37
recommended (Vigneswaran et al. 2016). Higher ratios lead to longer composting
periods due to slower decomposition whereas, at lower ratios, nitrogen can be rapidly lost by conversion into gaseous forms (as ammonia or nitrogen), affecting the
compost quality. Thus, it is necessary to mix straw with a high-quality organic material such as manure in order to have a suitable ratio of C/N (25–30) for composting
process (Ameen et al. 2016). Due to the low C/N ratio of cattle manure, it was
adjusted to 25 by adding sawdust or rice straw (Qiu et al. 2013; Jusoh et al. 2013).
3.1.5 Moisture Content of Substrates
The moisture content of the composting materials affects the availability of oxygen
for microbial processes. Water is essential for the decomposition process and water
stress is among the most common limitations on microbial activity on solid substrates. However, when moisture levels exceed 65%, air in the pore spaces of the
raw materials is displaced by water, which leads to anaerobic conditions, odors, and
slower decomposition (Pace et al. 1995; Sherman 1999). Moisture content of the
mixture was maintained at 60%, which is the optimum level for microbial activity
(Goyal and Sindhu 2011; Diaz et al. 2007). To maintain the moisture content at an
optimal range of 50–65% (wet basic), water is added to the compost during turning
periods. After the turning process, a plastic sheet is used to cover the windrow to
retain the moisture content and prevent excessive loss of heat (Vigneswaran et al.
2016; Jusoh et al. 2013). At the end of the composting process, the moisture content
of the compost should be about 30% to prevent any further biological activity in the
stabilized material (Diaz et al. 2007).
3.2 Current Practices for Rice-Straw Composting
3.2.1 Vermi-composting
Vermi-composting is a biological process of bio-oxidation and stabilization of
organic material involving the joint action of earthworms and microorganisms (Aira
et al. 2002). While microbes are responsible for the biochemical degradation of
organic matter, earthworms serve as the important drivers of the process in conditioning the substrate and alteration of biological activity. The end product, or vermicompost, is a finely divided peat-like material with high porosity and water-holding
capacity that contains most nutrients in forms that are readily taken up by the plants
(Dominguez and Edwards 2004). The invertebrates have indirect effects on the
structure and activities of bacterial and fungal communities through inoculum dispersal, grazing, litter combination, gut passage, and aggregate formation (Anderson
1987). The use of earthworms in compost heaps, beds or boxes makes the process
3 Rice Straw-Based Composting
recommended (Vigneswaran et al. 2016). Higher ratios lead to longer composting
periods due to slower decomposition whereas, at lower ratios, nitrogen can be rapidly lost by conversion into gaseous forms (as ammonia or nitrogen), affecting the
compost quality. Thus, it is necessary to mix straw with a high-quality organic material such as manure in order to have a suitable ratio of C/N (25–30) for composting
process (Ameen et al. 2016). Due to the low C/N ratio of cattle manure, it was
adjusted to 25 by adding sawdust or rice straw (Qiu et al. 2013; Jusoh et al. 2013).
3.1.5 Moisture Content of Substrates
The moisture content of the composting materials affects the availability of oxygen
for microbial processes. Water is essential for the decomposition process and water
stress is among the most common limitations on microbial activity on solid substrates. However, when moisture levels exceed 65%, air in the pore spaces of the
raw materials is displaced by water, which leads to anaerobic conditions, odors, and
slower decomposition (Pace et al. 1995; Sherman 1999). Moisture content of the
mixture was maintained at 60%, which is the optimum level for microbial activity
(Goyal and Sindhu 2011; Diaz et al. 2007). To maintain the moisture content at an
optimal range of 50–65% (wet basic), water is added to the compost during turning
periods. After the turning process, a plastic sheet is used to cover the windrow to
retain the moisture content and prevent excessive loss of heat (Vigneswaran et al.
2016; Jusoh et al. 2013). At the end of the composting process, the moisture content
of the compost should be about 30% to prevent any further biological activity in the
stabilized material (Diaz et al. 2007).
3.2 Current Practices for Rice-Straw Composting
3.2.1 Vermi-composting
Vermi-composting is a biological process of bio-oxidation and stabilization of
organic material involving the joint action of earthworms and microorganisms (Aira
et al. 2002). While microbes are responsible for the biochemical degradation of
organic matter, earthworms serve as the important drivers of the process in conditioning the substrate and alteration of biological activity. The end product, or vermicompost, is a finely divided peat-like material with high porosity and water-holding
capacity that contains most nutrients in forms that are readily taken up by the plants
(Dominguez and Edwards 2004). The invertebrates have indirect effects on the
structure and activities of bacterial and fungal communities through inoculum dispersal, grazing, litter combination, gut passage, and aggregate formation (Anderson
1987). The use of earthworms in compost heaps, beds or boxes makes the process
3 Rice Straw-Based Composting