Corn–Soybean Rotation Effects on Nitrate Leaching
2003
Zhu, Y. | Fox, R. H.
Because agricultural production is a primary nonpoint source of NO⁻ ₃ in the nation's waters, a better understanding of the effects of cropping systems on NO⁻ ₃ leaching is required for developing agricultural production practices that reduce NO⁻ ₃ leaching. A 4-yr experiment was conducted to study the effect of a corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation on NO⁻ ₃ leaching using passive capillary fiberglass wick lysimeters. The experiment had five N rates on corn (0–200 kg N ha⁻¹ in 50-kg increments). Corn was planted in 1997 and 1999, and soybean was planted in 1998 and 2000. The increase of soil residual NO⁻ ₃–N concentrations in the surface 25 cm of soil after crop harvest was not significant (p = 0.05) when N fertilizer rates applied to corn increased from 0 to 100 kg ha⁻¹ but was significant when N rate increased from 100 to 200 kg ha⁻¹ in the corn years. The 2-yr average soil residual NO⁻ ₃–N concentrations and annual flow-weighted NO⁻ ₃–N concentrations in leachate were significantly higher (p = 0.05) in soybean years than in corn years at 0 and 100 kg N ha⁻¹ applied to corn, but the differences at the 200 kg N ha⁻¹ rate were not significant. The results indicate that at recommended N rates applied to corn in a corn–soybean rotation, NO⁻ ₃ leaching potential is similar for corn and soybean, but at less than 100 kg N ha⁻¹ rate, a greater NO⁻ ₃ leaching potential exists under soybean than under corn.
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