Impact of controlled drainage on corn yield under varying precipitation patterns: A synthesis of studies across the US Midwest and Southeast

Controlled drainage (CD) is a valuable management practice for reducing drainage volume and nutrient loss, but its impact on corn (Zea mays L.) production is not completely understood. The objectives of this study were to investigate the regional effect of CD on corn grain yield compared to free drainage (FD), investigate the factors influencing corn yield response to CD, provide management recommendations for optimizing corn yield under CD, and identify future research needs for corn production on poorly drained soils with subsurface drainage systems. This synthesis included data collected from 13 field sites where corn was planted under both FD and CD in six U.S. Midwestern states and North Carolina totaling 55 site-years of data from 2006 to 2017. On average, there was no statistically significant difference in corn grain yield between CD (10.62 Mg/ha) and FD (10.53 Mg ha-1). However, 42% of the dataset indicated that CD either increased or decreased corn yield by 4% or more compared to FD. Further analysis was conducted on this subset of data in order to evaluate underlying factors (i. e., weather conditions during the season, soil type, and drainage system design and management) influencing corn yield response to CD. Results of this analysis showed that CD was effective in alleviating plant stress caused by mild to moderate drought conditions and subsequently increased corn grain yield by 4-14% in 12 site-years. In contrast, CD reduced corn grain yield by 4-10% during wet growing seasons (6 site-years). Variability in growing season precipitation has been identified as a key factor influencing corn grain yield under CD, and more active management or CD system automation is recommended. General recommendations are provided for managing manually operated CD systems in the U.S. Midwest to improve growing season water management and corn yield. Additional research to develop technologically advanced water management systems for crop pro-duction on poorly drained soils is needed in order to adapt to changing weather patterns.