Effects of tillage intensities on spatial soil variability and site-specific management in early growth of Eucalyptus grandis P. González Barrios a,⇑ , M. Pérez Bidegain b , L. Gutiérrez a a Departamento de Biometría, Estadística y Cómputo, Facultad de Agronomía, Universidad de la República, Montevideo, Uruguay b Departamento de Suelos y Aguas, Facultad de Agronomía, Universidad de la República, Garzón 780, Montevideo, Uruguay article info Article history: Received 28 October 2014 Received in revised form 13 February 2015 Accepted 19 February 2015 Keywords: Site preparation Spatial variability Geostatistics Zone delimitation abstract Soil tillage is one of the most common and important site preparation managements in forestry. However, in highly variable soils, uniform management practices might not be the best alternative. Site-specific management on the other hand, allows an optimal resource management as well as decreased environmental impact. However, the choice of a suitable strategy to manage areas with high soil variability is still a challenge. Our goal was to compare strategies that use soil characteristics to improve the comparison of tillage managements on Eucalyptus grandis growth. Specifically, we aimed to: compare strategies that incorporate soil characteristics into the models to compare tillage treatments; to determine the most useful soil characteristics for zone management delineation; and to compare tillage methods for site-specific management. We compared tillage intensities in contrasting soil types in a randomized complete block design with four and five replications. Tillage treatments included pit-planting, disc harrowing, and subsoiler. Experimental units consisted of three rows of fifteen trees each. Soil characteristics as well as plant height and diameter were evaluated periodically during the first 30 month after implantation. Intra-plot variability was described with multivariate geostatistical models. Using soil properties as covariates in the model to compare tillage treatments improved model fit. When root development is limited by soil conditions and electroconductivity is high, tillage intensity makes a difference in plant growth; subsoiler is the best treatment when electroconductivity is high, while disc harrowing is the best when electroconductivity is low. However, when root development is not limited by soil conditions, no differences were found between subsoiler and disc harrowing. We show how the use of soil characterization is a tool that provides better comparisons among treatments when high intra-plot variability is present. Additionally, the use of soil characterization either directly into the model or to determine zones provides useful information for site-specific management. Site-specific management could therefore easily be implemented to decrease the environmental impact of soil tillage as well as to increase wood production in forestry. Ó 2015 Elsevier B.V. All rights reserved. 1. Introduction The Eucalyptus genus has more than 500 species used for afforestation and is the single most important genus in terms of rapid-growth species (Flynn, 2005). Specifically, Eucalyptus grandis is one of the species with the largest area of afforestation having a sustained area expansion since the 1990s (Gonçálvez et al., 2004). Afforestation is generally established in low fertility or degraded soils and therefore, a general consensus exists in the literature about tillage benefits. Tillage is beneficial for weed control (McLaughlin et al., 2000; Wetzel and Burgess, 2001; Villalba et al., 2010), and improving soil physical conditions for root (Smith, 1998) and plant growth (Worrell and Hampson, 1997; Querejeta et al., 2001). On the other hand, it is not well established whether low or high intensity tillage systems are more beneficial. The reports regarding the effect of tillage intensities on tree growth parameters are not consistent and may be site-specific (Carnerio et al., 2008; Graham et al., 2009). Tillage systems used for forest plantations range from intensive tillage such as subsoilers (Schönau et al., 1981) to reduced tillage systems such as disking (Norris and Stuart, 1994; Madeira et al., 1999; Du Toit, 2008). Some studies found a benefit of tillage sys- tems when compared to no-till systems, but no improvement in increasing tillage intensity (Morris and Lowery, 1988; Madeira et al., 1999; Lowery and Gjerstad, 1991; Garcia Préchac et al., 2001). However other studies found a clear advantage on more intense tillage systems such as subsoilers (Schönau et al., 1981; http://dx.doi.org/10.1016/j.foreco.2015.02.031 0378-1127/Ó 2015 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +598 23549475. E-mail address: pablog@fagro.edu.uy (P. González Barrios). Forest Ecology and Management 346 (2015) 41–50 Contents lists available at ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco