Physical and economic benefits of subsurface drainage by soil type in eastern Ontario

Abstract

This study investigates the benefits from subsurface drainage for corn production in eastern Ontario, Canada by concentrating on the interrelationship among crop yields, natural soil drainage classes, precipitation levels, soil texture, and artificial drainage. Corn yields on drained and undrained land are estimated from production functions. The data are obtained from farm observations and cover the period 1979–1986. The independent variables are soil texture, natural soil drainage classes, and monthly precipitation levels in May, June, July, and August. The first two appear as dummy variables, while precipitation is included in quadratic form. Average annual yield on drained and undrained land is estimated from the production functions by substituting the long-term mean of monthly precipitation levels in the equations. These mean values are computed from precipitation records from 1890–1986. Additional yield due to subsurface drainage is obtained by deducting the estimated average annual corn yields on undrained from that on drained land. It was found that the highest incremental yield from subsurface drainage in the study area is obtained on light and heavy soils. The economic analysis of these incremental yield records revealed that the internal rates of return ( irr) are high on light soils. Although heavy soils show relatively high incremental yields from subsurface drainage, their irrs are low because of high installation costs. The payoff of artificial drainage on heavy soils for the sole purpose of increasing corn yield is low even at high corn prices. The big payoff occurs from being able to switch cropping patterns from low- to high-value crops on naturally poorly drained land where these latter crops cannot be grown economically without artificial drainage.