Agriculture, Ecosystems and Environment 80 2000 29–45
Systematic method for rating soil quality of conventional, organic, and integrated apple orchards in Washington State
J.D. Glover
a,∗
, J.P. Reganold
a
, P.K. Andrews
b
a
Department of Crop and Soil Sciences, Washington State University, Pullman, WA 99163-6420, USA
b
Department of Horticulture and Landscape Architecture, Washington State University, Pullman, WA 99163-6420, USA Received 9 June 1999; received in revised form 12 October 1999; accepted 16 December 1999
Abstract
Much remains to be known concerning the complex relationships between specific soil property measurements and overall soil quality. The objective of this study was to advance our understanding of these complex relationships by further developing
and applying a systematic method for evaluating the effects of conventional, integrated and organic apple production systems on soil physical, chemical, and biological properties using a modified soil quality index. This index utilizes 1998 soils data from
these three treatments. The study used four, 0.14 ha replicates of each of the three treatments in a randomized complete block design. Experimental plots were planted to ‘Golden Delicious’ apples Malus domestica Borkh. in 1994 on a commercial
orchard in the Yakima Valley of Washington state. Organic soil management practices included additions of composted poultry manure and bark mulches and the use of mechanical tillage for weed control. Conventional soil management practices included
additions of synthetic fertilizers and the use of herbicides for weed control. The integrated system utilized practices from each of the other two systems. Increased aggregate stability, microbial biomass, and earthworm abundance were associated
with improved soil quality under integrated management when compared to conventional management in 1998. Organic management resulted in lower soil bulk densities and generally improved biological soil properties compared to conventional
management. Few significant differences in soil properties were measured between the integrated and organic systems. The integrated production system received a soil quality index rating of 0.92 out of 1.00, which was significantly higher than the
index rating of 0.78 for the conventional production system; the organic production system received a rating of 0.88, which was not significantly different from the other two systems. The study indicates that a well-developed soil quality index can
provide an effective framework for evaluating the overall effects of different orchard production practices on soil quality. © 2000 Elsevier Science B.V. All rights reserved.
Keywords: Compost; Integrated farming; Orchard management; Organic farming; Soil quality index
1. Introduction
Washington state, the leading apple producer in the US, harvested 2.3 million tonnes of apples from nearly
∗
Corresponding author: Tel.: +1-509-335-5893; fax: +1-509-335-8674.
E-mail address: jerrygwsunix.wsu.edu J.D. Glover
63,000 ha in 1997 Washington State Department of Agriculture, 1998. As apple production in Washing-
ton state has intensified to meet market demands over the past decades, concerns in the marketplace and on
the farm about the negative impacts of conventional food production practices on human health Hardell
and Eriksson, 1999 and environmental quality Doran et al., 1996; Williamson et al., 1998 have
0167-880900 – see front matter © 2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 8 8 0 9 0 0 0 0 1 3 1 - 6
30 J.D. Glover et al. Agriculture, Ecosystems and Environment 80 2000 29–45
also increased. These concerns have led to increased grower interest in developing environmentally sound
management practices. Organic and integrated apple management systems
offer alternative practices that address environmental concerns National Research Council, 1989; Conacher
and Conacher, 1998. Organic management practices exclude chemical pesticide and fertilizer inputs and
use naturally derived products as defined by organic certification programs. Integrated farming systems,
successfully adopted in some of the major apple growing regions in Europe Sansavini, 1997, utilize
methods of conventional and organic production sys- tems in an attempt to optimize both environmental
quality and economic profit. Although studies have found that alternative management practices may
improve soil quality as compared to conventional management practices Reganold et al., 1987, 1993;
Gunapala and Scow, 1998; Swezey et al., 1998, to our knowledge no study has specifically compared
the effects of conventional, organic, and integrated management on soil quality in apple orchards.
Doran and Parkin 1994 defined soil quality as “the capacity of a soil to function within ecosystem
boundaries to sustain biological productivity, maintain environmental quality, and promote plant and animal
health.” Accurate, consistent assessment of soil qual- ity requires a systematic method for measuring and in-
terpreting soil properties that adequately serve as soil quality indicators Granatstein and Bezdicek, 1992.
Although such methods exist for monitoring and eval- uating air and water quality, no single method has been
widely accepted for assessing soil quality due to the great complexity and variability of soil systems.
Much remains to be known concerning the complex relationships between specific soil property measure-
ments and overall soil quality. Advancement of our understanding of these relationships requires develop-
ment and application of a methodology for assessing and monitoring soil quality as already exists for air and
water quality assessments. The objective of this study was to further develop and apply an existing system-
atic method for evaluating the effects of conventional, organic, and integrated apple production systems on
soil quality. Such an evaluation methodology advances understanding of soil ecosystem relationships and aids
in the interpretation of soil data for apple production systems.
2. Soil quality index
