APPLYING A SOIL QUALITY INDEX TO CONVENTIONAL, INTEGRATED

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APPLYING A SOIL QUALITY INDEX TO CONVENTIONAL,
INTEGRATED ORGANIC APPLE PRODUCTION SYSTEMS

• JD Glover, PK Andrews
• JP Reganold
• Washington State University
• Pullman, USA

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ACKNOWLEDGMENTS

• Funding supported by
• USDA National Research Initiative Competitive
  Grants Program
• Washington Tree Fruit Research Commission
• Organic Farming Research Foundation
• Cooperating growers
• Andy Eric Dolph

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JUSTIFICATION

• Groundwater contamination
• Food quality safety
• Agricultural chemical use
• International competition

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OBJECTIVES

• 1. Develop soil quality methodology appropriate
  for fruit orchards
• 2. Evaluate effects of management practices on
  soil quality

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SOIL QUALITY

• The capacity of the soil to function within
  ecosystem boundaries to
• 1) sustain biological productivity,
• 2) maintain environmental quality, and
• 3) promote plant and animal health

Doran Parkin. 1994.
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SOIL QUALITY INDICATORS

• Encompass ecosystem processes
• Integrate soil physical, chemical biological
  properties processes
• Sensitive to variations in climate management
• Applicable to field conditions
• Accessible to users
• Components of existing databases

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SITE DESCRIPTION

• Columbia River Basin, N. America
• Commercial orchard planted 1994
• Golden Delicious/M.9
• 2430 trees/ha
• Conventional, integrated organic
• Four, 0.14 ha plots in RCB
• Fine sandy loam soil
• Previously managed grass pasture

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SOIL MANAGEMENT
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SOIL PARAMETERS

• Physical
• Bulk density, infiltration, aggregate stability,
  water-filled pore space
• Chemical
• Total N, NO3-N, P, CEC, pH, soluble salts
• Biological
• Microbial biomass C N, organic C, earthworms

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METHODOLOGY

• Numerically-weighted values (0-1)
• Soil functions
• 1. Accommodate water entry (0.2)
• 2. Accommodate water transfer/absorption (0.2)
• 3. Resist surface structure degradation (0.2)
• 4. Support fruit quality productivity (0.4)
• Multi-level soil-function indicators
• Normalized scoring curves (0-1)

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MULTI-LEVEL INDICATORS

• Soil function
• Resist degradation (0.2)
• Soil-function indicators
• Aggregate stability (0.6)
• Microbial processes, upper 7.5 cm (0.4)
• Organic carbon (0.4)
• Microbial biomass N total N (0.3)
• Microbial biomass C organic carbon (0.3)

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SCORING CURVES
Scoring value
B baseline value where normalized value 0.5 L
lower threshold X value of measured
parameter S tangential slope at XB
Wymore. 1993. Model-based systems engineering.
CRC Press
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SCORING CURVE TYPES

• More is better - positive slopes
• Less is better - negative slopes
• Optimum - positive curve reflected at upper
  threshold

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INDEX CALCULATION

• 1. Multiply soil-function indicator scoring value
  by its numerical weight (0-1)
• 2. Sum products of indicators at each level for
  each soil function (0-1)
• 3. Sum soil function scores ? soil quality index
  (0-1)

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PHYSICAL PROPERTIES
Z 0-15 cm soil depth y Mean separation by LSD0.05
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CHEMICAL PROPERTIES
Z 0-15 cm soil depth y Mean separation by LSD0.05
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BIOLOGICAL PROPERTIES
Z 7.5-15 cm soil depth y 0-7.5 cm soil depth x
Mean separation by LSD 0.05
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SOIL QUALITY INDEX
Z Mean separation by LSD 0.05
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RESULTS

• Integrated organic systems had improved soil
  physical properties
• Integrated system had higher chemical nutrient
  levels
• Integrated system had improved biological
  properties
• Integrated organic systems had higher soil
  quality index
• Facilitate water transfer absorption
• Resist soil degradation
• Sustain fruit quality productivity

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CONCLUSIONS

• Advantages
• Flexible
• Crop systems
• Regions
• Assessment objectives
• Comparative
• Iterative
• Focus research
• Replant syndrome
• Nitrate leaching

• Limitations
• Subjective methodology
• Limited data sets
• Soil functions only