Environmental Engineering Reference
In-Depth Information
Picture 3.1
Pasture in Para State, Brazil, created by land clearing of virgin forests.
Courtesy of Eugenio Arima, reproduced with permission.
350
300
250
200
Potash
150
Phosphate
100
Nitrogen
50
0
Corn
Soybeans
Wheat
Cotton
Rice
Figure 3.3
Typical fertilization rates of nitrogen, phosphate, and potassium (potash) for selelected crops
in the United States.
Adapted from United States Geological Survey, 1999.
In essence, plants require nitrogen, phosphorus, potassium, sulfur, magnesium, calcium,
some trace elements, carbon dioxide, and water. However, nitrogen and phosphorus are the
most important elements because along with water they are limiting nutrients in most soils
(Tilman and Lehman, 2001). Nitrogen is an abundant element in nature; but, it is present in the
incorrect form for plants to assimilate. Atmospheric nitrogen (N
2
) is a stable molecule that
