Nutrient Management Act 2002 - Incorporation of Liquid and Solid Prescribed Materials

Agdex#:	720/538
Publication Date:	November 2004
Order#:	04-079
Last Reviewed:	November 2004
History:	new
Written by:	Michael Payne - Nutrient Management Specialist/OMAFRA.

Table of Contents

1. Introduction
2. What is Incorporation?
3. Why Incorporate Manure Or Non-Agricultural Materials?
4. Preventing Preferential Flow And Tile Drain Interaction
5. Methods Of Incorporation
6. Alternatives To Incorporation
7. Incorporating Nutrients: Best Management Practices And Nutrient Management Protocol
8. Do You Know About Ontario's New Nutrient Management Act?

Introduction

The evolution of farming systems over the last few decades has had considerable impact on the management of manure produced on livestock farms. The trend towards less tillage and improved residue management in crop production systems has challenged the conventional manure management systems of the past. New technologies and adaptations have had to be developed to allow for incorporation of the manure with limited tillage and maximum maintenance of surface residue coverage. Incorporation of agricultural and non-agricultural source materials has the potential to reduce nutrient and bacteria movement to surface water, it places nutrients closer to the crop roots and minimizes odours. However, conventional injection or incorporation of manure and other materials can reduce surface residue and leave soils more vulnerable to wind and water erosion. Fall application of manure using these systems can leave soils vulnerable longer, resulting in potentially greater offsite movement of soil and nutrients. Therefore using both agricultural and nonagricultural source materials in today's cropping systems becomes a trade-off between nutrient and pathogen retention, odour reduction and the potential for soil erosion due to reduced surface residue coverage.

What Is Incorporation?

Incorporation involves the mixing of nutrients into the surface of soil by some form of tillage. Tillage should have a minimum depth of soil disturbance of 10 cm and for optimum nutrient retention occur immediately after or during application. Direct injection of a liquid material into the soil is considered to be a form of incorporation.

Why Incorporate Manure Or Nonagricultural Materials?

The three main reasons for incorporation or injecting manure and nonagricultural source materials are limiting odours, reducing surface runoff and improving nutrient and pathogen retention. Shallow incorporation and the mixing of these materials with the crop residue will also promote the decomposition of the residue.

Figure 1. Pre or immediate post application tillage can reduce the potential to lose valuable nutrients.

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Odours

As the number of rural dwellers increases the need to be sensitive to odours has become more important.

Immediate incorporation or injection of highly odorous materials will minimize the impact on neighbours. Avoiding application during weekends and holidays, and trying to apply when the wind is blowing away from neighbours is also advised. Spreading in the morning when air is warming and rising, instead of in late afternoon and avoiding spillage on public roads also assist with neighbour relations. Table 1 lists the odour thresholds for different methods of spreading manure. This demonstrates that incorporation is an effective means of controlling odour since it results in essentially the same odor units as unmanured ground.

¹ Ratio of fresh air to odorous air (fresh: odorous) to dilute the odour to where it is just detectable.

Source: Livestock and Poultry Environmental Stewardship Curriculum Lesson: 44 Emission control strategies for Land Application

Nutrient Retention

Nitrogen
Manure contains stable and unstable forms of nitrogen. Unstable nitrogen occurs in urine as urea and may account for more than 50% of the total nitrogen in manure. The more stable organic nitrogen occurs in feces and is slowly released. The amount of nitrogen available from liquid manure to crops depends on how long it is exposed to the air before incorporation into the soil. If incorporated directly as a sidedress for corn during the growing season 100% is available for plant growth. If manure is spread during the spring prior to planting and incorporated immediately roughly 65% of the nitrogen will be available. If the manure is not incorporated the percentage lost increases by about 12% per day left exposed. These figures, although general guidelines, create a strong argument for incorporation for economic reasons as well as the decreased possibility of surface runoff which poses both nitrogen and phosphorus threats to surface waters.

Phosphorus
Phosphorus is the least mobile of the major plant nutrients in the soil. It tends to bind within the soil matrix and is only slightly susceptible to leaching. The most significant water quality concern is generally in surface runoff and erosion situations. Incorporating materials soon after spreading reduces contamination risks, yet continual tillage also has drawbacks, with increased erosion and compaction potential. For more detailed information on the impacts of phosphorus erosion refer to OMAFRA Factsheet Determining the Phosphorus Index for a Field, Order No. 03-109.

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Potassium
Potassium is not presently considered a threat to water quality, partially due to its relative immobility in the soil. However potassium should be managed properly to improve crop production, reduce loss and prevent excessive build up in the soil. Excessive potassium in the soil may create feeds that are a risk to milk production and herd health.

Pathogens
Bacteria and other pathogens are potentially harmful to humans, livestock and other living organisms. Care must be taken to prevent pathogens from entering water. The best way to do this is to keep applied materials in the field where soil organisms and crops can breakdown and utilize the different components of these materials.

Preferential Flow
Preferential flow describes the movement of nutrients, pathogens and other substances taking the path of least resistance down the soil profile. Wormholes, root channels, cracks and other tunnels that run through the subsurface soil structure can provide a pathway to the drainage tiles. The number of macropores and the depth of the tunnels leading from the surface to below ground are influenced by soil type and organic matter. Higher organic matter, clay-loam to loam soils provides the best environment for soil life and allows stability of the macropores once formed. Heavy clay soils, on the other hand, tend towards waterlogged, low oxygen conditions not favourable to worm tunneling. Coarse sands with low organic matter have significantly less stability, causing tunnels to collapse and coarse sands rub against soft bodied soil life dehydrating and killing these species.

Preventing Preferential Flow And Tile Drain Interaction

Pre-tillage is recommended to break macropores. Pre-tillage may compromise no-till fields; however, shallow tillage will deter the flow of manure down macropores towards the field tile.

Applying manure to wheat or spring grain fields after harvest followed by a shallow incorporation offers many advantages. Shallow cultivation does not disturb earthworm channels below the surface incorporation and the worms rebuild these channels, nitrogen in the manure helps straw to breakdown and manure will be incorporated, limiting nutrient losses and odour.

For purposes of the Nutrient Management Act, 2002, (NMA) materials are considered incorporated into land only if they are incorporated with a minimum depth of soil disturbance of 10 cm. Land is considered pre-tilled only if the tillage occurred not more than 7 days before the application of materials to it.

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Methods Of Incorporation

The method of spreading and incorporating (or not incorporating) manure on crop acres influences the amount of nitrogen available for the crop.

Incorporation may involve turning the soil over by plow or chisel plow so surface soil, plus any applied materials, are buried. Incorporation is most effective when the material is mixed with soil, instead of being buried. Less aggressive methods of incorporating include disc ripping or cultivating that mix the soil and applied material within the top few inches of the surface of the soil. Still less aggressive tools for disturbing the soil surface are equipment such as a rolling knife-blade injector or a less aggressive shallow cultivation.

Other shallow incorporation tillage implements (s-tine cultivators and concave disks) are options on many liquid manure tank wagons. These systems are most commonly used for pre-plant applications. Materials are applied near the tillage tool that immediately mixes the materials into the soil. Speed of application, low power requirements and uniform mixing into the soil are advantages of this approach. In addition, such systems are being used to side-dress manure on row crops. However, extra attention is necessary. S-tines can trap and drag residues and in some cases have taken out a long row of corn when plugged tines behind the tanker were not noticed. Side dressing expands the season during which manure can be applied and improves the use of manure nutrients.

Shallow tillage of the soil prior to manure or other material applications disrupts the soil surface, decreasing the flow of nutrients down wormholes, cracks and other macropores towards the field tile. Soil cultivation before material application greatly increases the soils ability to absorb applied materials and resist immediate runoff.

In the past, application on grassland, legume crops and cereal grains has been limited to surface broadcasting. Alternative application methods are appearing. Flexible drop hoses supported on a boom can apply manure beneath the crop canopy on the soil surface. A variation is a sliding shoe to which the drop hose is attached. The sliding metal shoe rides on the surface, scraping it free of residue and creating a depression for the manure. This method reduces ammonia losses and minimizes odour due to reduced mixing of air and manure. Yield improvements suggest that side-dressing nutrients into the crop can more than offset any crop damage by the sliding shoe.

Injecting liquid materials is another way of incorporating. Here liquid flows through a tube attached to a knife that places the material in a band below the soil surface. While this method is effective be careful to prevent soil smearing and compaction when the soil is too wet. Caution is also needed in soil conditions susceptible to macropore flow. In these situations the liquid material must be placed higher than the depth the injection knife is traveling through the soil. The soil disturbance the knife action causes below the applied material helps to seal off the macropores so the material does not reach the tiles.

Figure 2. A tanker mounted injection unit used to inject sewage biosolids and liquid manure.

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Injector knives, the traditional injecting option, cut 30-40 cm deep into the soil. The result is high power requirements and little mixing of the soil and applied materials. Injector knives with sweeps that run 10-15 cm below the soil surface allow manure placement in a wider band at a shallower depth. The materials are mixed with the soil better than straight injector knives and the material is higher in profile, minimizing potential leaching and reducing power requirements. Sweeps can be used to apply a higher rate of manure than a conventional injector knife.

Figure 3. Incorporation of liquid manure.
Source: University of Nebraska, Institute of Agriculture and Natural Resources

Alternatives To Incorporation

Incorporation can lead to soil erosion when loose soil is blown by the wind or washed from the field by water. Incorporation may not be feasible at all times since saturated soils compact under the weight of equipment tires. Injection into saturated soils containing clay may smear in the seedbed making next season's crop slow to emerge and slow to develop roots.

Alternatives to incorporation include using high residue (over 30%) on the soil surface or live crops to reduce wind and water erosion. Residues, cover crops and live crops can also absorb and trap nutrients that may otherwise wash off the soil surface or leach down to tile drains. Where feasible, high crop residues left to trap nutrients can make a positive alternative to tillage.

Set back distances from surface water as required by the NMA may be reduced when materials are applied to living crops or to land with crop residue covering at least 30% of the soil. Wheat stubble and/or a red clover cover crop, standing corn stalks, alfalfa, grassy hay and growing row crops are examples where set back distances can be reduced. Nonagricultural source materials cannot be applied within 20 m from the top of the nearest bank of the surface water regardless of the application method or residue level.

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Incorporating Nutrients: Best Management Practices And Nutrient Management Protocol

Timing

In general, the closer to planting time manure is applied, the greater the availability of nutrients for plant growth. Early spring application of manure before planting, thus allowing for the mineralization of organic nitrogen, is the best for crop production. Fall application of manure, even with incorporation, can result in increased nitrogen losses because of the time between application and the next growing season.

Application rates

The maximum application rates, as determined by your nutrient management program, may be increased as the risk of material flowing over the soil surface is decreased. For example, the maximum single application rate for liquid materials (agriculture or nonagricultural) may be increased when the materials are injected or incorporated into the land or if the land is pretilled (refer to the NMA and your specific Nutrient Management Plan).

Methods of decreasing surface runoff include:

• Injecting or incorporating applied materials. This mixes soil and nutrients together so nutrients have a greater chance of staying where applied.
• Pre-tilling soil. This method destroys cracks and macropores thereby blocking the pathways so nutrients can leach through to field tiles. Land is considered pre-tilled only if the tillage occurred not more than 7 days before the application of the liquid prescribed materials to it.

Set back distances

The distance required for a set back from the top of the nearest bank of surface water may be decreased with certain agricultural material application methods such as those listed below.

• Incorporation or placement of agricultural source materials in a band below the soil surface means the materials are not exposed to the threat of traveling over the soil with water flow toward the surface water.
• Land that is pre-tilled before applications has the benefit of reduced macropore flow and higher absorption potential compared to surface application onto untilled soils.
• Crop residue and living crops trap and utilize applied materials so that they are not a threat to the environment.

The NMA 2002 and Regulation 267/03, as amended, provide details of the regulations that are in place for all nutrient spreading. A listing of publications related to the NMA and course information can be obtained from the OMAFRA web site.  

Do You Know About Ontario's New Nutrient Management Act?

The provincial Nutrient Management Act (NMA) and the Regulation 267/03, as amended, regulates the storage, handling and application of nutrients that could be applied to agricultural crop land. The objective is to protect Ontario's surface and groundwater resources.

Please consult the regulation and protocols for the specific legal details. This Factsheet is not meant to provide legal advice. Consult your lawyer if you have questions about your legal obligations.

For more information on the NMA, call the Nutrient Management Information Line at 1-866-242-4460,  
e-mail nman.omafra@ontario.ca or visit the omafra website.

Factsheets are continually being updated so please ensure that you have the most recent version.

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