Applying Manure and Other Agricultural Source Materials in Winter

Agdex#:	720/538
Publication Date:	08/2004
Order#:	04-069
Last Reviewed:	08/2004
History:	New
Written by:	Keith Reid - Soil Fertility Specialist/OMAFRA

We are updating this page to reflect current regulations.

Information on this page about regulations under the Nutrient Management Act, 2002 and the Environmental Protection Act is out of date. On September 18, 2009 new regulations affecting those applying non-agricultural source materials on agricultural lands were filed. Please visit www.ontario.ca/nasm-omafra for more information.

Table of Contents

1. Introduction
2. Winter Application Not Recommended
3. The Nutrient Management Act, 2002
4. Guidelines For Farm Operators
5. Considerations For Spreading Other Prescribed Materials
6. Alternatives To Winter Spreading

Introduction

Livestock and non-livestock farmers alike can attest to the positive value of manure and other agricultural source materials 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.

At the same time, agricultural source materials rich in nitrogen and phosphorus can contaminate water sources if applied improperly.

Proper management of manure and other agricultural source materials will maximize their value while minimizing their environmental impact.

Winter Application Not Recommended

Winter applications of manure and other agricultural source materials increase the risk of polluting the environment. The risk of runoff to surface water is greater when applying on frozen or snow-covered ground than other times of the year. 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 1/10^th of an inch of water for every inch of depth, but the water content per inch 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. Winter applications also mean that no growing crops are available to absorb nutrients.

The increased risk of losses also means that fewer nutrients in winter-applied manure will be available for crop production in the following season.

Possible reasons for winter application

If winter applications are undesirable, why would you consider applying manure during the winter? The reasons may fall into the broad categories of contingency plans, agronomics or economics.

Contingency Plans

Contingencies that may require winter application include insufficient storage or an inability to spread during the planned period. Excessive precipitation may fill the manure storage so that over-topping is a risk. Livestock may be held longer than planned so the volume of manure produced is greater than planned. In either case, field application of manure using proper precautions is preferable to allowing a spill to occur at the storage.

Wet fall conditions can prevent planned manure applications, because soil conditions either did not allow the spreader into the field or delayed harvest until after the fall application window.

Agronomics

Agronomic reasons for applying manure in the winter are related to soil conditions. Many heavy textured soils are susceptible to compaction in the spring, and waiting until they have sufficiently dried will delay crop planting until yields are seriously affected. Manure application when the soil has some frost allows traffic without excessive soil compaction.

Economic Advantage

The economic advantage to applying manure in winter is spreading the workload, so there is one less job to do during the busy spring planting or fall harvest season. This can also improve the timeliness of spring planting, increasing crop yields and economic returns.

Figure 1. Winter application is not recommended, but may be allowed provided certain restrictions are met.

In any of these circumstances, it is important to take extra precautions to avoid, as far as possible, the negative effects of manure application during the winter. The conditions to allow application during winter will not occur every year, so it cannot be considered to be normal practice. A nutrient management plan should never include winter spreading as a normal practice, or as a way to reduce the amount of manure storage required.

The Nutrient Management Act, 2002

As farmers receiving and/or producing manure or other agricultural source materials are phased into the requirements of Ontario Regulation 267/03 under the Nutrient Management Act (NMA) they must submit a nutrient management strategy (NMS) and/or a nutrient management plan (NMP). The Regulations regarding winter application apply on farms requiring a NMS/NMP. These Regulations exist to protect Ontario's water quality and environment, and as such are good habits for all farmers to adopt. Some municipalities have requirements for farmers that are not phased into Regulation 267/03 that may include or exceed the requirements of the NMA.

A good strategy or plan starts with the basics of best management practices for nutrient management. The NMA has regulations designed to build upon these best management practices.

Best Management Practices help limit affect of winter applications

The Regulations under the NMA place limits on manure application during winter, which may be defined by either calendar date (Dec. 1 to Mar. 31 of the following year), or by conditions (frozen or snow covered ground). There are some limitations that apply in either of these circumstances, such as increased setbacks, and some are specific to particular conditions. The flow chart in the centre of this Factsheet should guide you through the decision of whether you are able to apply or not, and with what limitations.

During any time that meets the criteria for winter, no applications of manure are allowed:

• to land where water collects during a rain storm or thaw and flows directly into surface water or
• to land that is subject to flooding once or more every 5 years, according to flood plain map provided by a municipality or conservation authority.
• If flood plain maps are not available then setback requirements are as listed in the Regulations. Whether maps are available or not, avoid areas that often flood during spring thaw.

Restrictions to manure applications are broadly categorized into the period between Dec. 1 and Mar. 31 when the soil is not frozen or snow-covered, and any time of year when the soil is frozen or snow covered. The restrictions are further refined according to whether the manure is liquid or solid.

Figure 2. Water may collect during a rainstorm or thaw and flow directly into surface water or to land that is subject to flooding.

Soils not frozen or snow-covered between Dec. 1 and Mar. 31

The key requirements during this period are that the manure must not be left on the surface (unless there is a living crop or surface residue to impede runoff), and setbacks to surface water are increased.

• Either liquid or solid manure must be incorporated within the same day it is applied. The exception to the requirement for incorporation is on ground covered with crop residue that covers at least 30% of the soil surface, or a living crop such as winter wheat or forages.
• For liquid manure, this includes either broadcast application followed by incorporation, or injection.
• The minimum setback for liquid manure application is 20 m from the top of bank adjacent to surface water.
• The minimum setback increases to 100 m from surface water if the slope is greater than 3% for liquid manure application, or 6 % for solid manure.

Soils frozen or snow-covered at any time of the year

For liquid manure the requirements for frozen or snow-covered applications are the same as for unfrozen or bare soils except that if the manure is to be incorporated this must be done within 6 hr. (instead of having the whole day to incorporate). Surface applications are not permitted.

For solid manure incorporation must also be within 6 hrs hours of application. Where the sustained slope of the land is greater than 6%, a minimum setback distance of 100 m from surface water is required.

There is an allowance for surface application of solid manure to snow-covered or frozen soil in certain low-risk situations. The requirements that must be met are:

• a field slope of less than 3%
• a setback from surface water of greater than 100 m
• the depth of snow cannot exceed 15 cm (6 in.).

Injecting or incorporating applied materials mixes soil and nutrients together so that the nutrients have a greater chance of staying where they are applied. Tilling soil destroys cracks and macropores thereby blocking the pathways that nutrients can travel through to end up in field tiles. Materials are considered incorporated into land only if they are incorporated to a minimum depth of soil disturbance of 10 cm. Land is considered pretilled only if the tillage occurred not more than seven days before the application of materials to it.

Guidelines For Farm Operators

For the Regulations to make sense, it is important to understand what is meant by the terms frozen and snow covered.

Snow-covered soil means soil with a layer of snow on the surface that has an average minimum depth of 5 cm.

• Measure snow depth in the area where the actual spreading will take place.
• Fields with high residue may be prone to snow drifting higher up against stalks. In these fields measure the depth of snow where no residue is present and also where snow has drifted against crop residue. The average of these measurements is the overall snow depth of the spreading area.
• Follow the same technique in tilled fields where snow is in the depressions between the furrows. This does not, however, allow manure to be spread on drifted areas at the edge of the field because most of the field is bare, since there would still be significant risk of runoff when this snow melts.

Frozen soil means soil with a layer of ice a minimum thickness of 5 cm located within the top 15 cm of the soil. A shovel or soil probe is useful in locating frozen layers (Figure 4). Generally, if you cannot get a shovel through the frozen layer it is deeper than 5 cm.

• If the layer is difficult to penetrate, use a cordless drill with a 2.5 cm bit to investigate below the frozen layer to determine more precisely how deep the frozen soil penetrates. When the drill resistance lessens compared to the frozen top layer, unfrozen soil has been found.
• Use a measuring tape or ruler to measure the distance the drill bit traveled through the frozen layer. (Figure 5).
• Use the same method to look for changes in resistance from unfrozen soil to frozen soil deeper that the top 15 cm.
• Conditions may vary throughout the same day as sunshine warms the soil and snow cover and/or frozen layers thaw. Under normal late winter conditions, a soil that freezes during the night and then thaws during the day will not exceed the 5 cm limit.
  
  

Figure 3. Flow Chart for Determining Winter Applications

Text Equivalent of Graphic

Pdf version of flow chart - 45 kb

Figure 4. Measure the depth of snow cover by inserting a ruler through the snow and noting the depth at the surface, or clearing a small patch of snow with a shovel. This field is just above the limit for surface application of solid manure on a level field.

If winter application is intended, prepare a second set of field sketches outlining areas that could potentially, if conditions allow, be used for winter application of their particular type of manure. Clearly mark flood plains and any areas where runoff occurs from the field in a concentrated manner.

Slope is the change in elevation of the land over a horizontal distance. It is normally expressed as a percent, where the change in elevation is measured over 100 horizontal units. A field that drops 18 in. (1½ ft.) in 50 ft., for example, has a 3% slope. The steepest field slope in the area intended for application will determine whether application is allowed or not, so it is beneficial to divide fields into sections if there are variable slopes.

Considerations For Spreading Other Prescribed Materials

This Factsheet outlines the requirements for applying manure during the winter. The requirements for other materials may differ somewhat, particularly for non-agricultural source materials as follows:

• Land application of sewage biosolids is prohibited between Dec. 1 and Mar. 31, or any time the ground is frozen or snow-covered.
• Land application of pulp and paper biosolids is not restricted during winter.
• Other nonagricultural source materials may be applied with the same restrictions as liquid manure.

Figure 5. Depth of frost can be determined by inserting a shovel or probe into the soil to establish the depth of resistance, or, as shown here, by drilling through the frozen layer with a portable drill equipped with a spade bit.

Application limits apply in winter as well as other times

All of the setbacks and application limits in a NMP still apply with winter application, so if the Plan dictates a wider setback than the minimum winter spreading setback, the wider distance will apply. Other requirements, such as the minimum of 30 cm of unsaturated soil at the time of application and the ban on high trajectory irrigation guns, must also be followed.

Alternatives To Winter Spreading

If winter spreading is a regular occurrence in your operation consider alternatives for managing manure in your operation. Some alternatives include:

• temporary field nutrient storage sites for solid manure
• higher rates of application at other times of the year if the NMS and NMP allow
• transferring the nutrient to a broker or other storage facility, and,
• if possible, acquiring access to more land through ownership or control or by means of an application agreement, rental or other agreement.

The rope transect method can be used to determine the percent residue in a particular field. Use a light rope about 8 m in length with knots or other markings spaced along the rope at 15 cm intervals so that there are a total of 50 knots. This rope is laid out across the soil surface at an angle to the crop rows. The number of knots that are touching pieces of crop residue at least 2 mm by 2.5 cm are counted. Multiply this number by 2 to calculate the percent residue. This should be repeated 4 times in different parts of the field and the results averaged.

A living crop as defined by the NMA is a crop that has been planted and has emerged from the soil, and if it is dormant, that must be reasonably expected to resume growing under suitable conditions. Examples would be alfalfa or winter wheat.