Graphite crystal expansions were derived as a function of temperature using the theoretical relationships of ~i ley(' ); the resultant 1 equations provide reasonable f i t s t o the measured l a t t i c e expansion . I data over the temperature range 300' t o 3000°K.

The germination of the salt-tolerant grass Diplachne fusca (L.) Beauv. was investigated because of its potential as a pasture species to be used in the reclamation of salt-affected land. Fresh seed was dor- mant. Dormancy was not broken by stratification, but gradually broke down during air-dry storage, indicating an after-ripening period of at least 1 year. The germination of germinable stored seeds at various temperature regimes (combinations of day and night temperatures between 11 and 31°C) was assessed on a thermogradient plate. The germination after 21 days was greatest at high temperatures (40-90% when both day and night temperatures were between 24 and 31°C, either constant or alter- nating). Germination was completely inhibited when both day and night temperatures were 5 18.5°C. Germination percentage was more strongly correlated with night than with day temperature. Seeds for which dormancy had been broken by scarification were capable of germinating at lower temperatures (19% germination at 11°C) than stored seeds. From the observed temperature dependence of germination and the mean daily maximum and minimum temperatures recorded at Tatura and Deniliquin (latitudes 36° 26̸2S. and 35° 32̸2S. respectively), it is expected that germination in the field, in the Riverine Plain of south-eastern Australia, would be limited to the summer months (December-February).

The incidence of sclerotinia soft rot of lettuce and survival rate of sclerotia of Sclerotinia sclerotiorum were reduced by the addition of organic amendments to field plots at the Frankston Research Station, Seaford, Vic. Of the 6 materials tested, stable manure, fowl manure, and lucerne hay were the best, and all except brown coal significantly reduced disease compared with control. Composting of the already mature materials (as supplied) made no difference to their effectiveness. Incorporating the amendments into soil increased the number (to 229% of the control) and fresh weight (to 202% of the control) of marketable lettuce. Stable manure provided the greatest number of marketable heads (270% of the control), while fowl manure gave the greatest increase in head weight per plot (268% of the control). These benefits were less evident following the first applications of amendments (experiment 1) than the second to the same soil plots (experiment 2).

The responses -of germination of the salt-tolerant grass Diplachne fusca (L.) Beauv. to salinity and various temperature regimes are described. At temperatures of 30/20°C (12 h light and dark periods), final germination was 70% in distilled water, decreased to 50% in 175 mol m-3 NaCl (π = - 0.8 MPa) and 7% in 380 mol m-3 NaCl (π = -1.8 MPa). Increasing salinity from 0-130mol m-3 NaCl decreased the final germination percentage, but did not modify the threshold temperatures (day or night temperature > 27°C) at which germination occurred. Presoaking in distilled water or 1% CaCl2· 2H20 solution did not significantly affect the final germination percentage of seeds which were subsequently placed in solutions with a range of salinities from 0-210 mol m-3 NaCl (*#960 = 0 to - 1.0 MPa). How- ever, addition of CaCl2 to NaCl solution increased the final germination percentage compared with that in pure NaCl solution. Presoaking in concentrated (400 mol m-3) NaCl solution caused a decrease in subsequent germinability of 20 or 40% in 0 and 40 mol m-3 NaCl, respectively. Under field conditions (in soil with mean daily maximum temperature of 33°C and mean daily minimum temperature of 15°C), rates of seedling establishment were similar (16% of seed sown) in soils irrigated with 0 or 50 mol m-3 NaCl, and were 1% in those irrigated with 100 mol m-3 NaCl. The inhibition of germination in NaCl solution was largely an osmotic effect since there was a similar reduction in the final germination percentage in iso-osmotic solutions of NaCl and mannitol. However, the proportion of seeds germinating in NaCl solution was enhanced by adding calcium. The inhibition of germination was greater in sulfate solutions compared with that in chloride solutions and, to a lesser degree, in potassium compared with sodium solutions. The practical implications of our results are discussed. The incorporation of gypsum into the soil and measures to leach salts from the topsoil are recommended before D. fusca is sown on saline land.

The O.D.R. values under tensiometer guided irrigation were found to be high at the time measurements were made. Under the set irrigation program, the O.D.R. were lowest for unamended soil, next lowest for peat amended soil, and highest for soil amended with lignified redwood and calcined clay. Root growth in containers receiving water on a set schedule was associated with the measured O.D.R. A value of about 0.15 µg cm−2min−1 appeared to be the lower limit for root growth. Each amendment promoted the development of a root system of unique characteristics.