Water quality is defined in terms of the elemental composition and concentration of salts dissolved in the irrigation water. The ratio of precipitation to potential evaporate-transpiration varies seasonally in arid and semi-arid climates. Salinity is a common problem in poorly managed container nurseries when fertilizer salts are allowed to build up in the medium without adequate leaching, but is not usually a problem in bare-root nurseries. Salts injure bare rootstocks in the following ways.

1. by increasing the osmotic pressure of the soil solution, causing stress and drought
2. by decreasing soil permeability owing to lose, soil structure and aggregation caused by the deflocculation of soil colloids (particularly in clays)
3. by direction toxicity from sodium, chloride, borate, other ions and
4. by the change in nutrient availability owing to changes in pH

Osmotic stress

The following values are often used to access the effects of salts on growth