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Eliminating Aluminum Toxicity in an Acid Sulfate Soil for Rice Cultivation Using Plant Growth Promoting Bacteria

Qurban Ali Panhwar 1, 2
1. Department of Land Management, Faculty of Agriculture, Universiti Putra Malaysia, UPM Serdang, Selangor 43400, Malaysia 2. Soil Chemistry Section, Agricultural Research Institute, Tandojam 70060, Sindh, Pakistan

Umme Aminun Naher 3, 4
3. Institute of Tropical Agriculture, Universiti Putra Malaysia, UPM Serdang, Selangor 43400, Malaysia 4. Bangladesh Rice Research Institute, Gazipur 1701, Bangladesh

Othman Radziah 1,3
1. Department of Land Management, Faculty of Agriculture, Universiti Putra Malaysia, UPM Serdang, Selangor 43400, Malaysia 3. Institute of Tropical Agriculture, Universiti Putra Malaysia, UPM Serdang, Selangor 43400,Malaysia

Jusop Shamshuddin 1, 3*
1. Department of Land Management, Faculty of Agriculture, Universiti Putra Malaysia, UPM Serdang, Selangor 43400, Malaysia3. Institute of Tropical Agriculture, Universiti Putra Malaysia, UPM Serdang, Selangor 43400, Malaysia

Ismail Mohd Razi 3
3 Institute of Tropical Agriculture, Universiti Putra Malaysia, UPM Serdang, Selangor 43400, Malaysia

Abstract/ Executive Summary:

Aluminum toxicity is widely considered as the most important limiting factor for plants growing in acid sulfate soils. A study was conducted in laboratory and in field to ameliorate Al toxicity using plant growth promoting bacteria (PGPB), ground magnesium limestone (GML) and ground basalt. Five-day-old rice seedlings were inoculated by Bacillus sp., Stenotrophomonas maltophila, Burkholderia thailandensis and Burkholderia seminalis and grown for 21 days in Hoagland solution (pH 4.0) at various Al concentrations (0, 50 and 100 μM). Toxicity symptoms in root and leaf were studied using scanning electron microscope. In the field, biofertilizer (PGPB), GML and basalt were applied (4 t·ha^-1 each). Results showed that Al severely affected the growth of rice. At high concentrations, the root surface was ruptured, leading to cell collapse; however, no damages were observed in the PGPB inoculated seedlings. After 21 days of inoculation, solution pH increased to >6.0, while the control treatment remained same. Field study showed that the highest rice growth and yield were obtained in the bio-fertilizer and GML treatments. This study showed that Al toxicity was reduced by PGPB via production of organic acids that were able to chelate the Al and the production of polysaccharides that increased solution pH. The release of phytohormones further enhanced rice growth that resulted in yield increase.

Keywords: Al speciation; Chelation; Indoleacetic acid; Phytohormone; Ameliorative effect

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Start Date:

End Date:

Program Area: Risk Management in Agriculture

Commodity: Rice

Objectives:

The present study was undertaken: (1) to determine methods of increasing rice production in high Al containing soils using environmentally-friendly PGPB and/or soil amendments; and (2) to explain the possible mechanisms involved in this process.

Methodology:

It is proven that higher number of PGPR/PGPB is associated with rice rhizosphere and they have the potential to produce a large amount of organic acids, which resulted in P binding by chelation, and may also be a possible mechanism for reducing Al toxicity of roots. The better performance of the PGPR/PGPB for the plant growth promotion occurs with the mixture of strains rather than individual strains. In addition, the application of these beneficial microorganisms enhances the economic efficiency in terms of reduced production cost of phosphorus fertilizers. Addition of these potential PGPR would enhance the growth of rice grown on soils with high Al content. Low pH soils, especially acid sulfate soils, contain low total microorganisms, with their amount varying considerably according to vegetation type and soil management practices. Due to food security, attention is now focusing on rice production in less fertile acidic soils which are usually subjected to Al toxicity.

Source of Information: Pak. J. BioI. & Agric. Sci. 12(1): 74-83,1969.

Article Link (Online Journal):

Funding Source:

1.

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Total Budget (Tk.) :

Achievement/Findings:

Aluminum toxicity is a common problem reducing the yield of rice grown in acid sulfate soils. This problem was alleviated by application of PGPB. The mechanism involved in the ameliorative process was chelation of free Al by the organic acids produced by the bacteria. These bacteria also increased soil pH that precipitated Al and produced phytohormone; both phenomena enhanced rice growth. Scanning electron micrographs of the roots and leaf tissues showed the clear ameliorative effects of PGPB inoculation. Furthermore, rice by itself was able to secrete organic acids via its roots when it was under the stress of high Al concentration. For the rice growing in the field, application of bio-fertilizer containing PGPB had increased yield due to the reasons mentioned above. Rice yield can also be increased further by applying GML or basalt at the appropriate rate. Low exchangeable and weakly-bound Al observed in the bio-fertilizer treatment were clear evidences for the chelation of Al by the organic acids. Hence, the PGPB under investigation can be used for the production of bio-fertilizer for rice cultivation in acid sulfate soils.

Knowledge Management: Journal