Soil Science Society of America Journal Soil Sci. Soc. Am. J. 78: 609–623 doi:10.2136/sssaj2013.10.0426 Received 2 Oct. 2013. *Corresponding author (malkaisi@iastate.edu). © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. Residue Removal and Management Practices Effects on Soil Environment and Carbon Budget Soil & Water Management & Conservation I n agricultural systems, like any other ecosystem, the alteration of one part of the system may have large efects on the system as a whole. Under current agri- cultural practices, crop residue is let on the soil surface ater harvest with NT systems, or is incorporated into the soil with CT, where the residue decomposi- tion environment is more suitable (Franzluebbers et al., 1995; Al-Kaisi and Yin, 2005). However, crop residues let ater harvest is being considered as a potential feedstock source for bioethanol production which can contribute to the reduction of fossil fuel use and net greenhouse gas (GHG) emissions (Wilhelm et al., 2004; Graham et al., 2007). It is most likely that lignocellulosic ethanol production will become a viable option and could create an annual market for crop residue from approximately 143 million tons to potential 583 to 805 million tons (U.S. tons; U.S. Department of Energy, 2011). Jose G. Guzman Carbon Management and Sequestration Center The Ohio State Univ. Columbus, OH 43210 Mahdi M. Al-Kaisi* Agronomy Dep. Iowa State Univ. Ames, IA 50011 Agriculture management practices can signiicantly affect soil C storage through changes in C inputs and losses. This study investigated the short- term 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 (ine-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 signiicant 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 signiicantly 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 ield to sustain soil C in 2010 and 5.23 and 5.18 Mg ha –1 in 2011 for AC and ASW sites, respectively. These inding 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. Abbreviations: AC, Ames Central Iowa; ASW, Armstrong Southwest Iowa; CT, conventional tillage; DAP, days after planting; NT, no tillage; R m , microbial respiration; R R , root respiration; SOC, soil organic carbon; UAN, urea-ammonium nitrate 32% nitrogen. Published April 8, 2014