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Nutrient Management: Manure Injection

alternative practice names:

Subsurface Application; Low-Disturbance Manure Injection (LDMI)

Manure injection is the practice of placing livestock manure directly beneath the soil surface during application. This reduces odor, nutrient runoff, and ammonia losses. It also typically disturbs soil less than surface spreading, followed by tillage for incorporation. It requires specialized application equipment but can be accomplished with both tankers and drag hose manure application setups. First adopted in annually cropped fields, low-disturbance injection equipment is now suitable for no-till, grass/hayland, and pasture fields.


The types of injection setups include:


  • Knife injection

  • Chisel/sweep injection

  • Discs or coulters

When used, in what regions in the U.S. is the practice found: 

Northwest, West, Upper Midwest, Southwest, Northeast, Southeast

FARM SIZE 

When used, typically found on farms of the following sizes:

Over 100 cows

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Practice Benefits 

Nitrogen conservation: When manure is surface-applied, a significant portion of the nitrogen is lost to the atmosphere, reducing its availability to plants. By injecting manure into the soil, the nitrogen is better protected from volatilization, which increases the proportion that remains available for plant uptake.


Flexibility in states with a Phosphorus Runoff Index (P-Index): For farms that may be limited to phosphorus-based manure applications, injecting the manure allows those same phosphorus-based applications to provide significantly more nitrogen than surface applications, sometimes eliminating the need for additional commercial nitrogen fertilizer. In addition, injection reduces phosphorus loss risks, so in states with a P-Index, injection will allow more flexibility in manure applications and may open up fields for manure applications that were previously restricted, also replacing the need for purchased fertilizers. 


Improved planting conditions: Injected manure doesn't form a mat on the soil surface that is difficult to plant through in the spring.


Reduced odors: Manure injection reduces odors associated with manure spreading by placing the manure directly into the soil, which minimizes surface exposure and limits the release of odor-causing compounds into the air. When combined with drag hose application and direct pumping from manure storages, manure injection can be so discreet that nearby residents may be unaware that manure spreading is occurring, further reducing the potential for odor-related concerns.

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Implementation Insights

Site-specific or Farm-specific requirements 

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  • Requires liquid or slurry manure: Due to the nature of the equipment and the method of application, manure injection is only feasible with liquid or slurry manure. Injection systems rely on the manure's ability to flow through hoses, pumps, and applicators, which is only possible when the manure has a high moisture content, typically found in liquid or slurry forms. 

  • Well-suited to drag line systems: Injecting is well-suited to drag hose manure systems as it is challenging to manage multiple toolbars, especially on tankers. See Drag Lines to learn more. 

Required Capital Expenditures (CapEx)

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The practice will present little to no equipment and/or infrastructure costs for smaller operations that choose to utilize a custom applicator with a tank truck to inject manure below the soil surface. 


Larger operations may opt to transport manure to injection equipment via draglines; capital expenses for this approach are detailed below:


  • Application equipment: Equipment needs include a toolbar, injection implements (discs/coulters, shanks with sweeps, closing wheels, etc.), distribution/equalization manifold and chopper/macerator, and distribution hoses. 

  • Fabrication: Attaching the toolbar to the tank may require additional fabrication costs.

  • Vehicle modifications: Farmers may need to transition current trucks or tankers to nurse tankers and retrofit the injection tractor to stay in the field (tires, tanks, pumps, etc.).

Required Operational Expenditures (OpEx)

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  • Custom application: A custom applicator often charges a per-acre fee to inject manure. This should be added to the base costs of the manure application, though some contractors include injection in baseline costs.

  • Fuel: Additional fuel is required to pull the toolbar through the soil (it requires more horsepower) and for the additional time and passes it may take if the injection toolbar has a working width that is narrower than a splash plate used in broadcast applications. 

  • Labor: More experienced labor may be required and/or if the injection toolbar has a narrower working width than the broadcast applications happening previously, it will require more passes and more time. However, if farms are currently broadcasting and then following with an incorporation pass, this could actually reduce labor costs.

  • Maintenance: Regular maintenance of toolbars and mounted equipment is recommended, including grease, point/disc replacement, shoes, hose replacement, and sheared bolt replacement.

Implementation Considerations

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  • Nutrient management planning: Spreading rates and volumes may need to be adjusted to account for the increased nitrogen conservation and reduced runoff and losses of nitrogen and phosphorus. 

  • Nutrient leaching in no-till soils: In certain no-till soil with large pores, the practice may contribute to nitrogen leaching through the soil profile.

  • Compatibility with no-till and perennial crops: Manure injection equipment has many low-disturbance options and can be compatible with no-till management and perennial rotations. Farms may consider using toolbars designed especially for grass, perennial forages, and cover-cropped fields. These often operate at very shallow depths and have closer disc spacing, and sometimes, a boot or shoe will follow behind, depositing manure in the narrow, shallow slot made by the discs.

  • Non-manure waste: It is not uncommon for non-manure waste (ear tags, hoof blocks, milking rags, etc.) to enter manure storage and cause clogging. 

  • Manure solids: While separated manure liquids work well with injection, many farms successfully inject raw liquid dairy manure without significant issues when they pay attention to these details. A larger-diameter hose and macerator as part of the manure distribution system can reduce clogging risks. Farms may also adjust to shanks over disks when manure contains more solids. 

  • Manure transport: Farms that inject with tankers will often operate separate nurse trucks or tankers on the road to move manure from the storage to the field and then transfer to the spreading tractor/tanker in the field, optimizing the injection tractor’s working time in the field. For farms that use drag hose but do not have manure storage in close enough proximity to pump directly to the spreading tractor in further fields, they can offload to a frac tank or side-loading manure ‘dumpster’ from which they can pump directly to the injecting drag hose tractor.  

  • Sand bedding: Sand-laden manure can settle and clog hoses (depending on diameter and flow rates).

Financial Considerations and Revenue Streams

FEDERAL COST-SHARE PROGRAM

Funding is available for this practice through USDA's Natural Resources Conservation Service (NRCS) Environmental Quality Incentives Program (EQIP).

Notes:

  • Check with the local NRCS office on payment rates and practice requirements relevant to your location. 

  • A Nutrient Management Plan (NMP) may be required to receive implementation funding for this practice.


FINANCIAL RESOURCES, TOOLS & CASE STUDIES

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Environmental Impacts

MAY REDUCE FARM GREENHOUSE GAS FOOTPRINT

The impact of manure injection on greenhouse gas (GHG) emissions is complex, with potential benefits and drawbacks. Manure injection into the soil tends to reduce ammonia emissions by minimizing contact with the air. However, it can also lead to increased nitrous oxide emissions under certain conditions, particularly when the soil is wet and denitrification occurs. Studies have shown varying results, with some reporting increased nitrous oxide emissions following slurry injection compared to surface broadcasting, especially in conditions that favor denitrification. However, in other scenarios, particularly when denitrification is less likely, manure injection can reduce ammonia emissions without significantly increasing nitrous oxide emissions (see research highlights below). Overall, manure injection may present a trade-off between reducing ammonia emissions and potentially increasing nitrous oxide emissions depending on soil conditions and timing.


See research highlights:

  • Yan et al. (2024) found that shallow injection of manure for field application reduces NH₃ emission by 62%–70% but increases N₂O emission. 

  • Webb et al. (2010) conducted a review of existing research and concluded that NH₃ abatement is most effective with open-slot injection (70–80%) and trailing shoe (65%) methods, compared to trailing hose (35%). There is significant variability in the reported efficiency of these methods, particularly with trailing hose (0–75%) and open-slot injection (23–99%). Immediate incorporation of slurry or solid manure into arable land by ploughing is the most effective technique, reducing NH₃ emissions by at least 90%. Delays of even 4–6 hours in incorporation significantly reduce its effectiveness. While some methods to reduce NH₃ emissions may increase N₂O emissions, these increases are not guaranteed. Rapid incorporation of solid manure can reduce NH₃ emissions without increasing, and potentially reducing N₂O emissions.


MAY IMPROVE WATER QUALITY

Depositing manure below the soil surface can also decrease nutrient losses in storm and irrigation runoff following land application. Shallow-disk injection is an effective practice for reducing dissolved phosphorous and total phosphorous losses without negating the erosion-reducing benefits of no-till however care should be taken to reduce the risks of nutrient leaching.¹ 


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¹ Injecting manure close to or after crop growth begins can help minimize potential nutrient losses. When switching from surface applications to injection methods, it's important to recalculate manure application rates. This is because injection typically increases nitrogen availability, which often means lower application rates are needed to avoid overapplication. 

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Alignment with FARM Program

FARM Environmental Stewardship (ES) V2-V3 Alignment

FARM ES Version 3 includes an optional crop module, allowing users to enter their cropping practices including manure injection.

Contents

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We're always eager to update the website with the latest research, implementation insights, financial case studies, and emerging practices. Use the link above to share your insights. 

We're always eager to update the website with the latest research, implementation insights, financial case studies, and emerging practices. Use the link above to share your insights. 

Contents

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Practice Overview

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Practical Insights.png
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Research Results.png
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Manure injection is the practice of placing livestock manure directly beneath the soil surface during application. This reduces odor, nutrient runoff, and ammonia losses. It also typically disturbs soil less than surface spreading, followed by tillage for incorporation. It requires specialized application equipment but can be accomplished with both tankers and drag hose manure application setups. First adopted in annually cropped fields, low-disturbance injection equipment is now suitable for no-till, grass/hayland, and pasture fields.


The types of injection setups include:


  • Knife injection

  • Chisel/sweep injection

  • Discs or coulters

Practices and technologies

Nutrient Management: Manure Injection

alternative practice name:

Subsurface Application; Low-Disturbance Manure Injection (LDMI)