of 30 percent dry matter silage (3 tons/acre) dry matter yield). 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 of grain per acre.
Based on Plant Height –
If little or no grain is expected, a rough preharvest 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 at 3 to 4 feet will produce about 3 to 4 tons per acre of silage at 30 percent dry matter (about 1 ton per acre of dry matter).
Bundle and 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 the row width and the cut the corn plants from one row the length needed based on the row width using the following table.
Next weigh the amount of whole corn plants 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.
| Row Length | Row Width |
|---|---|
| 32.5 ft. | 30″ |
| 28.75 ft. | 36″ |
| 27.5 ft. | 38″ |
| 26.25 ft. | 40″ |
For example – If the row width was 30″ and 32.5 ft. or row was cut that weighed 64 lbs., this field would yield 16 tons of corn silage /acre. (64 divided by 4 = 16 tons)
In order to obtain actual tonnages that were harvested you would have to weigh wagons as they are filled or count how many feet of silage went into the silo after settling. If you know the silo size, how many feet of silage was put in and what moisture was you can contact me at the Extension Office – 328-9440 and I can tell you how many tons were harvested.
The Relationship between Corn Grain and Silage Yield
Written by Joe Lauer, UW-Extension Corn Agronomist
Edited by Mark Mayer UW-Extension Agriculture Agent
The relationship between corn grain Table 1. Approximate bushels of grain yield and silage yield is important for determining silage value. This ratio is also used in calculating federal loan contained in a ton of corn silage determining silage value. This ratio is (silage at 65% moisture). also used in calculating federal loan deficiency payments (LDPs).
The current method for calculating this relationship first appeared in 1972. Since that time much progress has been made in breeding adapted, high yielding hybrids that are more resistant to biotic and abiotic stresses. These breeding changes have resulted in corn hybrids that produce a higher proportion of grain than those grown in the 1970s.
Comparing corn grain and silage yield. To describe the relationship between grain and silage yield, data were used from Wisconsin’s corn silage trials. These 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).
Grain equivalents at 65% silage moistures is shown in Tables 1. 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.
Table 1. Approximate bushels of grain contained in a ton of corn silage (silage at 65% moisture).
| Grain Yield | Silage Yield | Grain Equivalent |
|---|---|---|
| Bu/Acre @ | Wet Tons | Bu/Ton |
| 15.5%moisture | Per Acre | Corn Silage |
| 25 | 7.1 | 3.5 |
| 50 | 9.0 | 5.5 |
| 75 | 11.1 | 6.8 |
| 100 | 13.4 | 7.5 |
| 125 | 15.9 | 7.9 |
| 150 | 18.7 | 8.0 |
| 175 | 22.2 | 7.9 |
