|Pikul jr, Joseph|
Submitted to: International Nitrogen Conference
Publication Type: Proceedings
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, usa. International Nitrogen Conference. 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.