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Soluble salts are not leached from these soils, and in some cases they build up to levels that curtail plant [49] and microbial growth. [50] Soil profiles in arid and semi-arid regions are also apt to accumulate carbonates and certain types of expansive clays ( calcrete or caliche horizons).
Detrimental effects on plant growth and yield; Damage to infrastructure (roads, bricks, corrosion of pipes and cables) Reduction of water quality for users, sedimentation problems, increased leaching of metals, [6] especially copper, cadmium, manganese and zinc. Soil erosion ultimately, when crops are too strongly affected by the amounts of salts.
Soluble fluoride salts, of which sodium fluoride is the most common, are toxic, and have resulted in both accidental and self-inflicted deaths from acute poisoning. [4] The lethal dose for most adult humans is estimated at 5 to 10 g (which is equivalent to 32 to 64 mg elemental fluoride per kg body weight).
In agriculture, leaching is the loss of water-soluble plant nutrients from the soil, due to rain and irrigation. Soil structure, crop planting, type and application rates of fertilizers, and other factors are taken into account to avoid excessive nutrient loss.
Consequences include corrosion damage, reduced plant growth, erosion due to loss of plant cover and soil structure, and water quality problems due to sedimentation. Salination occurs due to a combination of natural and human-caused processes. Arid conditions favour salt accumulation. This is especially apparent when soil parent material is saline.
Sodium fluoride (NaF) is an inorganic compound with the formula Na F.It is a colorless or white solid that is readily soluble in water. It is used in trace amounts in the fluoridation of drinking water to prevent tooth decay, and in toothpastes and topical pharmaceuticals for the same purpose.
A third model is based on the method of partial regression, [15] whereby one finds the longest horizontal stretch (the range of no effect) of the yield-ECe relation while beyond that stretch the yield decline sets in (figure below). With this method the trend at the tail-end plays no role.
It has been found that food contamination from fertilizer is of little concern as plants accumulate little fluoride from the soil; of greater concern is the possibility of fluoride toxicity to livestock that ingest contaminated soils. [98] [99] Also of possible concern are the effects of fluoride on soil microorganisms. [98] [99] [100]