Page 37 - Enzymes in Tropical Soils

Enzymes in Tropical Soils 25

ATMOSPHRERE

FERTILIZERS/IRRIGATION

SOIL SYSTEM

EROSION NUTRIENTS PLANTS

Weathering
Ads./Des.
PRIMARY LEACHING Dec. ANIMALS/MEN

MINERALS Presipit
asi/Diso
SECONDARY lusi ORGANIC MATTER
MINE RALS

Fig. 3.1. Relationship between soil – plants – animals/humans (Salam, 2012).

However, the available nutrients in soils also leak through some processes
such as erosion, leaching, volatilization, and plant root absorption. Assuming the
nutrient losses through soil erosion, leaching, and volatilization are low, the plant
root absorption becomes the most significant nutrient leak from the soil system.
Therefore, the losses of nutrients in an intensive agriculture becomes the most
important aspect to consider.
The absorbed nutrients are then transfered to food chains through animals
and human beings. The dead parts of plants, animals, and humans will eventually
contribute great amounts of organic matters in the soil system. The organic matter
decays, accelerated by the presence of soil enzymes, then transform the
unavailable nutrients in organic matters back into inorganic forms of nutrients
available to plants. These inorganic forms of nutrients are then subjected to
various fates. They may encounter adsorption processes by soil secondary
minerals or organic matters, precipitate to be secondary minerals, as well as leak
out of the soil system through soil erosion, volatilization, or leaching. Most of them
may be re-absorbed by plant roots and come into another food chain.
It is obvious then, in a closed system, where all organic matters from plant
and animal residues as well as from dead parts of plants, animals, and humans are

Abdul Kadir Salam - 2014