Crunch the numbers on drainage
Experts with the South Dakota NRCS are developing a Drainage Decision Tool to help producers run the numbers on installing tile on specific fields. Mark Larson, hydraulic engineer with the Natural Resources Conservation Service based in Huron, previewed the new tool during the recent SDSU Drainage Forum.
He explained that the tool is housed within a detailed Excel spreadsheet, with some cells open for the user to plug in their data and some cells directly connected to data sets that will be helpful in making calculations. Once the user adds their County and field location information, the spreadsheet connects to the Web Soil Survey, pulling in details on all the types of soils found there and the drainage class for each.
The drainage class will show “acres with little to no benefit” or “acres with potential benefit,” to help users decide whether or not installing drain tile would benefit the field, and if so, whether it would benefit the entire field or only parts of it.
In addition to being connected to the Web Soil Survey, the spreadsheet is paired with data from Mitchell Tech’s annual producer survey to provide some baseline average costs of production. These cells are automated, but there is some opportunity for users to personalize their production costs if they have more specific data.
Larson noted that the Drainage Decision Tool is meant to give a truer comparison of pre- and post-drainage profitability, yield potential pre- and post-drainage, net profit change, and years to payback. The years to payback is based on a 25-year “practice lifespan,” which may be lower than actual but is what NRCS currently uses in its guidelines.
The NRCS Drainage Decision Tool is still in the development phase and not quite ready for public use, according to Larson, as he and his team are still vetting all the information that stands behind the calculations. He’s hopeful that the agency can work with the necessary organizations to finalize the data used, then the Drainage Decision Tool can become a tool used by NRCS field staff.
It could then either be picked up by an organization, business, or university to be further developed, or “it will stand on its own as a tool for starting a discussion on subsurface agricultural tiling,” Larson commented.
Drain tile is one of many useful tools
According to the 2017 U.S. Census of Agriculture, the most recent one available, 3% of South Dakota cropland is now tiled. This may seem like a modest number, but it’s interesting to note that it’s a 69% increase over the 2012 census. South Dakota showed the third highest increased in tiled cropland acres 2012 to 2017, behind a 73% in Kansas and a 109% increase in North Dakota.
Nationwide, a total of 56 million acres were reported as being drained by tile in the 2017 census, up from 49 million acres in the 2012 census. This represents a 14% increase over the 5 years, as well as tile now being present on 14% of U.S. cropland.
SDSU’s Dr. McMaine commented that, in South Dakota, conversations on drain tile often fall into two camps: tile is either the worst thing ever, or the best thing ever. “In South Dakota, there’s a pretty even split,” he observed of people’s views.
“I think people need to view it more as a tool,” Dr. McMaine continued. “It is not a perfect solution, but it is a useful tool. Figuring out how it fits in each individual’s operation and installing it in a way that can manage water both in the wet times and the dry times.”
Dr. McMaine is a proponent of controlled drainage, which allows more options for managing your water table at different times of the year and in different moisture conditions.
Drainage Water Management (DWM), as described by the NRCS, is the process of managing the timing and the amount of water that discharges from ag drainage systems. A structure for water control is installed in the tile line, which allows for management of the tile outlet elevation. DWM works best on very flat ground, but still may provide value on a variety of field conditions.
By stacking or lowering riser boards within the water control structure, the water table can be raised or lowered depending on land-use needs. Spring and fall, water table levels could be lowered to allow more optimal field work conditions. Mid-year, levels could be brought up, if needed, to bring moisture to developing roots.
Talk to your local NRCS office about developing a Drainage Water Management plan, or talk to your tiling contractor about adding the necessary components to your system.
Build up your soils
In our current wet weather cycle, water infiltration rate and water-holding capacity will be critically important to our soils. Dr. McMaine encourages producers to look at introducing more organic matter into your system, using higher biomass crops, trying cover crops, and employing minimal tillage.
“Organic matter is kind of a win-win for both wet and dry cycles,” he commented, noting that you get better water infiltration but also better water-holding capacity.
He acknowledges that these changes take some time to implement, but long-term the benefits will definitely be felt.
“In general, improving the ability to manage water also improves the ability to manage a lot of other things down the road,” McMaine commented.
Marcia Deneke, NRCS Conservation Agronomist, offers a couple pieces of advice for wet conditions as well.
“If we anticipate saturated conditions in the spring, and the opportunity arises, producers can potentially dormant seed a cool-season cover crop,” Deneke said. “This would allow it to start growing and utilize some of the water prior to planting a cash crop.”
She noted that producers would need to follow the cover-crop termination guidelines to meet crop insurance requirements, and work with their crop insurance agent to ensure that the termination guidelines are met.
“Another consideration would be to select a moderate- to deep-rooted, high water-use cash crop or perennial vegetation in those portions of the field that are annually the wettest,” Deneke added, such as alfalfa, corn, safflower, sunflower, spring wheat, or oats.
“Another consideration would be to select a moderate- to deep-rooted, high water-use cash crop such as corn, safflower, sunflower, spring wheat, or oats. In those areas that are annually wet, it may be beneficial to plant perennial vegetation in or adjacent to those portions of the field to use or intercept excess moisture,” Deneke added. “We need to think about managing our crop field at the sub-field level.”
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