The economics of tile drainage systems depend on crop yield response, initial capital outlay for the materials and installation of the system, and any annual operation and maintenance costs (pumped outlets) involved. While crop yield response to drainage can be assessed directly, the impacts of inadequate drainage on soil quality (structure, microbial activity, etc.) are more difficult to measure and assign economic value. Most field crops show a positive response to drainage, often with the best response from a combination of surface and tile drainage. The level of yield increase for a given year depends greatly on how poorly drained the soil was prior to drainage, and seasonal rainfall. Typical yield increases might be 10-30 bu/ac for corn and 5-10 bu/ac for soybeans. Wheat has been shown to yield only 58% of potential yield and sugarbeets 71% of potential yield when the watertable is 15"-20" below the surface for long periods of time, on a clay loam soil. Drainage systems can return the cost of investment in 3 to 10 years.