Journal of Pure and Applied MicrobiologyVol. 8 No. Special Edition Nov. 2014

Changes in Colour and Germination Index as Indicators for Compost Maturity

Fahad Nasser Alkoaik1, Ahmed Ismail Khalil1,2*, Majdi Ali Al-Mahasneh1, Ronnel Blanqueza Fulleros1 and Ahmed Mohamed El-Waziry3

1Department of Agricultural Engineering, College of Food and Agriculture Sciences, King Saud University, Saudi Arabia. 2Department of Environmental Studies, Institute of Graduate Studies and Research, University of Alexandria, Alexandria, Egypt. 3Department of Animal Production, College of Food and Agriculture Sciences, King Saud University, Saudi Arabia.

Received on 09 September 2014 and accepted on 22 October 2014

 

ABSTRACT

Changes in colour and germination index as indicators of the compost maturity were monitored during the composting of Conocarpus erectus residues. The residues (leaves and small stems) were collected, cut into small pieces, moistend (65%) and mixed and placed in 2 bioreactors. The total volume of the bioreactor was 0.03 m3. Airflow was supplied at a rate of 10 L/min. The results showed that the temperature increased and reached its maximum (54oC) after 36 hrs and then decreased to 26oC. The C/N ratio decreased from 25.22 to 18.48. A gradual darkening took place and the final compost was black in colour. The colour variables (L*, a*, b*) decreased with time and consequently, the DE*ab increased with time as indication of the colour change. The germination (G%) of radish seeds was 75.84, 65.50, 86.18, 99.96, 103.41 and 103.41%, the root length (RL%) was 83.33, 79.17, 116.67, 175, 191.67 and 202.08%, and consequently, the germination index (GI%) was 63.34, 52.14, 100.83, 175.37, 198.2 and 208.97% after 0, 3, 6, 9, 12 and 15 days, respectively. It can be concluded that the changes in colour and germination index could be used as indicators for the progress of composting and compost maturity.

Keywords : Conocarpus erectus residues; Compost; Colour; Germination index.