As we all know, farming is what supplies most of our food. There are many types of farms and many ways to farm. It is the way farmers farm that can have an effect on what happens downstream. Farmers need to feed their crops nutrients, and it is these nutrients that can impact water quality, especially in lakes.
As part of my conservation work, I look at two aspects of farming. One is soil erosion, and the other is water quality. The two can go hand in hand. By keeping the soil and nutrients on the farm field, we keep them out of the water.
What causes erosion? The easy answer is rain, but more important, it is a combination of the inability of rain to infiltrate into the soil and the effect of raindrops on soil particles causing them to disperse in water solution. With a light rain, the soil has the ability to infiltrate the rain. With a heavy storm, the soil becomes saturated. The raindrop’s impact on the soil particle pushes the soil off the field carrying nutrients and anything else in the field with it.
The topography of the land will dictate where it ends up. The slope, soil type and soil structure dictates how much infiltration can take place. Also, tillage can breakup soil structure and reduce infiltration. If the runoff ends up in a stream, wetland, or lake, now it is a water quality problem.
The impact of farm runoff on the water quality of Geneva Lake is based on these factors. For farmers to produce a crop, they need to add inputs such as nitrogen, phosphorus, other fertilizers, or manure. How, where and at what rates they add these inputs determines if the soil and nutrients will make it to the lake.
When dealing with water quality in a lake, the main concern is phosphorus. Phosphorus is a nutrient that can cause weed growth and algae blooms. Once in the farm field, it binds tightly to the soil particle, so the main way phosphorous gets into the stream or lake is through soil erosion. Once in the lake, phosphorus can quickly be utilized to grow weeds or algae, or stay in the sediment for future release. If phosphorus fertilizer or manure is applied on the soil surface and then runs off, the result is likely to be algae blooms. One pound of phosphorus creates 500 pounds of algae.
There is not a perfect solution to reducing runoff; Mother Nature makes sure of that. The best way to reduce runoff is to protect the soil surface, increase infiltration, and incorporate nutrients, thus keeping the soil and nutrients on the field. Having grass planted in a field is an excellent way to protect the soil and improve infiltration, but unless you are grazing the grass with animals, it may not be economical.
Practicing no-till (where you plant directly into the old crop without tilling up the soil) is another way to protect the soil with residues while increasing infiltration. This practice needs to be used over many years to improve soil structure.
Another good practice is to use cover crops. A cover crop is a practice of planting a crop just to provide cover when nothing else is growing. Corn or soybeans typically are harvested in August or September. A cover crop such as radishes or rye grass can then be planted to hold the soil in place, provide excess nutrient uptake and improve soil health during the fall and spring.
Farmers can manage their nutrient applications through nutrient management plans. Nutrient management plans are a practice that lays out the type, timing and placement of nutrients, including manure, in a manner that will reduce nutrient runoff. When done correctly and followed, these plans are a good tool to ensure nutrients are applied at the right rate, at the right time in the right place.
If storm events unleash too much precipitation and create runoff, there are conservation practices to help. When runoff becomes concentrated, it not only delivers sediment and nutrients to surface water, but also increases erosion with its high velocity that drags additional soil from stream banks that create channels to the surface water. A grassed waterway is a conservation practice that can deliver runoff to a surface waterway without eroding the soil and allows the sediment to be trapped before it reaches the surface water.
Properly placed grass can create filter strips along a stream, wetland or waterbody and can help to remove sediment and nutrients, both above ground and for water traveling below the surface. Water control structures can temporarily store runoff in a field, slowing the release of the water over time. This allows sediments to settle out in the field instead of the stream or lake.
Runoff is regulated through a variety of rules and regulations. Concentrated Animal Feeding Operations, which are animal facilities with greater than 1,000 animal units, are required by the Wisconsin Department of Natural Resources to obtain a discharge permit. The permit requires the operator to control all runoff of pollution from the animal facility. The state also requires the operator to develop and a follow a nutrient management plan. Animal operators that have constructed a manure storage structure are required to develop and maintain a nutrient management plan.
Ultimately, regulations will not ensure the water quality we need. Program requirements and nutrient management plans are certainly helpful in reducing soil erosion and runoff, but I do not believe it is enough to obtain the required reductions to obtain good water quality.
Farmers need to adapt practices that will improve water quality. It is up to the farmer to adapt practices that go above the basic requirements to both keep the soil healthy and on the fields and to treat the sediment if it runs off. It is our job to work with these farmers to achieve this goal.
“Keeping It Blue” is written by Geneva Lake Task Force members to inform and educate the public about water quality and other issues impacting Geneva Lake and how the public can help to address them. Comments and questions can be sent to firstname.lastname@example.org.
Brian Smetana is senior conservation technician for the Walworth County Conservation Office and a member of the Geneva Lake Task Force.
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