SAMPLING GUIDELINES
GUIDELINES
Soil Sampling Guidelines
A properly taken soil sample is essential to obtaining reliable soil test results. The interpretation of any soil
test depends on the accuracy of the results.
Equipment
Use clean equipment, washed with fresh water between locations. Never use a shovel or tool that is rusty as this will contaminate the soil sample. A soil probe is best because it provides soil cores that represent the soil profile. Mark the probe to the depth of sampling. A 2-3 lb. rubber mallet or sand filled hammer can be used to drive a probe into hard or rocky soil. If a shovel is used, dig a hole to the sampling depth. Take a uniform slice from the edge of the hole and trim this slice down to a 1”-wide section, simulating a core.
Sampling depth
Always remove 1-2 inches of surface soil before sampling. In general, it is best to sample to the depth were a crop’s feeder roots are established. Turf is sampled to a 4-6” depth, removing all thatch. A depth of 6-8” is appropriate for most crops. Deeper samples can be taken separately in order to determine subsoil characteristics.
Sampling location
Divide a soil sampling area into separate sections based on topography, degree of soil erosion, crop history, and soil type. Each unique part of a field represents a separate sampling location. In general, a sample location’s area should not exceed 20 acres. A composite soil sample should have at least 12-15 cores per location. Each sample should be collected into a clean bag and allowed to breath. Never use any kind of heat to dry soil samples.
Sampling patterns
Sampling can be done in a zigzag, diamond or “X” pattern across a location. Maps and benchmarks within a field are useful for future reference.
Sampling precautions
It is best to sample a soil that has been harrowed or tilled prior to applying any fertilizer or amendments.
If a soil has already been amended, allow the limestone or compost to breakdown before sampling the soil.
When sampling soil that has a producing crop, do not take samples after a recent fertilizer application. Wait until it has dissolved and diffused into the root zone.
Do not include any visible fertilizer in soil samples. Remove all plant residues.
Avoid sampling field depressions or wet soil, unless these samples are taken separately.
Avoid sampling near field borders/corners, fence lines, roadways, buildings, or water.
Where fertilizer has been banded or drip injected, several soil cores must be taken in order to dilute the potential effect of concentrated fertilizer within the sample.
Stockpiles of topsoil should be sampled and tested from several locations and depths within the pile. Remove surface soil before
sampling stockpiles.
Check with Pete for guidelines on taking samples for plant, water or compost analysis. Contact Pete here with any questions.