Across arid and irrigated regions, two soil problems are routinely treated as one. They are not. Salinity is an excess of soluble salts, which raises osmotic pressure and makes it harder for a plant to take up water even when the soil is wet. Sodicity is an excess of exchangeable sodium relative to calcium and magnesium, which disperses clay particles, collapses soil structure and destroys infiltration. A soil can be saline, sodic, both, or saline-sodic — and the correct purchase is different in each case.
The remedies are not interchangeable
A saline soil with intact structure is corrected primarily by water: leaching salts below the root zone, which requires drainage that actually functions and a leaching fraction applied on purpose rather than by accident. No amendment removes salt. Buying a soil conditioner to fix a drainage problem is money spent on the wrong constraint.
A sodic soil is different. Here the requirement is to displace sodium from the exchange sites with calcium, and then to leach the displaced sodium away. That is why calcium sources — agricultural gypsum above all — are the standard remedy, and why applying gypsum to a merely saline soil often achieves very little. On calcareous soils, elemental sulphur or an acidifying amendment can be used to mobilise the calcium already present in the profile, which is a genuinely different mechanism and needs time and biological activity to work.
What to specify when you buy
Reclamation materials are bought by the tonne and used by the hectare, and the gap between those two units is where value is won or lost. For gypsum, purity and particle size govern how much calcium is actually delivered and how quickly it dissolves. A coarse, low-purity product may be cheaper per tonne and considerably more expensive per unit of effect, once freight and spreading are counted.
- Gypsum: calcium sulphate content, moisture, and the percentage passing the specified sieve. Fineness drives dissolution rate.
- Agricultural lime: neutralising value and fineness, which together determine the effective neutralising capability — not simply the calcium carbonate figure.
- Elemental sulphur: purity, particle size, and whether the product is a dispersible granule intended for field application.
- Humic and fulvic products: the extractable acid content on a dry basis, and whether the figure quoted is for the acids or for the raw source material.
- Composted organics and peat: organic matter, moisture, pH, electrical conductivity, and freedom from contaminants and viable weed seed.
Two figures that decide the freight
Reclamation is a bulk business. Application rates are measured in tonnes per hectare, not kilogrammes, which means the delivered cost per tonne dominates the economics and the sourcing decision is often about geography rather than product. A regional origin at a modest premium frequently beats a distant origin at a lower mill price once ocean freight, port handling and inland haulage are added.
The second figure is moisture. A material bought at a price per tonne and delivered wet is a material bought partly by the tonne of water. On products where moisture content can legitimately vary by several percentage points, a moisture cap in the specification is worth more than a small concession on price.
Sequence, not shopping list
The order of operations matters more than the brand. Test the soil and, where sodicity is suspected, obtain the exchangeable sodium percentage or sodium adsorption ratio rather than electrical conductivity alone. Confirm that drainage can carry displaced salts away; without it, reclamation redistributes the problem rather than removing it. Then size the amendment to the measured requirement, and only then ask for prices.
Buyers who arrive with a soil analysis and a hectare figure get a materially better answer than buyers who arrive with a product name — because at that point the conversation can be about whether the product is the right one at all.
