By Vinayak Shedekar, PhD
Why do Ohio farmers drain their crop land? In the 1850s, early settlers began digging ditches to drain swamps. Drainage transformed the swamps of northwest Ohio into some of the best farmland in the state.
After some major advances in drainage technology during the mid- to late-1900s, most of the drainage materials and technologies remained steady (these included new designs of drainage plows, tile trenching machines, corrugated-wall plastic tubing, and laser-beam grade-control). In the past 10 to 15 years, however, the drainage design and installation has been revolutionized by the availability of computer software for drainage design, machine control, and high-precision differential (RTK) GPS technology for surveying and installation of drainage systems.
Most of modern-day subsurface tile drainage work is now largely focused on replacing and/or improving aged tile systems (replacing old, randomly placed clay tile systems with corrugated-plastic tubing in a more systematic fashion), installing new systems in soils where wetlands are not threatened, and retrofitting existing systems to enable farmers’ adoption of drainage related conservation practices.
When it comes to planning for a drainage system, many factors affect your decision making. Engineering design of subsurface drainage systems involves: 1. Estimating maximum discharge capacity (drainage coefficient) of the system, 2. Determining size, slope, depth and spacing of laterals and main pipes for the given drainage coefficient and then 3. Planning the layout of the pipe network. The main objective is to remove excess water quickly and safely to reduce the potential for crop damage.
In a situation where water is ponded on the soil surface following a rainfall event, a general rule of thumb for most agricultural crops grown in Ohio is to lower the water table to about 12 inches below the soil surface within a 24-hour period, and 12 to 18 inches below the soil surface within a 48-hour period. The required drawdown of water table, along with soil’s ability to transmit water, can help determine the depth and spacing of parallel drains in the field. Many other factors need consideration before a drainage system can be designed and installed. For example, presence of drainage outlet, wet spots within a field, upstream/downstream impacts – especially on neighbors and watersheds, and regulatory permit requirements for the project.
With the growing water quality issues in the region and changing climate, the future drainage systems will play a critical role in managing waters across the landscapes. Many governmental and non-governmental environmental incentive programs like the H2Ohio and EQIP programs now offer financial support for adoption and management of drainage-related practices. For example, a recently completed multi-state project (transformingdrainage.org) recommends a suite of futuristic practices that may help capture, storage, recycling, and reuse of drainage water for irrigation. Practices include controlled drainage, saturated buffers, and drainage water recycling using subsurface or overhead irrigation. Thus, current and future on-farm drainage should take into account ways to optimize the performance and management of such practices.
If you are thinking about improving drainage on your farm, start by contacting your local NRCS or SWCD office. Most of the local technical service providers maintain a directory of local drainage contractors. The drainage contractors and engineering service providers (e.g. local soil water districts) are usually equipped to design systems. However, understanding key aspects of drainage design may help you make informed decisions on the system design that will facilitate your future farm planning.
From a farmer or land-owner’s perspective, the benefits of drainage outweigh the negative impacts. However, it is important and cost-effective to invest into a drainage system that will keep providing these benefits while minimizing the environmental impacts. An improperly designed or installed system may result in issues that are usually difficult to fix without the associated excessively large costs. Therefore, proper design and installation of these systems is critical.
Virtual Drainage Workshop, June 9
A virtual drainage workshop will be held June 9, 9:00 am to 12:00 noon. There is no cost to attend, but advanced registration is required. More details are available at the website: go.osu.edu/drainageschool. (This short workshop replaces, for this year only, OSU Overholt Drainage School, the five-day hands-on drainage design and installation training, that has been held in March for more than 50 years.)
The half-day webinar will feature a panel of professional engineers from state and federal agencies, drainage contractors, and tile manufacturers, who will discuss standard practices, common issues, and troubleshooting associated with drainage design, installation, and repairs. Featured speakers include Prof. Larry Brown (OSU), Justin McBride (ODA), Bob Clark II (Clark Farm Drainage, Inc), Mark Seger (ODA), Paul Chester (Retired NRCS Engineer), Greg Wells (NRCS), Rick Galehouse (OLICA Historian), and Dave Schweiterman (VP, OLICA). Dr. Peggy Kirk Hall, OSU Agriculture Law field specialist, will provide an update on recently passed H.B. 340 – Ohio’s “petition ditch laws” that address the installation and maintenance of drainage works of improvement in Ohio.
CEU credits are available for CCAs and Professional Engineers. The event is supported by the Ohio Land Improvement Contractors of America (OLICA).
Visit go.osu.edu/drainageschool for more details.
Vinayak Shedekar can be reached at firstname.lastname@example.org. This column is provided by the OSU Department of Food, Agricultural and Biological Engineering, OSU Extension, Ohio Agricultural Research and Development Center, and the College of Food, Agricultural, and Environmental Sciences.