No-Till and Strip-Till Soybean Production with Surface and Subsurface Phosphorus and Potassium Fertilization

Published in Agron. J. 103:1862–1869 (2011) Posted online 6 Oct 2011 doi:10.2134/agronj2011.0149 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. S is an important crop in the United States, with 31.1 million ha planted in 2010 (USDA/NASS, 2010). In 2008, 62% of full-season soybeans and 76% of double-cropped (planted aft er wheat harvest) soybeans in the United States were planted under no-tillage or some other conservation tillage system (CTIC, 2008). No-till is oft en preferred over conventional tillage because it can result in operational cost savings to farmers, reduce soil erosion (Trewavas, 2004), and conserve soil water (Williams et al., 2009). No-till soybean production has challenges, however. Soybean typically follows corn in rotation, and the large amount of corn crop residue on the soil surface at planting can be a challenge for no-till soybean production. Soils covered with crop residue have higher albedo, which slows warming and evaporation of water in the soil surface, oft en resulting in delays in planting or germination, and slow early growth (Jones et al., 1994). Such delays can be detrimental to soybean yield (De Bruin and Pedersen, 2008). Th e strip-till system is one in which a narrow (15–25 cm wide) band is tilled to a depth of 10 to 20 cm and the new crop row planted atop this strip. Th is system provides most of the soil and water conservation benefi ts of no-till, while improving seedbed condition similar to conventional tillage systems (Jones et al., 1994; Morrison, 2002). Improved seedbed conditions by removing crop residue from the planting row in strip-till relative to no-till has been shown to enhance seed germination, faster early plant growth, and grain yield for corn in soils that tend to be cool and wet in the spring (Vyn and Raimbault, 1992; Morrison, 2002; Vetsch and Randall, 2002; Randall and Vetsch, 2008). Compared to corn production, relatively less work has been done to assess benefi ts of strip-till for soybean production (Vyn et al., 1998; Randall and Vetsch, 2008). Another possible advantage to strip-till is the opportunity it provides for simultaneous deep banding of fertilizer materials. Deep banding of fertilizer, especially P, may be benefi cial to reduce surface P concentrations and lower potential environmental concern related to water runoff from fi elds with high P levels at the soil surface (Duiker and Beegle, 2006; Randall and Vetsch, 2008). In addition, deep banding of fertilizers has been hypothesized as an alternative to increase nutrient availability and improve fertilizer use effi ciency. In much of the U.S. Corn Belt soybean production is rainfed. In nutrient-stratifi ed systems where P and K concentrations are high in the soil surface, excessive drying of that layer during reproductive stages—when soybean accumulate about 75% of their total P and K (Hanway and Weber, 1971)—may limit nutrient uptake (Yin and Vyn, 2002). However, Fernandez et al. (2008, 2009) showed greater apparent K uptake in the top 5 cm of a vertically stratifi ed no-till soil when intermittent rainfall provided adequate moisture during the growing season. Similarly, inconsistent response to deep banding of fertilizers has been reported for soybean seed yield. Some have reported yield advantages with deep band compared to broadcast fertilizer (Ebelhar and Varsa, 2000), while others have reported no advantage (Borges and Mallarino, 2000; Yin and Vyn, 2002; Rehm and Lamb, 2004). Th e limited amount of information on soybean production in strip-till and the ABSTRACT