Considerations of all areas involves
Most soils in throughout the world would remain wet for several days after a rain without adequate drainage, which then preventing timely fieldwork, and causing stress on growing crops. Soils which are saturated do not provide sufficient aeration for the development of crop root, and can also be an important source of plant stress. That is why artificial drainage of poorly draining soils has become integral to maintaining a profitable crop production system. Planning an effective drainage system takes time and requires consideration of a number of factors, including:
- Present and future cropping strategies
- Environmental impacts associated with drainage discharge
- Easements and right-of-ways
- Quality of the installation
- Local, state, and federal regulations
- Soil information
- Wetland impact
- Adequacy of system outlet
- Field elevation, slope, and topography assessment
- Economic feasibility
It is very important
that the landowner, system designer, and contractor understand other applicable
federal laws, as well as the local watershed and state laws dealing with soil drainage.
People considering installation of a drainage system should also know their
rights and responsibilities concerning the removal of water from land and its
transfer to other land. While developing a drainage plan and specifications, it
is useful to consult a number of information sources. These include county soil
and site topography surveys, local drainage experts, Farm Service Agency aerial
photos, and ditch and downstream water management authorities. It is also a
good idea to do some surface and subsurface evaluation of a field. Other
potential sources for yield response information related to improved drainage.
Many soil surveys have also identified the potential yield for each soil type
for common crops using sound management practices.
Soil drainage system capacity and drainage
coefficient
To protect crops, a subsurface drainage system must be able to remove excess water from the upper portion of the active root zone in 24 to 48 hours after a heavy rain. The drainage system capacity selected for most farmlands should provide the desired amount of water removal per day, commonly referred to as the drainage coefficient. Any refinement of drainage coefficient guidelines should be done after consulting with drainage experts and local drainage contractors.
Soil drainage topography and system layout
Where ever it is necessary to convey surface water to the subsoil drainage system through surface inlets. The selected coefficient should be applied to the entire watershed which is contributing runoff to the surface inlet unless a portion of the runoff is drained by other means. The goal of drainage system layout and design is to provide adequate and uniform drainage of a field or area. The field topography and outlet location and elevation are typically the major factors considered in planning drainage system layout, with topography greatly influencing what layout alternatives are possible.
The system
outlet, be an open channel or a closed pipe, must be large enough to carry the
desired drainage discharge from a field quickly enough to prevent significant
crop damage. Drainage outlets are typically placed three to five feet below the
soil surface. Sometimes pumping is required to create an adequate outlet. The
bottom of an outlet pipe should be located above the normal water level in a
receiving ditch or waterway. It is expected that floods or high water levels which
may submerge the outlet briefly. In drainage outlets, it must be kept clean of
weeds, trash, as well as rodents.
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