Nitrates and phosphorus

Nitrogen and phosphorus are elements essential to all forms of life and are therefore relevant to soil systems and food crops. Although they are important plant nutrients, excessive application may lead to nitrogen or phosphate saturation in the soil, and eventual contamination of the groundwater. The amount of leaching depends on the soil, the local climate and the style of crop management.

Phosphorus
Phosphorus accumulates in the upper layer of soil in regions with high livestock densities. In soils saturated with phosphorus, especially those with shallow groundwater, high phosphorus concentration occurs in the upper groundwater layer and in surface water, resulting in eutrophication.

Nitrogen
The problem of nitrate pollution is recognised internationally and is usually associated with intensive agriculture practices. Good agricultural practices that alleviate the problem are:

• the selection of crops that require fewer nutrients;

• a timely application of fertiliser (in the growing season);

• improved methods of manure application;

• shortening the length of the grazing season; and

• reducing the intensity of grassland use (by lowering cattle density).

More: