ARS | Publication request: Change in surface soil carbon under rotated corn in eastern South Dakota

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 22, 2008
Publication Date: N/A

Interpretive Summary: Corn captures significant amounts of carbon. However, only a small fraction of plant carbon may be retained in the soil. Objectives were to determine effect of crop rotation and nitrogen fertilization on soil carbon sequestration. Continuous corn fertilized for a grain yield of 8.5 Mg/ha returned about 34% more plant carbon to the soil compared with the four-year rotation of corn-soybean-wheat-alfalfa. Yet, soil organic carbon loss under continuous corn was nearly ten-fold greater than the four¿year rotation. Soil productivity is related to both quantity of soil organic carbon and quality of soil organic matter as well as other factors. The plant integrates across many biological, chemical, and physical soil properties and the historic good yield of corn on the four-year rotation may reflect soil-improvement from this rotation. Our findings on carbon storage are relevant to the top ten corn production counties in eastern South Dakota as an estimate to reasonable rates of soil organic carbon accumulation or loss. With respect to corn production, average (1990-2005) non-irrigated corn grain yield was 7.2 Mg/ha (115 bu/acre) for the top producing counties in South Dakota. Average corn yield (1990-2005) for continuous corn fertilized for 8.5 Mg/ha was 6.8 Mg/ha (108 bu/acre). Therefore, the quantity of corn residue returned to the soil of our plots under continuous corn would be typical for eastern SD. Continuous corn produces a large amount of crop residue; residue considered to be a potential source of cellulosic feedstock for ethanol production. There are risks associated with wholesale removal of crop residues, and the long-term consequences of residue removal are poorly understood. These risks include exacerbating soil erosion by water and wind, depletion of soil organic matter, degradation of soil quality, and reduction of agronomic productivity. In this study, despite crop residues being returned to the soil, we showed the potential to sequester C was very limited under rotated corn and not possible under continuous corn grain at a production level of 6.8 Mg/ha/year.

Technical Abstract: Diversified crop rotation may reduce fertilizer nitrogen (N) input for corn (Zea mays L.) and increase soil organic carbon (SOC) storage. Objectives were to determine effect of rotation and N on soil C sequestration. The experiment was started in 1990 on a Barnes sandy clay loam near Brookings, SD. Since 1996, primary tillage was chisel plow, and all crop residues were returned to the soil. Crop rotations were continuous corn (CC), corn-soybean [Glycine max (L.) Merr.] (CS), and corn-soybean-wheat (Triticum aestivum L.) companion seeded with alfalfa (Medicago sativa L.)-alfalfa hay (CSWA). Non-cropped treatments included perennial grasses. Nitrogen treatments for corn were corn fertilized for a grain yield of 8.5 Mg/ha (N1), 5.3 Mg/ha (N2), and no N (noN). Corn yield under CSWA with noN was 91% of the yield under CC with N1. Soil organic C (0 to 15 cm) under grass increased 3.8 Mg C/ha from 1996 to 2006. Continuous corn under N1 returned about 34% more above-ground plant C (PC) to the soil compared with the CSWA rotation, but this was not enough to offset SOC loss. Under N1, there was a loss of 2.3 Mg C/ha (0 to 15 cm) from CC and a gain of 0.3 Mg C/ha from CSWA (1996 to 2006). A combination of greater crop diversity and less tillage on CSWA, compared with CC, likely contributed to a balance of SOC (return of PC ¿ loss of SOC).