SUGARBEET SOIL NITROGEN MANAGEMENT UNDER SUBSURFACE DRAINAGE CONDITION

Abstract

Drainage and flooding are critical problems in the Red River Valley of North Dakota and Minnesota due to the flat topography and dominant poorly drained clay soils (Jin et al. 2008). Since 1993 excess water has significantly affected crop production in the Northern Great Plains. The precipitation received at critical growth stages has a greater impact than total annual rainfall. In June 2011, the North Dakota state average precipitation was 4.51 inches, which is above the 1971-2000 normal of 3.19 inches according to the North Dakota Agricultural Weather Network (NDAWN). The Prosper NDAWN observation site recorded 3.14, 5.17, and 5.91 inches rainfall in May, June, and July respectively in 2011. Water-logging has been shown to quickly decrease root-zone oxygen through displacement of the soil air by water. One option to manage waterlogging is through subsurface tile drainage. Although subsurface drainage is common in the Corn Belt, the adoption of tile drainage in the Red River Valley is relatively new. Installing subsurface drainage can reduce the chance of water logging and prevent saturation by lowering the water table. Shifting water and temperature regimes influence the below ground nitrogen (N) dynamics (Bouwman et al. 2010). Saturated conditions (undrained) increase the potential of available N loss in the form of nitrous oxide (N2O), known as denitrification. Denitrification is an anaerobic process and saturated field conditions accelerate the denitrification process. Hence, subsurface drainage has the potential to reduce denitrification N losses through the reduction of saturation. Nitrogen (N) fertilization is essential for optimizing crop yields and economic returns. Nitrogen is the most limiting nutrient in row crop production systems and N fertilizer is extensively applied to corn, wheat, and other non-leguminous crops. Common N-fertilizer management strategies include split applications of the total recommended rate and application of nitrification or urease inhibitors. Poorly-drained soils in the Red River Valley that warrant targeted N management include soils with high clay content. Knowledge of the trade-offs between N2O emissions from N fertilizer management practices and crop yield under subsurface drainage is therefore an essential requirement (Millar et al. 2010).