Farm Drainage System
ADI has a very simple three-part farm drainage philosophy, with 35 years of proven success. We use this approach to Control the Underground and our vertical integration makes pattern tiling affordable.
- Narrow Lateral Spacings: We typically install 3" tile on 30' to 40' spacings to level your farm's water table.
- Shallow Depths: ADI installs lateral drainage lines at a level in the soil profile where they can perform.
- High Capacity Mains: ADI lets your farm drainage breathe. At the very minimum, drainage coefficients of 3/8" must be met to achieve success. Proper surface and subsurface drainage go hand-in-hand. Without surface drainage, 3/8" drainage coefficients must be increased to 1/2" or greater.
The Science Behind Farm Drainage
Main Coefficient: A main coefficient is how much water (in inches) can we drain per acre in 24 hours. A main that is set on a 3/8” coefficient will drain 3/8” of rain water every day. Of course, soil has water holding capacity within itself, but the tile will still only drain the 3/8” of water in 24 hours. The grade of the main does play a major factor in sizing of the main. Even the grade is determined by the topography of the ground, which means that increasing the coefficient is mainly done by increasing the size of the main. These charts have been available for years and can be trusted. Below are some examples:
- A 12” main with .1 % grade will only drain about 62 acres if we want to drain 3/8” of water daily.
- A 12” main with .1% grade will only drain about 55 acres if we want to drain 1/2” of water daily.
Lateral Spacing: Frankly, what good does it do to have a large main if you can’t get the water into the main? This is where permeability and spacings come into play. For example, a common soil in central Illinois is a rather tight or low permeability soil. This soil has a flow rate of .2 to .6 inches per hour. How long do you think it will take for water to travel 40’ (This is same as 80’ spacing)? Regardless of your guess, the real answer is “way too long.” Plus, it takes just as long to travel a 6” tile as it does a 3” lateral. Once water is inside of tile, size is important but it needs to get there first. Because these are gravity drainage systems, a 5” tile does not drain a wider spacing than 3” tile.
In central Illinois soil we are now recommending 25’ spacings, and in many instances when dealing with depressed areas, we split those down to 12 1/2’. Remember, we must get the water table down in 48 hours to prevent root damage and 24 hours is a big improvement.
Lateral Size: Once we have the water in the tile, the next factor to consider is tile size. Back to our central Illinois soil example and using our 3/8” coefficient, a 1300’ length on 25’ spacings represents .75 acre (75% of 1 acre). However, a 3” tile using the 3/8” guideline on a .1% grade will handle about 3 acres!
Now, if you’re simply uncomfortable with the 3” tile, we say use 4”. However, to just widen out the lateral spacings is entirely the wrong way to go.
The goal of a good farm drainage system is first to get the water into the tile and then get it out. Lateral sizing is not the main concern. First, we need to get the adequate sized main. Then, get the laterals close enough together to capture the water. At that point, we can then size the laterals to move it to the main.
After 35 years of doing this work, we have noticed most mains are undersized and the laterals are way too wide. Much of our work today is supplementing mains and splitting many of the 40’ and 50’ laterals that were done years ago.
Farm Drainage Results
So, what does all of this information mean for you, the farmer? Getting the right combination of Main Coefficient, Lateral Spacing, and Lateral Size is imperative to making sure you get the best bang for your buck out of your farm drainage system. We understand that every field is different and have the experience to make sure that you are getting the most successful results out of your investment. ADI's farm drainage systems provide proven results. Contact us today for a professional consultation.