Which one of the following with regard to Aridisol, one of the soil orders, is not correct?

The correct answer is B, High organic matter. Aridisols are the soils of deserts, and they are poor in organic matter, so this statement about them is not correct. Aridisol is one of the twelve soil orders of the USDA soil classification. These soils form in dry climates where rain is too little for most of the year to support thick plant cover, so very little leaf litter or humus is added. Because water rarely moves down through the whole soil, salts are not washed out; calcium carbonate, gypsum and other salts build up in layers at some depth, often as a hard calcic horizon. Aridisols are usually light in colour, sandy or gravelly, and cover much of the Sahara, Arabia and the Thar Desert. Option A is wrong because a lack of water for plants through most of the year is a true feature of aridisols. Option C is wrong because a large accumulation of carbonates at depth is also typical of them. Option D is wrong because deep, wide cracks belong to Vertisols, the clay-rich black soils, so their absence is correct for aridisols. Exam tip: Aridisols, dry, low humus, carbonates at depth; Vertisols, swelling clays with deep cracks.