Manure management plans: what goes in one, and where pit and lagoon treatment fits
By PitCharger · Published
A manure management plan documents how much manure an operation produces, where it is stored, how it is tested, and how much goes on which fields and when. Nutrient management plans and NRCS comprehensive nutrient management plans (CNMPs) cover the same ground with different scope. Which one you need depends on your state, your size, and whether you hold a permit or take cost-share.
Rules change and vary by state. Everything below is a plain-language summary of published agency and extension material, not legal advice. Check with your state agency and your local NRCS office before you act on any number here.
What is the difference between a manure plan, a nutrient plan, and a CNMP?
The names overlap, and it trips people up. In plain terms:
- Manure management plan. The term several states use for their required plan, Iowa and Minnesota among them. It focuses on manure production, storage, testing, and where and how much gets applied.
- Nutrient management plan (NMP). The term in the federal CAFO rule and in NRCS Practice Standard 590. NRCS describes nutrient management as managing the amount, source, timing, and placement of nutrients while limiting environmental harm (NRCS 590 overview). Commercial fertilizer is in scope, not just manure.
- Comprehensive nutrient management plan (CNMP). NRCS's whole-operation plan. It covers the production area, meaning the barns, feed storage, and manure handling and storage, and the land treatment area, meaning every field the manure may go on (NRCS CPA 102). It folds in storage condition and capacity, soil and manure testing, erosion and nutrient risk, odor and air quality, mortality handling, and records.
A CNMP contains a nutrient management plan. A state manure management plan is often a narrower, state-specific version of the same idea.
What has to be in a nutrient management plan under the federal CAFO rule?
The EPA says all NPDES-permitted CAFOs must implement a nutrient management plan, and non-permitted Large CAFOs must implement nutrient management planning (EPA). Under 40 CFR 122.42(e)(1), a permitted CAFO's plan has to address nine minimum practices (eCFR):
- Adequate storage for manure and wastewater, and keeping that storage maintained.
- Proper handling of mortalities.
- Diverting clean water away from the production area where appropriate.
- Keeping animals out of direct contact with surface water.
- Keeping chemicals out of manure and stormwater systems not designed for them.
- Site-specific conservation practices, such as buffers, to control runoff.
- Testing protocols for manure, wastewater, and soil.
- Land application protocols.
- Records that document all of the above.
Permitted CAFOs keep those records for five years. Large CAFOs also have to recalculate their maximum land application amounts at least once a year using nitrogen and phosphorus tests taken within 12 months of application.
Notice item one. Storage and its upkeep come first on the federal list. That is where pits, lagoons, sludge, and anything you do to manage them belong in the plan.
What do the Midwest states require?
A few examples, summarized from state sources. They are not complete, and they change.
Iowa. Confinement operations built or expanded after May 31, 1985 need a manure management plan unless they are a small animal feeding operation of 500 animal units or less. Plans are updated every year with a compliance fee of $0.15 per animal unit. Application records are kept for five years after application or the length of the crop rotation, whichever is longer. Liquid manure applied within 750 feet of a neighboring residence, school, church, business, or public use area must be injected or incorporated within 24 hours unless the neighbor waives it in writing (Iowa DNR Form 542-4000, rev. 07/2024).
Minnesota. Facilities that can hold 100 or more animal units need a manure management plan when they apply for an NPDES, SDS, interim, or construction short-form permit. The plan has to be reviewed every year. Storage serving 300 or more animal units tests manure once a year for at least three years, then at least once every four years, with retesting after changes that affect nutrient content. Application records are kept for the most recent three years, or six in special protection areas (Minnesota Rules 7020.2225).
Nebraska. Under Title 130, confined livestock operations need at least 180 days of available storage before winter, and NDEE guidance sets 1.5 feet of freeboard on earthen structures to cover a 25-year, 24-hour storm. The operation and maintenance information has to give the operator a maximum sludge accumulation depth (NDEE Guidance 05-079, October 2021).
Wisconsin. DATCP says all Wisconsin farms should have a nutrient management plan, with the Wisconsin NRCS 590 standard as its basis and state rules ATCP 50 and NR 151 layered on top. Farms in Farmland Preservation, farms taking cost-share for a plan or for manure storage, WPDES-permitted operations, and farms under local livestock siting or storage ordinances are among those that follow one (Wisconsin DATCP).
If you operate in Kansas, Missouri, South Dakota, Illinois, or Indiana, your state has its own version. Start with your state environmental or agriculture agency and your county NRCS office.
How often should you test manure, and what does the test tell you?
University of Minnesota Extension recommends testing manure each year for the first three years of an operation, then every three or four years, and retesting whenever a change in feed, animals, or storage could change nutrient content. It also warns that book values are only a rough guide because actual nutrient content often differs (UMN Extension).
A manure analysis should report at least:
| Item | What it tells you |
|---|---|
| Total nitrogen (TN or TKN) | All the nitrogen, organic plus inorganic |
| Ammonium nitrogen | The part available to the crop right away, and the part most at risk of loss as ammonia gas |
| Organic nitrogen | Total minus ammonium. Has to be broken down by soil biology before a crop can use it |
| Phosphorus (P or P2O5) | P2O5 = P x 2.29 |
| Potassium (K or K2O) | K2O = K x 1.2 |
| Moisture or solids | Needed to convert results to lb per 1,000 gallons or per ton |
Penn State's lab report splits total nitrogen into ammonium and organic nitrogen the same way, and shows how much of the ammonium a crop gets depends on how fast the manure is incorporated (Penn State AASL). Why the split matters for your fertilizer bill is covered in organic vs. ammonium nitrogen in manure.
Sample during land application when you can, from agitated manure. A sample from the top of an unagitated pit will understate what is in it.
How does storage capacity fit in?
Every plan starts with volume: how much manure you produce, and how many days you can hold it. That is where solids quietly cause trouble.
A storage sized for 180 days of manure is only a 180-day storage if the space is still there. Crust on top and settled solids on the bottom take volume, and lagoon sludge takes treatment volume. Nebraska's guidance assumes sludge will build and requires a maximum sludge depth in the operating plan for exactly that reason. If your pumping dates keep creeping earlier with the same herd, the plan and the storage have drifted apart. See how much lagoon capacity solids are costing you and lagoon sludge removal.
Where does pit and lagoon treatment fit in the plan?
Be clear about what the agencies say: none of the federal or state sources above endorse any particular manure additive or treatment. What they do require is that storage is adequate and maintained, that manure is tested, and that records back it up. So any treatment program belongs inside your plan, documented, rather than off to the side.
Practically, that means:
- Record it in your operation and maintenance notes the same way you record agitation and pump-out dates.
- Measure before and after. Sludge depth, crust thickness, agitation hours, and manure test results, on the same schedule your plan already uses.
- Watch the ammonium line. PitCharger's biology works on the organic material in the pit. It helps convert more of the existing nitrogen into plant-available ammonium. It does not create additional nitrogen, and your plan's application rates should follow your actual test results, not a product claim.
- Keep the safety rules. Treatment does not change agitation ventilation or confined space rules. See manure gas dangers.
Manure Digester is the flagship monthly treatment for pits and lagoons and N-Loc is for maximum odor reduction. For hog operations, a common starting point is about one gallon per month per 1,000 head. A common monthly rate for cattle and dairy is about one gallon per 75 animals. Most producers should notice a difference within the first month, and significant results are normally measured after about six months, which lines up with most plans' seasonal pump-out and testing cycle. Work the numbers in the calculator or get a treatment plan.
Frequently asked questions
Do I need a manure management plan?
It depends on your state, your animal units, and whether you hold a permit or take cost-share. Iowa, for example, requires one for confinement operations above 500 animal units built or expanded after May 31, 1985. Minnesota requires one at 100 animal units when you apply for certain permits. Check with your state agency.
What is the difference between an NMP and a CNMP?
A nutrient management plan covers nutrient rates, sources, timing, and placement on your fields. A CNMP is NRCS's broader plan for the whole operation, including the barns and manure storage, and it contains a nutrient management plan inside it.
How often do I have to update the plan?
Iowa and Minnesota both require an annual review or update. NRCS says a nutrient management plan should be revised when the soil test cycle ends or when manure volume, handling, or analysis changes. Your state may set a different schedule.
How long do I keep records?
The federal CAFO rule requires five years for permitted CAFOs. Iowa requires five years or the length of the crop rotation, whichever is longer. Minnesota requires three years, or six in special protection areas.
Does a manure additive count toward plan requirements?
No agency source we found credits any additive toward plan requirements. Treat it as an operating practice you document, measure, and evaluate inside your plan, like any other change to how you manage storage.