Nitrate Loss in Subsurface Drainage as Affected by Nitrogen Fertilizer Rate

TLDR

"Low rates exceeded the drinking‑water nitrate limit only during corn years, while medium and high rates exceeded it every year; nitrate loss was greatest at the high rate (48 kg N ha⁻¹), and although economically optimal rates were 67–135 kg ha⁻¹ (1996) and 114–172 kg ha⁻¹ (1998), the system was not sustainable due to soil nitrogen depletion." That is one sentence. Ensure no semicolons? It's okay.

Abstract

ABSTRACT The relationships between N fertilizer rate, yield, and NO 3 leaching need to be quantified to develop soil and crop management practices that are economically and environmentally sustainable. From 1996 through 1999, we measured yield and NO 3 loss from a subsurface drained field in central Iowa at three N fertilizer rates: a low (L) rate of 67 kg ha −1 in 1996 and 57 kg ha −1 in 1998, a medium (M) rate of 135 kg ha −1 in 1996 and 114 kg ha −1 in 1998, and a high (H) rate of 202 kg ha −1 in 1996 and 172 kg ha −1 in 1998. Corn ( Zea mays L.) and soybean [ Glycine max (L.) Merr.] were grown in rotation with N fertilizer applied in the spring to corn only. For the L treatment, NO 3 concentrations in the drainage water exceeded the 10 mg N L −1 maximum contaminant level (MCL) established by the USEPA for drinking water only during the years that corn was grown. For the M and H treatments, NO 3 concentrations exceeded the MCL in all years, regardless of crop grown. For all years, the NO 3 mass loss in tile drainage water from the H treatment (48 kg N ha −1 ) was significantly greater than the mass losses from the M (35 kg N ha −1 ) and L (29 kg N ha −1 ) treatments, which were not significantly different. The economically optimum N fertilizer rate for corn was between 67 and 135 kg ha −1 in 1996 and 114 and 172 kg ha −1 in 1998, but the net N mass balance indicated that N was being mined from the soil at these N fertilizer levels and that the system would not be sustainable.