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CRH is good carrier of inoculant

April 14, 2010


April 7, 2010, 3:41pm

Carbonized rice hull (CRH) can be an environment-friendly alternative to wood charcoal as a carrier component in making Rhizobium inoculant, according to a study conducted by Dr. Constancio Asis Jr. and Julie Elijay of the Philippine Rice Research Institute (PhilRice) in the Science City of Muñoz, Nueva Ecija.

The use of microbial inoculant such as Rhizobium inoculant in crop production is now being widely adopted by farmers all over the country as this has resulted in increased yield and added profit because the application of synthetic nitrogenous fertilizer is reduced by up to fifty percent.

“The atmosphere has 78 percent nitrogen but this is in inert form which is not readily available for plant use due to the triple bond connecting the two nitrogen molecules,” says Asis. At this point, he said that the use of Rhizobium inoculant can be beneficial because the bacterium Rhizobium releases nitrogenase, an enzyme that cuts the bond between nitrogen molecules, making it available to the plants. In other words, nitrogenase helps in fixing atmospheric nitrogen and converting it into ammonia, a form which is usable by plants.

When used to inoculate seeds, by coating the seeds prior to planting, Rhizobium induces the formation of nodules on the roots of certain leguminous plants, and this bacterium in the nodules fixes the nitrogen for use by the plant.

To utilize Rhizobium, it is often necessary to provide a dependable inoculant to ensure effective nodulation of the inoculated leguminuous crops.

Asis said that the commercially available inoculant uses wood charcoal as the carbon source for the Rhizobium inoculant carrier. Other components include garden soil, rice hull ash and ipil ipil leaves. However, they consider the use of wood charcoal as not so environment friendly as it contributes to the cutting of trees.

That is the main reason why Asis and Elijay thought of replacing wood charcoal with carbonized rice hull because the latter is also a source of carbon and rice hull is abundant in the Philippines as a waste product in rice production.

“CRH can be produced using PhiRice-designed rice hull carbonizer which costs only P800 per unit,” says Asis. While charcoal needs a grinder that consumes higher energy before these are made available as carrier component, CRH only requires lesser energy because these are easily broken down into smaller form, Asis added.

In their research titled “Use of Carbonized Rice Hull as Carrier Component of Rhizobium Inoculant,” Asis and Elijay directly substituted the wood charcoal with CRH. They used two treatments which are CRH and CRH-acidic soil carrier mixtures.

The inoculant carrier components in each treatment were pulverized, sieved, mixed in plastic bags and sterilized. Then the Rhizobium broth culture was prepared and aseptically inoculated into the carrier mixtures at room temperature for 120 days. The researchers adopted the MPN (most probable number method) to determine the Rhizobium population.

From the results, the researchers concluded that the CRH-based mixtures were comparable to wood charcoal in maintaining the viability of Rhizobial cells. This was after the carrier mixtures met the acceptable standard of viable Rhizobia per gram of inoculant at 120 days after inoculation.

Asis revealed that their next step would involve the introduction of the technology to the mixing plants of Rhizobium inoculant in strategically located areas in the country. One very successfully adopted microbial inoculant locally is the Bio-N which is effective for use in rice, corn and vegetables. It is now being produced by a good number of farmer-cooperatives nationwide with the help of the National Institute of Molecular Biology and Biotechnology (BIOTECH) at the University of the Philippines Los Baños.

Asis and Elijay also plan to work on the extension of the storage life of Rhizobium inoculant with CRH carrier component up to six months to maximize its benefits. Aside from reducing environmental impact, the researchers said that the use of CRH as a carrier component for Rhizobium inoculant results in a cheaper product as processing of CRH does not require much energy.

This research was featured in the poster exhibit under the Biological Sciences, Agriculture and Forestry, and Veterinary Medicine Cluster of the National Research Council of the Philippines during its 77th General Membership Assembly held on March 10, 2010 at the Manila Hotel.

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