Soil testing for Organic and Ecological Farms

Rob Dunn, FarmWise Inc., Lethbridge

rdagric@gmail.com

403-382-8154

Why soil test?

“Can’t manage what you don’t measure.” (Drucker)

• Evaluate soil fertility status• Characterize soil properties• Diagnosing poor growth areas, problem

soils• Baseline to track mid to longer term soil

improvement

What should we be testing for …?

Limitation to any test (disclaimer)

• At best, only a snap shot into the physical, chemical or biological condition at a given point in time

• Sample timing and depth is important (especially biology)

• Challenge: What does it mean for my situation?

➢Is the test calibrated against a “management response”

Before you head to the field

Think about the purpose for sampling …1. Nutrient status to inform fertility inputs?

2. Evaluating benefits of soil treatments or green manures?

3. Diagnosing unproductive field areas?

4. Benchmarking to inform management strategies and track longer term soil health improvement?

Google Imagery is a great tool before you head to the field

Call before you dig&

Don’t forget about sanitation

From: CARA soil health sampling protocol

Benchmark

2

3

Standard soil testing for nutrients and soil characteristics• Conventional farms test to determine fertilizer

needs, usually in late fall/winter

• More complex for organic/ecological farms• Need to account for nutrients contributed through

covers, green manures and organic amendments

In what way are organic farms different?

From: Tools for Assessing Nutrient Status on Organic Farms. J.T Martens, U of M

To address the challenge and account for nutrients within green manures, U of M developed an innovative approach

Principle:✓ Plant will take up as much of each nutrient from soil

unless a nutrient is deficient

Soil nutrient can be supplied by:Soil Organic MatterDecomposing plant residuesSoil biological processes

Then the concentration in above ground biomass will be lower than normal

If the soil nutrient supply is deficient

Strategy:Couple a soil and

green manure biomass sample

• Biomass nutrient content at termination

• Quantifies N fixed

• Did the soil supply adequate P, K and S?

• Soil test for available nutrients at time of biomass sampling

• Indication of soils functional fertility level

Plant biomass x Plant nutrient concentration

= Plant nutrient uptake

Next level: used as a tool to do a budget for field or farm level nutrient budgeting

Standard soil test• Representative sample!

• Key is an appropriate sampling plan (imagery helps!)

• Composite of at least 15 to 20 sample sites

• Sample depths• Best is 0-6, 6-12 and 12-24 inch

• Most common approach is 0-6 and 6 to 24

Labs for standard soil testing:

• Down to Earth Labs - Lethbridge

• Biovision – Edmonton

• Element (formerly Exova) - Edmonton

• Farmers Edge - MB

• A&L Canada – ON

Tests for evaluating physical soil characteristics

• Compaction (penetrometer resistance)

• Aggregate stability

• Water infiltration

From: CARA soil health sampling protocol

Justin Duban farm – Coalhurst, AB

Steps for a water infiltration test(from: CARA soil health testing protocol)

Justin Duban farm – Coalhurst, AB

Other approaches for soil assessment or benchmarking soil quality

Direct and indirect methods

Organic AB soil quality toolkit

• Part of an initiative that includes both research and extension

• User friendly toolkit for collecting baseline soils information

• 16 farmers participating in a pilot this past year• Soil Quality Card – “self assessment of soils”

• Soil samples sent to the CARA Soil Health Lab

•Chinook Applied Research Assn. (Oyen)

•Main goal: • To allow producers to have access to

biological and physical assessments to build the bridge for improving their soil health base on localized and side specific constraints.

CARA Soil Health (CARA-SHealth)

Laboratory Initiative

Slide provided by Yamily Zavala, CARA

What soil indicators should be measured ?

Compaction

Infiltration

StructureTexture …..

Soil Aggregation

Respiration (CO2)Active Carbon

C to N ratioMicrobial activitiesSoil Food Web

Fungi, bacteria, nematodes, etc…..

Physical Chemical

Biological

Soil health: Integration of biological chemical & physical functions

Slide provided by Yamily Zavala, CARA

Residues from a buckwheat (Fagopyrum esculentum) green manure crop grown with phosphate rock influence bioavailability of soil phosphorusArcand, M. M., D. H. Lynch, R. P. Voroney and P. van Straaten. 2010. Canadian Journal of Soil Science. 90:257-266

AFFIRM – Manure nutrients

▪ Manure source (beef, dairy, poultry, etc.) and form (solid or liquid)

▪ Considers application timing, method and rate

▪ Nutrient levels (book values or input if test results available)

Summary

• Soil testing is a useful tool to evaluate nutrient status, diagnose problem field areas or benchmark for long term soil quality monitoring

• Innovative approaches (eg., U of M Biomass assay) are new approaches for organic/ecological farms

• Several approaches for assessing soil physical characteristics and biology (direct or indirect)