Page 42 - Enzymes in Tropical Soils

30 Enzymes In Tropical Soils

Wise uses based on research data may enable the use of organic residues to lower
the use of commercial fertilizers significantly. In addition to use their potential
contents, their uses in agriculture may also solve the enviroment and social
problems.

3.3 Nutrient Cycling in the Soil – Plant System

Using organic matters to provide some nutrient elements for plants means
that we have to make a reverse process from that occurs in plants. In plants,
nutrient elements are chemically combined to form some organic compounds such
as sugars, proteins, and fats. Conversely, as will be shown in Fig. 5.1., in soils the
organic compounds (sugars, proteins, and fatss) are chemically decomposed back
to inorganic nutrient elements as shown in Fig. 3.2. Examples of ionic inorganic
+ - - 2- + 2+ 2+
nutrient elements are NH 4 , NO 3 , H 2 PO 4 , HPO 4 , K , Zn , Mg , etc. The organic
compounds can not be absorbed by plant roots, but inorganic nutrient elements
can be easily absorbed. Therefore, the inorganic nutrient elements that are initially
transformed into organic compounds finally decomposed back to form inorganic
nutrient elements. The process of synthesis and its reverse process called
decomposition form a cycle called Nutrient Cycle.

Decomposition
• CO + H O in Soils • CO + H O
2
2
2
2
• Other Inorganic •Sugars • Inorganic
Elements Elements
• Proteins
• Energy •Energy
• Fats
Synthesis in Synthesis in
Plants Plants

Fig. 3.2. Decomposition of organic compounds forming a nutrient cycle.

Abdul Kadir Salam - 2014