Chemical Exchange Processes in Soil

FIGURE 10.2 Soil cation exchange and uptake by plants in the example shown, nutrient K is desorbed from soil into the soil solution, in which it is absorbed by a plant root and transported upward into the plant tissue by the osmotic flow of water. The water eventually enters the atmosphere as water vapor through the process of transpiration, leaving the IC in the plant, where it participates in essential metabolic processes. 

Soil acidity in the form of IT ion builds up as plant roots exchange for other cationic nutrients in soil. When acidity reaches excessive levels, the soil is no longer productive. Acidity can be neutralized by the addition of lime, CaCOj, which neutralizes acidity according to the following reaction  

This process also adds calcium to soil. 

The essential plant nutrient nitrogen is very much involved with nature s nitrogen cycle, which is significantly modified by human activities. Major aspects of this cycle are as follows  

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