Searching for potential nitrogen suppliers applicable to reforestation and plantation in tropical peat soil
2007
S. Tahara | I.R. Sitepu | Melling, L. | Hashidoko, Y | N. Ogita
Nitrogen is a limiting factor for plant growth in tropical acidic peat soil of deforested open land, because native plants grown in acidic peat land soil are always exposed to nitrogen starvation due to severe mineral leaching and tannization in organic N-sources. As a mean of supplementing nitrogen, chemical fertilizer is commonly used, but it often causes severe N2O emmision land also water pollution. To minimize the usage of chemical fertilizers in plantation and crop production in peat soil, we searched for free-living and edophytic nitrogen fixers on and in the rhizoplane, rhizosphere and stem marrow of acidic peat soil-adapting plants, in which Xyris complanata (monocot), Oryza sativa (monocot), Metroxylon sagu (monocot), and some dipterocarpaceae plants (Shorea spp. and Hopea spp., dicots) are involved. N-fixing edophytes often showed a synergistic increase of acetylene reduction activity under combinations with certain non-N-fixing bacteria. In M. sagu, Acetobacter sp. accelerated the N-fixation of Mesorhizobium sp., while Sphingomonas sp. EC-K085 isolated from X. complanata also accelerated growth of many other bacteria, including Frateuria sp., Herbaspirillum sp. and Burkholdera sp. In investigation of bacterial growth-promoting principles produced by the Sphingomonas sp. EC-K085, the active substance was identified as linear (R,R,R,R)-3-hydroxybutyrate tetramer. These plant-associating endophytic bacteria combined with microfloral conductors are probably the most effective and bio-rational biological agents for bio-fertilizaion applicable to acidic soil-adapting plants cultivable in peat soil ecosystem.
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