Drainage Management Systems
Water recycling feasibility
By Ben Reinhart
The latest on the Transforming Drainage project.
By Ben Reinhart
The Transforming Drainage project is capitalizing on the network established during our first year with new research to advance our understanding of drainage water storage systems (e.g. controlled drainage, saturated buffers, and drainage water recycling), foundations for innovative tools, and continued outreach to stakeholders across the Midwest.
Research in Iowa, led by Chris Hay of the Iowa Soybean Association and Matt Helmers of Iowa State University, evaluated the feasibility of drainage water recycling systems to meet growing season irrigation requirements for corn and soybeans across 12 locations and 17 years between 1990 and 2011. Rain-fed cropping systems, which predominate across much of the Midwest, rely on seasonal rainfall to meet crop water requirements. If the amount of rainfall infiltrated and stored within the root zone cannot meet crop water requirement during certain periods, then a water deficit exists and supplemental irrigation can potentially increase crop yield. This study found there was an average water deficit of nearly six inches for soybeans in Ames, IA, over the study period. This represents a worst-case scenario, since soil water stored in the root zone in the spring was not included in this assessment. Deficit amount tended to increase from east to west and from north to south across Iowa. After comparing water deficits with the drainage volumes from Iowa State University drainage research plots, storing subsurface drainage water could potentially have been sufficient to meet the demand for irrigation in nine of the 17 years, even at this upper limit of water deficit. “This research provides a great foundation for future work in evaluating the impact, both in regards to crop yield and water quality, and management strategies for drainage water recycling in Iowa and elsewhere across the Midwest,” Hay says. “As we continue to refine the research to incorporate soils information, impacts on crop yield and economics across more sites, we can better understand the feasibility of this practice.”
In other efforts, Mohamed Youssef, agricultural engineer at North Carolina State University, led the development of an approach to estimate the impact of controlled drainage systems on reducing annual drainage volume and nitrogen loss. Using the field-scale modeling program, DRAINMOD, the team at North Carolina State conducted thousands of simulations across various climates, soil types, drainage designs, and cropping scenarios in the Midwest. The results were used to build simple statistical relationships that estimate annual drainage volume and nitrogen loss as functions of readily available data (e.g. precipitation, soil texture, soil organic matter, depth and spacing of tile drainage, grown crop, fertilizer rate). This will allow users to define site-specific, and management-specific, estimates of how much tile drainage water and nitrogen would be expected under both free drainage and controlled drainage scenarios. Packaged as a web-based interface, these regional empirical equations could represent a user-friendly tool for future drainage system designers and planners.
The Transforming Drainage project has now joined social media as another way to share work from the project. Folks can follow us on Twitter @TD_drainage and participate in the conversation using #transformingdrainage. One of the primary goals of the Transforming Drainage project is to support and grow the network of individuals and organizations out there working in agricultural drainage. Sharing ideas and feedback on tools, research and outreach or education opportunities is a great way to participate in the Transforming Drainage project and can lead to greater collaborations down the road. We encourage you to visit the website (www.transformingdrainage.org), sign up for our online newsletter, and follow us on social media. We look forward to working with all of you to advance drainage water storage for more resilient cropping systems.