Potassium is one of the most plentiful plant nutrients in majority of soils and comprises about 2.6% of the earth’s crust. However, the maximum fraction of soil potassium is combined to basic and derived minerals, and therefore can’t be accessed by plants. Accessibility to plants is dependent on its transport from bound or transferable state to the soil medium and its quantity present in the soil medium. For best plant growth, a constant restock of soil solution is required by potassium ion release from weathering of re potassium ion serves or by applying potassium fertilizers. As a result of potassium ion binding, certain added potassium supplements to these soils frequently become slowly available or completely unavailable to plants. Although the fixed potassium ion does not release readily to fulfill the plant’s necessity, they may be discharged from soil in the soil medium when soil medium contains low potassium ion content.
Although the soil salinity modifies the uptake of nutrients by plants but the use of potash fertilizers ameliorates to some level the deteriorating impacts of moderate salinity and help to recover the agronomic productivity. Consequently, along with other agricultural activities, effective productivity on soils slightly influenced by salinity requires cautious consumption of plant nutrients, principally potassium. Potassium ion discharge from the nutrient minerals also depends on the content of rest of the ions particularly sodium, calcium and magnesium, besides the form of clay minerals present in soil and the content of potassium ion. It becomes easy for the desorbed potassium ion to discharge and even be vanished from the soil, though over a specific time period, it becomes easily accessible to plants root.
Naturally existing and applied potassium ion from the soil can be desorbed and leached by irrigation water high in sodium ion. More need of potassium ion is exhibited by sophisticated crop production systems and high yielding crops, in which whole of the plant components are eliminated from the farmland in the form of crops. This demand can be fulfilled by regular supplementations of potassium, as only a very minute portion of the required supply is made available by the slow discharge of potassium ions from soil particles. Stress caused by sodium ion relates with the sodium ion in the leaf cells, causing necrosis of aged leaves initiating at their edges. As a consequence of reduced life of each leaf, decline in development and productivity occurs, therefore decreasing crop yield and net productivity. Efficacy of sodium ion partitioning inside the leaf cells and tissues along with the rate of storage of sodium ions in leaves decide the time period over which the adversity caused by sodium ion is obvious.
Main factor contributing towards the metabolic adversity of sodium ion is its capability to compete with potassium ions for binding sites crucial for cell performance. Enzymatic mechanisms of the cytoplasm can be interrupted by increased sodium ion content, since sodium ion cannot substitute potassium ion for its role of activating more than 50 enzymes. Disruption of different enzymatic mechanisms in the cytoplasm can result as a consequence of increased level of sodium ion or elevated sodium to potassium ratios. In addition, with respect to potassium ion requirements for the fixation of transfer RNA to ribosomes and probably other characteristics of ribosome function, protein synthesis needs higher concentrations of potassium ion. Plant tolerance towards salinity correlates with the amount of potassium ion in plant tissues.