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Lagoon supernatant can be irrigated onto standing crops in some situations
<p> Lagoon supernatant can be irrigated onto standing crops in some situations, using a lower per-gallon application method than injection. Eventually, the lagoon sludge, a higher-phosphorus material, needs to be removed by agitation (floating agitator shown) and pumping, or mined off the bottom of the lagoon by a floating dredge.</p>

Outlining Nutrient Management Plans

When a swine producer is first confronted with the need for a nutrient management plan, his reaction might be: “Bottom line, what do I have to do?”

Once he learns that a nutrient management plan has less to do with swine nutrition and more to do with tracking the crop nutrient ingredients in manure, he may be tempted to tune out the nutrient management message, concentrating instead on feeding and caring for his animals.

But it’s all connected — from feed management to manure collection, storage and land application to crop uptake. It’s a system that works together and demands attention from start to finish.

Downstream, the ultimate goal of nutrient management is to keep nitrogen and phosphorus — potential pollutants of surface water — in the root zone for use by crops and out of public waters. Every swine facility needs a workable nutrient management plan (NMP).

A good NMP for your livestock facility:

• Optimizes the use of feed nutrients to the animals, properly balances diets for animal performance and works to reduce excretion of nitrogen and phosphorus in manure.

• Recognizes and improves crops’ use of principle plant nutrients and micronutrients in manure.

• Protects the environment, especially water quality.

• Provides a structured base for discussion of management practices between the producer and other interested parties.

Streamline Your Plan

The nutrient management plan is far more complicated for a livestock facility than for a crops-only farm. Because of the complexity, a major task for producers implementing an NMP is to find ways to streamline the plan and its maintenance to properly manage the process.

But be sure all the necessities are in the plan. State and/or federal requirements dictate threshold facility sizes for the respective manure management plans and the details that are required. Larger facilities and outdoor manure storage usually mean more complex nutrient management plans. Find out how your facility fits into your state agencies’ capacity schemes and whether you can simplify your plan.

Some integrators or production systems already do an excellent job of writing plans for their member farms, but even the professional plan writers in production systems tend to have a blind spot or two.

 Compliance Checklist

Given the need to be thorough and identify a complete nutrient management plan that fits your situation, begin by getting familiar with your state’s requirements. The National Pollutant Discharge Elimination System (NPDES) plan for concentrated animal feeding operations (CAFOs) thoroughly spells out minimum regulatory requirements for the NMP. States promulgate their own rules to implement the regulation.

Next, if you have a Comprehensive Nutrient Management Plan (CNMP) as part of a contract with your state Natural Resources Conservation Service (NRCS), it is also very specific about the records and annual updates required. The producer has certain responsibilities in regularly maintaining the types of NMP mentioned above, and these are spelled out by the respective agency.

Even if you are not required by a regulation or contract to have an NMP, you still can and should build a plan to cover the main features for your operation.

The two most important functions in maintaining a valid NMP are:

1) The year-to-year basic balancing of manure nutrients to crop requirements, and

2) Keeping good records.

The responsibility for keeping the necessary records, updating calculations and sending in routine reports often lies with the on-site operator. A plan that sits on a shelf and is never updated soon has little value.

Ask yourself: Are the right people involved and committed to making my plan work? Neglect maintaining your plan and you will likely over- or under-apply plant nutrients for your crops. There are other consequences. You could:

• Lose funding under an Environmental Quality Improvement Plan (EQIP) contract,

• Face penalties under the NPDES CAFO program, and/or

•  Lose legal protection under the Agricultural Stormwater Exemption in the Clean Water Act.

Establishing Value

Manure’s value is not limited to the available nitrogen (N), phosphorus (P) and potassium (K) it contains. Manure also supplies water, micronutrients and organic matter, which makes manure a great soil builder.

However, pricing manure to crop producers is often based on N, P and K contents shown in sample analyses obtained from the testing laboratory. Commercial fertilizer replacement cost is a common method for striking a starting price for negotiation. Since manure comes as a package of blended nutrients, it’s not always fair to call the composite price for manure the sum of its parts. Whenever a target crop field would not otherwise be supplied with a commercial fertilizer nutrient, that nutrient component should be devalued in the manure’s price.

For example, if manure is to be spread on a field where the soil-test phosphorus is above the agronomic optimum for crop production, then the phosphorus in the manure shouldn’t be priced in the package. Raising the phosphorus test of the field by applying unneeded manure phosphorus may actually be a liability.

Another example is pricing the nitrogen in the manure when the product is going on a field where a legume crop, such as soybeans, will be planted. While the legume may preferentially use the nitrogen supplied in manure, the crop could have fixed its own nitrogen from the atmosphere. In that case, commercial nitrogen would not have been purchased if manure had not been applied.

Manure Choices

Based on the criteria above, the producer supplying manure to crops has two choices:

1) Supply the entire blended package and devalue one or more nutrients as appropriate, or

2) Use storage management and/or technology to partition the manure nutrients to better fit crop needs.

Given that most producers will go with the first option, fields for manure application should be prioritized according to soil type, soil fertility, crop rotation, hauling distance, application rate and, of course, the environmental sensitivity of the field and its perimeter. If you have a choice, apply manure on fields that have:

• Lower soil erosion risk, so there’s less chance of nitrogen and phosphorus moving off-site with runoff;

• Low to moderate soil fertility — capture all of the value of the nutrient package plus the organic matter;

• Deep-rooting crops with high-nitrogen uptake potential, reducing risk of nitrate leaching to groundwater or into drainage tiles; and

• Crops able to take best advantage of the balance of nutrients in the manure package that you will deliver.

Water Management

Make water work for you, not against you. Don’t give up valuable manure storage to otherwise clean water, such as drinking water wastage, rainwater or snow melt that could otherwise be kept out of the system.

Even under-floor pits can lose storage capacity due to drinking water wastage or roof water that is not properly drained away from the foundation. Certainly, the outside structures are vulnerable as well.

If the data on extreme weather events are any indication, the minimum amount of manure storage needed on a given-sized farm today is greater than was needed in the 1980s. Keeping water clean reduces manure hauling and application costs and gives more insurance storage volume in the face of extreme weather events and those abnormally wet seasons when farmers are usually in the fields applying manure.

Speaking of water, when is there an advantage of two manure streams vs. one? After all, manure is mostly water.

Some manure storage systems, such as anaerobic lagoons, have inherently dilute nutrients (i.e., lots of water). Some nutrient partitioning occurs due to stratification in the lagoon; phosphorus and some of the organic nitrogen tend to settle into the bottom sludge layer, leaving a relatively nutrient-poor solution/suspension in the supernatant that can be irrigated onto growing crops using a fairly high gallons-per-acre rate.

Actually, the nutrient value of lagoon supernatant is so low per gallon of liquid that it is difficult to justify using expensive injection methods to land-apply it. Sprinkle irrigation is the ticket.

Short on acres to spread manure? Don’t discount the opportunities afforded by irrigation of dilute wastewater onto crops like perennial grasses, which can take up huge amounts of water in the growing season, while alleviating runoff concerns. Again, it’s about water management; know your system and know whether your storage capacity is vulnerable to extreme rainfall events.

While the producer is enjoying the lower per-gallon application of supernatant via irrigation, the sludge in the lagoon — the second manure stream — eventually builds up over a period of several years to a depth requiring removal. At that time, the sludge can be agitated and pumped out with the supernatant or it can be “mined” from the bottom using a floating barge. Either way, one would plan for the more concentrated nutrients to be spread over large areas during that infrequent de-sludging process.

It takes more than just settling in a tank or lagoon to attain more aggressive partitioning of the manure nutrients in order to balance them to crop needs or to sell one or more components.

Partitioning out nutrients from swine manure is not a simple process. Do your homework before investing in a technology that turns one manure stream into two streams or more. The most common goal for swine producers would be to separate much of the phosphorus from the liquid manure; the per-gallon cost is fairly high but may still provide bottom-line benefits.


An in-cab flowmeter linked to GPS provides a convenient method of performing equipment calibrations and keeping a close check on manure application rates.


Testing Manure in a Drought Year

Build your manure-sampling history for the farm using the highest-quality samples available. Manure samples pulled during land application are best, but to calculate an application rate for manure coming from a storage that doesn’t have a history, get a composite sample that represents your pumping strategy for the storage. If a manure storage structure will be agitated, take samples top to bottom. If liquid will be taken from the non-agitated middle or top, sample appropriately. See the bulletin from Midwest Plan Service MWPS-18 Section 1, “Manure Characteristics” for sampling method recommendations (

The nutrient management plan question we all dread and tend to avoid in a drought year is this: How do we account for nutrient uptake by the crops, especially nitrogen and phosphorus?

We try to supply nutrients based on the expected yields of those crops. So, following a year when yields were low, we tell ourselves that 1) we supplied more nutrients than needed, and 2) the nutrients are left over for next year. This throws a wrench in our plan for the next cropping season.

Following a “checkbook approach” to nutrient management would tell us to back off on the manure application rates for 2014 if the fields received normal rates in 2013 and had far below-normal yields. There should be nutrients left in the soil and available for the 2014 crop.

For farms using only commercial fertilizer, the purchased materials could be reduced. That could save money on inputs.

However, livestock producers who are depending on limited acreages for manure application (i.e., nutrient application rates via manure are already at the limits of normal-year crop update recommendations) have to face both the practical and regulatory ramifications of “staying the course” with average-year applications vs. some ratcheting back of application rates.

The best advice is to follow state land grant university soil fertility recommendations and be aware of state NRCS and/or regulatory agency guidelines for nutrient applications following a crop disaster year. In most cases, continue applying for the average expected yields of crops with the disaster year taken out of the yield-average calculation.

Last fall, University of Illinois crop scientists, with some extensive volunteer-supported soil-nitrate sampling from corn fields across the state, reestablished just how uncertain nitrogen accounting is (College of ACES, Dec. 6, 2012, “First results from the Illinois Soil Nitrogen Monitoring Project”). To access the university bulletin, go to Their hypothesis was that drought-stricken corn yields would leave lots of unused nitrate in the soil, and sampling would verify that. However, the sample results yielded a series of scatter plots and no clear trend no matter how the data were analyzed. Weather, soil moisture history and crop uptake patterns all confused the picture and confirmed once again that, in the words of the late University of Illinois soil scientist Ted Peck, soil nitrogen prediction “is a crap shoot.”

Regular soil testing for other nutrients besides nitrogen still yields useful data, and soil tests are essential for planning applications of manure and commercial fertilizer. Know what your soil tests are for all fields receiving manure. Know your state university’s latest recommendations for optimum soil nutrient levels (especially phosphorus and potassium). And know the maintenance requirements for crops.

The test results and long-term soil test history are also a required part of any NMP, as the phosphorus test in particular is one piece of the environmental risk assessment for crop fields targeted for manure application.

Your state land grant university is usually the best source for soil testing protocols; issues such as test frequency, grid size or soil management zones, soil test depth, and seasonal and crop rotation timing, are spelled out.

Keep Current

States regularly update their nutrient management standards to reflect and refine the federal NRCS standard requirements. As a livestock producer, stay abreast of changes in your state, since the NRCS Nutrient Management Practice Standard 590 may be referenced by your state’s regulations and is certainly a built-in requirement for any Environmental Quality Incentives Program (EQIP) participation that involves a CNMP.

The University of Illinois is on the verge of releasing new soil fertility recommendations for corn based on higher yields and more efficient plants. Until recently, Illinois had used some long-standing nutrient maintenance level tables for common field crops. The tables made it easy to run the numbers on manure application rates and decide, based on soil tests, whether to operate on a nitrogen- or phosphorus-limited application.


If you are new to nutrient management planning, consider hiring a professional to help build your plan and devise the regular recordkeeping needed for an efficient, defensible document.


Recognizing the focus on phosphorus and nitrogen pollution potential, researchers took another look at modern corn crop response to phosphorus and they revised downward the per-bushel maintenance requirement.

In short, today’s crop varieties are more efficient in their nutrient use. The same message has been sent out by several states in the region about nitrogen needs for corn. Language in the national NRCS 590 standard suggests the state land grant universities are the last word in crop nutrient removal rates, so producers applying manure on corn fields need to look for more acres on which to spread manure.

Additionally, they should explore ways to reduce animal excretion rates of phosphorus in manure compared to nitrogen to provide a better-balanced nutrient package. Synthetic phytase in swine diets has been a real help. Finally, partition the nutrients in ways that optimize the manure placement on cropland.

Your NMP might be due for major changes if your state’s nitrogen and/or phosphorus crop nutrient requirement figures are being ratcheted downward.

Precision Ag for Livestock

Simply put, with manure application, there are more variables than with commercial fertilizer but less control.

In many regions, the environmental pressures are greater on livestock producers than on crops-only farms. One technology that is available now is GPS-based, as-applied mapping of your manure application. Being able to show where manure has been applied and the setback areas — manure “no-fly zones” — is very important to defending your NMP. This is one of the simplest applications of precision agriculture, but one to definitely explore.

Technology Watch

What about nitrification inhibitors and nitrogen stabilizers? The nitrogen in fall-applied manure is at risk of loss from the soil root zone before the crops get a chance to use that valuable nutrient in the growing season. Warm, wet soils in the fall provide favorable conditions for nitrogen loss through a biological process known as nitrification.

High prices for commercial nitrogen products drive demand for additives known as nitrification inhibitors. Those additives are touted to slow down the transformation of ammonium nitrogen to nitrite and nitrate, thus conserving even fall-applied nitrogen in the soil for later uptake by plants. Companies have made manure-compatible versions of the products available for use in the livestock industry. It is very difficult to validate the claims made for these products because nitrogen accounting is tough in a real cropping system and because of all the variables that affect nitrogen transformations and uptakes from year to year.

However, there is a growing body of field-trial research — mostly results of crop yield responses — that is being used to support the use of these products in manure.

Questions to ask regarding these products in your NMP:

• Since manure is often applied at the annual nitrogen-limited rate on cropland, and nitrogen is supposedly being conserved by the product(s), how much should the manure application rate be reduced in order to meet regulatory requirements?

• Some nitrification inhibitor products are meant to be applied on a per-acre basis but are mixed by agitation in the pit prior to pumping. How does the applicator ensure an adequate amount of product?

• How does one justify performance of these products?

Cover Crops

Cover crops are mentioned in the new national NRCS 590 standard as a way of reducing winter-season soil erosion while cycling nutrients within the cropping system.

While the use of cover crops is far from being a new concept, there are new pressures for adopting cover crop strategies. Improved varieties for certain regions and applications may bring cover crops to economic viability in some operations. Groups such as the Midwest Cover Crops Council ( have established guidelines and sets of practices appropriate for producers in their regions. There may be a place for them in your operation.

Mobile-phone applications (mobile apps) for NMP nutrient balance calculations and field records are becoming available and should help streamline your plan. Remember, always be on the lookout for ways to make your NMP easier to maintain, more useful and more defensible.

Sampling Technologies Needed

It’s one thing to know how much liquid manure per acre you are applying, but it’s quite another to know the nutrient application rates.

Usually we apply manure based on the assumption that we know what’s in it. But nutrient content varies quite a bit, and we are concerned with primary plant nutrients that are in ratios that change as we pump down manure storage and apply the manure onto cropland.

What’s needed is a reliable, in-line nutrient meter for on-the-go measurement and control of the actual nutrient application rates, not just the liquid rate. We can’t expect every load of manure pumped from even a well-agitated pit storage to be the same; the first loads out are not as concentrated as loads from the bottom.

Another example is the lagoon agitation or dredging operation, where a lot of acres are covered in an infrequently performed pump-down and application process. At the time of de-sludging the lagoon, the nitrogen:phosphorus balance of the liquid coming out of the storage is really out of whack with year-to-year experience. An automatic control on the applicator could adjust the rate based on the nutrient application goal. We are still waiting for that technology.


Pork producers are busy people. Not many get into the business to manage manure. But many ask the straightforward question: “Just give me the bottom line—what do I have to do?”

Get a template and learn the basics. Keep records. Figure out how to streamline the process so it becomes second nature. Make it an asset, not a distraction. Hire a professional, a registered technical service provider if you need one. By all means, have an appropriate, up-to-date nutrient management plan for your swine


You might also like:

The Three P’s of an NMP

Properly Calibrate Equipment

Return to Maximizing Manure's Value

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