Reduction of Soil Acidity for Agriculture Activities in Malaysian Ultisols by Rhodopseudomonas palustris

Abstract

The potential of the phototrophic bacterium, Rhodopseudomonas palustris (R. palustris), to reduce the acidic soil pH of Malaysian Ultisols (Bungor Series) was investigated. The R. palustris was first adsorbed onto the dried pineapple leaves (DPL) before being applied. The most suitable broth condition for the bacterium that could be adsorbed onto the DPL was identified. Different conditions and amounts of R. palustris adsorbedonto the DPL % (w/w) were tested in soils where the soil pH was monitored. It was found that the maximum cell adsorption onto the DPL was obtained using an initial cell concentration of 1.5 x 107 colony-forming units (CFU) mL-1, at pH 8.0 with the ionic strength of 5 mmolL-1 ammonium nitrate (NaNO3). The R. palustris was adsorbed onto the DPL surface area of 64.33 Å. The acidic soil was treated with R. palustris adsorbed onto the DPL by direct application. The calcium carbonate (CaCO3) was introduced as a benchmark to reduce the soil acidity. The results showed that, with the application of R. palustris adsorbed on 5.0 % (w/w) of DPL, thesoil pH was improved from 4.9 to more than 6.0 after 12 d of application. This improved soil pH will make the soil more applicable for agricultural activity.