AGRICULTURE COMMON 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 (1/100^th) 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.

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.

Return to Common Agriculture Questions

How Much is Standing Hay Worth?

How much should a person charge or pay for standing hay? This is a frequent question each spring. There is no simple answer but one can come to a fair price by considering the following factors.

First, one should consider the price of hay. This spring the price of alfalfa hay was $45 to $130 per ton, depending on the forage quality and small square bales were even higher.. Since the price of hay falls as we near first harvest, this sets an upper limit on the price of hay. Longer term averages for overall hay prices have tended to be in the $70-75 range.

Second, the seller needs to consider the cash rental price of land in the region. This obviously becomes the lower value of the standing hay since the landowner will want some return in addition to the cash rental price to cover the cost of establishing the alfalfa.

Another consideration is who is going to harvest the hay or silage. The selling price of hay mentioned in the second paragraph includes the harvesting cost of the seller. If the seller is still providing harvesting then the price of standing hay may be near that of hay sold. Most often, however, the purchaser of a standing field of alfalfa will harvest the crop. This is usually preferable to the purchaser because then he can control the quality of forage harvested. Since harvesting costs in the range of $30 to $35 per ton this price must be subtracted from the value of the hay if the buyer is doing the harvesting.

Similarly, the buyer and seller must agree on who will pay for fertilizer and who will pay for insecticide if it is needed. This becomes especially important if the standing hay is bought for the entire season. These costs are also included in normal hay prices.

Lastly the issue of risk must be considered. The further ahead of harvest the contract is made the more risk the buyer assumes and the price should be adjusted down somewhat to reflect this. Similarly, if a standing crop is purchased near harvest, the price might be near to the selling price of hay (minus harvest cost if the buyer is harvesting). The price would still be less than purchased hay because the buyer is assuming the risk of having the low quality hay due to rain damage. Also, if the buyer buys the entire year's growth, the cost should be significantly less than the value of expected hay yield because the buyer has assumed the risk of reduced yield due to drought, insect infestation, disease, etc.

Lastly, the buyer should consider hauling costs. Longer distances to haul the forage obviously add to the harvesting costs of the forage.

For alfalfa, a fair price would consider a yield of 1.5 to 2 tons/acre for first cutting and about 4.5 tons/acre for the year (these are the average yields for Green County). If we value good quality dry hay at $75 per ton at harvest time and subtract the harvesting cost, if the buyer is harvesting, this works out to $35 to $40 per ton, or $60-85 per acre for first cutting.

It's best to set a per ton price rather than to price standing hay by the acre. This avoids one party benefiting over another due to unknown yields. If you need to calculate tons harvested you can weigh bales or wagons, or use silo charts. Dry matter weights can be calculated in forage wagons by taking the length x the width x the height of the silage in the wagon and then multiplying by 5. One cubic foot of wet haylage in a wagon will contain 5 pounds of dry matter.

The previous prices are for alfalfa, grassy fields would be valued slightly less due to lower yield and quality. The contract for purchase does not need to be particularly formal but should specify land involved, price, who pays for fertilizer, and when payments are due. The major purpose of writing out the conditions of sale is to make sure that each party has the same understanding.

Return to Common Agriculture Questions

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).

Return to Agriculture home