Soil sample upload

Zone Forge accepts CSV and Excel files from any major soil-test lab — and can detect and import exports straight from Soil Test Pro and AgLeader. Shapefiles are accepted for field boundaries. Auto-detection handles the column mapping for you, and four visualization modes let you understand your data before you commit to a prescription.

Your Soil Health report card

The moment your test is in, Zone Forge grades it. You get a report card that lists your nutrients worst-first, color- and word-coded, with variability hints and a fertility trend across your past uploads — so the thing that needs attention is the first thing you see.

In 26 states we grade nutrients in your own state university's published rating words (Arkansas "Very Low → Above Optimum," Delaware its Fertility Index Value, Oklahoma "Low / Sufficient"). In the other states we show the measured value with a note on why we don't grade that lab format yet — we'd rather be honest than hand you a wrong grade. pH and lime are calibrated for all 50 states.

CSV format

The minimum required columns are:

• Latitude — column named any of lat, latitude, y, northing
• Longitude — column named any of lon, lng, longitude, x, easting
• At least one nutrient column — anything Zone Forge recognizes (see below)

Coordinates can be in WGS84 decimal degrees (most common) or projected UTM. If you're using UTM, include a zone column or note the EPSG in your filename — Zone Forge can usually infer it from the magnitude of the values.

Nutrient columns Zone Forge recognizes

Column header matching is case-insensitive and tolerates common variations.

• pH — ph, soil_ph, ph_water
• Buffer pH (buffer-pH lime engines — Adams-Evans on Coastal Plain soils for DE/NJ/SC/FL/AL; SMP or Adams-Evans buffer in the Midwest) — buffer_ph, buf_ph, aebpH, adams_evans
• Exchangeable acidity (Penn State / WV Mehlich Buffer lime engine, reported as "Acidity" in meq/100 g) — acidity, exchangeable_acidity, exch_acidity, EA
• Phosphorus — p, p_ppm, p_m3 (Mehlich-3), p_b1 (Bray-P1), p_olsen
• Potassium — k, k_ppm
• Organic matter — om, om_pct, organic_matter
• CEC — cec
• Secondaries & micros — s, mg, ca, zn, b, fe, mn, cu, mo, cl, na

Phosphorus extractant detection

This is the single most important thing Zone Forge gets right that other tools get wrong. Bray-P1 and Mehlich-3 produce different P values for the same soil — typically Mehlich-3 reads slightly higher. Mixing them silently can drift recommended P₂O₅ rates by 20 to 40 lb per acre.

Zone Forge detects the extractant in this order:

1. Column header. If the column is named p_m3 or p_mehlich3, that's Mehlich-3. If it's p_b1 or p_bray, that's Bray-P1.
2. Lab name. If you've entered your lab name (e.g., "Servi-Tech," "A&L Heartland"), Zone Forge knows what method that lab uses by default.
3. Manual override. If neither hint works, Zone Forge asks you once. The answer is remembered for future uploads from the same lab.

Visualization modes

Once your samples are processed, you can switch between four lenses on the field map.

Points mode

Each sample is plotted as a colored circle at its lat/lon. Colors are bucketed into five quantile bands of your distribution — so each band contains roughly 20% of samples, and all five colors always appear on the map (no all-yellow fields where every sample happens to fall in the same band).

Heatmap mode

Inverse-distance-weighted (IDW) interpolation across the field, rendered as a smooth gradient PNG. Parameters:

• 8 nearest neighbors per cell
• Power = 2 for the distance weighting
• Distance metric: projected UTM (not raw lat/lon) so cells are actually equidistant
• Cell size: ~1 acre (208.7 ft × 208.7 ft), clamped to 50–500 cells per axis

Read the full IDW math in the calculations guide.

Hotspot mode

Density clustering to surface where your high-value (or low-value) zones cluster. Useful for spotting sampling artifacts.

Off mode

Hide soil viz to inspect the prescription overlay cleanly without underlying color noise.

Soft data quality warnings

Zone Forge surfaces five categories of data-quality concern. All are advisory — none block your work. Each can be dismissed per warning, and dismissals reset on regeneration so fresh runs surface fresh warnings.

• Stale samples — any sample over three years old (per Iowa State guidance). Soil chemistry changes; old samples may not reflect current conditions.
• Thin sampling — fewer than eight valid points. IDW interpolation becomes unreliable below this threshold; consider switching to three zones instead of five.
• Outliers — any sample with absolute z-score above 3 from the field's distribution. Likely lab error or transcription mistake; the warning shows the lat/lon and the z-score so you can investigate.
• Extrapolation heavy — more than 30% of the field is outside the convex hull of your samples. The engine is guessing in unsampled zones.
• Small field — under 2 acres or no boundary defined. Informational only; rate controllers ignore VRT at that scale anyway.

Field boundary clipping

All visualizations and the resulting prescription clip to the field boundary you've connected from your platform. If you don't have a imported boundary, you can draw one manually or upload a shapefile — Zone Forge accepts polygon geometry in any common projection.

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