|Pikul Jr, Joseph|
|Schumacher, Thomas - SOUTH DAKOTA STATE UNIV|
Submitted to: Soil and Water Science Research in the Plant Science Department
Publication Type: Experiment Station
Publication Acceptance Date: January 24, 2002
Publication Date: April 30, 2002
Citation: PIKUL JR, J.L., SCHUMACHER, T.E., VIGIL, M., RIEDELL, W.E. NITROGEN, WATER, AND SOIL CARBON AFFECTED BY ROTATION IN EASTERN SOUTH DAKOTA. SOIL AND WATER SCIENCE RESEARCH IN THE PLANT SCIENCE DEPARTMENT. 2002. Soil PR 01-25. Interpretive Summary: Diversified rotations have potential to reduce fertilizer N requirements for corn. There is a poor understanding of soil C storage related to fertilizer practice and crop rotation. Continuous corn returned about 2.3 times as much plant C to the soil as a 4-year rotation. Under conventional tillage methods, the rate of loss of soil organic C was nearly the same as the rate of C return from above-ground-plant material. The net result after 10 years was a loss of soil C from the top six inches of soil under all rotations receiving conventional tillage. Soil C remained unchanged in a corn-soybean rotation under reduced tillage. Soil productivity is related to both quantity of soil organic C and N composition. Ration of 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. Average corn yield under a 4-year rotation without additional N reflects potential to improve soil productivity without additional N inputs. Sustainability questions aside, continuous corn may appear as a viable way to sequester C because of the large amount of organic material returned to the soil under corn. However, from 1989-2000, all of the plant C returned annually under conventional tillage was subsequently lost to the atmosphere.
Technical Abstract: Diversified crop rotation may improve production efficiency, reduce fertilizer nitrogen (N) requirements for corn (Zea mays L.) and increase soil carbon (C) storage. Objectives were to determine effect of rotation and fertilizer N on soil C sequestration, water use, and N use. Soil is a Barnes clay loam (fine-loamy, mixed, superactive, frigid Calcic Hapludoll) near Brookings, SD. Primary tillage on all rotations was with a chisel plow. Rotations (started in 1990) were continuous corn (CC), corn-soybean [Glycine max (L.) Merr.] (CS), a 4-year rotation of corn-soybean-wheat (Triticum aestivum L.) companion seeded with alfalfa (Medicago sativa L.)-alfalfa hay (CSWA), and plots of perennial grass. 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). Average corn grain yield (1996-2001) was not different among rotations at 7.1 Mg/ha under highN. Corn yield differences among rotations increased with decreased fertlizer N. Average (1996-2001) corn yield with noN fertilizer were 7.3 Mg/ha under CSWA, 6.1 Mg/ha under CS, and 3.8 Mg/ha under CC. Rotation did not improve N use efficiency (NUE) or water use efficiency (WUE) under highN. With midN, NUE and WUE was about 40% greater under CSWA compared with CC. Soil C in the top 15 cm increased (0.7 g/kg) with perennial grass cover. C/N ratio significantly narrowed (-0.75) with CSWA and widened (0.72) under grass. We found no gain in soil C after 10 years regardless of rotation.