The present investigation was undertaken to study the effect of the intensity of organic matter - mineral soil mixing on organic matter decomposition and nutrient mobilisation in soil intensively cultivated for afforestation. Soil mixing produced in the field by the newly developed Rotary Mouldboard Forestry Plough was simulated in laboratory incubation studies. Rates of organic matter decomposition and mobilisation of nitrogen, phosphorus, potassium, calcium and magnesium were studied in different mixing intensities of organic matter and pure quartz sand, incubated in 1 metfc tall leaching columns. Levels of mobilised nutrients were determined in fortnightly leachates. Rates of mobilisation for all five elements were found to be consistently higher in the most intensively mixed treatment with the largest surface area of organic matter exposed. When calculated on an organic matter surface area basis, nutrient mobilisation was found to be constant per unit area of organic matter surface, regardless of the total surface area in the treatment. Amounts of leached nitrogen, potassium and particularly phosphorus from organic matter and sand mixtures were higher under waterlogged conditions than when the column samples were aerated daily. Nutrient mobilisation rates for incubation samples, calculated on a field basis, showed that at the greatest mixing intensity, it might take 200 years to completely mobilise the soil nitrogen and 100 years for soil phosphorus. At this mixing intensity, potassium, calcium and magnesium might be completely mobilised in less than 50 years. 18-40% of the annual nitrogen requirement for uptake by conifers could be supplied by mobilisation of soil nitrogen in the most intensive mixture and only potassium would be mobilised at a rate exceeding tree requirement for uptake. It is suggested that a low field mixing intensity, in combination with low fertilizer inputs, could sustain acceptable yields while maintaining soil fertility for future rotations.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:661399 |
| Date | January 1979 |
| Creators | Ross, Sheila M. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/14335 |
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