Controlled Drainage: Assessment of Yield Impacts and Education Effectiveness

Controlled drainage is the practice of using a water control structure to hold water in agricultural fields during periods when drainage is unnecessary. The use of this practice may increase crop yields compared to subsurface drainage because during the growing season controlled drainage can capture water from precipitation, and raise the water table for crop use. Results from published studies of controlled drainage impacts on crop yields have been mixed, and the effects of field characteristics and annual weather variation on these impacts are not well understood. For widespread adoption of controlled drainage, more information on how controlled drainage impacts crop yields is needed, as well as education on controlled drainage for more audiences. To analyze crop yield impacts, two controlled and two free draining quadrants at the Davis Purdue Agricultural Center were compared. A grid system consisting of 10 by 10-meter cells was created to obtain a balanced data set. Crop yield was analyzed by year, annual wetness classification, soil drainage class, and elevation. Controlled drainage significantly increased the corn yield in six out of nine years, and the nine-year corn yield average increased by 2.3%. Soybean yield was significantly higher under controlled drainage in three out of four years, but there was no significant difference in the four-year soybean average. Years were further classified by wet, normal, or dry based on growing season precipitation, and results indicated controlled drainage had the greatest significant impact on corn yield in the dry years. Analyzing yield by soil drainage class and elevation determined that the very poorly drained soils had the most significant response to controlled drainage, while the highest elevations (more than 60 cm above the outlet) were more impacted than elevations closer to the outlet level. An online learning module using virtual field trip videos was developed to increase student understanding of controlled drainage. It was implemented in an environmental hydrology class at Purdue University with the goal of determining student knowledge gain and perceptions of the module. Scores from the content knowledge pre-/post-test indicated students significantly scored higher on the post-test. Sixteen students were interviewed to glean more descriptive information, finding that students thought the videos helped them understand the concept of controlled drainage and appreciated that the module used real-world data from a research site. Students’ perceptions and knowledge gained after completing the online learning module suggests this can be an effective tool for teaching students about controlled drainag