Effects of Cover Crops in Reducing Nitrate-Nitrogen Leaching in Iowa

Nitrate-nitrogen (N03-N) has been deemed a main source of pollutant for both shallow groundwater and surface water bodies. The main source of N03-N in the Mississippi River Basin (MRB) is linked to tile drainage (Lowrance, 1992; David et al. , 1997). Approximately 25% of agricultural land is artificially drained in Iowa (Baker et al., 2004) and subsurface drainage is the main source of N03-N loss. Schilling and Zhang (2004) reported that while Iowa accounts for 5% of the area of the MRB it contributes approximately 25% of N03-N load (23 lb-N acre-1) over a 28-year period from 1972 to 2000. Plot scale experiments measured N03-N loss of 23 to 49 lb-N acre-1 year1 in northeast Iowa (Weed and Kanwar, 1996), 24 to 27lb-N acre-1 in central Iowa (Baker et al., 1975; Baker and Johonson, 1981 ; Kanwar et al., 1983) and 6 to 56 lb-N acre-1 year1 in northwest Iowa (Lawlor, et al. , 2008)