Abstract
The effects of sugar-cane trash and pineapple residue at the rates of zero, five and ten per cent (soil weight basis) on soil pH, redox potential (Eh), extractable Al, Fe and Mn were studied over a period of four months. Application of plant material increased soil pH and decreased Eh. These changes were larger during the early part of incubation than during the later part. A negative correlation was found between soil pH and Eh. The decrease in extractable Al on addition of organic matter was associated with an increase in soil pH. The concentration of extractable F changed very little during the four-month study. An increase in the concentration of water-soluble and exchangeable Mn was associated with increased rates of organic matter application. It is concluded that the addition of high rates of an undecomposed plant material in the manganiferous (high native Mn) soil would increase available Mn in the soil to the extent that Mn may be toxic to plant growth.
