Category: Manure Nutrients

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Land Application of Manure Nutrients

Is manure application to cropland…

A source of organic matter that improves soil quality and reduces soil erosion and runoff?   OR   A source of pathogens that limit the beneficial uses of surface water?

A means of recycling essential nutrients for crop production and reducing use of energy intensive fertilizers?   OR   A source of nutrients polluting surface and ground water?

A means of recycling and sequestering carbon in the soil?   OR   A source of gaseous emissions creating nuisance and air quality concerns?

manure spreaderManure Benefits and Risks Depend on Location, Amount, and Timing

These above statements can all be true. Manure is a desirable plant fertilizer and has positive impacts on soil and soil health, but management decisions during land application influence the relative environmental benefit or risk resulting from manure. Timing, location, and amount of manure applied all must be carefully considered.

  • Manure application at amounts that match the nutrient requirements of harvested crops is the foundation of protecting water quality.
  • Preferred timing must balance multiple factors including timing of crop uptake of nutrients and probability of rainfall events following manure application.
  • Location must consider site specific field characteristics that influence environmental risks. Related Information: LPES Curriculum Lesson 33 and Lesson 34 include details on site selection.

Nutrient Management Plans

A nutrient management plan (NMP) is a document that spells out rate, timing, location, and other manure and fertilizer application factors.  The two nutrients that are watched most closely, relative to water quality, are phosphorus and nitrogen.

An NMP for any farm generally follows the same outline. Regulated or permitted operations will have the most specific requirements. In some states, even small farms are required to develop NMPs. There is a great deal of technical assistance available for developing  NMPs from extension, agencies, and private consultants. In some areas, cost-share assistance may be available. There are also many software tools available; one example is the Manure Management Planner Software. Since every state is different, it is recommended to look for state-specific resources and requirement before developing your NMP.

Amount of Manure to Apply

One of the first steps in developing an NMP is to estimate the amount of manure produced on a farm. Some other important pieces of information include: nutrient content as determined by a manure test (Related information: Sampling Manure) and the availability of nitrogen from that manure (consult your state extension service to obtain calculations on nitrogen availability appropriate for your area). Last, but not least, it is important to calibrate manure application equipment to ensure that you know how much manure was actually applied to each field.

Location, Location, Location

Manure application should be set back from wells, streams, lakes, sinkholes, or other environmentally sensitive features. Most states have rules dictating exactly how farm this setback should be.

Tile-drained fields should also receive special consideration with regard to manure application. If manure is applied while soils are saturated or right before a rainfall event, the manure may preferentially flow through tile drainage to water bodies.

Related Information: Manure Application in No-Till and the controversial topic of Manure Application to Legumes

Timing Manure Application

Manure application in spring, shortly before crops are planted, is generally recommended as it allows a short window where nutrients are prone to leaching or runoff. When manure is applied to fruit or vegetable crops, this recommendation may differ.

Manure application during crop growth will closely match nutrient needs, but can be destructive to the growing crop. One way to avoid crop damage is to apply liquid effluent through irrigation systems. (Also see Ohio research on top-dressing liquid swine manure to wheat and side-dressing on corn).

Applying manure in the fall, after the main crop is harvested, is a common practice and helps ensure manure storage structures are emptied before winter–reducing the chances of a overflow. Given the high price of fertilizer and the increased awareness of water quality, more farmers are following fall manure application with a cover crop.

Winter manure application is a controversial topic in many areas. Manure applied to snow-covered or frozen soils may be more likely to runoff under some conditions. Winter applications should only be made in order to prevent a manure storage overflow and should be done in low-risk areas with little slope or potential for runoff to water.

Evaluating if Nutrient Management Is Working

Whole Farm Nutrient Balance (WFNB) is a way to evaluate if the farm is currently accumulating more nutrients than are being exported from the farm. If this analysis is repeated from time to time, the trend can tell if a farm’s efforts are working or not. This website includes a dairy example and a swine example of WFNB.

Related information: Snap-Shot Assessments of Nutrient Use on Dairy Farms

Impacts of Feed Management or Manure Storage

Regional Topics

Economic Value of Manure for Land Application

Page Manager: Becky Larson, University of Wisconsin ralarson2@wisc.edu and Nichole Embertson, Whatcom Conservation District nembertson@whatcom.com
Reviewers: Rick Koelsch, University of Nebraska, Doug Beegle, Pennsylvania State University, Ron Wiedreholdt, North Dakota State University.

Photo: CC 2.5 Rick Koelsch

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Calculating Manure Application Rate

How much manure can I apply to this field? is a common question when developing a nutrient management plan for the upcoming year. This type of planning allows a farmer to ensure there is enough crop land available to adequately use manure nutrients, plan for manure storage emptying, or estimate commercial fertilizer needs to take advantage of lower pricing. Manure is a very good source of nutrients for plants and organic matter for soils. These nutrients have significant value if managed properly. This page describes the information needed to make these calculations. While the process may seem complicated, it is not difficult and provides an easy template to follow in future years.

How Many Nutrients Will the Crop Use?

The starting point for determining manure application is to calculate the amount of nutrients, especially nitrogen (N) and phosphorus (P), expected to be used by that year’s crop. To find the values recommended for your area, do a web search for “crop nutrient uptake” or “crop nutrient removal” plus your state’s name. If your search turns up empty, contact your local extension service for assistance. The following pieces of information are usually needed to use your state crop nutrient tables.

  • What is the crop to be grown?
  • What is the soil type in the field? (Not needed in all states.)
  • What is the expected yield for this crop?

A realistic yield can be determined by taking the 5-year average yield for this field and crop and add 10% (some states may recommend a different factor to add) to account for improvements in hybrids and farming techniques. If the 5-year average includes a disaster or exceptionally low yield due to hail, flooding, or similar situation, remove that year from the calculation. The crop nutrient uptake tables for your state will usually provide a factor to calculate nutrient need of the crop based on the expected yield.

Nitrogen Credits from Legumes and Past Manure Application

Organic-nitrogen from past legume crops or past manure applications continues to mineralize into crop-available nitrate-nitrogen for several years. To estimate how much nitrogen will become available from past manure or compost applications, see “Estimating Crop Nutrient Availability of Manure and Other Organic Nutrient Sources“. Legume credits recommended for your state can be found by doing a web search for “legume credit” plus your state name.

What Level of Plant Available Nutrients Are Already Present In the Soil?

In addition to organic-nitrogen that may be already present in soils, there may be plant-available nitrate-nitrogen already present. The best way to determine this is to do a soil nitrate test. To find recommended procedures and labs in your state, do a web search for “soil testing” plus your state name.

Phosphorus and potassium form past manure applications are mostly plant-available right away. If overapplied year after year (as can be the case with a field that receives repeated manure applications) the levels will build up over time. For phosphorus, this is a concern because of the potential for runoff to water. In some states, soils with extremely high phosphorus levels may be off-limits for further manure application (due to the relatively high phosphorus content of manure in comparison to nitrogen). Most states have developed a phosphorus index which is a risk management tool for avoiding fields or situations with greater potential for phosphorus runoff to water. If you are concerned that some of your fields fall into this category, see “What is the P Index?”

How Many Nutrients Are In the Manure?

Manure is highly variable from farm to farm. The nutrient content changes based on how is the manure collected, stored, and treated. It also varies by animal species. When doing pre-season planning, the best indicator of nutrient content in the manure is to look at past manure tests from your own farm. If you are doing your nutrient planning close to the time manure will be land-applied, then sampling manure in your storage will provide good information. As a last resort, planning can be done using “book values” or averages based on research and testing done in your state (do a web search for “manure book values” plus your state name).

It is impossible for plants to use applied nutrients with 100% efficiency, regardless if source is animal manures or commercial fertilizers. Studies have shown that nutrient use efficiency for nitrogen ranges from 30% to 75%, and is dependent on the crop, the specific nutrient, weather, and many other environmental factors. The goal of a nutrient management planner and waste applicator is to obtain the best use of the manure nutrients. This requires intensive management.

Nutrient Management Planning

Nutrient management guidance is typically done at the state level. General guidance may be available at a regional or national level from USDA Natural Resources Conservation Service (NRCS). You can also seek the advice of a local expert who is with the Cooperative Extension Service, land grant institution, state department of agriculture, or the state regulatory agency to obtain manure nutrient generation values relevant to the area, specieds, and system you are working with.

Tables that offer production volumes for manure as well as manure nutrient concentration are available for planning purposes, but should not be used to determine application rates on a daily basis. Frequent manure sampling is the only way to make a good assessment of manure nutrient value. Then, with data that relates to loss potential as it relates to manure application method and timing, one can make good recommendations as to appropriate application rates that assure maximum crop use efficiency and minimize losses.

Author: Karl Shafer, North Carolina State University

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Solid Manure Application Equipment

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How is solid manure applied to cropland?

The most common equipment for applying solids to the land is a rear-discharge, box-type spreader equipped with beaters that broadcast the manure over a width of several feet (see Image 1).

Usually, the manure is conveyed to the beaters at the rear by slats attached at each end to a sprocket-driven chain. Some use a powered front end-gate to push the material to the beaters at the rear. To handle semisolid manure, a tight-fitting, closable rear end-gate is required.

Some spreaders have a side discharge; most of these have V-shaped hoppers and feed the material to the discharge with augers. A rotating expeller slings the material out of the discharge port. The application rate is varied by an adjustable gate opening, usually operated by a hydraulic cylinder.

Flail-type spreaders have a semicircular hopper bottom and a rotating shaft with chain-suspended hammers to fling the material from the hopper. The flail-type and the side-discharge spreaders are adapted to both semisolid and solid manure.

Image 1: Broadcasting manure on cropland.

Manure spreaders may be tractor-drawn models or they may be mounted on a truck. Most tractor-drawn spreaders are PTO operated, but some are driven from the ground wheels. Some are hydraulically powered for greater speed variation, especially for the apron drive, to vary the application rate. In the past, spreader capacities varied from about 30 to 400 cubic feet with tractor horsepower requirements ranging from 10 to more than 120.

Recommended Reading About Land application of Manure

Land Application Equipment for Livestock and Poultry Manure Management

Authors: Jon Rausch, Ohio State University and Ted Tyson, Auburn University.

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Liquid Manure Application and Irrigation Equipment

Liquid manure application to crop land

Direct injection of liquid animal manure
Direct injection of liquid animal manure

Liquid animal manure is land applied using liquid manure tankers or irrigation equipment. Liquid manure tanks are frequently pulled, much like a wagon, behind a tractor or mounted on a truck or other power source. Pull type tanks range in size from less than 1,000 gallons to over 8,000 gallons. Those that are mounted on a truck are generally between 3,000 and 6,000 gallons. Truck mounted tankers make over the road travel quicker and safer.

Drag-line direct injection of animal manure
Drag-line direct injection of animal manure

Liquid manure tankers generally discharge manure from the rear of the tank on the soil surface. Alternatively, various types of soil incorporation tools may be used and are generally mounted directly to the tanker. Manure from the tank is distributed through a series of hoses and discharges through the soil incorporation tool. Soil incorporation of liquid animal manure can minimize odors and conserve nutrients.

Irrigation of wastewater by hard hose traveling gun
Irrigation of wastewater by hard hose traveling gun

Land applications by sprinkler irrigation or by a drag-hose, tractor-mounted applicator are the current practical methods of applying large volumes of lagoon effluent or contained lot runoff. Drag-hose applicators can decrease odor problems and the loss of ammonia nitrogen to the air by incorporating the manure. The advantages of sprinkler irrigation include reduced cost because of lower energy and labor requirements.

Lagoon wastewater applied by pivot irrigation for hay production
Lagoon wastewater applied by pivot irrigation for hay production

Labor requirements can be further reduced by permanently installed underground pipes to sprinkler risers, center-pivot irrigators or hose attachment points for traveling guns or drag-hose applicators. However, land application of manure slurry and lagoon effluent with irrigation equipment requires a higher level of management than other methods of spreading to avoid pollution and nuisance problems.

Recommended Reading on Liquid Manure Application and Irrigation Equipment

Authors: Jon Rausch, Ohio State University and Ted Tyson, Auburn University

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Costs of Manure Application and Transport

When talking about the value of manure, costs are reported in terms of dollars. While reporting in terms of dollars is usually helpful, it is not the only metric for discussing costs. Any resource that is required to accomplish a task can be considered a cost. With this in mind, this page will discuss the cost of manure distribution in terms of dollars and time. The limiting resource, dollar cost or hours required, determines how manure is distributed. Hours could be converted to dollars but that would possibly obscure the management of these costs.

Factors Influencing Cost of Manure Management

The three major activities that influence the cost of manure management are loading, transporting and land applying. Each activity can require its own specialized equipment and can constrain the use of the manure. For example, except for an external manure storage structure, loading is best done when animals are not present and thus limited to those time periods. Transportation can be time consuming depending on the distance traveled and the amount of water hauled in the manure. Land applying requires proper soil and plant conditions and specialized equipment.

Livestock manure is either liquid, slurry or solid. Different types of manure will have different impacts on the cost of distribution. For example, solid manure can usually be hauled farther for less money because less water is being transported. Liquid manure, because of its high water content, can’t be transported as far but low cost irrigation systems can be used to distribute it relatively inexpensively. This page will address each manure type separately. Because the dollar cost of managing manure is so dependent on location, type of livestock, form of manure, availability of land, etc. No dollar estimate will be given in this page. The quickest way to get a cost estimate would be to contact a custom manure hauler and ask the price charged for different services.

The table below summarizes the relative costs of manure application and distribution. When reading it, compare the costs within a column, rather than within a row. In other words, use it to compare the cost of loading, transportation, or land application for each type of manure. The more dollar signs ($) a manure type has, the more expensive it is relative to the other types of manure. Click on a type of manure in this table to be taken to a description of why different manures will have different costs.

Summary of Manure Application and Distribution Costs
Manure Type Loading Transportation Land Application
Solid Manure      
Fresh $$ $$ $$$
Stockpiled $$$ $$ $$$
Slurry Manure      
Tanker $ $$$$ $$$
Dragline hose $ $$$ $$
Liquid Manure      
Dragline hose $ $$$ $$
Irrigation system $ $ $

Custom application

Because much of the equipment used in manure application is unique to manure application, many livestock producers choose to not own the equipment but rather hire custom operators to handle their manure. Custom operators can lower the cost of manure management, relative to owner operated equipment, by spreading the cost of expensive equipment over more units. Many custom operators can also apply the manure more quickly due to experience and because they have larger equipment or multiple pieces of equipment. Because they work for many livestock producers, they may not be able to apply an individual’s manure at opportune times. This uncertainty of when the manure will be applied is a cost that needs to be taken into account. Contracting Certified Manure Haulers contains instructions for comparing custom hauling with producer hauling of manure.

Livestock manures are an excellent source of organic nutrients. However, they are generally more expensive to transport and land apply than more concentrated commercial fertilizers. The cost of manure transport and distribution are critical to understand and manage in order to derive maximum value from manure. A research project completed in the late 1990’s includes this information. The actual costs presented may no longer be relevant but the conclusions are still valid.

A spreadsheet to estimate the cost of hauling various types of manure can be obtained at University of Missouri.

Related Web Pages

Authors: Ray Massey, University of Missouri and Josh B. Payne, Oklahoma State University

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Costs of Slurry Manure Application and Transport

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Manure Value and Economics

Livestock such as dairy and swine often have slurry type manure. The manure is liquid but does not flow easily. It is either stored directly below the animal pens, or scraped or pumped periodically into a holding pen outside of the building.

Loading Slurry Manure

Loading slurry manure is accomplished with a pump powered by a tractor or stationary engine. The slurry can be loaded into tractor-pulled or truck-mounted tankers, or pumped through a hose attached to a tractor that applies it as it is being pumped from the pit. The cost of loading slurry is usually low because the pump can do it quickly and the volume per animal is not usually high.

Slurry Manure Transport

Transportation of slurry by tanker can be expensive because a lot of water is being transported and the same equipment that is hauling the slurry is usually land applying the slurry. When tankers are used, the number of hours spent transporting the slurry is frequently the limiting cost. The land may become unavailable to receive the slurry, due to crop planting times or soil conditions, before all of the slurry can be land applied. Often, the distance transported is limited so that the time constraints can be met.

If the slurry is pumped through a hose to the field, the transport time is negligible. As the slurry is pumped, it is simultaneously injected or surface applied to the land. The important cost becomes the cost of purchasing pipe and hose that is sufficient for this method of land application.

Land Application of Slurry Manure

The cost of land application of slurry varies with the type of equipment used. Tankers can be expensive to own unless they are used for many animals on many acres. There is a definite economy of scale with tankers. Additionally, the tankers usually require fairly large tractors or trucks. If the livestock owner does not have a cropping enterprise that requires the large tractor, ownership of the tractor for manure distribution alone becomes expensive.

Tankers are economical for large-scale operations with slurry manure.

When slurries are applied via hoses (called dragline hoses), a tractor pulled distributor is used to move the hose around the field so that the slurry is evenly distributed. The cost of the equipment can be very expensive, but the amount of time is decreased considerably compared to using tankers because most of the time is spent in applying the slurry. Very little time is spent getting into and out of the field, as is the case when using tankers.

Authors: Ray Massey, University of Missouri and Josh Payne, Oklahoma State University

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Costs of Solid Manure Application and Transport

Poultry litter and beef feedlot manure are the most common types of “solid” manure. Separated solids from dairies can also be a source of solid manure. Solid manures must be scraped off the floor of the pen or house where the animals were raised. Scraping and loading onto trucks usually is done with a front end loader. If the manure is not land applied at the time the pens are cleaned, the manure can be stockpiled until needed. Poultry litter, in particular, when stockpiled is stored in covered sheds. The cost of the storage shed is an additional cost to manure loading.

Transport Costs of Solid Manure

As previously mentioned, solid manures are the least expensive to transport because most of the bulk transported is dry organic matter containing fertilizer nutrients (N, P and K). Water has little value in manure and adds a lot of weight that costs money to transport. Often, the manure is loaded into transport trucks that haul it to the receiving field, where it is unloaded and then loaded into an application truck.

Land application of solid manure. CC 2.5 Charles Fulhage or Joe Harner

Land Application of Solid Manure

Land application of dry manures is done with a flail type spreader. The manure, as it comes out of the truck-mounted or tractor-pulled spreader box, is flailed out in small pieces onto the surface of the soil. The spreader box is usually a specialized piece of equipment that can be expensive unless it is used to spread a lot of manure on many acres. If the manure needs to be incorporated into the soil, the cost of disking the manure into the soil could also be considered a cost of manure management.

Transportation Cost Assistance

To encourage appropriate use of the nutrients in manure, several government programs subsidize manure management costs. These programs can help reduce transportation costs, increasing manure value as it is more fully utilized as a soil amendment/fertilizer where it is most needed.

Examples of assistance include:

  • subsidy programs in Oklahoma and Arkansas that assist in moving poultry litter from nutrient sensitive watersheds to nutrient deficient areas;
  • loan guarantees to producers purchasing appropriate manure transportation equipment in Missouri;
  • USDA Environmental Quality Incentives Program (EQIP) that cost shares on certain manure investments depending on the priorities of each individual state.

Potential applicants for assistance programs could contact their local USDA Natural Resources Conservation Service office and state Departments of Agriculture or Environental Quality.

Authors: Ray Massey, University of Missouri and Josh Payne, Oklahoma State University

Page reviewers: Alan Lauver, NRCS and Chandra Theegal, Lousiana State University

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Costs of Liquid Manure Application and Transport

Livestock and Poultry Environmental Learning Center:

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What Systems Produce Liquid Manure?

Liquid manures are most common with pork production where the manure is flushed from the building and stored outside in lagoons. Liquid manures are mostly water with some organic matter and nutrients suspended in the water. Most of the organic matter decomposes in the lagoons and is not removed.

Options to Haul and Apply Liquid Manure

While some livestock producers haul liquid manure in tankers, it is usually considered cost prohibitive. The amount of water is so great that the hours spent distributing it and the resulting dollar cost exceeds the value of the manure supplied nutrients when using tankers.

Liquid manure is usually pumped through pipes and hoses to the land that will be accepting the manure. This means that loading costs and transportation costs are relatively low. Once the manure is at the field, it can be applied with a tractor that pulls the dragline hose through the field or via an irrigation system. The irrigation system can be a stationary sprinkler or a single big gun sprinkler that must be moved periodically by the operator.

Liquid manure can be land applied with a dragline hose.

Other options include, a big gun sprinkler or a center pivot irrigation system that move automatically through the field. The center pivot irrigation system is usually too expensive to own just for liquid manure distribution; it is usually part of an irrigation system that also pumps clean water. The stationary and big gun sprinklers are inexpensive and easy to use.

Authors: Ray Massey, University of Missouri and Josh Payne, Oklahoma State University

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Nutrient Planning on Small Farms

livestock and poultry environmental learning center logo with cow, pig, and chicken sillhouettes over a map of the U.S. with three circling arrowsThe LPE Learning Center hosted a webcast on Nutrient Planning on Small Farms in June, 2008.

Positive Impacts of Manure

When managed properly, manure can be a valuable resource on a farm. Manure can be a source of nutrients for crop production and improve soil quality. The organic matter present in manure can improve both tilth and water holding capacity of the soil. Livestock and poultry manure is a valuable fertilizer for crop and pasture production. Most farm owners do not realize the value of the manure that is produced on their farms.

Negative Impacts of Manure

When not managed properly, manure can pollute the environment; mainly as ground or surface water pollution due to the nutrients nitrogen (N), phosphorus (P), and carbon (organic matter). In addition manure can lead to air quality concerns, pathogens in water supplies, odors, dust, and the presence of vermin.

Manure Nutrients

Manure nutrients can be beneficial for the soil and plant growth; however, manure application rates should be based on plant growth needs. Excessive manure application to the soil can result in nutrient leaching and increased losses through runoff. In addition, manure contains soluble salts and minerals such as arsenic, copper, and zinc which in excessive amounts may negatively impact the soil quality.

Manure nutrients, (N, P, and organic matter) can be major pollutants in lakes and estuaries as well as rivers. Nitrogen and phosphorus attached to soil particles may reach waterways through surface runoff or wind deposition. Dissolved N and P may leach through the soil, ultimately reaching water bodies. Organic matter can enter water bodies in the form of manure, vegetative matter, or animal carcasses. Waters rich in minerals, organic matter, and nutrients promote a proliferation of plant life, especially algae. This process is called eutrophication. Algae growth and the decomposition of organic matter in water bodies reduces the dissolved oxygen content of the water, which may lead to the death of aquatic life.

Pathogens and Vermin

In addition to the concerns regarding nutrients, pathogens may be present in manure. Some examples of the pathogens are E. coli, Salmonella, and Cryptosporidium parvum. These pathogens can impair water bodies and potentially pose human health risks when manure or contaminated water comes in contact with food sources. Flies and rodents are other manure related concerns on livestock farms. These problems can be minimized by proper design of animal housing and manure storage, and proper handling procedures when turning or moving manure piles.

Air Quality

Air quality concerns arise from odors, particulate matter, and aerial pathogens. Ammonia released from manure can result in odor and may react with other compounds in the atmosphere producing particulate matter (PM 2.5) which can affect the environment and public health. There are a variety of other compounds released from manure such as hydrogen sulfide, green house gases (methane and nitrous oxide), and some volatile organic compounds that can also cause air quality concerns. Particulate matter that arises from dust and reaction of ammonia with other compounds in the atmosphere are also a concern.

Why Implement Nutrient Management Planning?

The purpose of nutrient management is to implement practices that permit the efficient use of manure for crop production while protecting potential environmental damage that may be caused by nutrients. Nutrient management planning is a site specific exercise; and, if the recommendations are followed, nutrient losses should be minimal. In general, nutrient management considers the nutrients available on a farm, how best to use them, and the potential impacts of the nutrients on the environment. Factors typically considered in nutrient management planning are: goals of the farming operation as well as any constraints; available farm resources (land, equipment, financial resources); potential critical areas on the farm (sensitive water bodies, neighbor concerns, erosion, manure storage); and nutrient balance analysis (shown in the figure below).

 

Recycling

CC2.5 Mike Westendorf

Farm nutrient inputs consist of animals, feed, fertilizer, legume nitrogen, and bedding. Outputs are animals, milk, meat, eggs, manure, and crops. Recycling also occurs on the farm with nutrients moving from feed through livestock, applied to soil, utilized by plants, and back to feed again. The optimal goal (Whole Farm Nutrient Balance) is for the farm to remain in balance between inputs and outputs without losses as runoff or leachate from either the soil or manure. Soil can store some nutrients assuming that the amount of manure applied to the soil is not excessive.

 

Small Farms are Different than Large Farms

The challenges of managing manure nutrients are different on a small farm than on many larger farms although the principles are similar. Small farms have fewer animals and sometimes several animal species on the same farm. They also may have limited acreage and/or lack equipment for spreading manure. The nutrient management planning section provides information on feeding animals and managing their diets; manure production; basic soil science and soil fertility; and nutrient (manure) management. The section details on- and off-farm use within the context of a nutrient management plan.

The following articles are coming soon!

  • Basic soil science and fertility
  • Nutrient management on the farm
  • Crop utilization
  • Nutrient management plans
  • Off-farm utilization
  • Soil and manure testing
  • Record keeping

Additional Resources

Nutrient Management–SIMPLIFIED! by Randall James, Ohio State University Extension

Authors: Jactone Arogo Ogejo, Virginia Polytechnic Institute and State University (Virginia Tech) and Michael Westendorf, Rutgers, The State University of New Jersey

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Estimating Crop Nutrient Availability of Manure and Other Organic Nutrient Sources

All manure should be applied at the rate and time that assures maximum utilization of the nutrients by the crop.  Manure testing will provide the quantity of manure nutrients, but during storage and after land application, there are many factors that affect how much will become available to the current crop.

Locating State-Specific Manure Nutrient Availability Information

Most states or regions have developed tables for estimates of mineralization rates based on the common types of manure handling methods, typical manure application windows, and typical environmental conditions that affect mineralization. These tables can vary significantly from state to state. The following options can help you find the resources based on research in your state:

    • Contact your local or state extension service
    • Do a web search for “manure nutrient availability” plus your state’s name and select extension publications (.edu addresses) from the list
    • State Specific Nutrient Management Resources

The sections below will discuss common calculations and rules of thumb.

Organic Forms of Nutrients and Mineralization Rates

Not all of the nutrients in manure are directly plant available. Organic forms must be mineralized into inorganic, or “plant-available” forms–such as nitrate. The rate of this mineralization changes depending on soil type, moisture, temperature, manure composition, and other factors. Researchers continue to improve and refine predictions, but it is still necessary to use assumptions and estimates when defining mineralization rates. Organic forms of nitrogen will continue to mineralize and become available to crops in years 2, 3, and even 4 after the initial application. Most availability tables will provide calculations to use when calculating nutrient availability in subsequent years.

Environmental Losses of Nutrients

There are some inherent losses of nutrients to the environment during and after manure application. The three macronutrients, nitrogen (N), phosphorus (P), and potassium (K), each have unique characteristics with respect to expected losses. These losses vary by manure application method (sub-surface injection versus surface application).

Nitrogen is the most dynamic nutrient when it comes to potential loss. Some of the N in manure is in ammonia form or is readily be converted to this form after application. Ammonia is volatile (quickly changes to gas and disperses to the atmosphere) and losses of ammonia from land-applied manure can be significant. Many of the state availability tables (referenced previously) have coefficients describing ammonia and other nutrient losses based on animal species, manure handling system, and manure application method. Some states will vary the N-availability tables for ammonia based on the time (usually hours or days) after manure application if the manure has been left on the ground surface.

Manure Collection, Storage, and Treatment Losses

How manure is managed on the farm will affect the nutrient availability once land applied. The more highly treated or processed the manure is, the more the nutrients are bound up chemically or organically and the less plant available they become. Some treatment and storage processes enhance organic nutrient development whereas others decrease it.

Composting manure is a treatment that results in a high degree of manure processing with a high resulting level of organic nutrients. Thus, the nutrients (especially nitrogen) are usually much less plant available at the time of application and must be mineralized over the course of several years to become plant available. Some forms of solids removal, including chemical flocculation or precipitation, also result in manure nutrients being physically or chemically tied up and thus more slowly plant available.

Manure composting with old hay. CC 2.5 Karl Shaffer.

Timing of Manure Applications

Manure application is generally scheduled to accommodate the crop planting and harvesting schedule. The size of manure storage may also factor in to the timing of manure application. Occasionally, lack of storage can require that manure be applied at times that are less than ideal for maximum crop nutrient uptake.

Organic nutrients applied in the spring will have a higher mineralization rate than the same nutrients applied during the fall. A nutrient management planner should apply the appropriate mineralization rate coefficients for these application periods. Fall applications could result in nutrient losses if they are simply pre-plant applications for the following spring. The nitrate form of nitrogen is very mobile in the soil and subject to leaching losses. Depending on the climate, significant conversion of ammonia to nitrate may occur, with subsequent leaching of nitrate.

Availability of Nitrogen (N), Phosphorus (P), and Potassium (K)

Nitrogen is the most dynamic of the three macronutrients. Availability factors for P and K are fairly consistent between states because these nutrients have minimal loss potential with volatilization or leaching (as compared to N), and they remain relatively stable in the soil. Most regions of the US show that 80-100% of the P and K in manure is considered plant available.

There are many factors that ultimately affect the amount of N that will be plant available. Manure management and application method, as stated above, are two of the key factors. Other factors are mineralization and volatilization factors. These are determined by the environmental conditions at the time of manure application (air temperature, humidity, wind, soil temperature, soil C:N ratios, etc.).

Because N dynamics have many variables, several factors can be applied to the manure N analysis to assess its availability for crop use. Some states assign a flat 50% ammonia loss factor for manure that is surface applied without incorporation. Some states will segregate these factors based on time of year. Others will apply an increasing scale of volatilization (hence a decreasing scale of availability) depending on how long manure sits on the soil surface before incorporation.

Typically, volatilization losses are assumed to cease after 7-10 days. Depending on the state, manure application method, manure type (animal species), and handling system, nitrogen availability can range from 10% to 95%. Producers that wish to minimize N losses (maximize the manure value) will use application methods such as injection or immediate incorporation.

Author: Karl Shaffer, North Carolina State University

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