Part 1 explains the CEMA 216 contract, Qualified Individual, laboratory, methods, and payment questions. This field guide begins after the producer, Qualified Individual (QI), and NRCS field office have agreed to the activity and before anyone removes soil from the field.
Version note. This guide was checked against the national CEMA 216 standard and job aid listed by NRCS as 04-2026, the April 10, 2026 CEMA 216 FAQ, and NRCS Technical Notes 470-07 and 470-16. Use the activity-specific CEMA 216 documents for a CEMA 216 contract when general soil-health sampling guidance differs [1][2][3][4][5].
The required 3 × 5 structure
| Planning level | Minimum count | What stays separate |
|---|---|---|
| Contracted CEMA 216 instance | 1 | Defined objective, PLU, design, and report |
| Representative main locations | At least 3 | Each location becomes one laboratory composite |
| Field collections per main location | 5: center + 4 surrounding subsamples | Mix only the five belonging to that location |
| Laboratory composite samples | At least 3 | Keep separate through labeling, handling, analysis, and reporting |
Step 1: Define the question and planning land unit
Write the monitoring question before placing points. Examples include tracking one management system through the contract, comparing a poor-performing area with a productive area, or representing major soil and landscape zones within a planning land unit (PLU). The planner and producer determine the sampling area from planning assessments and producer objectives; CEMA 216 does not impose one national acreage limit per instance [1][3].
Use soil type, land use, topography, slope position, drainage, crop rotation, tillage, grazing, amendments, yield history, and the locations of applicable resource-concern assessments to draw the PLU and identify meaningful variation. Web Soil Survey can support this review, but mapped soil information does not replace the laboratory texture measurement required by CEMA 216 [1][7].
Step 2: Choose the design that answers the question
CEMA 216 sampling strategies
| Design | Use when | Point-selection rule | Interpretation |
|---|---|---|---|
| Random | The PLU is reasonably homogeneous with few problem areas | Assign random numbers to grid areas and use the selected positions | Represents the defined uniform unit |
| Stratified | Soil types, landscape positions, drainage, or management form meaningful zones | Delineate strata, then choose random positions within them in proportion to their PLU area | Represents known sources of variation without averaging them blindly |
| Problem comparison | Distinct areas show uneven crop or forage performance | Purposefully sample the problem area, a productive comparison, and an undisturbed or reference area | Answers a targeted comparison; it does not estimate a whole-field average |
| Combined | The objective needs both representation and a defined comparison | Document which rule selected each point or contracted instance | Interpret each group according to its stated purpose |
Step 3: Select at least three representative main locations
Place at least three main locations according to the chosen design. CEMA 216 directs collection at the same locations where applicable in-field resource-concern assessments were completed. Align the sample points with those assessment records unless the agreed design establishes a documented comparison [1].
Avoid wheel tracks, drive lanes, field borders, depressions, saturated soil, soil-map boundaries, fertilizer bands, eroded and non-eroded soil mixed together, different landscape positions, different rotations, and row/inter-row positions unless the design specifically targets or separates that variation. A point can be representative of a defined problem area; it cannot be both an accidental hot spot and a whole-field representative point [1][4].
Step 4: Add four subsamples around every main location
At each main location, collect the center sample and four additional subsamples about 20–50 feet from the center. Keep all five within the same soil, land use, management, and comparison area represented by that main location. On a narrow zone or near a boundary, adjust directions while preserving the intended area and document the layout [1][3].
Step 5: Set the date, laboratory protocol, tools, and depth
Contact the selected laboratory before fieldwork. Confirm the required sample amount, containers, temperature, maximum holding time, shipping day, and any method-specific instructions. Collect during the crop year, at the same time of year for later monitoring, under moderate soil moisture and temperature, and away from recent tillage, amendments, fertilizer, or chemical inputs. General NRCS guidance suggests waiting 3–4 weeks after a chemical application when pre-application sampling is not possible; the QI and laboratory should confirm suitability for the selected CEMA methods [1][3][4].
Remove surface vegetation or debris. When practical, dig an 8-inch hole with a clean tile spade, sharpshooter, or straight shovel and remove a uniform rectangular vertical slice about 2 inches thick to the required 6–8-inch sampling depth. Keep the slice the same thickness from top to bottom. If a slice is impractical, use a soil probe with an inside diameter of at least 1 inch. Dutch and spiral augers are not acceptable because they destroy or compact aggregates [1][2][3].
Step 6: Build three separate composite samples
Place the five field collections from the first main location into one clean container. Gently break large clods, remove stones, roots, and debris, and mix without pulverizing natural aggregates. Transfer the laboratory-required amount into the first bag. Repeat independently for the second and third locations. Use three clean containers or clean equipment thoroughly between composites so soil is not transferred across locations [1][3].
All tools must be clean and free of residue before collection. When collecting PLFA, sanitize equipment between composite samples. Follow any more restrictive laboratory cleaning instruction [1].
Step 7: Label, map, and document each composite
At minimum, CEMA 216 directs the bag to carry the representative-location name and collection date. A stronger repeatability record also includes the PLU or instance ID, unique composite ID, collector, selected laboratory package, and matching point color or code. Record the PLU polygon and WGS84 latitude-longitude for the sampling locations [1][3].
What to record at each main location
| Record | Minimum or recommended content | Why it matters |
|---|---|---|
| Identity | PLU or instance ID, main-location name, composite ID, date, collector | Links the bag, laboratory report, map, and CEMA report |
| Location | WGS84 latitude-longitude and PLU polygon; retain the planned point map | Allows return to the same georeferenced locations |
| Field condition | Soil moisture, temperature category, saturation, recent weather, residue, crop stage | Explains biological and physical differences between dates |
| Management timing | Recent tillage, traffic, grazing, fertilizer, manure, compost, lime, pesticides, irrigation | Identifies short-lived disturbances or input pulses |
| Collection protocol | Design, depth, tool, center-plus-four layout, container, sample amount | Documents method consistency |
| Laboratory path | Laboratory, exact tests and methods, storage, shipment time, temperature | Protects comparability and sample integrity |
Step 8: Cool, protect, and ship the samples
Keep bags cool and out of sunlight. If samples are not sent immediately, store them in a cooler or refrigerator according to the receiving laboratory’s instructions. Use a rigid container when the laboratory requests protection for intact aggregates [1][3][4].
Handling by testing scenario
| Sample or test | CEMA 216 handling direction | Planning note |
|---|---|---|
| Scenario 1 soil-health suite | Keep cool; use a cooler or refrigerator if not shipped immediately; send promptly | Confirm the strictest requirement among the selected methods before collection |
| PLFA in optional Scenario 2 | Ice in the field, freeze immediately, and ship on ice as soon as possible by overnight service | Coordinate with the lab and avoid a shipment that arrives after the lab closes or over a weekend |
| Enzymes in optional Scenario 2 | Refrigerate, protect between ice packs, and ship overnight | Freeze only when the receiving laboratory instructs it |
Step 9: Preserve the baseline for the return visit
CEMA 216 monitoring is most interpretable when the final-year team uses the same georeferenced locations, sampling strategy, time of year, sampling depth, field conditions, laboratory, tests, and analytical methods. Store the field map, coordinates, photos, bag IDs, field sheet, laboratory submission form, shipping record, report, and any deviations in one project record [1][3][5].
Exact weather cannot be repeated. The objective is to keep controllable conditions as similar as practical and document differences. If the field boundary, management, laboratory, or method changes, record the break rather than presenting the two values as a seamless trend [1][3][5].
Pre-field conference checklist
- □ The producer, QI, and NRCS field office agree on the objective, PLU, contracted instance, and deliverables.
- □ The map shows the PLU boundary, applicable assessment points, soil or management zones, exclusions, and at least three main locations.
- □ The design is identified as random, stratified, problem comparison, or a documented combination.
- □ Four surrounding subsample positions can remain within the same represented area at every main location.
- □ The selected laboratory has confirmed every required method, sample amount, containers, temperature, holding time, and shipping day.
- □ The planned date avoids extreme soil moisture or temperature and recent disturbance or inputs.
- □ The collector has a clean spade or sharpshooter, an allowed probe if needed, clean composite containers, bags, labels, GPS set to WGS84, field sheets, cooler, and cold packs.
- □ The team knows how PLFA or enzyme samples will be cooled, frozen when required, and delivered overnight.
- □ APHIS soil-movement restrictions have been checked when the soil may be prohibited, regulated, or quarantined [1][6].
Common sampling-plan failures
What fails and how to correct it
| Failure | Why it matters | Correction |
|---|---|---|
| Mixing all 15 collections into one bag | Erases the required three-location structure | Create three composites of five and keep them separate |
| Calling a road-edge convenience route random | Selection is biased and cannot support the stated design | Use a grid or geospatial randomization method and retain the selected points |
| Crossing soil, management, slope, or wetness boundaries within one cluster | The composite blends different populations | Move the surrounding points inward or use a stratified design |
| Collecting only the 6–8-inch horizon | Misreads the activity’s vertical sampling-depth instruction | Collect a uniform vertical slice extending to the approved 6–8-inch depth |
| Using a Dutch or spiral auger | Destroys or compacts aggregates | Use the preferred spade slice or an allowed probe at least 1 inch in inside diameter |
| Sampling just after tillage, fertilizer, manure, or a chemical application | Creates a temporary physical or biological pulse | Reschedule under moderate, comparable conditions after the agreed waiting period |
Who is responsible for the plan?
Roles before, during, and after sampling
| Role | Sampling-plan responsibility |
|---|---|
| Producer | Defines objectives and management history; selects the QI; confirms access, timing, and practical field conditions |
| Qualified Individual | Leads the pre-work conference; designs or approves the strategy; verifies methods and handling; supervises collection; signs and completes the report |
| NRCS field office | Confirms the contracted activity, planning context, applicable PLU, deliverables, and acceptance requirements |
| Sample collector | Follows the approved map, depth, tools, cleaning, compositing, labeling, recording, and handling protocol under QI guidance |
| Laboratory | Provides method-specific collection and shipping instructions; receives three traceable composites; reports the selected approved methods and units |
The nine-step field sequence
- Define the monitoring question and PLU.
- Choose and document the random, stratified, problem, or combined design.
- Map at least three representative main locations and planned exclusions.
- Add four surrounding subsamples about 20–50 feet from each center.
- Confirm timing, laboratory protocol, tools, and a uniform 6–8-inch sampling depth.
- Collect five field portions per location and build three separate composites.
- Label every bag and record the matching WGS84 points, conditions, and management timing.
- Cool, protect, and ship according to the strictest selected test requirement.
- Archive the baseline so the final-year team can repeat the plan.
A defensible CEMA 216 result begins with a map and ends with a repeatable record. Part 3 explains how to interpret the five required soil-health indicators after the laboratory reports the three composites.