Nitrate Losses through Subsurface Tile Drainage in Conservation Reserve Program, Alfalfa, and Row Crop Systems

Abstract

Subsurface drainage of gravitational water from the soil profile through tiles is a common practice used to improve crop production on poorly drained soils. Previous research has often shown significant concentrations of nitrate‐N (NO3‐N) in drainage water from row‐crop systems, but little drainage research has been conducted under perennial crops such as those used in the Conservation Reserve Program (CRP). Four cropping systems (continuous corn, a corn‐soybean rotation, alfalfa, and CRP) were established in 1988 to determine aboveground biomass yields, N uptake, residual soil N (RSN), soil water content, and NO3 losses to subsurface tile drainage water as influenced by cropping system. Hydrologic‐year rainfall during the 6‐yr study ranged from 23% below normal to 66% above normal. In dry years, yields were limited, RSN accumulated at elevated levels in all crop systems but especially in the row‐crop systems, soil water reserves and RSN were reduced to as deep as 2.7 m in the alfalfa (Medicago sativa L.) and CRP systems, and tile drainage did not occur. Drainage occurred only in the corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] systems in the year of normal rainfall. In years of excess precipitation, drainage from the row‐crop systems exceeded that from the perennial crops by 1.1 to 5.3X. Flow‐weighted average NO3‐N concentrations in the water during the flow period of this study were continuous corn = 32, corn‐soybean rotation = 24, alfalfa = 3 and CRP = 2 mg/L. Nitrate losses in the subsurface drainage water from the continuous corn and corn‐soybean systems were about 37X and 35X higher, respectively, than from the alfalfa and CRP systems due primarily to greater season‐long ET resulting in less drainage and greater uptake and/or immobilization of N by the perennial crops.

RZWQM simulated effects of crop rotation, tillage, and controlled drainage on crop yield and nitrate-N loss in drain flow

“…On average, RZWQM simulated a 14% reduction in drain flow under CC compared to CS. This is in agreement with other studies in the Midwest of the USA (Randall et al, 1997;Huggins et al, 2001), although Kanwar et al (1997) observed greater amounts of drain flow under CC than under CS rotation using 3 years of data (1990)(1991)(1992). As shown in Figs.…”

“…However, if 150 kg N/ha was applied to corn for both CC and CS, the model simulated 42% lower in nitrate-N loss (7.3 vs. 12.6 kg N/ha/year) and 32% lower in flow-weighted nitrate-N concentration (7.6 mg/L vs. 11.1 mg/L) for CC than for CS. Therefore, lower nitrate-N loss under CS was partially due to lower N application rate (Karlen et al, 1991;Randall et al, 1997;Huggins et al, 2001;Kladivko et al, 2004). Tillage had minimum effects on N loss to drain flow under CC as reported by Randall and Iragavarapu (1995), with slightly lower N loss simulated under NT than under MP (5%) and CP (5%) under CS (Table 4).…”

“…Subsurface drainage is a common practice used in the Midwest Corn Belt of the USA (Randall et al, 1997;Fisher et al, 1999) and is believed to contributing to hypoxia in the Gulf of Mexico (Kladivko et al, 2004). Many field studies have been conducted under subsurface drainage conditions with various management practices to reduce N loss in subsurface drainage flow (Randall and Iragavarapu, 1995;Fisher et al, 1999;Huggins et al, 2001;Randall, 2002, 2004;Kladivko et al, 2004).…”

Targeting land-use change for nitrate-nitrogen load reductions in an agricultural watershed

“…Considerable research has demonstrated that introducing perennial vegetation into an agricultural landscape dominated by annual crops of corn and soybeans can improve water quality (Schulte et al 2006;Dinnes et al 2002). Nitrate leaching beneath perennial vegetation is substantially reduced compared to annual crops (Randall et al 1997) because perennial vegetation maintains or increases soil organic nitrogen content (Drinkwater et al 1998), maintains greater soil water content (Brye et al 2000(Brye et al , 2001, and provides more evapotranspiration during vulnerable leaching periods in the spring and fall (Schilling et al 2008a).…”

Convergence of agricultural intensification and climate change in the Midwestern United States: implications for soil and water conservation

“…Changing precipitation patterns, combined with effects of increasing temperature on plant growth, mean that nutrient uptake patterns will change as agricultural systems adapt to a new climate. The increased susceptibility of nutrients to runoff and/or leaching resulting from climate change needs to be recognised and considered through changes in current nutrient management practices, including better timing of appropriate application rates (Nangia et al 2008), better targeting of fertiliser rates to match the distributions of soil and crop conditions within fields (Delgado and Berry 2008), intensification of plant water use through incorporation of cover crops (Kaspar et al 2007) or perennials (Randall et al 1997), and implementation of conservation practices that are able to trap and treat nutrient losses downstream of cropped fields (e.g. nutrient removal wetlands) (Tomer et al 2012).…”