Economic Analysis of Subsurface Drainage Systems in North Central Iowa

An economic analysis was performed for predicting the rate of return and payback period for installing subsurface drainage on Okoboji and Canisteo soil types for three different drain line spacings of 12.2, 18.3, and 24.4 m. DRAINMOD model predicted significant yield improvements for both soil types when compared with undrained conditions. With the parallel lateral drainage design and its installation, payback periods for the two soil types were analyzed for three different corn grain market prices. Analysis showed that the payback period was seven years or less for all the drain line spacings. For Canisteo soil type, the analysis showed an increase in rate of return with quicker payback as the drain line spacing was reduced from 24.4 m (80 feet) to 12.2 m (40 feet) for all three corn grain market prices. This was not the case for Okoboji soil type indicating that the spacing impacts payback period under different corn grain market prices. Caution should be used when interpreting the results from this analysis as drain line installation costs vary by project design and type of installation. Higher subsurface drainage project costs will increase the payback period.