Fertilising calcareous and sandy soils
Quick answer
Two properties dominate: the soil is alkaline and calcareous, which locks up micronutrients; and it is sandy and low in organic matter, which means it stores very little of what you add. The first makes availability the problem rather than supply. The second makes timing and placement matter more than quantity.
What FAO documents about these soils
From the account of soils of the subtropical arid regions:
- Neutral to slightly alkaline reaction; good structure; not subject to leaching in the temperate sense; rather well supplied with K, S, Ca, Mg, B and Mo.
- Major limiting factor: inadequate water.
- Low to very low organic matter content, and low content of available and mobilizable nitrogen.
- Low storage capacity for mineral nutrients in sandy soils.
- Phosphate deficiency in sandy soils.
- Frequent iron and zinc deficiencies because of fixation under alkaline reaction.
- Occasional excess of soluble salts, adsorbed sodium and boron.
- High susceptibility to wind erosion; low biological activity; sometimes hardened lime crusts limiting usable depth.
On nutrients: nitrogen fertilization is almost always necessary, and all common nitrogen fertilizers act relatively quickly because of the high transformation capacity of these warm soils. On coarse-textured soils, phosphorus and potassium are often necessary for high yields; less so on medium and fine textures.
The two consequences that change decisions
1. Availability, not absence
Owing to high soil pH, micronutrient availability poses several problems — in particular acute iron deficiency as lime chlorosis, caused by immobilization of iron in the soil and also in the roots and leaves, with calcareousness playing an additional detrimental role. Zinc deficiency is frequent; copper deficiency is rare. Available manganese decreases as pH and calcareousness rise.
2. Losses, not storage
Low CEC means soluble nutrients are not banked for later. And nitrogen has a specific loss route here: losses as gaseous ammonia occur in the neutral to alkaline range where nitrogen fertilizers — particularly urea — are applied to the soil surface and left unincorporated.
What this means in practice
- Reaching for calcium or lime on a calcareous soil is almost always wrong.
- Yellowing usually indicates an availability problem, not an empty soil.
- Surface-applied nitrogen should be incorporated or watered in.
- Organic matter addresses the structural limitation that no mineral fertiliser can.
- Potassium shortage is less expected here than nitrogen, iron or zinc — with coarse-textured soils the stated exception.
Evidence limitation: all of the above is FAO's general characterisation of arid-region soils, not a Kuwait soil survey. PAAF was unreachable and KISR publishes no extension guidance, so no Kuwait measurement, threshold or rate is stated anywhere in this guide.
Common mistakes
- Adding calcium to calcareous soil.
- Broadcasting urea on a dry alkaline surface.
- Applying large single doses of soluble fertiliser to sand.
- Treating iron chlorosis as a soil-iron shortage.
- Assuming a nutrient reading alone describes the situation, without pH and ECe beside it.
Boundary
FAO notes that a certain lowering of high soil pH by acid-producing fertilizers is desirable for mobilizing iron, manganese and zinc. That is a treatment decision depending on your measured pH, your soil's buffering and your water — it needs an analysis and specialist sign-off, and no product or rate is given here.
Related glossary terms
Sources
- FAO — Fertilizer and Plant Nutrition Bulletin 16, Chapter 4 (Soils of the subtropical arid regions) and Chapter 3.
Accessed 26 August 2026. Last reviewed: 27 August 2026.