The myth of nitrogen fertilization for soil carbon sequestration

J Environ Qual. 2007 Oct 24;36(6):1821-32. doi: 10.2134/jeq2007.0099. Print Nov-Dec 2007.

Abstract

Intensive use of N fertilizers in modern agriculture is motivated by the economic value of high grain yields and is generally perceived to sequester soil organic C by increasing the input of crop residues. This perception is at odds with a century of soil organic C data reported herein for the Morrow Plots, the world's oldest experimental site under continuous corn (Zea mays L.). After 40 to 50 yr of synthetic fertilization that exceeded grain N removal by 60 to 190%, a net decline occurred in soil C despite increasingly massive residue C incorporation, the decline being more extensive for a corn-soybean (Glycine max L. Merr.) or corn-oats (Avena sativa L.)-hay rotation than for continuous corn and of greater intensity for the profile (0-46 cm) than the surface soil. These findings implicate fertilizer N in promoting the decomposition of crop residues and soil organic matter and are consistent with data from numerous cropping experiments involving synthetic N fertilization in the USA Corn Belt and elsewhere, although not with the interpretation usually provided. There are important implications for soil C sequestration because the yield-based input of fertilizer N has commonly exceeded grain N removal for corn production on fertile soils since the 1960s. To mitigate the ongoing consequences of soil deterioration, atmospheric CO(2) enrichment, and NO(3)(-) pollution of ground and surface waters, N fertilization should be managed by site-specific assessment of soil N availability. Current fertilizer N management practices, if combined with corn stover removal for bioenergy production, exacerbate soil C loss.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbon / metabolism*
  • Fertilizers*
  • Midwestern United States
  • Nitrogen / metabolism*
  • Soil / analysis*
  • Time Factors
  • Zea mays / metabolism

Substances

  • Fertilizers
  • Soil
  • Carbon
  • Nitrogen