Sm. Tiquia et al., CHANGES IN CHEMICAL-PROPERTIES DURING COMPOSTING OF SPENT PIG LITTER AT DIFFERENT MOISTURE CONTENTS, Agriculture, ecosystems & environment, 67(1), 1998, pp. 79-89
An ordinary pig pen employing the pig-on-litter system was set-up and
40 pigs were placed inside. After 12 weeks, the Digs were removed from
the pen and the spent litter was collected and piled up in an open sh
ed for further composting and maturation. Three piles of the spent lit
ter were set up with moisture content adjusted to 50% (Pile A), 60% (P
ile B) and 70% (Pile C). During further composting, the changes in tem
perature and chemical properties of the piles were monitored. Results
of the study revealed that moisture content affected the changes in te
mperature and chemical properties (i.e., concentrations of NH4+--N, [N
O3- + NO2-]-N, C:N ratio, cation-exchange capacity [CEC], total and wa
ter extractable K and pH value) of the spent litter. Pile C, the pile
adjusted to 70% moisture, had a delay in reaching peak temperature val
ues and the temperature never dropped back to the ambient level. Piles
A and B, the piles adjusted to 50 and 60% moisture content respective
ly, had very similar changes in temperature and chemical properties an
d had faster decomposition rates than pile C suggesting that moisture
content between 50 and 60% is the suitable moisture content for an eff
icient further composting of spent litter. The maturation of spent lit
ter was accompanied by changes, with periods of composting in pH, tota
l C, ash, various forms of N, CEC and C:N ratio. Results of the regres
sion analysis showed a curvilinear relationship between these chemical
parameters with period of composting and temperature. Moreover, chang
es in these chemical parameters were found to be either positively or
negatively correlated with temperature. (C) 1998 Elsevier Science B.V.