ASABE Technical Library - Abstract

Abstract.

Agricultural practices have substantial impacts on water quality by affecting the amount and timing of nutrient loss. The objective of this study was to determine the impacts of subsurface drainage management (SDM) and nutrient sources (NS) on surface and sub-surface nitrate losses. A state-of-the-art experimental infrastructure was used to automatically monitor surface runoff and tile drainage water from individual field plots in real-time and collect water samples in year-round basis. The controlled drainage-subirrigation(CDS) water management was compared to regular tile drainage (DR) on a clay loam under corn and soybean rotation at an application rate of 200 kg N ha^-1 of inorganic fertilizer (IF), liquid cattle manure (LCM) or solid cattle manure (SCM), respectively, to corn but not to soybean. Nitrate concentration in surface runoff from CDS exceeded the provisional long-term aquatic life limit (LT-ALL) for freshwater (4.7 mg N L^-1) in 28, 22 and 33% of the flow events for IF, LCM and SCM, respectively, whereas from DR, 22, 39 and 22%, correspondingly. The LT-ALL exceedances were considerably greater for tile drainage, with 39, 61 and 28% of the flow events for IF, LCM and SCM, respectively under CDS and, 50, 44 and 67%, correspondingly under DR. Water and nitrate losses by surface runoff were greater from CDS than from DR, vice versa for the losses by tile drainage. Relative to DR, CDS reduced annual nitrate losses by 49, 56 and 38% for IF, LCM and SCM, respectively. Most of nitrate losses by surface runoff likely occurred during growing season while during non-growing season for the most of losses by tile drainage, regardless of SDM and NS. The CDS was effective in reducing sub-surface and total nitrate losses.