What's Feedlot Manure Worth as Fertilizer?
July 11, 2008
Can manure be turned to gold?
Well, probably not gold, but manure is a potential source of extra income for feedlot owners. And right now there's a lot of interest in selling feedlot manure to farmers or homeowners as fertilizer, according to Dr. Judson Vasconcelos, UNL feedlot nutrition and management specialist based at the Panhandle Research and Extension Center.
Commercial fertilizer is more expensive than ever. Gary Hergert, extension soils specialist at the Panhandle Center, noted at a recent field day that nitrogen prices have more than doubled in the past two years, while phosphate prices have more than tripled. One factor behind fertilizer prices is increased demand, due partly to the growth in corn acreage for ethanol.
Feedlot operations produce a lot of manure - one ton per head per year is the standard rule of thumb, Vasconcelos said. But how to put a price on it? One way is to compare it to commercial fertilizer.
Commercial fertilizer lists the types and amount of various nutrients on the label. Two of the most important are nitrogen (N) and phosphorus (P). But manure's nutrient content can vary from one feedlot to the next, and Vasconcelos said several factors must be considered when comparing it to commercial fertilizer
First of all, manure is not a balanced fertilizer. Meeting a crop's need for one nutrient might result in exceeding it for another nutrient. Also, feedlot manure also usually has lower nutrient concentrations than commercial fertilizer, resulting in higher handling and application cost. Feedlot manure also can be a source of weed seeds if it is not composted, Vasconcelos said.
But manure also has some advantages. In some areas manure is readily available, and feedlots need to remove it regularly. Another advantage is that manure is an organic fertilizer, so not all of its nutrients will be immediately available for crop uptake. In other words, it is a slow-release fertilizer.
Vasconcelos said it is not easy to use manure easily as a source of both nitrogen and phosphorus.
Historically, he said, manure management programs have been based on crop N requirements. But often when manure is applied, the ratio of nitrogen to phosphorus changes, because some nitrogen is lost as ammonia to volatilization during handling, spreading and composting. The result: Applying manure based on nitrogen content will result in excess phosphorus, which can cause water contamination.
The bottom line is that UNL highly recommends that producers estimate manure land requirements based on phosphorus, Vasconcelos said. He said it is important to know each field's phosphorus index, which predicts the potential for contamination. The index is based on soil phosphorus levels, potential for runoff and erosion, and proximity to water, among other factors. A phosphorus index calculator is available at the UNL Comprehensive Nutrient Management Planning web site (cnmp.unl.edu).
"So soil testing is important to determine the nutrients that are really needed for profitable crop production, so we don't add too much nutrients," he said.
On the economic side, establishing a price for manure involves a process known as manure replacement value, which bases manure's value on the cost of using it to replace N and P from commercial fertilizer. Vasconcelos said Extension Educator Tom Holman has performed some calculations using assumptions and averages to suggest values.
Manure's actual nitrogen and phosphorus content can be determined only by laboratory analysis. But for calculation purposes, Vasconcelos assumed an average content of 15 to 25 pounds of N (at 70 cents a pound) and 15 to 25 pounds of P (at $1.00 per pound) in a ton of manure. UNL estimates that about 50% of the nitrogen in manure can be used the first year.
These assumptions produce an estimated value of $34 per ton. But remember that not all of manure's nutrients are immediately available for crop uptake. So an acceptable manure application rate can be calculated based on the phosphorus content and the assumption that the crop will use 90% of that phosphorus during the first year. Vasconcelos and Holman estimate a manure value of about $25 per ton.
"We don't really have a magical number to recommend, but these calculations could give us an idea of how much we might charge," Vasconcelos explains. "We do think that producers can make some money from manure produced in feedlots through composting or just selling as a fertilizer."
Historically, area feedlots have charged about $12 to $20 per ton at the feedlot, which is probably a good estimate, considering the nutrients actually used where the manure is spread.
Vasconcelos also points out that the nutrient profile of manure can vary based on the feedlot diet, so for instance manure produced in one feedlot might not be the same as another where more distillers grains are fed.
The UNL specialist says the actual price of manure should be negotiated between feedlots and buyers. Manure with higher nutrient content has potential for higher value.
Cost of transportation and distribution are critical, but that information is limited, so Vasconcelos said it was not considered. Data from a 2008 Nebraska survey indicate a charge of $50 to $75 per hour for loading, and $50 to $150 per hour for hauling and spreading.
For the farmer buying the manure, one key to maximizing its value is avoiding nutrient loss. Immediately incorporating manure at application will result in about 25 percent more available N due to reduced loss of ammonia. But Vasconcelos acknowledges that is not always feasible to incorporate right away.
Each producer has a different and unique situation, so anyone who needs more information should contact Vasconcelos at 308-632-1230 or Holman at 308-632-1480.
Panhandle Research and Extension Center