Agriculture management practices can significantly affect soil C storage through changes in C inputs and losses. This study investigated the shortterm effects of tillage (no-tillage [NT] and conventional tillage [CT]), residue removal (0, 50, and 100%), and N rates of 0, 170, and 280 kg N ha-1 on soil C storage. Studies were established in 2008 to 2011 on a Nicollet clay loam (fine-loamy, mixed superactive, mesic Aquic Hapludolls) and Canisteo clay loam (Fine-loamy, mixed, superactive, calcareous, mesic Typic Endoaquolls) soil association at Ames, central Iowa site (AC) and a Marshall silty clay loam (Fine-silty, mixed, superactive, mesic Typic Hapludolls) soil association at Armstrong, southwest Iowa site (ASW) in continuous corn (Zea Mays L.). Findings from the C budget show that under CT and N rate of 170 kg N ha-1 in continuous corn, there was no significant change in net soil C with no residue removal. Increasing N rate from 170 to 280 kg N ha-1 resulted in greater potential C inputs from above and belowground biomass, although C losses were not significantly different, especially with NT. Thus, a portion of soil surface residue could be removed without causing a net loss of soil C. Converting from CT to NT led to lower soil C losses, but C inputs varied due to soil temperature and water content differences and seasonal variability in a given year. Consequently, averaged across both tillage systems and at 280 kg ha-1 N rate for continuous corn approximately 5.10 and 4.18 Mg ha-1 of the residue should remain on the field to sustain soil C in 2010 and 5.23 and 5.18 Mg ha-1 in 2011 for AC and ASW sites, respectively. These finding suggest that residue removal needs to be approached on yearly basis with particular consideration to site's yield potential and weather condition as the residue biomass production can be variable. © Soil Science Society of America.
