Effects of charcoal pore size on nitrate retentiveness
2001
Mori, A. (Shikoku National Agricultural Experiment Station, Zentsuji, Kagawa (Japan)) | Fujino, M. | Takezaki, A.
The application of charcoal to the soil has a number of effects on the soil's chemical, physical and biological properties. Soil conditioning with charcoal sometimes results in improved crop yields, although at present it is not known which characteristic of charcoal promotes plant growth. This study was performed to investigate the degree to which charcoal retains nutrients, including nitrates. Two kinds of charcoal, made from Larix kaempferi (Japanese White Larch) and Quercus phillyraeoides (Ubame Oak) were employed. Conclusions obtained are summarized as follows. 1 ) The porosities of L. kaempferi charcoal and Q. phillyraeoides charcoal were 69% and 31% respectively. The median pore size of L. kaempferi charcoal was larger than that of Q. phillyraeoides charcoal. 2 ) The amount of nitrate adsorbed by the two charcoals was investigated as a function of pH. Nitrate adsorption by both charcoals increased with reduced pH, but at the same pH, nitrate adsorption by Q. phillyraeoides charcoal was greater than that of L. kaempferi charcoal. 3 ) The release of nitrate from 2-4 mm-diameter charcoal pellets presaturated with 10 mmol L**-1 KNO3 was analyzed to evaluate the nitrate-retentive ability of granulated charcoals. Greater amounts of nitrate were retained in L. kaempferi charcoal than in Q. phillyraeoides charcoal. 4 ) The movement of nitrate in charcoal-added soil columns was investigated. The amount of nitrate retained in the upper part of the column increased with addition of charcoal to the soil.
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