The relationships between soil aeration and other physical properties of two upland soils prone to waterlogging, a peaty gley in the Kielder forest region of Northumberland (Falstone forest) and a deep peat in Eddleston forest of the Borders region of Scotland, were investigated. The investigations examined the soil atmosphere composition, moisture potential, depth to water table, temperature and rainfall/ throughfall throughout 1978 and 1979 at Falstone, and during 1979 at Eddleston. Measurements were made under stands of Picea sitchensis and Pinus contorta, and neighbouring areas of the original vegetation. Samples removed from the soil pore space were analysed for oxygen and carbon dioxide concentrations by gas chromatography. Oxygen concentrations in the soil were found to be greaterunder the tree species than the unplanted areas, at all depths, duringthe moisture deficit period. During the moisture deficit period thesoil dried to a greater depth under the trees, and to lower matricpotentials above the water table. The oxygen concentrations were found3 -3to be near atmospheric (0.21 m m ) when the matric potential fell below3 -3-5kPa, and could be as low as 0.01m m , or even zero, at higher potentials. The oxygen concentrations were also found to decrease, and carbon dioxide concentrations increase, with increasing depth under all species corresponding to increasing matric potential. Statistical analysis revealed a small but significant improvement in aeration under Pinus contorta over Picea sitchensis on both soil types. It was also revealed that lower oxygen concentrations and higher carbon dioxide concentrations could be expected for matric potentials above about -5kPa, when soil temperatures were at their maximum (about 10?C). Thesetrends were observed in both soils and during both years of study. The moisture release characteristics, bulk density and porevolume fraction of the soils were also measured, and increasing oxygenconcentrations over a range of matric potentials from 0 to -lOkPa foundto correlate with an increase in gas filled pore volume. Gaseous diffusion through peat cores was measured over a range2 16of 0 to -lOkPa matric potential and the equation D/Dq = 0.65 e ? found to describe the increase in diffusivity (D/D ) with gas filled pore space (?g )- The respiration rate of peat cores was found to vary randomly over a range of gas filled pore volume fractions (from 0 to about 0.4) but increase with increasing temperature from 5?C to 30?C, having a Q of about 3. An investigation into root growth rate of Pinus contorta andPicea sitchensis cuttings grown in a range of carbon dioxide concentrations3 -3(0.01, 0.06, 0.12 and 0.18 m m ), showed no reduction in growth rate3 -3when oxygen concentrations were 0.21 m m , but growth ceased when oxygen3 _3concentrations were 0.01 m m and the carbon dioxide concentration greater than this value.

The extraction of cobalt from 3 soils with 0.5 M acetic acid was studied under conditions of varying temperature, duration of extraction and soil-solution ratio. The first two parameters significantly affected the quantity of cobalt extracted, but variation in soil-solution ratio had little effect. In an examination of 20 soils from south-east Scotland, the total soil cobalt content was found to be positively correlated with the concentrations of iron and manganese oxides. Extractability studies using 0.5 M acetic acid and 0.0b M di-sodium EDTA indicated that cobalt was associated to a greater degree with the manganese oxides than the iron oxides. However, the 0.01 M CaCl^-extractable cobalt concentration was not related to the soil oxide content, but was negatively correlated with soil pH. Isotopic exchange studies showed that the concentration of isotopically exchangeable cobalt was directly related to the soil oxide content. The equilibrium between isotopically exchangeable cobalt on the solid phase of the soil and in soil solution was highly dependent on soil pH. No relationship between total, extractable or isotopically exchangeable cobalt and soil organic matter was observed. In an incubation study waterlogging caused mobilisation of both indigenous and added cobalt, as determined by acetic acid extraction. Drying of the soil to 20 per cent moisture caused rapid immobilisation of this cobalt and, over a period of months, the supplementary cobalt became non-extractable. The specific sorption of cobalt by individual soil constituents and by 18 soils from south-east Scotland was examined. The equilibrium solution cobalt concentrations used were those likely to be found in soil ( 10 ^ M). Amorphous soil oxide material showed the highest capacity for sorption, followed by humic and fulvic acids and then montmorillonite. However, the reaction between cobalt and montmorillonite showed greater irreversibility than with humic acid. The sorption characteristics of the intact soils indicated that sorption took place predominantly on the manganese oxide fraction. Two pot experiments were carried out to study the uptake of native cobalt by perennial ryegrass and red clover and also the increase in the cobalt content of perennial ryegrass following application to the soil. The concentration of plant cobalt derived from indigenous soil supplies was negatively correlated with soil pH, as was the increase in plant content due to artificial addition to the soil. The latter quantity was also negatively correlated with the soil iron and manganese oxide contents. Field trials were set up in south-east Scotland to monitor the effect of top-dressing with cobalt on uptake by deficient pasture (mixed herbage). Over a 3 year period, the addition of 6 kg CoS0^.7H^0 per hectare raised herbage cobalt concentrations to above 0.08 pg/g (deficiency level) in less than half of the 15 soils studied. Applying the same amount of cobalt as the EDTA complex was still less effective. Although herbage cobalt concentrations decreased over the 3 year sampling period, there was no concurrent decrease in acetic acid-extractable soil cobalt. Most the applied cobalt was present in the top k cm of soil.

No description available.

No description available.

The object of this research programme was to investigate the stability of a silty clay under undrained repeated loading. Equipment has been designed and developed for the application of a quasi-sinusoidal compressive load form to triaxial samples. A series of monotonic strain controlled triaxial tests with pore pressure measurement was performed on normally consolidated and overconsolidated samples of saturated reconstituted Keuper Marl. These tests defined the critical state parameters, and hence the stable state boundary surface for this soil, and provided a basis for a comparison with the results of cyclic stress controlled triaxial tests. Two series of cyclic triaxial compression tests were performed: firstly, single stage tests using a constant level of repeated stress; and secondly, multistage tests. These aimed to investigate: a) stress conditions at failure under cyclic loading; b) strength of non-failed samples after cyclic loading; and c) strain and pore pressure behaviour under repeated loading. Criteria for the stability of a soil under cyclic loading are presented and a model is developed based on the pore pressure behaviour of the soil under repeated loading. This model can be used to predict pore pressures and failure for normally consolidated and lightly overconsolidated soils.

No description available.

No description available.

No description available.

No description available.

The residual strength of three different natural soils, lower Lias clay, London clay and a clay fron Baghdad, Iraq were investigated using the shear box and a modified Bromhead ring shear apparatus.