Discovery Farms are real working Wisconsin farms in different geographic areas, facing different environmental challenges.  The Discovery Farms program takes a real-world approach to finding the most economical solutions to overcoming the challenges environmental regulations placed on farmers.   One of the things that is done on these farms is to monitor water and nutrient runoff from fields to help determine those weather conditions and management practices that contribute to surface water pollution.  Collecting this type of data is both time consuming and expensive.  To date, here are some of their findings: 

Surface Water Losses:

·     A majority of surface water runoff occurs when the ground is frozen (or thawing).

·     Annual runoff cannot be predicted by annual precipitation amounts.  In other words, WHEN the precipitation occurs is more important than how much has occurred.  It should also be noted that when precipitation occurs is an uncontrollable factor.

·     Runoff amounts during the frozen ground period cannot be explained by the total amount of snowfall. Annual runoff rates are largely determined by percent of soil moisture.  At one of the farms, 96 percent of the surface water runoff events occurred at soil moisture levels at or above 35 percent. 

Soil and Nutrient Losses:

·   Nearly all sediment (soil) losses to surface water occurred when the soil was NOT frozen.

·   A significant amount of total nitrogen losses to surface water occurred when the ground IS frozen.

·   Ammonium losses to the atmosphere are significant when manure is applied to frozen, snow-covered ground shortly preceding snowmelt.

·   There are significant phosphorus losses when the ground is frozen, suggesting that these losses are not correlated with sediment losses.  The phosphorus is dissolved in the water that is running off.

·   When soils are thawed, most of the phosphorus losses are particulate (attached to the soil that is being lost).
 

Using the findings 

        There are several management implications that are inherent with these “discoveries.”  Frozen, snow- covered ground, shortly preceding a snowmelt is clearly a bad time to be thinking about spreading manure.  The risk for nutrient runoff is huge and this translates into fewer nutrients for the subsequent crop and more nutrients into surface waters such as streams, rivers, and lakes. 

        Manure applications to wet soils results in both soil compaction and a much higher likelihood of significant water and nutrient loss if rainfall continues at or around the time of the manure application.  Hence, it is important to consider both soil moisture and impending weather conditions when making manure applications. 

        These findings reinforce the concept that over application of nutrients from manure simply leads to higher nutrient runoff losses.  It continues to be a bad practice from both an economical and environmental standpoint.  

        EVERYTHING we can do to keep soil and water on the field is critical for maximizing production potential and reducing the amount nutrient runoff to surface waters.  The means of accomplishing this are not new, but often disregarded.  Once again, here’s a partial laundry list of practices:

·     Establish and maintain grass waterways where needed (gully formation in the spring is a good indication that a waterway may be in order)

·     Maintain crop residue levels through planting.  You don’t have to be a no-tiller to accomplish this.

·     Why is so much soybean ground fall tilled?  It doesn’t need to be.

·     Maintain or establish buffer strips along critical surface water areas where they border fields.

·     Big field or not, contour strips are still a good thing where slopes dictate such a practice.