Subsurface Drainage in Heavy Clay Soils in a Northern Climate and Its Effect On Various Soybean Cultivars.

SUBSURFACE DRAINAGE IN HEAVY CLAY SOILS IN A NORTHERN CLIMATE AND ITS EFFECT ON VARIOUS SOYBEAN CULTIVARS

Jack A. Brodshaug, Nathaniel J. D. Lungren, Evan J. Twedt, Chad Deplazes, Hans J. Kandel, Joel K. Ransom and Dean D. Steele

            The Red River Valley of the North in North Dakota and Minnesota is an area with unique, heavy clay soils.  Since 1993, the area has seen increased annual rainfall which has caused seasonal waterlogging, inhibiting yield potential.  Subsurface (tile) drainage is relatively new to the region and offers an option farmers are exploring to help curb waterlogging.  The objective of this research was to identify the effect of tile drainage in an environment with heavy clay soils in a northern climate and its interaction with various soybean [Glycine max (L.) Merr.] cultivars.  Two experiments (2009-2010) were conducted in the Red River Valley. The experimental area is unique as it has eight tiled units which can each regulate drainage with a control structure. The experimental design is a RCBD in a split-plot arrangement with four replicates. The whole plots were drained and undrained (control structures open and closed, respectively), and the sub-plots were twenty-nine soybean cultivars.  Soybean cultivars were selected based on iron chlorosis resistance, phytophthora root rot tolerance, and growing capability in wet soils.  Penetrometer readings (kPa), water table depth, soil water content, and soil temperature were measured weekly.  In 2009 and 2010, the drained ground had a higher penetration resistance, meaning it is capable of holding more weight compared to the undrained ground.  The water table was lower on drained ground early and late in the season.  Soil water content was lower on drained ground and temperature tended to be higher, especially in the spring. Soybean yields between drained and undrained were not different in 2009.  Soybean cultivars differed in root disease in 2010 based on drainage.  Overall, tile drainage has the potential to change how farming is conducted in the heavy clay soils in eastern North Dakota and northwestern Minnesota.