Page 175 - Enzymes in Tropical Soils

Enzymes in Tropical Soils 163

11.1 The Supplies of Nutrient Elements

The most abundant nutrient sources of nutrient elements are soil minerals,
particularly in young soils with a great deal of nutrient-rich minerals. However, due
to massive absorption of nutrient elements from soils by plant roots, the residues
of plants and also their consumers (animals/humans) may accumulate great
amounts of soil nutrients. Abundant literatures show that these organic materials
are good sources of nutrient elements for agriculture production (Banuwa et al.,
2003a; 2003b; Banuwa and Damai, 2003; Yusnaini et al., 2007; Bintoro, 2008). For
example, Bintoro (2008) showed that some organic residues were potential as
nutrient element sources (Table 3.4). Yusnaini et al. (2007) also showed that some
plant and animal residues are potential as nutrient element sources for plant
growth. Parts of chemical fertilizers were possible to be substituted by these
organic residues, that increase the soil N and P contents in soils. ‘Night soil’ is also
demonstrated to increase the soil total N, available P, and exchangeable K, and also
the growth of corn (Table 5.14) (Banuwa et al., 2003a; 2003b; Banuwa and Damai,
2003).
The release of nutrient elements from these organic residues is, however,
relatively slow. By this reason alone, most organic matter is a matter of fact
inferior compared to the commercial fertilizers, that may dissolve in soil water and
provide available forms of nutrients relatively fast. However, regulating the soil
C/N ratios, pH, moisture content, and O 2 is usually employed to speed up the
nutrient release from the organic structures. This technique is actually to control
the soil microorganisms at particular conditions so that the enzyme producing
agents may live at suitable conditions. The suitable conditions for microorganisms
are enough energy sources in the form of hydrocarbon, enough N to avail nutrient
needed for protein formation, and a suitable soil pH to neutralize the acidification
as a result of organic matter decomposition catalyzed by soil enzymes (Eq. 4.5 and
Eq. 4.8). Enough water mositure is also very important to provide enough water
needed for speeding up the decomposition reaction that involve hydrolisis process
and enough O 2 needed by microorganisms for conducting respiration to obtain
energy. The suitable conditions may stimulate the soil microoganisms to produce
enough soil enzymes so that the soil enzymatic activities are high enough to speed
up the nutrient release from organic sources.
The suitable environment for soil microorganisms in conducting decay
processes is usually maintained by the above technique. The energy sources are
usually abundant in the soil system by incoorporating organic residues into the soil
system. Nitrogen element needed by the soil microoorganisms is usually sufficed

Abdul Kadir Salam - 2014