Growers have used tile in fields for decades, but it’s just been in the last few years that the science of drainage water management (DWM) has advanced to where precision techniques are being used to design and run them better. The progress couldn’t be more timely, with growing concerns about controlling nutrient run-off and preserving water. Then too, effective drainage helps ensure the right moisture levels for the best yields.
One approach has been to use “control structures” with tile lines to raise and lower the water table in fields. The structures — sort of boxes — are placed at the end of tile lines just before an outlet and are connected to the existing drainage tile. Inside each structure, attached to the sides are tracks to hold vertical plastic panels called stoplogs.
Stoplogs can be added or removed to raise or lower the water table. Rainfall or a high water table can cause water to rise in the structure and flow over the stoplogs and out of the outlet.
Fields need to be relatively flat to utilize DWM systems. Flat land allows users to control the water table within 12 inches. If there are elevation changes in a field, more controlled drain structures would need to be installed within the field itself to control water flow — instead of just at the outlet at the edge of the field.
To design systems, drainage contractors can now start with GPS maps of soil type and topography, explains Dr. Harold Reetz, president of Reetz Agronomics. GPS can also be used to help install the tiles and other drainage components.
More tools are becoming available for this complex process. For instance, Trimble has a number of water management products, including WM-Drain farm drainage solution, FieldLevel II for land leveling and Farm Works Surface software. They can be combined to allow users to survey a field, analyze the field data, design a drainage system and do installation.
Another software program is Pipe Pro from AGPS (Advance Geo Positioning Solutions) Inc. It automatically calculates tile depth and slope, then controls installation. Among other capabilities, it can design tile layouts that don’t require a point-to-point drainage path for lasers. AGPS’s Vertical Curve Technology feature enables users to design layouts where pipe can be placed in more challenging, unfavorable landscapes. They set preferred parameters for their project and VCT designs a drainage solution that uses a finite number of grade breaks through the drainage path.
Now systems are available that network and electronically control DWM systems across a watershed. The Smart Drainage System, exclusively from Agri Drain Corp. is a remotely programmable, solar powered unit that allows users to manage the outflow from drainage systems, monitor and record rainfall data, water level in the soil profile, flow rates, and quantify the reduction of water and nutrient loss. If the producer has a water source available, they can add water into the system to reverse the drainage process and sub-irrigate their crops as well.
Assessing The Need
Drainage problems are caused by a combination of soil type and topography and the amount and timing of rainfall, explains Reetz. Soils with higher clay content tend to have more drainage problems. Many soils have a layer of clay accumulation below the surface that restricts water flow down the profile.
Many fields have low spots where water accumulates as it flows from higher elevations. Changes in field elevation play a role as well, and variations of only a few feet can result in drainage problems.
Surface drainage can be accomplished with grassed waterways and ditches that carry excess water to larger ditches and streams, and on relatively flat fields, excess water can be removed with shallow ditches that are reformed each year, says Reetz. For more complex drainage issues, subsurface tile systems are needed.
In recent years, he says extensive drainage fixes have been needed in key farming regions such as the central Corn Belt, parts of the Mississippi Delta and increasingly, areas of the Red River Valley and the Lake Erie Basin.
Areas of lower rainfall and areas with course textured soils generally have fewer drainage problems. But management of water is a growing issue for most crop production areas.
“As managing water becomes more sophisticated and farmers need assistance with the details, there may be opportunities for retailers to provide some water management services in conjunction with other crop scouting and management services,” suggests Reetz. Dealers can help with soil moisture sensors, crop stress monitors and various remote sensing technologies — items that can all support drainage management.