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Articles by R.R. Ratnayake
Total Records ( 2 ) for R.R. Ratnayake
  R.R. Ratnayake , G. Seneviratne and S.A. Kulasooriya
  Chemical fractionation and quantification of Soil Organic Matter (SOM) pools involve laborious and time-consuming processes, which are also not very accurate. Therefore an attempt was made here to quantify the Fulvic Fraction (FF), Humic Fraction (HF) and soil litter which are known to be very important in nutrient availability in tropical ecosystems, by using weight Loss on Ignition (LOI) method. Cambisols in Sri Lanka was used to extract the humic substances and soil litter. The result indicated that the soil litter combusted at temperatures 170-190°C. Peak weight losses of the FF occurred between 200-250°C. The weight losses of the HF occurred at 500°C. The study clearly showed that soil litter combusted at temperatures <190°C whereas FF and HF showed weight loss signals at temperatures >190°C. Therefore the LOI can be used as a quick and simple technique for the determination of soil litter, in particular and further the FF and HF, compared to conventional extraction methods. This will be very much useful in comparative studies where there are large numbers of samples to be analysed.
  R.R. Ratnayake , G. Seneviratne and S.A. Kulasooriya
  Conversion of native land, into a cultivated system causes precipitous degradation of the soil organic matter. It is reported that C stored in the clay mineral fraction contributes more to the long-term stability of C than sand and silt fraction. This study reports on the soil organic carbon in the clay mineral fraction of some cultivated lands in Sri Lanka and how it deviates from the adjacent natural forests. The field sites included 7 cultivated lands (tea, rubber, coconut, mixed crops, potato, home garden, chena cultivation) and 7 tropical forest types (wet evergreen, semi evergreen, moist monsoon, dry monsoon, montane, dry mixed evergreen). The significant differences in carbon content of the clay fraction between the cultivated land and the adjacent forest in the same location revealed that cultivation has decreased the carbon content in all sites. The highest C content shown by the mixed crop and rubber plantations showed that minimum land management and soil tillage involved with this reduced the rate of decomposition. High temperature of dry mixed evergreen forest and dry monsoon forest may have increased the decomposition rates and lowered the SOC in the clay fraction compared to the other forests. Significant correlations were observed in forests with in clay fraction and climatic parameters but to a lesser extent in cultivated lands. Considerable variations in organic matter input in cultivated lands will be the reason for these weak relationships. The study confirmed that clay mineral fraction was also equally affected during long term cultivation although it was reported to be more stable against rapid decomposition.
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