Rainfed Wheat and Soybean Productivity in a Long-Term Tillage Experiment in Central Italy Marco Mazzoncini,* Claudia Di Bene, Antonio Coli, Daniele Antichi, Monica Petri, and Enrico Bonari ABSTRACT
Tillage
Tillage plays a key role in cropping system sustainability due to its impact on soil properties, crop yields, economic returns, labor, and energy requirements. The objective of our research was to compare the effects of no-tillage (NT) and conventional tillage (CT) on durum wheat (Triticum durum Desf.) and soybean [Glycine max (L.) Merr.] productivity in a long-term, 2-yr rotation field experiment initiated in 1986 under a Mediterranean climate. The 16-yr (1990–2005) average grain yield for NT wheat was 8.9% lower than that for CT wheat (3.97 vs. 4.36 Mg ha–1). Differences between tillage systems were significant in 6 out of the 16 seasons and were small when planting was early, weed control was good, and rainfall deficit occurred during the grain fi lling period. The 16-yr average grain yield for soybean was significantly lower under NT than under CT (2.60 vs. 3.08 Mg ha–1) but differences between tillage systems were small and not significant in 12 out of the 16 seasons. In comparison to wheat, NT soybean had higher weed pressure. Nitrogen concentrations in wheat and soybean were little affected by tillage. Phosphorus concentrations in wheat grain and straw were generally higher under NT, while differences in soybean tissue P due to tillage were negligible.
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oil tillage choice is strategic to defining sustainable agriculture systems because of its impact on soil properties (i.e., physical, chemical, and microbiological characteristics), crop yields, production costs, and energy requirements. The widespread use of CT and, in particular, deep tillage may negatively affect soil fertility in the long term (Lal, 1991; Holland, 2004). In contrast, conservation tillage systems (e.g., minimum tillage [MT] and NT) increase soil organic carbon (West and Post, 2002), conserve soil moisture (Brandt, 1992; Hatfield and Stewart, 1994), and reduce labor and energy requirements (Unger and McCalla, 1980; Guy and Oplinger, 1989). Despite its widespread use, the effects of conservation tillage on crop productivity can be inconsistent from season to season and depend on soil type, climatic conditions, and agroecosystem management (Rhoton, 2000; McConkey et al., 2003). Therefore, longterm trials performed under specific soil and climatic conditions can provide invaluable information for determining whether agricultural practices are sustainable (Camara et al., 2003). The influence of tillage management on crop productivity has been investigated extensively around the world. Winter cereals have shown better adaptability to simplified tillage techniques than other crops (Bonfil et al., 1999; López-Bellido et al., 2000; Díaz-Zorita et al., 2004; Hunt et al., 2004; Ozpinar M. Mazzoncini, Dep. of Agronomy and Agroecosystem Management, Univ. of Pisa, via San Michele degli Scalzi n. 2, 56124 Pisa, Italy; C. Di Bene, D. Antichi, M. Petri, and E. Bonari, Land Lab, Scuola Superiore Sant’Anna, Piazza Martiri della Libertà n. 33, 56127 Pisa, Italy; A. Coli, Enrico Avanzi Interdepartmental Cent. for Agro-Environmental Res. (CIRAA), Univ. of Pisa, via Vecchia di Marina n. 6, 56122 San Piero a Grado (PI), Italy. Received 22 May 2007. *Corresponding author (
[email protected]). Published in Agron. J. 100:1418–1429 (2008). doi:10.2134/agronj2007.0173 Copyright © 2008 by the American Society of Agronomy, 677 South Segoe 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.
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and Cay, 2006). Among spring crops, NT soybean [Glycine max (L.) Merr.] has also been widely investigated (Vyn et al., 1998; Pederson and Lauer, 2002; Yin and Al-Kaisi, 2004). Soybean grain yield has been reported to be similar for NT and CT under different climatic conditions and soil types (Elmore, 1987; Deibert, 1989; Borin and Sartori, 1995). However, others found that soybean grain yield was lower under NT than under CT (West et al., 1996; Yin and Al-Kaisi, 2004). The effect of tillage on nitrogen and phosphorus concentrations in wheat and soybean tissues was generally small relative to the effect on crop productivity (McGonigle et al., 1999; Hunt et al., 2004). In Italy, interest in evaluating crop response to tillage practices that are alternatives to CT increased after the energy crisis of 1973. In general, CT in Italy means moldboard plowing (MP) deeper than 30 to 35 cm. At that time, the main goal of researchers was to evaluate the agronomics and energy savings in primary tillage by reducing the depth of plowing and introducing MT (Lo Cascio and Venezia, 1986; Bonari et al., 1995). It was only in the late 1980s and early 1990s that Italian researchers started to consider the feasibility of replacing MP with NT, as a consequence of NT equipment availability. The interest in MT and NT in Italy is based not only on economics and energy savings but also on mitigating soil erosion and loss of nutrients and maintaining or increasing soil organic carbon in the upper layer of soil. Nonetheless, the area under NT in Italy has increased little since then. Two likely reasons, although not necessarily the most important, are Italian farmers’ distrust of new techniques and their uncertainty about appropriate management for the NT system. Moreover, the Mediterranean rainfall regime (abundant and sometimes heavy in autumn–spring; scarce and not reliable in late spring–summer) and the clayey soils implicate the need to increase water infiltration (to increase water storage and reduce flooding or erosion) and root depth, which is normally achieved by CT before rainy periods. Abbreviations: CT, conventional tillage; MP, moldboard plowing; MT, minimum tillage; NT, no-tillage.
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Table 1. Soil physical and chemical characteristics of the top layer (0–30 cm) at the beginning of the experiment (1986) at the Enrico Avanzi Interdepartmental Center for AgroEnvironmental Research, University of Pisa, Italy.
Most Italian tillage experiments have been performed for short periods; few experiments have been conducted for 5 yr or more (Caliandro et al., 1992; Bonciarelli and Archetti, 1997; Basso et al., 2000). These studies found both yield increases and reductions when changing from CT to MT and NT. Winter cereals, wheat in particular, are the crops most widely studied because they adapt better to the conservation tillage techniques and average wheat yield losses of 5 and 10% under MT and NT, respectively, have been reported (Sartori and Peruzzi, 1994). On the other hand, the effect of tillage system on soybean productivity under Mediterranean conditions has scarcely been investigated. The few reported studies have compared different tillage practices (e.g., plowing at different depths, chiselling, MT, and ridge tillage) (Borin et al., 1997; Mazzoncini et al., 2001), but studies with NT have been rarely performed. Soybean yields under MT and NT are generally 10% less than under CT (Borin and Sartori, 1995). The lower yield obtained with NT is often linked to lower soil temperature and excess soil moisture during the early growth of spring sown crops, especially when crop residues are maintained on the soil surface. This is more marked in clayey soils or those with poor structure (e.g., silt rich soils) (Toderi and Bonari, 1986a; Borin and Sartori, 1995). The objective of this study, therefore, was to evaluate the long-term effects of NT and CT on wheat and soybean productivity in a 2-yr rainfed crop rotation in the central Italian region of Tuscany.
Property Physical Soil texture, g kg–1† Sand (2 mm-50 mm) Silt (50–2 mm) Clay (F 0.12 Straw yield CT 7.50 NT 7.54 P>F 0.93 Total biomass yield CT 12.76 NT 12.44 P>F 0.62 Harvest index CT NT P>F
1991
1992
1993
1994
1995
1996
4.77 4.64 0.76
4.88 4.76 0.77
3.84 4.20 0.16
2.75 2.16 0.03
4.10 3.37
