Except for nutrient solutions, values ranked as L or VL are desirable. It is an indicator of the level of management required to successfully use the solution. It is useful in predicting the tendency for Na to accumulate in soil where the water is routinely used for irrigation. Where overhead irrigation is used, toxic levels of Na can accumulate on the foliage. Since SAR is a ratio, it has no units.
Total alkalinity is the sum of carbonate and bicarbonate ions reported in ppm.
Most alkalinity is in the bicarbonate form. This value indicates the tendency of water to increase soil pH where irrigation is routinely used. In some plant production systems, alkalinity must be neutralized to avoid increasing soil pH to levels that do not support plant growth. Hardness indicates the amount of calcium and magnesium in water, expressed as equivalent calcium carbonate in ppm. It is useful in evaluating water quality for aquaculture and domestic uses.