Page 176 - Enzymes in Tropical Soils

164 Enzymes In Tropical Soils

by the application of a particular level of Urea-N or other sources of N, particularly
if the organic residues or soils lack of N or show high C/N ratios. To regulate the
soil pH, lime such as calcite or dolomite is usually employed by mixing it with the
decomposting organic residues. Enough water and O 2 can be managed by adding
enough water into the decaying organic matters and providing enough spaces
between organic mater chuncks to allow O 2 to diffuse from atmosphere into the
organic matters.

11.2 Preparation of Organic Compost

Theoretically, making use of nutrient elements of organic matters employing
enzymes can be done by two methods: (a) by composting organic matters off-fields
before their applications to the fields or (b) by applying enzymes into the organic
matters in the fields. Composting is to prepare partially destructed organic matters
so that they can be applied less bulky and more practical with simpler biochemical
reactions in soils. Upon application into soils, organic compost may give inorganic
elements and decompose further to give more inorganic elements and to become
more stable organic matters. However, this method is usually not practical if
organic composts are applied at relatively high amounts. Organic composts are
-1
usually applied in the soil system at rates of more than 5 – 10 ton ha (Salam et al.,
1997j; 1997k). The size of optimum rate of organic compost is technically and
economically difficult to apply for commercial uses, particularly for small size farms.
To make compost, organic residues are prepared in small chuncks; smaller
size will be better to accelerate the organic matter decays. Inorganic N is added at
levels enough for microorganims to develop their populations and to conduct
activities in soils so that they may produce various soil enzymes to decompose the
various structures of organic matters. The amount of inorganic N added may be
higher if N contents in organic residues are low or their C/N ratios are relatively
+
high. Since some reactions of the organic matter decomposition produce H ions,
which may acidify the system, a particular amount of lime is also added to maintain
the soil pH. For all type of organic matter decomposition, water is an essential
reactant. Therefore, the moist condition must be maintained by adding enough
water regularly. Since for the oxidation of organic matters by soil microorganisms
O 2 is needed, as the electron acceptor, the piles of organic materials must allow a
free entry of O 2 from the atmosphere and free exit of produced CO 2 to the
atmosphere. A source of microorganisms such as animal dungs is also important to

Abdul Kadir Salam - 2014