Subsurface Drainage in Clay Soils in a Northern Climate and its Effects on Various Soybean Cultivars and Soil Properties

Abstract

The Red River Valley of the North in North Dakota and Minnesota is a region with unique clay soils. Since 1993, the region has seen increased annual rainfall that has caused seasonal soil waterlogging, inhibiting crop yield potential. Prolonged waterlogging may cause debilitating physiological and chemical problems in plants. Subsurface (tile) drainage is relatively new to the region and offers an option farmers are exploring to help reduce excess water in the rootzone. The objective of this research was to identify the effect of subsurface drainage on soybean [Glycine max (L.) Merr.] productivity using various cultivars and to evaluate differences in soil temperature, soil penetration resistance, and water table depth between drainage treatments. 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 using control structures. The experimental design was a randomized complete block (RCB) in a split-plot arrangement with four replicates. The whole plots were drained or undrained ( control structures opened and closed, respectively), and the sub-plots were 29 soybean cultivars. Soybean cultivars were selected based on iron chlorosis resistance, phytophthora root rot tolerance, and growing capability in wet soils. Penetrometer readings, water table depth, and soil temperature were measured weekly. Soybean yields between drained and undrained treatments were not significantly different according to the combined analysis. This was due to 2009 being a relatively dry year and 2010 a relatively wet year. However, in 2010, the non-genetically modified (non-GMO) soybean cultivars and the cultivars chosen for their resistance to Phytophthora sojae were significantly better on the drained soil. In 2009 and 2010, drained treatments had a significantly higher soil penetration resistance, indicating that the drained soil is capable of a higher carrying capacity compared to the undrained soil. The wheat measurement site had a value of 1,420 k:Pa in the drained soil, while the undrained soil had a value of 1,267 k:Pa. The soybean measurement site had a value of 1,137 kPa in the drained soil, while the undrained soil had a value of 1,021 k:Pa. Finally, the bare ground measurement site had a value of 1,077 k:Pa in the drained soil, while the undrained soil had a value of 1,001 k:Pa. The water table was lower on drained soil compared to the undrained soil early and late in the growing season, causing the differences in soil penetration resistance. Temperature was significantly higher only on the drained soil planted to soybean compared to the undrained soil planted to soybean. The temperature difference was most pronounced in the spring. Subsurface drainage is a valuable tool for farmers in the Red River Valley. Despite the clay soils, cold winter, and shorter growing season, subsurface drainage works and helps to improve the efficiency of farming large fields in an area that has consistently battled wet weather for the last ten years. At a time when commodity prices are at a record high, improving efficiency and productivity with subsurface drainage might be an option. Overall, tile drainage has the potential to drastically change how farming is conducted in the clay soils in eastern North Dakota and northwestern Minnesota.