Use of effective micro-organisms (EM) and urea in accelerating the decomposition of Rice Straw

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.