MSU Extension Field Crops

Shallow drains refer to subsurface (tile) drain pipes installed at a depth of 2.5- to 3-ft. Shallow drains have a higher initial cost because they require a narrower drain spacing than deep drains to achieve the same water removal rate, but they are worth considering because of their benefits. These benefits include lowering of the water table more quickly, removing less total water from the soil profile, reducing nitrate loss, retaining more moisture in the root zone, and increasing crop yield under certain conditions (Figure 1). Another benefit is that shallow drains are not limited to relatively flat slopes like controlled drainage. They can be used on rolling or sloping land without any need of management.

In sections 2 and 3 of this bulletin, soil profile suitability and spacing needs of shallow drains are presented. In sections 4 to 9, results from a DRAINMOD modeling study from seven locations are summarized, which show the impacts of shallow drains on water-table depth, drainage discharge, crop yield, water quality, and profitability (Ghane and Askar 2021). In that computer modeling, 2.5-ft shallow drains installed at narrower optimum spacings were compared with 4.1-ft deep drains installed at wider optimum spacings, where in both cases the optimum drain spacing maximized economic return on investment. In Section 10, general considerations of shallow drains are presented.

To read more about this, go to the MSU Extension Drainage Website.