Considering Manure As a Viable Alternative to Commercial Fertilizer
As fertilizer prices rise, questions to consider before making the manure switch.
Compiled by staff
Published: Aug 25, 2006
The ever-increasing cost of natural gas (and commercial fertilizer) is making manure look more attractive to farmers every day.
Extension specialists across the Midwest are encouraging crop producers to consider manure as a viable alternative to commercial fertilizer, says Ted Funk, agricultural engineer and Extension specialist at the University of Illinois.
Although the use of manure is not without its challenges, says Funk, manure is a valuable resource and needs to be treated as such during land application.
"Producers, especially those who are only familiar with commercial fertilizer, can gain considerable nutrient value from manure by looking at some basic management options," says Funk. "Fortunately, the same management options that retain and recycle manure nutrients are also the same practices that protect the environment."
Some of the questions farmers need to consider include:
What are your crop needs? Soil tests determine the amount of phosphorus (P) and potassium (K) in your fields. "If you've got some poor ground, where your soil phosphorus and potassium tests are low, that's where you should put manure first," says Funk. "If a field is already rich in P and K, making repeated applications of manure at a nitrogen rate to ensure high-yield corn crops can create environmental problems down the road due to excessive phosphorus and potassium."
What manure is available within a three- to five-mile radius? Hauling manure is part of the cost of application, and transporting manure up to three to five miles is generally doable. As a rule, the cost of manure application should be kept below a penny or a penny-and-a-half per gallon. Many commercial applicators have purchased equipment that allows them to increase the distance they can efficiently haul manure. The farther you haul manure, the more you want to be hauling the most nutrient rich manure to the most needing fields.
What is the form of the manure? Solid manure must be spread on top of the ground, and is sometimes incorporated, or disked in, afterwards. This can mean there is a noticeable odor when spread and a significant loss of nitrogen through volatilization until the manure is incorporated, says Funk. Incorporation not only decreases the odor, but also helps retain the nitrogen and reduce the risk of runoff.
"And if you're on highly erodable land or in an impaired watershed, surface application is not a good economical or environmental choice," says Funk.
Liquid manure can be applied using sprinkler irrigation or injection. Sprinkler irrigation of liquid manure should only be done on fields remote from public roads or residences because of the intense odors released. In addition, the loss of increasingly valuable nitrogen can be appreciable. Injection allows you to place the nutrients below the surface, in the root zone, where odors, runoff and evaporation are much less of a problem. However, says Funk, application by injection normally costs about four times as much as sprinkler irrigation, so again, be sure you are placing the nutrients where the crops will most utilize them.
What is the sampling history of the manure? It's important to know how long and how frequently the producer has been sampling the manure, and if the sampling results are available to help you make your decision, says Funk.
"One question a crop producer can reasonably ask the livestock producer is, how confident are you in the composition of the manure you're offering for sale?
"Manure differs from commercial fertilizer in that commercial fertilizer supplies the amount and ratio of nutrients you ordered," says Funk, "while manure supplies the amount and ratio of nutrients it contains. You need to know what's in the manure you're applying to your fields, so that you can provide the rest with commercial fertilizer if needed."
A livestock producer who has a history of sampling that spans several years can often show that the manure does not change much, or that it changes seasonally, by building, etc., says Funk. When this information is made available, informed decisions can be based on the particular situation.
What is your cropping system, and when can you apply manure? In the spring, manure can be applied after the ground dries out and supports the tractor and spreader without soil compaction. However, that's also when the fields need to be prepared for planting. For this reason, many farmers prefer to apply manure in the fall. This can be done anytime after harvest, up until the ground freezes. The downside of fall application is a higher nitrogen loss over winter months, says Funk.
"Depending on the soil temperature, you can lose up to one-third to half of the manure nitrogen if it is fall applied," he says. "This can be avoided by spreading manure after the soil temperature is below 50 degrees. Cover crops can also be a benefit to reducing runoff and nutrient losses."
"The challenges of manure application may discourage some producers from using this alternative to commercial fertilizer," Funk says. "But new technology, including improved manure storage practices, and advances in manure application, is making the process easier," he concludes, "and rising commercial fertilizer prices are making it economically feasible."
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Tagged: fertilizer, Irrigation, Extension, Harvest, SURE
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