Salt-Affected Soil & Find the Reclamation Path
Classifies saline
A saline and a sodic soil look alike on an EC meter but need opposite treatments. Enter your ECe, ESP (or SAR) and pH to get the USDA Handbook 60 class, the binding factor, and the correct reclamation order — leach, or amend-then-leach.
Your soil test (saturated-paste)
Reclamation route
Amend FIRST (do NOT leach blind). Apply gypsum to convert it to a saline soil, THEN leach — leaching salts off a high-ESP soil before adding Ca disperses the clay and seals it.
- Amendment
- Gypsum (or acid on calcareous soil) to supply Ca before/with leaching.
- Leaching
- High, but only WITH or AFTER the Ca amendment.
- Order
- 1) Add gypsum (supply Ca) → 2) Leach. NEVER leach first — that disperses the soil.
Crops viable at ECe 8.5 dS/m
Salt- and sodicity-tolerant crops; recheck ECe and ESP after each leach cycle.
Next: this is the trap case — amend first, leach second. Apply gypsum to supply Ca and convert it to a saline soil, THEN leach. Leaching the salts off a high-ESP soil before adding Ca disperses the clay and ruins infiltration.
Classification follows USDA Agriculture Handbook 60 (Richards 1954): saline ECe > 4 dS/m, sodic ESP > 15 (SAR > 13), saline-sodic both. SAR→ESP via the Handbook-60 regression. Reclamation routes per FAO Soils Bulletin 39 / Abrol et al. 1988. Confirm gypsum rate with a separate gypsum-requirement calculation; results assume adequate sub-surface drainage.
Salt-affected soil — key facts
- Saline
- ECe > 4 dS/m, ESP < 15
- Sodic (alkali)
- ECe < 4, ESP > 15, pH often > 8.5
- Saline-sodic
- ECe > 4 AND ESP > 15
- Normal
- ECe < 4 and ESP < 15
- SAR ↔ ESP
- SAR 13 ≈ ESP 15
- Saline fix
- leach — no amendment
- Sodic fix
- gypsum first, then leach
- Source
- USDA Agriculture Handbook 60 (Richards 1954)
- Privacy
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The four classes and their reclamation routes
| Class | Diagnosis | Amendment | Order of operations |
|---|---|---|---|
| Normal (non-salt-affected) | ECe < 4 dS/m and ESP < 15 — neither salinity nor sodicity is limiting. | None required. | Maintain drainage and a maintenance leaching fraction. |
| Saline | ECe > 4 dS/m but ESP < 15 — excess neutral soluble salts, structure intact. | None (gypsum is NOT required for purely saline soil). | 1) Ensure drainage → 2) Leach with good water. Amendment is unnecessary. |
| Sodic (alkali) | ECe < 4 dS/m but ESP > 15 (pH often > 8.5) — excess exchangeable sodium has dispersed the clay. | Gypsum (CaSO₄·2H₂O); on calcareous soil elemental S / sulphuric acid can substitute. | 1) Add gypsum → 2) Incorporate → 3) Leach the displaced Na. Order matters. |
| Saline-sodic | ECe > 4 dS/m AND ESP > 15 — both excess salts and excess sodium. | Gypsum (or acid on calcareous soil) to supply Ca before/with leaching. | 1) Add gypsum (supply Ca) → 2) Leach. NEVER leach first — that disperses the soil. |
Thresholds: USDA Agriculture Handbook 60 (Richards 1954). Reclamation routes: FAO Soils Bulletin 39; Abrol, Yadav & Massoud (1988).
Crop salinity-tolerance thresholds (Maas–Hoffman)
| Crop | Threshold ECe (dS/m) | Salt-tolerance rating |
|---|---|---|
| Bean | 1 | sensitive |
| Carrot | 1 | sensitive |
| Onion | 1.2 | sensitive |
| Maize | 1.7 | moderate |
| Potato | 1.7 | moderate |
| Rice (paddy) | 3 | moderate |
| Wheat | 6 | moderate |
| Sorghum | 6.8 | tolerant |
| Sugar beet | 7 | tolerant |
| Cotton | 7.7 | tolerant |
| Barley | 8 | tolerant |
Yield begins to fall once ECe exceeds the threshold. Source: Maas & Hoffman (1977) / USDA Handbook 60.
Why classifying first saves you money
Salt-affected soils fall into three problems and one healthy state, and each problem needs a different fix. A saline soil simply has too much neutral salt — leach it out and it recovers, no amendment needed. A sodic soil has too much exchangeable sodium that has dispersed the clay; here leaching alone makes it worse, so you must supply calcium with gypsum first, then leach. A saline-sodic soil has both, and is the trap: leach it before adding calcium and you disperse the clay and seal the soil shut. Getting the class — and the ORDER — right is the difference between reclamation and ruin.
This tool plots your ECe against your ESP on the USDA Handbook 60 quadrant, names the binding factor, and gives the correct route and amendment. It also lists which crops still yield at your salinity so you keep land productive while you reclaim. Pair it with the Gypsum Sodic-Soil Reclamation tool to size the calcium and the Soil Salinity EC tool to convert field readings.
How to classify your soil in five steps
- 1
Get a saturated-paste lab test
Have ECe (dS/m), ESP (or SAR) and pH measured on the saturation extract — field 1:2 readings must be converted first.
- 2
Enter ECe
Type the saturated-paste ECe; above 4 dS/m flags salinity.
- 3
Enter sodicity
Enter ESP %, or switch to SAR and the tool converts it to ESP; above 15 flags sodicity.
- 4
Read the quadrant
Your point lands in normal, saline, sodic or saline-sodic, with the binding factor named.
- 5
Follow the route in order
Leach a saline soil; gypsum-then-leach a sodic or saline-sodic soil. Never leach a high-ESP soil first.
Frequently Asked Questions
Is my soil saline, sodic or saline-sodic?+
Use the USDA Handbook 60 thresholds. If the saturated-paste ECe is above 4 dS/m but ESP is below 15, the soil is saline. If ECe is below 4 but ESP is above 15 (SAR above 13), it is sodic (alkali). If BOTH ECe is above 4 AND ESP is above 15, it is saline-sodic. If both are below the limits, the soil is normal. Enter your three numbers and the tool plots you into the correct quadrant.
What is the difference between a saline and a sodic soil?+
A saline soil has too much neutral soluble salt but its structure is intact, so the fix is simply to leach the salt out with good water — no amendment is needed. A sodic soil has too much exchangeable sodium that has dispersed the clay and sealed the soil; leaching alone makes it worse, so you must add a calcium source (gypsum) first to displace the sodium, then leach. They look similar on an EC meter but need opposite treatments.
Why must I add gypsum before leaching a sodic or saline-sodic soil?+
Sodium on the clay exchange disperses the particles and collapses the pores. If you leach the salts off a high-ESP soil before supplying calcium, the soil disperses, infiltration stops and you seal it shut. Gypsum (or acid on calcareous soil) supplies calcium that replaces the sodium on the exchange; only then does leaching carry the displaced sodium safely out of the root zone. The order — amend first, leach second — is the whole point.
Does a purely saline soil need gypsum?+
No. A saline soil (ECe above 4, ESP below 15) has excess neutral salts but no excess exchange sodium to displace, so gypsum does nothing useful. The correct and cheapest fix is to ensure drainage and leach with good-quality water. Buying gypsum for a saline-only soil is a common and wasteful mistake the classification prevents.
What is ESP and how does it relate to SAR?+
ESP is the exchangeable sodium percentage — sodium held on the clay exchange divided by the cation-exchange capacity, times 100. SAR is the sodium adsorption ratio of the saturation extract. They track closely: ESP 15 corresponds to about SAR 13. The tool accepts either; if you give SAR it converts to ESP using the Richards (1954) Handbook-60 regression before classifying.
What ECe makes a soil saline?+
The USDA Handbook 60 boundary is an electrical conductivity of the saturated-paste extract (ECe) greater than 4 dS/m (equal to 4 mmhos/cm). Below 4 dS/m the soil is non-saline. The 4 dS/m line is where salinity begins to reduce the yield of many crops; salt-sensitive crops are affected well below it, while barley and cotton tolerate far more.
What ESP makes a soil sodic?+
An exchangeable sodium percentage above 15 defines a sodic (alkali) soil under USDA Handbook 60, usually with a pH above 8.5. Above ESP 15 the sodium begins to disperse the clay and damage structure. Some sensitive soils show problems from ESP 6, but 15 is the diagnostic threshold used worldwide.
Can I still grow crops on a salt-affected soil while reclaiming it?+
Often yes — choose crops by their salt-tolerance threshold (Maas–Hoffman). At an ECe of 7 dS/m, barley (threshold 8), cotton (7.7) and sugar beet (7) still yield, while beans and onions (around 1) fail. The tool lists which common crops remain viable at your measured ECe so you keep land productive during reclamation.
Why is leaching first dangerous on a sodic soil?+
Leaching dilutes the soil solution. On a high-ESP soil, dilution without calcium triggers clay swelling and dispersion — the particles spread, plug the pores and infiltration collapses, so water ponds and no more salt leaves. Supplying calcium with gypsum keeps the clay flocculated as you leach, which is why amend-first is non-negotiable for sodic and saline-sodic soils.
What is the saturated-paste extract and why use it?+
It is the standard laboratory basis for salinity and sodicity: the soil is saturated with water, the extract is drawn off and ECe, SAR and the soluble cations are measured on it. It standardises results across soil textures so the 4 dS/m and ESP 15 thresholds mean the same thing everywhere. Field EC meters in 1:1 or 1:2 ratios read lower and must be converted before comparing to these limits.
How much gypsum will reclaiming a sodic soil need?+
That depends on the gypsum requirement — the amount of calcium needed to bring ESP down to a target, which is driven by the CEC, the depth treated and the current ESP. This classifier tells you THAT gypsum is needed and in what order; pair it with a gypsum-requirement calculator to size the tonnes per hectare, then a leaching-requirement step to size the water.
My pH is 9.2 but ECe is low — what is that?+
A low ECe with a high pH (above 8.5) and high ESP is the signature of a sodic (alkali) soil — sodium has hydrolysed and raised the pH while the soluble-salt level stays low. It is the classic case where an EC meter alone misleads you: the soil is not salty, it is sodic, and it needs calcium-then-leach, not just leaching.
Is the result precise enough to act on?+
The class itself is a hard USDA Handbook 60 decision from your three numbers, so it is definitive given good lab values. The reclamation route is the agronomically correct sequence; the exact gypsum tonnage, leaching depth and timing still depend on your CEC, drainage and water quality. Treat the class and order as firm, and size the inputs with the linked amendment and leaching tools.