About Us | Help Videos | Contact Us | Subscriptions



This article in JEQ

  1. Vol. 36 No. 6, p. 1821-1832
    Received: Feb 2, 2007

    * Corresponding author(s): mpcnlink@gmail.com
Request Permissions


The Myth of Nitrogen Fertilization for Soil Carbon Sequestration

  1. S. A. Khan *,
  2. R. L. Mulvaney,
  3. T. R. Ellsworth and
  4. C. W. Boast
  1. Department of Natural Resources and Environmental Sciences, Turner Hall, 1102 S. Goodwin Ave., Univ. of Illinois, Urbana, IL 61801. This study was performed with partial funding under Project 875397, Illinois Agric. Exp. Stn., and with support generated through the 15N Analysis Service


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 CO2 enrichment, and NO3 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.

  Please view the pdf by using the Full Text (PDF) link under 'View' to the left.

Copyright © 2007. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyAmerican Society of Agronomy, Crop Science Society of America, and Soil Science Society of America