Optimized Lab Protocols for Testing Soils

By Jared L. DeForest

Disclaimer: Most of these methods are modified for testing acidic, fine-texture forest soils commonly found in Eastern Deciduous forests. Some methods may not directly apply to other soils (e.g. agricultural, calcareous, or sandy soils). Adjustments in the amount of soil (g) used and standard range might be necessary.

• This information also is contained in an indexed pdf for printing. [PDF]

Sampling & Preparing

Soil Physical Properties

• Texture

General Soil Chemistry

• Soil pH
• Lime Requirement (SMP)
• Organic Carbon (wet combustion)
• Total C and N (elementar)
• Exchangeable Acidity & Aluminum
• Extracting for Base Cations — Volumetric
• Extracting for Bioavailable Base Cations — Gravimetric
• Phenolics (micro plate)
• Ammonium Analysis (micro plate)
• Nitrate Analysis (micro plate)

Soil Phosphorus

• Ascorbic Acid Method
• Ascorbic Acid Method - For Anion Exchange Membranes (micro plate)
• Modified Ascorbic Acid Method

The advantage of the modified ascorbic acid method is it does not include orthophosphate derived from the hydrolysis of polyphosphates and/or acid-labile organic P. If the research question involves just general determination of P, then both methods are fine or use an ICP. However, if the research question involves determining specifically inorganic ortho-P (e.g. resin P) then the modified method is recommended.

• Phosphorus Fractions (Hedley Fractionation)
• Available Phosphorus (Bicarb Extraction, Total and Inorganic)
• Phosphorus Sorption
• Microbial Phosphorus

Microbial Fuction & Community

• Phospholipid Fatty Acid (PLFA) Analysis
• Hydrolytic Enzyme Activities
• Nitrogen Mineralization

Litter

• Litter Fractionations

Major Analytical Equipment

• HP 6890 GC-FID w/ autosampler
• Synergy HT Multi-Detection Microplate reader