Long-Term Tillage and Poultry Litter Impacts on Soybean and Corn Grain Yield

Published in Agron. J. 103:1479–1486 (2011) Posted online 3 Aug 2011 doi:10.2134/agronj2011.0073 Copyright © 2011 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. 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. N (no-till) using mechanized agricultural equipment has been encouraged in the southeastern United States since the 1960s (Phillips and Young, 1973), following the development of broadleaf herbicides 2,4-D and atrazine [6-chloro-N-ethyl-N¢-(1-methylethyl)-1,3,5,-triazine2,4-diamine] (Derpsch, 2004). Interest in no-till was primarily driven by the need to reduce soil erosion and fuel consumption (Larson, 1981; Campbell et al., 1984). Since that time, considerable effort has been spent on developing better technology for weed control and planting equipment to increase the success and productivity of no-till. In the southeastern United States, achieving benefits from the implementation of strict no-till was extremely challenging due to the hot, humid climate that promotes rapid surface residue decomposition and easily compacted soil types. This facilitated implementation of conservation systems that integrate practices such as reduced tillage (strict no-till, para-till, or strip-till), maintaining 30% crop residue on the soil surface, increasing soil surface coverage by growing winter cover crops, and use of crop rotations. Soils in the southeastern United States are characteristically sandy in nature, low in organic matter, have low water holding capacities, and are easily compacted by rainfall and machine traffic (Carreker et al., 1977). These soil conditions often limit water availability and restrict root growth, decreasing crop production. This has hindered the adoption of strict no-till. Use of deep tillage (turning the soil over) or in-row subsoiling has generally been recommended to alleviate root restriction and allow more vigorous growth for water and nutrient exploration (Vepraskas and Guthrie, 1992; Raper et. al., 1994; Torbert and Reeves, 1994; Reeves and Mullins, 1995; Torbert and Reeves, 1995; Mullins et al., 1997; Zou et al., 2001; Rosolem et al., 2002) and to increase yield potentials (Threadgill, 1982; Busscher et al., 1995; Frederick et al., 1998; Busscher et al., 2000; Schomberg et al., 2006). Specifically, the use of strip tillage to alleviate soil compaction zones has increased in recent years. This practice disturbs only a small zone, leaving the inter-row soil surface area undisturbed, which allows greater residue retention on the soil surface compared to conventional moldboard tillage and disking operations. Implementing crop rotations in a conservation tillage system also has the potential to increase yields for the Southeast. For instance, crop rotations can provide better weed control, interrupt insect and disease cycles, and improve crop nutrient use efficiency (Karlen et al., 1994). When grown in rotation, corn grain yields were 10 to 17% greater than under continuous corn (Higgs et al., 1990). Significant yield increases for corn grown in rotation also have been observed in experiments where N, P, and K soil test levels were high and pest populations were managed (Copeland and Crookston, 1992). The greatest impact of crop rotations on yield has been reported in the Corn Belt. However, use of crop rotations in the southeastern United States has been mixed. For example, rotating dryland cotton (Gossypium hirsutum L.) with other crops increased yield only 3% compared with continuous cotton in Alabama (Mitchell, 1996), whereas cotton rotated with corn produced 12% higher yield than monoculture cotton in Arkansas (Paxton et al., ABSTRACT