Most of the silicon absorbeb by plants remains deposited on the external part of the cell walls as a layer of amorphous silica (SiO2.nH2O), probably affecting straw mineralization in soils. An experiment was performed with the aerial part of oat plants, cultivated in nutrient solution with and without silicon addition, to evaluate this hypothesis. Dried aerial parts of oat plants tissue was mixed with soil or washed quartz sand and placed in PVC tubes. Distilled water was percolated through the mixture at 6, 14, 30, 66, 100 and 182 days after the beginning of the experiment. Silicon, soluble organic carbon, mineral nitrogen, calcium, magnesium, sodium and potassium were analysed in the leachetes. Results were calculated as the amount of the element liberated from the tissue per kg of substrate (soil or sand) and interpreted as an indication of straw mineralization. No differences were found between the amounts percolated from the oat straw with and without silicon, except for silicon in the sand treatments. It was concluded that, during the period considered (182 days), a greater silicon amount in the oat straw did not affect its mineralization.
silica; oat; percolation