535 Increased CO 2 release from soils resulting from agricultural practices such as tillage has generated concerns about contributions to global warming. Maintaining current levels of soil C and/or sequestering additional C in soils are important mechanisms to reduce CO 2 in the atmosphere through production agriculture. We conducted a study in northern Alabama from 2003 to 2006 to measure CO 2 efflux and C storage in long-term tilled and non-tilled cotton (Gossypium hirsutum L.) plots receiving poultry litter or ammonium nitrate (AN). Treatments were established in 1996 on a Decatur silt loam (clayey, kaolinitic thermic, Typic Paleudults) and consisted of conventional-tillage (CT), mulch-tillage (MT), and no-tillage (NT) systems with winter rye [Secale cereale (L.)] cover cropping and AN and poultry litter (PL) as nitrogen sources. Cotton was planted in 2003, 2004, and 2006. Corn was planted in 2005 as a rotation crop using a no-till planter in all plots, and no fertilizer was applied. Poultry litter application resulted in higher CO 2 emission from soil compared with AN application regardless of tillage system. In 2003 and 2006, CT (4.39 and 3.40 μmol m −2 s −1 , respectively) and MT (4.17 and 3.39 μmol m −2 s −1 , respectively) with PL at 100 kg N ha −1 (100 PLN) recorded significantly higher CO 2 efflux compared with NT with 100 PLN (2.84 and 2.47 μmol m −2 s −1 , respectively). Total soil C at 0- to 15-cm depth was not affected by tillage but significantly increased with PL application and winter rye cover cropping. In general, cotton produced with NT conservation tillage in conjunction with PL and winter rye cover cropping reduced CO 2 emissions and sequestered more soil C compared with control treatments. Carbon Dioxide Elux from Soil with Poultry Litter Applications in Conventional and Conservation Tillage Systems in Northern Alabama T. Roberson, K. C. Reddy,* S. S. Reddy, and E. Z. Nyakatawa, Alabama A&M University R. L. Raper and D. W. Reeves USDA-ARS J. Lemunyon USDA-NRCS G rowing public concern over environmental issues and increasing scientific proof of human interference with the earth’s climate has pushed climate change into the political arena in the past 30 yr. he Kyoto Protocol, which resulted from the United Nations Framework Convention on Climate Change, advises developed nations to reduce greenhouse gas emissions to 5% below their 1990 levels and allows them to meet their reduction limits by C sequestration in terrestrial sinks (United Nations, 1998). Although the USA has indicated that it will not participate in the agreement, the US government has taken efforts to target C sequestration in forests and croplands in the USA (USDA, 2003). Agricultural ecosystems play an important role in the storage and release of C within the terrestrial C cycle (Lal et al., 1999). hese systems are important in the global context because of their large CO 2 flux to the atmosphere and because C storage in these systems can be sensitive to management practices such as tillage and cropping systems (West and Post, 2002). Soil conservation practices that increase soil organic C levels include conservation tillage, planting cover crops such as winter rye [Secale cereale (L.)], and applying manures such as poultry litter (PL) (Reeves, 1997; USDA, 2003). Worldwide restoration of soil C levels is important for reducing atmospheric CO 2 concentrations (Lal, 2004; Lal et al., 2004). Although US agriculture has seen a 17% increase in no-tillage (NT) practice and an 11% decrease in conventional till- age (CT) practice from 1990 to 2004 (CTIC, 2004), there is still major potential for reducing CO 2 efflux through greater adoption of soil conservation tillage practices to sequester C. Soil CO 2 emission is affected by agricultural practices such as tillage and residue management and varies with climatic condi- tions (Yavitt et al., 1995). Intensive tillage can lead to C loss from agricultural soils due to exposure and subsequent oxidation of previously protected organic matter (Reicosky et al., 1995). Cover crops provide needed organic material that increases soil Abbreviations: AN, ammonium nitrate; CF, cotton-fallow; CR, cotton-rye; CT, conventional tillage; MT, mulch tillage; NT, no tillage; PL, poultry litter; 100 ANN, ammonium nitrate at 100 kg N ha −1 ; 100 PLN, poultry litter at 100 kg N ha −1 . T. Roberson, E.Z. Nyakatawa, K.C. Reddy, and S.S. Reddy, Dep. of Natural Resources and Environmental Sciences, Alabama A&M Univ., P.O. Box 1208, Normal, AL 35762; R.L. Raper, USDA-ARS, National Soil Dynamics Lab., 411 S. Donahue Drive, Auburn, AL 36832-5806; D.W. Reeves, USDA-ARS, J. Phil Campbell Sr. Natural Resource Conservation Center, 1420 Experiment Station Road, Watkinsville, GA 30677; J. Lemunyon, USDA- NRCS, Central National Technology Support Center, 501 W. Felix Street, FWFC, Bldg. 23, P.O. Box 6567, Fort Worth, TX 76115. Copyright © 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including pho- tocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Published in J. Environ. Qual. 37:535–541 (2008). doi:10.2134/jeq2006.0386 Received 21 Sept. 2006. *Corresponding author (reddykcs@gmail.com). © ASA, CSSA, SSSA 677 S. Segoe Rd., Madison, WI 53711 USA SPECIAL SUBMISSIONS