Abstract:
Slow decomposition rate of rice straw associated with its fibrous nature limits its use as
organic manure even though it is widely available in Sri Lanka. Influence of effective
microorganisms (EM) and urea on the decomposition of rice straw was tested using six
treatments as control, EM, urea rate 1 (U1), urea rate 2(U2), EM+U1 and EM+U2. The rate of
decomposition was evaluated using C:N ratio, weight loss and tensile strength throughout an
eight-week period. The results showed that the EM treatment significantly reduced the C:N
ratio only after 4th week of application. By the8,h week C:N ratio of the control was reduced
from 50.3 to 18.5 whereas the others attained a similar value in shorter periods amounting to
6.5, 5.5, 5 and 4 weeks in EM, U1,U2, Ul+EM and U2+EM treatments respectively. Urea
applied treatments showed lower C:N ratio, higher weight loss and lower tensile strength than
the EM applied and control, showing faster decomposition. This study reveals that EM
increased the rate of decomposition of straw but when urea was applied the decomposition
rate was higher. Using urea as N source and increasing the activity of indigenous microbial
population seem to be more cost effective in straw decomposition, than applying EM of
unknown composition.
