Incorporation of Liquid and Solid Prescribed Materials
Table of Contents
The evolution of farming systems over the last few decades has had considerable impact on how manure produced on livestock farms is managed. New technology is fostering a trend towards less tillage and improved residue management in crop production systems. This in turn is challenging conventional manure management systems.
Incorporation of agricultural and non-agricultural source materials (NASM) reduces nutrient and bacteria movement to surface water, places nutrients closer to the crop roots and minimizes odours. However, conventional methods to inject or incorporate manure and other materials can reduce surface residue, leaving soils more vulnerable to wind and water erosion. Fall application of these materials using these application methods only increases the risk by leaving soils vulnerable longer, resulting in potentially greater offsite movement of soil and nutrients.
Using both agricultural and non-agricultural source materials in today's cropping systems is a trade-off between nutrient and pathogen retention, odour reduction and the potential for soil erosion due to reduced surface residue coverage. This Factsheet outlines management options to help meet goals of nutrient and pathogen retention, odour reduction and reduced soil erosion.
Incorporation involves mixing nutrients into soil through tillage. Till the soil to a minimum depth of 10 cm., and for optimum retention till either immediately after or during application of the nutrients. Direct injection of a liquid material into the soil is also a form of incorporation.
Three main reasons to incorporate or inject manure and NASM are :
Shallow incorporation and mixing these materials with crop residue also promotes the decomposition of the residue.
Figure 1. Pre or immediate post application tillage can reduce the potential to lose valuable nutrients.
As the number of rural dwellers increases it is more important to be sensitive to odours. Below are suggestions for ways to minimize odours and maintain neighbour relations.
Table 1 lists the odour thresholds for different methods of spreading manure. It shows that incorporation is an effective means of controlling odour as it results in essentially the same odour units as unmanured ground.
Source: Livestock and Poultry Environmental Stewardship Curriculum Lesson: 44 Emission control strategies for Land Application
Manure contains stable and unstable forms of nitrogen. Unstable nitrogen occurs in urine as urea and may account for more than 50 per cent 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 not injected or incorporated, similar losses are anticipated for the volatile nitrogen sources found in NASM such as sewage biosolids.
Although general guidelines, these figures support a strong economic argument to incorporation, as well as an environmental one that it decreases surface runoff, reducing the threat of nitrogen and phosphorus to surface waters.
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.phosphorus erosion see OMAFRA Factsheet Determining the Phosphorus Index for a Field, Order No. 05-067.
Potassium is not presently considered a threat to water quality, partially due to its relative immobility in the soil. Manage potassium properly:
Excessive potassium in soil may create feeds that are a risk to milk production and herd health.
Bacteria and other pathogens are potentially harmful to humans, livestock and other living organisms.
It is important 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 use the different components of these materials.
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.
Pre-tillage is recommended to break macropores. While pre-tillage may compromise no-till fields, shallow tillage deters the flow of liquid materials down macropores towards the field tile.
There are advantages to applying manure or NASM to wheat or spring grain fields after harvest followed by shallow incorporation. Shallow cultivation does not disturb earthworm channels below the depth of incorporation and the worms readily rebuild these channels to the surface. Also nitrogen in the manure and NASM helps straw to breakdown and material will be incorporated, limiting nutrient losses and odour.
According to the Nutrient Management Act, 2002, (NMA) materials are 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 material is applied to it.
The method of spreading and incorporating, or not incorporating, manure and NASM on crop acres influences the amount of nitrogen available for the crop.
Shallow Tillage Implements
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 incorporation include disc ripping or cultivating that mixes 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 was limited to surface broadcasting. But alternative application methods are now appearing.
Flexible drop hoses supported on a boom can apply liquid manure and NASM beneath the crop canopy on the soil surface. A variation is a sliding metal shoe to which the drop hose is attached. The shoe rides on the surface, scraping it free of residue and creating a depression for the liquid. This method reduces ammonia losses and minimizes odour since there is reduced mixing of air and applied liquid. 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.
Figure 2. A tanker mounted injection unit used to inject sewage biosolids and liquid manure.
Injector knives, the traditional injecting option, cut 3040 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 1015 cm below the soil surface allow liquid placement in a wider band at a shallower depth. The materials mix with the soil better than straight injector knives and the material is higher in profile, minimizing potential leaching and reducing power requirements. Use sweeps to apply a higher rate of material than a conventional injector knife.
Figure 3. Incorporation of liquid manure. Source: University of Nebraska, Institute of Agriculture and Natural Resources.
Incorporation is not always possible. Examples include when:
Alternatives to incorporation include using high residue (over 30 per cent) 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 otherwise wash off the soil surface or leach down to tile drains. High crop residues left to trap nutrients can be a feasible alternative to tillage.
The maximum application rates determined by each 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 non-agricultural) may be increased when the materials are injected or incorporated into the land or if the land is pretilled. [See O.Reg. 267/03 and the specific nutrient management plan.]
Methods of Decreasing Surface Runoff
Set Back Distances
The NMA regulates set back distances from surface water. The distance required for a set back from the top of the nearest bank of surface water may be decreased under certain conditions such as those listed below.
Set back distances for NASM differ from those for agricultural source material such as manure and are determined by the quality of the material. Refer to.the regulation for details.
Crop production can reap the benefits of agricultural and non-agricultural source materials through added nutrients and organic matter, but with benefits come responsibilities to manage these resources with care for soil, air and water quality.
Different farming systems require adjustments to conventional methods. For manure and NASM incorporation this may mean adopting new technology that replaces or adds to the plow and other conventional tillage tools. Each generator and user of these materials must evaluate alternative management techniques and make choices that are most positive for Ontario's natural resources.
The NMA 2002 and O. Regulation 267/03 provide details of the existing rules for all nutrient spreading. A listing of related publications can be found on the OMAFRA web site.
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