Why you should avoid spreading in the winter and what you can do so you don’t have to
Submitted by: Lilian Schaer, on behalf of Farm and Food Care Ontario (F&FCO)
There are various reasons why farmers apply manure in the winter. Lack of storage capacity or an attempt to avoid soil compaction caused by heavy equipment are two common motivators for a practice that has negative impacts on the environment while also attracting added scrutiny to farmers and farming methods.
As we learn more about nutrient losses and how phosphorus moves in the environment, it has become abundantly clear that frozen ground and nutrient application don’t get along. Which means farmers should avoid applying manure, whether solid or liquid, on frozen or snow covered ground wherever and whenever possible.
Here’s why. Manure is rich in nutrients and micronutrients that are important for healthy crop growth. It can also help build underground biodiversity and add structure that will improve the water-holding capacity of soil, especially when used together with cover crops, no-till or minimum-till, and other practices that boost soil health.
Manure applications can always be susceptible to run-off and nutrient loss, but winter manure applications in particular are prone to nutrient losses. That’s because after freeze-thaw events, air pockets in the soil that have filled with water can refreeze to form an impervious, concrete-like layer. That means water from melting snow combined with winter or early spring rains isn’t absorbed into the soil; instead, it carries manure and nutrients across this impervious layer and off the field into water courses.
Phosphate can move off the field dissolved in water or attached to eroding soil particles and flow into lakes, streams, and water ways where it can promote algae growth. As algae die and decompose, they use up available oxygen in the water, which impacts aquatic life.
Research has shown that there’s a higher risk that manure from winter application will move during spring thaw. In fact, 60-80% of sediment and phosphorus loading occurs between November and April and surface runoff accounts for about 80% of dissolved phosphorus loss.
It’s important to remember that both solid and liquid manure can run off, and even though solid manure might still be visible in the field after application, some nutrients will still dissolve and find their way into waterways.
So, what to do?
Build additional storage. Make sure your farm has adequate manure storage capacity for the size of your herd or flock, including a contingency in case a wet fall or delayed harvest make it difficult to get all the manure out before winter.
Cover existing storages. Extend the holding capacity of your existing manure storage by putting a roof over to keep out rainwater. Calculations by Christine Brown, Field Crop Sustainability Specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs show, for example, that a 115-head dairy barn with a 12’ x 145’ circular liquid manure tank can store up to 121 extra days of manure if it is covered.
Add temporary storage. For solid manure, temporary storage in-field is one approved solution when barn storage is limited for bedded-pack manure from cow or heifer barns, or even calf hutches. The key is identifying the best location that will have minimal impact on water and neighbouring properties.
Make a deal. Look at your excess manure as a resource that can help reduce commercial fertilizer costs and consider selling it to other farmers in your area without livestock.
Rotate crops. Adding an extra crop to your rotation is one way to have additional options for spreading manure over the course of the year. Wheat is one of the easiest crops to add for expanded manure management options, but winter barley, winter canola or even hybrid rye are also options for consideration.
Use technology. Manure application technology is continually evolving, making it easier to apply manure into crops during the growing season. Not only does this take the pressure off during spring and fall, but it offers yield boosting potential too.
Using manure is a sustainable agricultural practice but it’s important to manage it responsibly in order to minimize environmental impact, so timing really does matter. More information about all of these topics is available at: https://www.farmfoodcareon.org/timing-matters/.