Rapid Rice Straw Composting

Ordinary composting, which requires three months for complete decomposition, is too slow for farmers who plant two or three rice crops a year. The IBS rapid composting method (named after the Institute of Biological Sciences at the University of the Philippines, Los Baños), speeds up the process with a compost fungus activator, Trichoderma harzianum. The activator complements soil microbes as a source of waste cellulose decomposers, thereby increasing the number of decomposers and the rate of decomposition so that farmers can use the compost sooner.

Rapid composting requires carbon-rich materials such as rice straw, nitrogen-rich materials like animal manure and the activator Trichoderma harzianum. A combination of three parts carbon to one part nitrogen substrate is best. If animal manure is difficult to obtain, it may be replaced with leguminous plants such as azolla and sesbania. Trichoderma harzianum, is widely produced in the Philippines by the Departments of Science and Technology and Agriculture, state universities, non-government organizations and farmers' cooperatives.

The Process

At harvest time, rice straw is heaped to one side of the paddy. It saves labor later to have one compost pile for each paddy instead of one central pile.
Rice straw is soaked overnight in irrigation water or in the rain until saturated.
A simple platform is made in the middle of the paddy (size is relative to the size of the paddy).
A layer of saturated rice straw 10-15 cm thick is loosely piled on the platform.
On top of the layer, one or two handfuls of the activator is broadcast (25 kg /ha).
Straw is alternately layered with the activator until all the straw has been used.
Manure and nitrogenous plants are put on top of the straw layers. The nitrogen substrate is 15-25% of total composition.
The compost is covered (with plastic, banana leaves, or coconut fronds) and heats up within 25 hours.
The compost must be moistened frequently to compensate for evaporation.
The compost is left unturned and matures within one month. It is ready for use when the pile has cooled and is 30% of its original size.

Benefits

Income gains resulting from a healthy crop are the most immediate return. But more importantly, the soil benefits from continued use of compost in the long term. Results include improved soil texture and tilth, better aeration and water-holding capacity, increased fertility and less acidity. Because rice straw is composted and not burnt, less carbon dioxide is released into the atmosphere. Compost reduces the need for chemical fertilizers which contaminate surrounding waters and encourage algae blooms that compete with fish for oxygen. Additionally, as farmers gain self-reliance they become less dependent on off-farm inputs.

Possible Drawbacks

Rapid composting, like composting in general, often means more work for the farmer. Labor inputs can be reduced by composting in the paddy and in small heaps that are easily transportable. A reliable supply of T. harzianum is critical to facilitate the rapid decompostion process. Contaminants reduce the effectiveness of the activator and may cause skin irritations. Also, limited manure supply may result in compost with low N content.

Conclusion

Rapid composting turns a problem into a solution by using formerly wasted rice straw to benefit the soil. The process fits into farmers' busy planting schedules and can help to make them more independent of chemical inputs purchased externally. Virginia Cuevas. 1993. Rapid Composting Fits Rice Farmers. ILEIA. 9 (2), pp. 11-12.

Contact:

Virginia Cuevas
University of the Philippines at Los Banos
Laguna, PHILIPPINES 4031
Fax: 63-94-3472