Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 31, 1997
Publication Date: N/A
Technical Abstract: The magnitude of greenhouse gas emissions from soil degradation depends on land use, cropping systems and tillage intensity. This study evaluated the impact of 30 years of continuous corn (Zea mays L.) silage removal vs. grain removal under low and high fertility on tillage-induced CO2 and soil C. Tillage-induced CO2 loss was measured using canopy gas exchange after moldboard plowing in the spring of 1996. Soil C and N analysis were done using standard analytical techniques. The 24-h cumulative CO2 loss differences were not significant with annual silage or grain removal treatments. There was no change in the total C or N or the C:N ratios. All four treatments had the same organic C content of 21.9 g kg**-1 in the 0-15 cm depth after 30 years. The cumulative total of 217 Mg ha**-1 of aboveground stover compared to none yielded no differences in total organic C. Twice as much N added had no effect on total C or C:N ratios. These results suggest intensive tillage by moldboard plow caused rapid decomposition that masked fertility affects on total C. New approaches to enhance C sequestration are needed in agricultural systems that require less tillage before there is a positive buildup in soil organic matter.