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

APPLYING A SOIL QUALITY INDEX TO CONVENTIONAL, INTEGRATED & ORGANIC APPLE PRODUCTION SYSTEMS JD Glover, PK Andrews & JP Reganold Washington State University Pullman, USA

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

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

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

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.

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

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

SOIL MANAGEMENT

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

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)

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)

1 = 1 + ( ) 2S(B+X-2L) B - L X - L SCORING CURVES Scoring value B = baseline value where normalized value = 0.5 L =lower threshold X = value of measured parameter S = tangential slope at X=B Wymore. 1993. Model-based systems engineering. CRC Press

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

INDEX CALCULATION 1. Multiply soil-function indicatorscoring 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)

PHYSICAL PROPERTIES Z 0-15 cm soil depth y Mean separation by LSD0.05

CHEMICAL PROPERTIES Z 0-15 cm soil depth y Mean separation by LSD0.05

BIOLOGICAL PROPERTIES Z 7.5-15 cm soil depth y 0-7.5 cm soil depth x Mean separation by LSD 0.05

SOIL QUALITY INDEX Z Mean separation by LSD 0.05

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

Advantages Flexible Crop systems Regions Assessment objectives Comparative Iterative Focus research Replant syndrome Nitrate leaching Limitations Subjective methodology Limited data sets Soil functions only CONCLUSIONS

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