There currently are soil type maps available (similar to the USGS DLG files). However, I don't think you can download them (you need to pay for them). Also, at this point in time Farm Site can not import the maps. However, we are planning an update (probably this Spring or Summer) that will give you the ability to import them.
For the time being, I believe this may help you: 1. Go to Layer Management and create a new layer. Make sure that it is an Area Layer with a name like Soil Types. 2. You will want two data items on the layer. The first will be Soil Type, which should have Choice for the Type. The second will be size or area that should have Size for the Type. 3. Display this layer as the Active layer and trace out each soil type. 4. Use the Define Area tool (in the Mapping or Layer Tools) to click inside each soil type. The area will be displayed and you will be able to add the appropriate soil type. 5. When you are done you can use the Edit Legend option to assign a legend for the layer. Be sure to select Soil Type for the Data Item, then select All Choices from the Fill menu. You can now click on the grey button next to each soil type to assign a color and pattern to each soil type. I like to use patterns only (with Transparent Background selected for the Background Color). This allows you to display your soil types on top of another layer (such as yields) to see through and see how they relate to each other.