The reaction is initiated by 1 mole of CO(NH2)2
hydrolyzing intracellularly to 1 mole of ammonia
(NH3) and 1 mole of carbamate (H2COOH) as
described in Eq. (1), which spontaneously hydrolyzes
to 1 mole of NH3 and carbonic acid (H2CO3) in Eq. (2).
These products subsequently equilibrate in water to
form CO3
2- and two moles of NH4
+ and hydroxide
(OH) ions in Eqs. (3) and (4). These chemical
sequences can be summarized and rewritten by Eq. (5).
Production of NH4
+ results in increase of pH. In the
presence of sufficient Ca2+ and CO3
2- ions, this will
subsequently result in formation of CaCO3
precipitation in Eq. (6). Some Ca2+ ions are bound to
the cell wall of bacteria can result in the formation of
CaCO3 crystals on the bacterial cell and some Ca2+ ions
are bound to soil particles can also result in the
formation of crystals on the surface of particles. In
addition, precipitation of CaCO3 can also occur in the
bulk phase of the liquid (see also Fig. 1). Those
presences of CaCO3 can fill the soil pores, bind soil
particles together and increase solid content in soil [2,
10-12].