Published November 11, 2014
Soil & Water Management & Conservation
Tillage and Residue Management Effects on Soil Carbon and Nitrogen Under Irrigated Continuous Corn M.R. Schmer* V.L. Jin B.J. Wienhold G.E. Varvel (Retired)
USDA–ARS Agroecosystem Management Research Unit Rm 118, Keim Hall Univ. of Nebraska–East Campus Lincoln, NE 68583
R.F. Follett (Retired)
USDA–ARS Soil, Plant, and Nutrient Research Unit Bldg. D, Ste 100 2150 Centre Avenue Ft. Collins, CO 80526
Demand for corn (Zea mays L.) stover as forage or as a cellulosic biofuel has increased the importance of determining the effects of stover removal on biomass production and the soil resource. Our objectives were to evaluate grain yield, soil organic C (SOC), and total soil N (0–150 cm) in a 10-yr, irrigated, continuous corn study under conventional disk tillage (CT) and notill (NT) with variable corn stover removal rates (none, medium, and high). Natural abundance C isotope compositions (d13C) were used to determine C additions by corn (C4–C) to the soil profile and to evaluate the retention of residual C3–C. After 10 yr of management treatments, mean grain yields were 7.5 to 8.6% higher for NT when stover was removed compared with no stover removal, while grain yields were similar for CT in all stover removal treatments. Turnover of SOC occurred as C3–C stocks were replaced by C4–C in the 0- to 120-cm soil profile. Total SOC and N stocks changed mainly in surface soils (0–30 cm), with no detectable cumulative changes at 0 to 150 cm. Specifically, SOC declined after 10 yr under CT at 0 to 15 cm and was affected by residue management at 15 to 30 cm. Total soil N was greater when no stover was removed (P = 0.0073) compared with high stover removal at 0 to 15 cm. Long-term NT ameliorated medium stover removal effects by maintaining near-surface SOC levels. Results support the need to evaluate SOC cycling processes below near-surface soil layers. Abbreviations: CT, conventional tillage; NT, no-till; SOC, soil organic carbon.
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orn residue or stover (leaf, stalk, husk, and cob) is increasingly harvested and used as a dry forage replacement in feedlot and backgrounding diets for beef cattle in the western Corn Belt (Klopfenstein et al., 2013). Additionally, corn stover will probably be the primary feedstock in the Corn Belt region for an emerging cellulosic biofuel industry (USDOE, 2011), with estimated stover harvests ranging from 54 to 123 Tg yr−1 for the United States (Graham et al., 2007; Muth et al., 2013). However, excessive corn stover removal to meet forage or energy demands may lead to increased soil erosion and decreased soil organic C (SOC) that could decrease soil productivity and negatively affect grain yields (Blanco-Canqui and Lal, 2009; Wilhelm et al., 2010). Whether stover is being harvested for dry forage or bioenergy purposes, research is needed to quantify how SOC is affected by residue removal and by associated conservation management practices intended to ameliorate residue removal impacts. Conservation practices such as no-till have been recommended to maintain SOC and reduce erosion in corn cropping systems with residue removal ( Johnson et al., 2006; Sheehan et al., 2003; Wilhelm et al., 2007). Although the adoption of no-till farming has increased in the United States because of increased conservation benefits, improved weed control, and reduced production costs, Soil Sci. Soc. Am. J. 78:1987–1996 doi:10.2136/sssaj2014.04.0166 Received 23 April 2014. *Corresponding author (
[email protected]). © 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.
Soil Science Society of America Journal
tillage is still a common practice within corn cropping systems (41°9¢43.3² N, 96°24¢41.4² W; 349 m asl). The soil is Tomek (Economic Research Service, 2013). Corn stover collection silt loam (a fine, smectitic, mesic Pachic Argiudoll) and Filbert technologies are currently capable of recovering 40 to 70% of the silt loam (a fine, smectitic, mesic Vertic Argialboll). Long-term (1981–2010) mean annual precipitation is 74 cm and temperastover, but there is uncertainty about collection thresholds essenture is 9.8°C. The study has been in continuous corn since 2000. tial to maintain SOC for different soil types, cropping systems, The experimental design is a randomized complete block with tillage practices, and field locations (Wilhelm et al., 2010). factorial treatments arranged in split plots. The whole-plot factor Soil organic C is derived more from root inputs than from is tillage treatment (NT or CT) and the subplot factor is none aboveground biomass, but C allocation from aboveground (0%), medium (?35%), and high (?70%) stover removal calcubiomass plays a role in soil C dynamics (Doran et al., 1984; lated on a mass basis. Nitrogen fertilizer was applied at 202 kg N Kätterer et al., 2011; Wilhelm et al., 2004; Wilts et al., 2004). ha−1 yr−1 in 2001, 2002, 2004, 2007, 2008, 2009, and 2010, 190 Aboveground corn residue decomposition has been proposed to either enhance or decrease SOC decomposition partly through kg N ha−1 yr−1 in 2003, and 168 kg N ha−1 yr−1 in 2005 and shifts in microbial substrate utilization and composition (Cheng 2006. Treatments (tillage) and subplot treatments (residue reet al., 2003; Fontaine et al., 2003; Kochsiek and Knops, 2012; moval levels) were randomly assigned in a factorial arrangement Lehman et al., 2014). Retention of residue C in SOC pools into whole-plot experimental units (9 by 45.6 m) and subplots volves complex environmental and biological controls including within the whole plots (9 by 15.2 m) in six blocks. initial SOC content, mass of C inputs, tillage practices, climatic The previous crop for the entire area in 2000 was corn under factors, soil N content, and chemical composition of the residue rainfed conditions. Before 2000, the study site was historically (Wilhelm et al., 2004). In addition, surface residue protects the cropped with corn, soybean [Glycine max (L.) Merr.], oat (Avena soil from raindrop impact, reducing the potential for erosion loss sativa L.), and alfalfa (Medicago sativa L.). In the spring of 2001, and maintaining soil aggregation in the surface layer (Wienhold residue was removed from the medium and high stover removal treatments using a flail chopper. The entire study was then disked et al., 2013). Soil C dynamics at shallow depth ( F Total biomass Grain yield 0.0438 0.0287 0.3759 0.0502 0.0212 0.0088
