Economic Analysis of Subsurface Tile Drainage Spacing

This study examined the optimal tile drainage spacing using data for the 1984– 2021 period for a drainage experiment in southeast Indiana. Four drainage spacings were compared: 16 feet, 33 feet, 66 feet, and 133 feet. Gross return per acre was highest for the 16-foot spacing. However, net return per acre was highest for the 66-foot spacing. The 66-foot tile drainage spacing also had a higher certainty equivalent of net returns and was the preferred drainage spacing using second-degree stochastic dominance (SSD). Sensitivity analysis related to the discount rate used, the cost of tile installation, and the useful life of the tile drainage system confirmed the attractiveness of the 66- foot spacing. The conceptual framework developed in this study would be useful when examining the feasibility of installing subsurface drainage in poorly drained soils in the U.S. Midwest.