When most people think about agriculture, they immediately think of the crops or food produced – corn, wheat, potatoes and cranberries. However, at the heart of food production is one key ingredient. It is the basic component that all of these crops need to grow – the soil!
Here are the basics. Soil is composed of minerals, air, organic material and water. The type of soil is determined by its physical structure, nutrients, trace elements, PH and organic matter. Based on these combined factors, there are over 700 soil types in Wisconsin! These factors also determine its growing ability. So, when it comes to agriculture, farmers must understand the type of soil they are working with in order to decide which crops to grow.
The physical structure of the soil is determined by the proportion of sand, silt and clay in the soil. Sand particles are the largest and clay particles are the smallest. The importance of a soil’s physical structure was evident during this summer’s drought. The soil’s physical structure determined how well it was able to hold onto the available water. This is a good example of where the science of irrigation comes into play, and why farmers pay such close attention to it to make sure their crops get just the amount of water they need.
So, here’s how different soil types compare. Sandy soil has large pore space. In a wet year, sandy soils drain better, but in a dry year, they struggle to retain water. It also has fewer available nutrients. At the other end of the spectrum are clay soils. Clay is made of smaller particles making it denser (smaller pore spaces). Clay will retain more water, but in a spring with lots of rainfall its poor drainage can make it difficult to farm. In the middle are loamy soils. These have almost equal portions of sand, silt and clay. If you had a garden, this is the type of soil you would want because it has the best balance of water retention and drainage.
To reflect the value of this soil type, the official state soil is Antigo Silt Loam. This soil is found in north-central Wisconsin. It is ideal for farming because of its composition of a silty top layer that holds water with a sandy layer underneath for proper drainage. But, soils vary across Wisconsin, and the type of soil in each region of the state determines the crops and other plants that grow on the landscape.
For example, potatoes and cranberries need fertile, well-drained soils like sands, sandy loams or silt loams located in central Wisconsin. But, in comparison, corn and alfalfa should be grown in soils that are rich in nutrients and able to lock in moisture. Wisconsin is home to a variety of crops, and it is the diversity of our soil types across the state that makes this possible.