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RESEARCH PRODUCT

Tillage effects on yield and nitrogen fixation of legumes in Mediterranean conditions

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Published in Agron. J. 104:1459–1466 (2012) Posted online [DATE] doi:10.2134/agronj2012.0070 Copyright © 2012 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. I agricultural practices that involve the use of agrochemicals such as fertilizers, pesticides, and herbicides have greatly increased the global food supply but often with detrimental effects on the environment, such as contamination of ground and surface water, air pollution, and loss of biodiversity. Thus, there is a need to give more attention to the sustainable agricultural systems that rely, as much as possible, on the use and effective management of internal resources (Bohlool et al., 1992). Cultivating N-fixing plants is a valuable approach to curbing the increasing reliance on chemical inputs. Introducing legumes into cereal-dominated cropping systems can provide many advantages, such as fixing great amounts of atmospheric N which will then be partly available to the subsequent crop; reducing the occurrence of pests and weeds; and improving the quality of the soil (Peoples et al., 1995; Stevenson and van Kessel, 1996; Unkovich et al., 1997; van Kessel and Hartley, 2000). Unfortunately, legumes are often considered crops of secondary importance, particularly in the Mediterranean regions (Lopez-Bellido et al., 2003), and as a consequence, they are usually grown without adequate crop management. To take advantage of all the benefits legumes can provide, it is necessary to develop more sustainable and environmentally friendly crop management methods, such as conservation tillage and NT. Reducing the intensity of tillage helps mitigate soil erosion (Jordan et al., 2000), increase soil organic matter (West and Post, 2002), improve soil biodiversity (Kladivko, 2001), enhance aggregation and aggregate stability (Madari et al., 2005), and increase water storage in the soil (Radford et al., 1995). Although these improvements often have positive effects on crop growth and yield (De Vita et al., 2007; He et al., 2011; Cullum, 2012; Giambalvo et al., 2012), contradictory results (as well as considerable year-to-year variation) have been reported for comparisons of conservation tillage and CT. For instance, in environments with a cold spring and poorly draining soil, plowing can result in quick soil warming and rapid drainage, leading to an increase in crop yield (Lal, 2007). Much research around the world has compared the performance of cereal crops grown under CT and conservative tillage, but few studies have examined legume crops, particularly in Mediterranean regions, and even fewer have done so by investigating more than one species. Thus, we studied the effects of the use of NT on the productivity of four grain legumes (chickpea, faba bean, field pea, and lentil) typically grown in semiarid Mediterranean regions. As the value of legume crops lies in great part in their ability to fix N2, an ability that can be affected by agronomic management practices such as soil management systems (Horn et al., 1996; Matus et al., 1997; van Kessel and Hartley, 2000), we also studied the effects of the tillage system (NT vs. CT) on N2 fixation and N accumulation by the four species and constructed a simple N balance to assess the incremental changes in soil N associated with each species and tillage technique. AbSTrACT