29 May / pattern tiled field spring of 2012
This is a 60 Acre field that we pattern tiled this spring
Managing agricultural drainage water in the Midwest could represent the next great step forward in agriculture, with benefits that reach from conserving subsoil moisture on individual tile-drained fields to reducing nutrient loading all the way down in the Gulf of Mexico. Control structures with movable weirs, or “stop logs,” allow growers to hold water in their soil or release it depending on the needs of their crop, their fieldwork schedule and the environment.
“The first step was to drain the land so it was farmable,” notes Don Pitts, state water and air quality specialist with the USDA Natural Resources Conservation Service (NRCS) in Champaign, Ill. “Now it’s time to manage that drainage.”
Pitts points out that most tile systems are designed to drain water as quickly as possible, combining tile line diameter, depth and spacing to achieve a drainage coefficient of 3/8 inch or more — the ability to remove 3/8 of an inch or more from the soil in a 24-hour period. That’s important for drying out the soil during wet springs to accommodate fieldwork and planting, or to avoid crop damage from heavy rains or flooding. But in the drier months of summer, long-awaited rainwater can just flow down the drain.
Worse, drainage water can carry nitrates and phosphorous downstream, helping nurture blooms of algae that eventually die by the billions. Those dying algae cells tie up oxygen from the water as they decompose, creating an oxygen-starved hypoxic “dead zone” in the Gulf of Mexico that can be hundreds of miles across.
Research shows that drainage water management can reduce annual nitrate losses from tile-drained fields by 15 to 75 percent, depending on location, climate, soil type and cropping system. Most of the reduction in nitrate results from the reduction in water flow from the field through the tile. However, there is some indication that a portion of the nitrate may be seeping deep into the ground or be denitrified by soil microbes.
No matter what the mechanism, trapping nitrates during the fall and winter fits well into the Midwestern crop cycle, notes Pitts.
26 Feb / Benefits of drain tiling your fields
The purpose of agricultural drainage is to remove excess water from the soil in order to enhance crop production. In some soils, the natural drainage processes are sufficient for growth and production of agricultural crops, but in many other soils, artificial drainage is needed for efficient agricultural production.
Surface drainage is the removal of water that collects on the land surface. Many fields have low spots or depressions where water ponds. Surface drainage techniques such as land leveling, constructing surface inlets to subsurface drains, and the construction of shallow ditches or waterways can allow the water to leave the field rather than causing prolonged wet areas.
Subsurface drainage removes excess water from the soil profile, usually through a network of perforated tubes installed 2 to 4 feet below the soil surface. These tubes are commonly called “tiles” because they were originally made from short lengths of clay pipes known as tiles. Water would seep into the small spaces between the tiles and drains away.
The most common type of “tile” is corrugated plastic tubing with small perforations to allow water entry. When the water table in the soil is higher than the tile, water flows into the tubing, either through holes in the plastic tube or through the small cracks between adjacent clay tiles. This lowers the water table to the depth of the tile over the course of several days. Drain tiles allow excess water to leave the field, but once the water table has been lowered to the elevation of the tiles, no more water flows through the tiles. In most years, drain tiles are not flowing between June and October.
Read whole article at epa.gov