|Evans, S - WCROC, UNIV OF MINNNESOTA|
Submitted to: Journal of Soil and Water Conservation Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 19, 2002
Publication Date: September 15, 2002
Citation: REICOSKY, D.C., EVANS, S.D., CAMBARDELLA, C.A., ALLMARAS, R.R., WILTS, A.R., HUGGINS, D.R. CONTINUOUS CORN WITH MOLDBOARD TILLAGE: RESIDUE AND FERTILITY EFFECTS ON SOIL CARBON. JOURNAL OF SOIL AND WATER CONSERVATION. 2002. V. 57(5). P. 277-284. Interpretive Summary: The carbon dioxide increase in the atmosphere has attracted interest due to potential global warming and the prospect of using the soil to sequester and store carbon released by other human activity. The cumulative effect of tillage and many cropping rotations has been a 30-50% decrease in soil carbon that caused undesirable changes in soil physical, chemical and biological properties. Recent tillage studies indicated major gaseous carbon losses immediately after tillage. This study determined the effect of residue removal as silage on soil carbon content and the short-term tillage-induced CO2 and H2O fluxes from a soil in west central Minnesota, U.S.A. Gas exchange measurements were made on both spring moldboard plow tillage and no-tillage where silage had been removed or where stover was returned and only the grain removed. Large amounts of residue removed as silage or residue returned to the surface made no difference in CO2 loss or rsoil carbon content after 30 years of continuous corn with plow tillage. Tillage-induced CO2 and H2O fluxes immediately after plow operations were larger than corresponding fluxes from plots not tilled. The results show the immediate impact of intensive surface tillage on gaseous carbon loss and the lack of impact of residue removal. This information will be helpful to scientists and policy makers around the world by demonstrating the impact of intensive tillage. These results illustrate the importance of improved residue management in conservation tillage systems with less soil disruption to maximize the retention of the soil carbon and minimize the impact on global climate change. This information will be of direct benefit to farmers to enable them to maintain crop production with minimal impact on the environment.
Technical Abstract: The magnitude of greenhouse gas emissions from soil degradation depends on land use, cropping systems and tillage intensity. Impacts of 30 years of continuous corn (Zea mays L.) silage removal vs. grain removal on tillage- induced CO2 and soil C was evaluated under low and high fertility. Tillage-induced CO2 loss was measured using canopy gas exchange after moldboard plowing in the spring of 1996. Soil C and N analyses were done using standard analytical techniques. The 24-h cumulative CO2 loss differences were not significant between treatments with annual silage or grain removal and showed no fertility effects. Total C or N or the C:N ratios remained virtually unchanged after 30 years. All four treatments had the same organic C content of 21.9 g kg**-1 in the 0-15 cm depth. The cumulative total of 217 Mg ha**-1 of aboveground stover from the high fertility grain treatment compared to none from the high fertility silage treatment yielded no differences in total organic C. Comparative fertilizer N rates of 87 and 166 kg ha**-1 had no effect on total soil C or associated C:N ratios. These results suggest intensive tillage by moldboard plow caused rapid organic matter decomposition that masked fertility and stover removal/return effects on total C. Agricultural production systems need new approaches to enhance C sequestration with less tillage intensity before there can be a positive increase in soil organic matter.