Managing manure and water in the wet season

Chery Sullivan
WSDA Dairy Nutrient Management Program

This dairy farm lagoon is pumped down and ready for winter storage.

Each season brings another round of annual tasks for farmers. If you are a dairy farm producer, preparing now for winter manure and water storage will help you avoid a manure management disaster and help protect Washington State’s water quality. 

Manure storage 

As the days grow short and feed bunkers fill with the summer crops, it is time to make sure manure storage structures are emptied and ready to store manure and rainwater through the winter and early spring months. 

Farms storing manure in lagoons must have capacity to store four-to-six-month’s worth of manure, while maintaining a foot of freeboard to protect the lagoon embankment from failure – plus, additional space for a severe rainstorm. Upright storage tanks must keep six inches of freeboard to prevent overtopping from waves created by high winds.

Manure application 

October manure nutrient applications come with special risks because fields may be compacted from harvest equipment and because heavy rains are on the way. If manure that is applied does not soak into the soil before the next rain event, it could run off to surface waters or puddle in the low-lying portions of the field. Solid manure should be disked into the soil or only applied to areas that are not at risk of flooding or runoff to surface water. 

Keep a close eye on the weather forecast. Manure applied to a saturated
field can spell trouble. 

Before applying manure, applicators should: 

• Look at three-day weather forecasts.
• Check the field’s nutrient needs and ability to absorb the manure applied.
• Avoid applying to areas prone to runoff.
• Use large buffers from all waterways. 

Also, consider that weather forecasts may not be entirely accurate, with either more or less rain falling than predicted.

If a farm does not have safe locations to apply nutrients due to crops or weather conditions, they should work with neighbors, custom manure applicators, and the local Conservation District to find the best application sites or extra storage areas.

Feed bunker and yard runoff 

A vegetated treatment area (VTA) can be used to filter and absorb nutrients. The VTA must be designed to treat the volume of runoff expected, and must be healthy enough to trap and absorb the nutrients carried in the runoff. If not designed well, concentrated runoff from the feed area can “burn” the grass and destroy these treatment areas.

Keep gutters and downspouts clear and functional to divert
water away from manured areas. 

If you collect and transfer the runoff from the feed area to storage, make sure drain grates are clear and pumps are operational.

Gutters and clean water diversion 

Fall rains arrive quickly. It pays to double check that gutter downspouts are functional and that water is diverted away from manured areas where possible. Remember, an inch of rain collected from 1,000 square feet of surface equals 600 gallons of water.

If you have questions about winter manure management, please contact your local conservation district or Kyrre Flege with WSDA’s Dairy Nutrient Management Program at kflege@agr.wa.gov, or 360-902-2894.