Subsurface Drainage Tiling

• Drainage tiles are segments of perforated tubing. This piping is assembled into a network beneath the ground surface and then receives excess moisture from the soil, channeling it to a location where it can run off. Before installing a system of this nature, a farmer must consider -- besides the cost -- the environmental impact of the tiling network, the type of soil through which moisture must travel, the presence of cable or other subsurface easements, the proximity and capacity of the runoff outlet and, of course, the cost. Reducing the flow of such piping requires modifying its slope. Expensive and time-consuming, this procedure requires digging up the tiles and retrenching the soil.
  
  

Surface Drainage Methods

• Other techniques remove pooling from the ground surface. Like tiling, these methods are effective at lowering the water table -- the highest point of saturation in the soil profile. Unlike subsurface drainage systems, the surface methods work from above. Leveling and smoothing the land inhibits water concentration. Ditches and canals accumulate and transport excess water to nearby creeks and rivers. Surface removal can also work in tandem with subsurface drainage to extract superfluous moisture from the soil. Consequently, the tempo of drainage can be slowed by reducing the dimensions of these engineered boundaries.
  
  

Wetlands

• When excess water is drained from farmland and transported to adjacent ponds and waterways, it travels with residual nitrogen and phosphorus from chemical fertilizers. Other elements from herbicides and pesticides may also be present. To preserve the environmental integrity of the farm's surroundings, a property owner is wise to staunch the flow of this tainted water. One effective means of purifying the water is the placement of wetlands on the property. The wetlands act as holding compartments, removing up to 80 percent of accumulated nitrates in a given year, according to a 1993 study by agricultural engineers.
  
  

Crop Rotation

• While agricultural drainage can carry moisture away from the soil, it has the simultaneous, if unintended, effect of robbing the crops of nutrients. Thus, it benefits a farmer's yield to control the loss of nitrates and other sources of nourishment by regulating the drainage process. Inserting wheat, alfalfa and brome grass into the crop rotation with corn and other feed grain benefits the soil, since these crops do better at retaining the fertilizer's nutritious components at the root level. Doing so, however, is not always financially feasible for grain farmers in need of every spare stand.