Winter Application of Manure
and Other Agricultural Source Materials
|History:||Replaces OMAFRA Factsheet 10-043, Winter Application of Manure and Other Agricultural Source Materials|
|Written by:||J. Laporte - Environmental Specialist/OMAFRA|
Livestock and non-livestock farmers can attest to the positive value of manure and other agricultural source materials (ASM) used in crop production. Valuable nutrients and organic matter are supplied through these products. Nutrients help reduce crop input costs while increases in organic matter lead to better soil structure and higher crop yields. Proper management of manure and other agricultural source materials will maximize their value while minimizing their environmental impact.
However agricultural source materials, rich in nitrogen and phosphorus, can contaminate water sources if improperly applied. This is particularly true when the soil is frozen or snow-covered, since this increases the potential for runoff to surface water. Therefore, it is important to understand the factors affecting the application of manure and other agricultural source materials to land during winter and other times when soil is snow-covered or frozen.
The Nutrient Management Act, 2002, with its regulation O. Reg. 267/03 (Regulation) addresses two time periods that may or may not overlap. The first is based on calendar dates - December 1 to March 31 or "winter". The second period is any other time when the soil is frozen or snow-covered. Frozen soil is any 5 cm layer of frozen moisture in the top 15 cm of soil. Snow-covered soil is soil with a layer of snow on the surface with an average minimum depth of 5 cm.
The Regulation is most restrictive for winter applications.
Figure 1. As snow melts, manure and other agricultural source materials can be carried into surface water.
Winter applications of manure and other agricultural source materials increase the risk of polluting the environment.
During winter manure tends to be applied on fields most readily accessible and not necessarily the fields that need the manure the most. In addition, only parts of a field may be available due to snow drifts, wet areas or other physical factors further limiting the area available for application.
The risk of runoff to surface water increases when applying on frozen or snow-covered ground. If a thick layer of snow on the soil's surface melts quickly, rapid surface water runoff will flush nutrients to adjacent surface water sources. Fresh snow contains about 0.25 cm of water for every 2 cm of depth (1/10th of an inch for every inch) but the water content increases as the snow ages and settles. Frozen soils have limited or no infiltration, so immediate runoff occurs if there is rainfall before the soil thaws.
Research shows that:
Avoid spreading if the weather report indicates either precipitation is likely or temperatures that will result in snowmelt.
With winter applications there are no growing crops available to absorb the nutrients. The increased risk of losses also means that fewer nutrients in winter-applied manure are available for crop production in the following season.
There are several environmental laws that make it an offence when manure enters surface water. The main pieces of legislation to be aware of would be the Environmental Protection Act, the Ontario Water Resources Act, and federally, the Fisheries Act. All Ontario statutes can be found at e-laws. For more information see the article on winter spreading.
Spreading dark manure on white snow may also draw unwanted attention to your farm. This may increase the number of complaints lodged against the operation and the industry as a whole.
Figure 2. Manure spread on snow can bring unwanted attention to the farm.
For all the above reasons, it is not recommended to spread manure or other agricultural source materials in the winter.
There are alternatives to winter spreading. These include:
According to the Regulation some farms may require a nutrient management strategy (NMS) or nutrient management plan (NMP). A nutrient management strategy outlines how manure and other ASM are to be stored and managed, while a nutrient management plan details land application rates and timing.
A contingency plan is a written plan of what to do in the event that a nutrient management strategy or plan cannot be followed. The plans must address what will be done if:
Even if you do not have a nutrient management strategy or plan, good planning could reduce the need for winter spreading and lessen any adverse environmental effect.
If winter application of manure or other ASM is required, farms with a NMP must follow the standards outlined in the Regulation. For all other farms, these standards are recommended as best management practices.
If manure must be applied in the winter, choosing appropriate fields can reduce the potential for environmental impact.
Figure 3. If it is absolutely necessary to spread manure in the winter, site selection is important. Sloped fields close to surface water are not recommended due to the increased potential for runoff.
There are minimum setbacks for applications near surface water.
However, consider the dry matter content of the manure, slope of
the land, depth of snow cover and drainage before applying manure
in winter or other times when the soil is frozen or
Injection or Incorporation
During winter when the ground is not frozen or snow-covered it may be possible to use tillage and application practices to reduce the potential for runoff.
Injection or incorporation into the soil when it is frozen or snow-covered is even more strictly regulated. It is difficult at best, and impossible for most.
Reducing the application rates may decrease the potential for environmental impacts from application in winter or other times when the soil is frozen or snow-covered. Apply the minimum amount of manure that enables managing the remaining manure with available storage until spring.
As stated earlier, avoid manure application if precipitation is in the forecast or if the temperature is forecasted to rise to a level where snowmelt is likely to occur.
Winter application of manure is not recommended because of increased risk of nutrient loss due to runoff, leaching through saturated ground or preferential flow to tile drains. For farms required to have a NMP, there are regulatory requirements to be followed for winter application. Even if a farm is not required to have a NMP, there is an increased risk of adverse effect with winter spreading, which can result in charges under environmental regulations. If a farm is considering manure application during winter, consider the following: