What is meant by leaching?

Hint: When soil lacks the necessary water-soluble nutrients required for crop growth due to excessive rainfall or irrigation, the process is referred to as leaching. Based on factors such as soil structure and local climate, some soils can leach more than others.

Complete answer:
Leaching occurs when extra precipitation, flooding or drainage, extracts water-soluble nutrients from the soil. The lost particles are transported downwards and are usually repositioned in a lower layer. This transport results in a porous and accessible upper layer and a dense, rigid lower layer.
- Leaching is the key process responsible for the transportation of chemicals in soil. Plants are no longer able to absorb these nutrients and they are transferred into groundwater or other water bodies. Excessive phosphorus accumulation negatively affects human water consumption and encourages algal growth (i.e. eutrophication), which can lead to a decrease of water oxygen levels and thereby affect fish and other marine species.

- Leaching extracts essential nutrients and micronutrients, such as water-soluble boron, from the soil, creating possible crop shortages. In addition, as nutrients leave the soil, the soil itself becomes more acidic, causing more damage to the crop and reducing future uses of the soil until the nutrients are substituted.
- Toxic soil removes the microorganisms, which are necessary for sustaining safe soil pH levels and for composting rotting leaves and plants. On the other hand, excessive leaching will dissipate soil nutrients, especially nitrates and phosphorus.

Note: The rate of leaching rises with the amount of rainfall, high temperatures and the destruction of the protecting vegetation. Many plant nutrients are lost in areas with intensive leaching.