Water availability is often a tale of two extremes: too much or too little. "Before installing tile to manage the water table you need to know your soil characteristics, soil profile depth and hydraulic conductivity, the ease with which a liquid can move through soils," says Isaac Ferrie with Crop Tech Consulting. The higher the hydraulic conductivity, the farther apart you can space the tile because the soil will pull the water to the tile.
Knowing the hydraulic conductivity and acre amounts of each soil type allows you to pick a tile depth and spacing that best fit the majority of the field.
Ferrie advises the following steps when considering tile:
- Evaluate the topography of your fields to determine if contour or pattern tiling works best. Accurate GPS planting or harvest elevation maps are a good place to start.
- Consider existing mains and outlets. Shallow tile and narrow spacing will move large amounts of water in a short period of time. To accommodate the large fluctuation in water flow, make sure you have adequate-sized mains. Deeper tile with wide spacing will eventually move more water than shallower, narrow tile but will do so over a longer period of time, creating less fluctuation in tile flow. If your mains are undersized or you have concerns about your tile outlets, go with the deeper tile with wider spacing.
- To view soil survey data, visit http://casoilresource.lawr.ucdavis. edu/gmap/. The interactive map shows the entire soil profile, hydraulic conductivity, drainability and a soil's ability to pull water from the profile.
- Consider installing tile gates to preserve water and prevent nutrients and chemicals from leaving the field. As the growing season progresses, taking out gates lowers the water table to promote root depth. Gates should then be added after harvest to keep water and nutrients in the field. Then, groundwater levels can be managed to coincide with rooting depth and field operations the next season.
Drainage Impacts Field and Fertilizer Efficiencies While Boosting Yield
An ongoing study, now in its 14th year, that Farm Journal Field Agronomist Ken Ferrie is conducting on a 240-acre field in central Illinois documents drainage's impact on efficiency of field operations, soil health, fertilizer use and, of course, yield.
Thanks to tile, the days available for planting without causing soil compaction significantly increased when wet soil was drained.
Improved drainage facilitates less intensive tillage, which saves time and fuel and improves soil health. During the growing season, installing drainage provided 12 more days to sidedress fertilizer without creating wheel-track compaction, Ferrie says.
At harvest, while nearby fields are experiencing delays and combine ruts, tiled fields can be harvested on schedule. "Timely harvesting, in turn, allows timely fall fertilizer and lime applications‚Äîand tillage if the farmer needs to do any," he adds.
Installing drainage also paid off in more efficient fertilizer use. "Because the drained soil is better
aerated, micro-organisms release more nutrients and less nitrogen is lost through denitrification," Ferrie says. "The amount of applied nitrogen per bushel of corn produced has fallen from 1.1 lb. to 0.7 lb."
The yield average for the field has jumped by nearly 20 bu. per acre when planted in corn. With soybeans, yields have ranged from a slight decrease to an increase of 3 bu. to 4 bu. per acre.