Of the 13 fly ashes from Australian power stations, all were dominated by both amorphous and crystalline aluminosilicates and quartz, and these were associated with minor amounts of Fe oxides, lesser amounts of Ca, Mg, Na, K, Ti and P oxides, and variable levels of incompletely combusted C. The ashes consisted of particles predominantly in the silt plus fine sand fraction (67-98%), and electron microscopy revealed that ash matrices consisted of glassy spherical particles and less regularly shaped spongy particles. The available water capacity was high and varied from 27 to 105% with 11 of the 13 samples having values > 40%. Twelve of the 13 ashes were alkaline to strongly alkaline (pH range 8.0-12.8). Soluble salt levels were related to the coal source, and electrical conductivity of the saturation extracts (ECse) varied from 0.63 to 7.0 mS cm -1 for 11 of the samples; two ashes produced from brown coal had ECse values of 46.0 and 55.0 mS cm-1. The nutritional status of the ashes was assessed on samples leached with water to reduce the soluble salts to equilibrium levels. The ashes contained negligible amounts of N, but their P status was variable. The amounts of NH4OAc-extractable Ca and Mg were generally high in most samples and were considered more than adequate for most plant species; however, NH4OAc-extractable K values were generally low. Adequate levels of sulfate-S existed in 12 of the 13 samples, and levels of DTPAextractable Cu, Zn, Mn and Fe were high when compared with published critical values. Most of the unleached samples contained potentially toxic levels of B. The results are discussed with reference to the establishment of vegetation on ash dumps and to the use of fly ash in ameliorating the properties of soils.

SUMMARY Waterlogging the soil promotes epinastic growth of tomato petioles and increases the concentration of ethylene which can be extracted from various parts of the shoot. These concentrations exceed those normally required to promote epinasty when applied to the shoots of non‐waterlogged plants. Waterlogging also results in a rapid decline in the concentration of dissolved oxygen in the soil water. Low concentrations of oxygen around the roots of plants growing in nutrient solution promote epinastic growth and also increase ethylene concentration in the leaves. Experiments with detached shoots indicate that the root system is required for the response to low O2concentrations to develop. Ethylene concentrations in the soil can increase during waterlogging to levels which may allow sufficient movement into the shoot to stimulate epinasty. Treatment with substances which can inhibit the action of ethylene, such as carbon dioxide or 7‐chloro‐4‐ethoxycarbonylmethoxy‐5‐methyl‐2, 1,3‐benzothiadiazole also inhibit the epinastic response in waterlogged plants, in plants with low O2 concentrations around the roots and in plants treated with ethylene. The internal level of carbon dioxide in the lower leaves is little affected by waterlogging for up to 96 h.

SUMMARY Epinastic growth by petioles of tomato (Lycopersicon esculentum Mill., cv. Moneymaker) is stimulated by waterlogging the soil and the responding leaves and other shoot parts contain higher concentrations of ethylene than those of non‐waterlogged plants. Waterlogged soil also contains increased amounts of ethylene in solution and the possibility that ethylene from this source can move to the shoots of waterlogged plants has been tested by applying the gas to the roots of plants growing in water culture. When concentrations of 2 ppm and above are supplied in this way, petiole epinasty develops in association with increases in ethylene extracted from the responding petioles. When 100 ppm is applied to the roots, increases in ethylene in the petioles precede the development of epinastic growth. Use of [14C] labelled ethylene indicates that the gas can move rapidly, unchanged from roots to shoots. The movement of ethylene and epinastic growth are both reduced if plants are previously steam‐girdled near the base of the stem, suggesting that much ethylene moves by a route other than the transpiration stream. Ethylene supplied to the roots is shown to promote adventitious rooting and downward rolling of the young leaf laminae and to modify the orientation of shoot growth in the tomato mutant‘diageotropica’. It is proposed that increases in soil ethylene and movement of the gas to the shoot system are factors contributing to the development of epinasty and other responses of the shoots to waterlogging the soil.

No abstract

Fly ash from a coal-fired power station was incorporated with each of a 'fine' (0.2-0.5 mm) and 'coarse' (1.4-2.0 mm) sand fraction to give mixtures containing 0, 10, 20, 30, 40, 50, 75 and 100% fly ash by weight. The addition of 10% by weight of ash increased the available water capacity by factors of 7.2 (1.0-7.2% by weight) and 13.5 (0.4-5.4% by weight) for the 'fine' and 'coarse' sands respectively. Subsequent additional 10% increments of ash increased the capacity by smaller amounts. The saturated hydraulic conductivity of the sands decreased markedly with ash addition. The changes in available water capacity and hydraulic conductivity were associated with an increase in capillary pores at the expense of non-capillary pores. Addition of fly ash to both sand fractions resulted in a bilinear relationship between void ratio (volume voids/volume solids) and fly ash percentage in the mixes which was closely related to that theoretically predicted for binary mixtures. The measured void ratios of the mixes exhibited minimum values at 36% and 20% ash by volume for the 'fine' and 'coarse' sand mixes respectively, which compared with the theoretical void ratios for these mixes of 27% and 23% respectively.