Will Spreading Bans Reduce Manure Runoff Events?

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The Wisconsin Discovery Farms Program was one of the first on-farm evaluation projects to identify the risk of manure applications in the late winter period.  Data from several of our farms have shown that manure applied during February and March has an increased risk of running off and contributing to high nutrient losses in surface water.  This data has been used to justify the establishment of recommendations, rules and regulations on winter manure spreading.  But, do bans on winter manure spreading (spreading on frozen or snow covered ground) actually reduce the risk of manure runoff?  A close evaluation of the data indicates that spreading during early winter (November – January) is much different than during late winter when frost can extend deeper and be more solid in the soil profile. Total winter application bans also increase the volume of manure that needs to be stored and increase the risk of runoff during the spring spreading season.

Based on the data from the Wisconsin Discovery Farms Program, manure spreading bans should be established based on field conditions, and not a calendar.  There are times when applying manure early in the winter is optimal because lack of snow and/or frost affords the opportunity for manure to come into contact with the soil.  There are also times when manure can be safely applied in late March, when the soils have thawed, snowmelt is finished and the fields are fit.  Not allowing farmers to begin fieldwork based on calendar dates can greatly increase the potential for runoff because the window for manure applications is smaller and the potential for runoff from saturated soils and spring rains is greater.

Why Did the Discovery Farms Project Study Nutrient Runoff?

The Wisconsin Discovery Farms Program was established in 2001 with leadership from farmers, their advisors and their industry groups to gather water quality data from working farms around Wisconsin and to use that data to educate farmers, industry personnel, consumers and policymakers. At the time, there was little reliable year-round information on actual phosphorus, nitrogen or sediment loss from fields with different management practices, physical settings or weather related events.

What Did We Do?


Average runoff timing and frequency from Wisconsin Discovery Farms, 2003-2008

The US Geological Survey partners with the Discovery Farms Program to provide high quality year-round data collected from agricultural fields, in streams, and within tile drainage. Monitoring has been conducted on more than 10 farms all around the state, totaling over 150 site years of data.

What Have We Learned?

The Discovery Farms data shows losses from the edge of field are, on average, 667 pounds of sediment, 2 pounds of phosphorus and 7 pounds of nitrogen.  While these numbers are important, the real value is in the variation, factors, and the management decisions that can influence nutrient and sediment losses. One of the most important lessons learned is the impact of the timing of manure application on nutrient loss. The key to reducing loss of nutrients from manure applications is to maximize the time between a manure application and a runoff event. As a producer, you need to understand the factors that cause runoff and options you have when manure spreading is not feasible.

Approximately 90% of the annual runoff in Wisconsin occurs from December through June. From December through March, most of the runoff is caused by snowmelt or rain on frozen/snow covered ground. During every year and on every site monitored, there has been runoff in March. Avoiding manure application during February and March can reduce nutrient loss, as 50% of the annual runoff happens during these two months. From April through June, runoff is driven by intense storm events or saturated soil conditions. In any given year, there can be times when fields are fit for manure application during this same time period based on little to no snow cover, early spring conditions, or droughty periods.

Future Plans

Prohibiting spreading based on calendar dates does not allow producers to assess the conditions in their immediate location. Management by calendar dates can force producers to spread during conditions when the risk for runoff is high because storage facilities are full. The conditions vary each year, and waiting for a specific calendar date can make producers miss opportune times for manure application so that field activities can be completed in a timely manner.

To prepare producers for assessing their own situations, Discovery Farms has provided intensive education and outreach on the factors that cause runoff in Wisconsin. By understanding the factors that cause runoff and management strategies that reduce nutrient loss, Wisconsin agriculture producers can maintain and improve water quality resources and farm productivity.


Amber Radatz, Outreach Specialist, UW Discovery Farms, aradatz@wisc.edu

Eric Cooley, Outreach Specialist, UW Discovery Farms

Dennis Frame, Director, UW Discovery Farms

Additional Information


UW Discovery Farms on Facebook

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