|Pikul Jr, Joseph|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 9/14/2001
Publication Date: 3/16/2002
Citation: Pikul Jr, J.L., Schumacher, T.E., Vigil, M.F. 2002. Nitrogen use and carbon sequestered by corn rotations in the northern corn belt, U.S. Galloway, J., E. Cowling, J.W. Erisman, J. Wisniewski, C. Jordan. Editors. A.A. Balkema Publishers, Lisse, The Netherlands. Optimizing Nitrogen Management in Food and Energy Production and Environmental Protection, pp. 707-713. Interpretive Summary: Diversified rotations have potential to increase nitrogen (N) use efficiency and reduce fertilizer N requirements for corn. Long-term field experiments provide benchmarks that define quantity of C sequestered in soil and the time frame involved in that sequestration. This experiment was started in 1990. Tillage systems for corn-soybean rotations were conventional and ridge tillage. Additional rotations under conventional tillage were: continuous corn and a 4-year rotation of corn-soybean-wheat companion seeded with alfalfa-alfalfa hay. Non-cropped treatments included plots under perennial grasses. Continuous corn returned about 2.3 times as much plant C to the soil as a 4-year rotation. Under conventional tillage, the rate of loss of soil organic C was nearly the same as the rate of C return from plant materials. Net result after 10 years was a loss of soil C from the top six inches of soil under all rotations with conventional tillage. Soil C remained unchanged in a corn-soybean rotation under reduced tillage. Ratio of soil C:N narrowed under the 4-year rotation because of an increase in soil organic N. A wider C/N ratio developed under perennial grass. Corn yield under a 4-year rotation without additional fertilizer N was 91 percent of the yield attained under continuous corn fertilized with inorganic N. Competitive corn production under the diversified 4-year rotation reflects the potential to improve soil productivity without additional N inputs.
Technical Abstract: Diversified crop rotation may reduce fertilizer nitrogen (N) input for corn (Zea mays L.) and increase soil carbon (C) storage. Objectives were to determine effect of rotation and N on soil C sequestration and N use. The experiment, started 1990, was on a Barnes clay loam near Brookings, SD. Tillage for corn-soybean [Glycine max (L.) Merr.] rotation were conventional tillage (CS) and ridge tillage (CSr). Rotations under conventional tillage were: continuous corn (CC) and corn-soybean-wheat (Triticum aestivum L.) companion seeded with alfalfa (Medicago sativa L.)- alfalfa hay (CSWA). Additional plots were perennial grasses. N treatments for corn were: corn fertilized for a grain yield of 8.5 Mg/ha (highN), 5.3 Mg/ha (midN), and no N fertilizer (noN). Total (1990-2000) corn yield was not different among rotatons at 81 Mg/ha under highN. Corn yield differences among rotations increased with decreased N. Total (1990-2000) corn yields under noN fertilizer were 69, 53, and 35 Mg/ha under CSWA, CS, and CC with highN and 13 Mg/ha on CSWA with noN. Soil C in the top 15 cm significantly increased (1.7 g/kg) under CC, CS, and CSWA. C/N ratio narrowed (-0.75) under CSWA and widened (0.72) under grass. We found no gain in soil C after 10 years regardless of rotation under conventional tillage.