Manure is a year-round resource

MADISON, Wis. – Laura Paletta urges farmers to consider the value of manure and how intentional spreading can benefit farm land. Instead of viewing manure as a waste to be disposed of, she encourages farmers to consider it a resource to be utilized.
“Here in Wisconsin, we see a lot of different weather throughout the year,” Paletta said. “We have four seasons, and our fields look vastly different throughout the year.”
Paletta is an outreach specialist at the University of Wisconsin-Madison Division of Extension’s Agriculture Water Quality Program. She spoke during a Jan. 31 webinar entitled, “Manure and water quality: Why looking at the calendar matters.”
With farm land in different stages throughout the year, Paletta said it is important to understand when fields suffer the most nutrient losses in order to carefully choose which manure management practice to utilize to avoid those losses.
Data from Discovery Farms, a research division of UW-Extension, shows that March is the month where the most runoff occurs due to snowmelt and thawing of the soil. In May, June and July, when farmers are often tilling and planting, soil is most susceptible to loss. Roughly 77% of all soil loss occurs during those months, Paletta said.
Research reveals those same months are when 70% of a farm’s particulate phosphorus is lost. The particulate is the portion of the phosphorus that is bound to the soil particle, Paletta said. So, when there is soil loss, there is also typically a decrease in particulate loss. Particulate soil loss produces an increase in sedimentation in water bodies that impacts wildlife.
“I want to connect it back to what our fields typically look like in May, June and July,” Paletta said. “We’re out there tilling, we’re in and out of the fields with the tractor, and tilling up our soil. That’s typically why we see that increase in soil and particulate loss.”
Keeping fields covered, especially in the spring, is the most effective way to avoid soil loss. To alleviate the impact, farmers can overwinter crops in order to have something growing and provide soil coverage come spring.
Paletta said reducing tillage keeps residue on the soil, which allows crops to be planted into living matter. This eliminates bare ground and helps retain nutrients in the soil. Low-disturbance manure injection is another way to maintain coverage and limit soil losses in spring and fall.
“We know our manure adds great nutrients to our soil,” Paletta said. “Now that we know when we see our biggest losses, we want to add manure into it.”
The windows of time to spread manure on most dairy farms is in the spring before planting and in the fall after harvesting. Research from Discovery Farms indicates the best time to spread manure in the fall is when the soil temperature drops but is not yet frozen, typically late October. This timeframe coincides with the reduction in microbial activity when the temperature drops.
“When microbial activity reduces, that nitrifying bacteria also decreases,” Paletta said. “That can help reduce nitrogen losses through the winter and into the spring.”
Paletta said once soil freezes, it acts as a concrete layer, reducing infiltration. Then, when the spring melt occurs, a large runoff event occurs.
Paletta said research shows spreading manure in the summer, when the growing crop can actively take in the nutrients, helps increase yields. Specifically, studies showed spreading manure with a dragline hose on corn in a V3 to V4 stage allows the corn to pop back up; the manure will increase yields.
“This just opens up a window for potentially spreading when it is better weather,” Paletta said. “There’s a crop there that can take up those nutrients.”
When spreading during warmer months, it is important to be aware of the potential for large runoff events. When soil loss is increased in a runoff event, phosphorus loss is typically higher as well. The easiest way to avoid a large runoff event is to watch the weather and try not to spread before a rainfall is expected, Paletta said.