The germination (i.e. the first emergence of the radicle) of Medicago denticulata Willd., M. confinis Koch, M. tribuloides Desr., and Juncus vaginatus R. Br. under controlled moisture conditions has been examined. Moisture regime was defined by the soil moisture suction (pF). The influences of temperature and light, which would otherwise obscure the importance of soil moisture, have been minimized by comparing the number of seeds germinated under each physical regime with the maximum number germinated for each species under identical physical conditions when suction was approximately zero (i.e. standard cotton wool germination count procedure). The differing water regimes were obtained by using methods common in soil physics – the tension plate and pressure membrane methods – the seeds being in contact with the plate or membrane kept at a constant water suction. Additionally, two soil media, were used with the Medicago spp. It was found that: For all species an increase in suction produced a decrease in rate of germination until at 10 atm, germination practically ceased. Medicago spp. showed a smaller decline in rate as suction increased than did J. vaginatus. The moisture conditions to allow J. vaginatus to germinate at rates comparable with those for the Medicago spp. were quite restricted and corresponded to high water-tables or soils wetter than field capacity. The moisture condition of the soils controlled the germination rate not only by means of the suction effect, but also in terms of hydraulic conductivity (or permeability). A drier soil having less ability to transmit water than a wetter soil reduced the rate at which water could reach the seed, with a consequent decline in the germination rate. As the relationships between: (a) moisture content and suction, and (b) moisture content and hydraulic conductivity, are soil characteristics, it is necessary to define the soil moisture characteristic as well as moisture content in germination experiments.

The components of total soil moisture energy of consequence to a biological system are matric potential and osmotic potential. An experimental procedure, which allows the effects of the potentials to be considered independently, is described and discussed. Germination behaviour does not support the hypothesis that matric and osmotic potentials should have similar biological consequences because their free energy measurements are identical. The results support a diffusion phenomenon hypothesis with movement of solute from the soil solution through the cell membranes, so that any biological consequence is that of an internal "toxicity" rather than an osmotic "drought". For some osmotic systems, 100 cm of matric potential is as effective as 10 000 cm of osmotic potential in retarding seed germination rates.

FILTER is an innovative, CSIRO developed system for treating effluent using high rate land application and subsequent effluent recapture via a closely spaced, subsurface drainage network. We report on the summer performance of a FILTER system established in a subtropical environment on a relatively impermeable swelling clay soil underlain by a deep regional water table. Using secondary treated sewage effluent, the FILTER system produced effluent of tertiary nutrient standards (< or = 5 mg/L TN; < or = 1 mg/L TP), with salinity levels suitable for subsequent irrigation reuse (EC < or = 2.5 dS/m). Removal of faecal coliforms was considerably less effective. The hydraulic loading rate achieved was about two and a half times large than conventional irrigation demand, but this was associated with high deep percolation losses (c 3 mm/day). Comparisons are made with the original FILTER system developed and tested by Jayawardane et al. in temperate Australia. Suggestions are made for modifications to, and further testing of FILTER in a subtropical environment.

The objective of this research was to assess the effect of soil cracks on soil moisture distribution under various sprinkler irrigation applications and to identify the optimal irrigation strategy that enhances soil moisture distribution and reduces water drainage for the upper soil layer 0-250 mm. The assessment was made for six irrigation events: the first two were for 10 and 46 mm water applications using a hand shift-set sprinkler system. The second set was for 43 and 19 mm water applications using the lateral move system with fixed sprayer heads and the third pair of events were for 43 and 32 mm water applications using the lateral move system with rotating sprinklers. The experiments were conducted on two adjacent fields at the University of Queensland, Gatton, Australia. Each field was divided into 2 m 9 2 m grids that covered 62 sampling locations. For each event, the initial soil moisture content (SMC) was measured at each sampling location before irrigation. After irrigation, catch can readings were recorded for each sampling location. After 12 h overnight, the second set of soil moisture measurements was taken at each location. The area1 distribution of SMC for the studied applications was quantified. An attempt was made to identify the relationship between the applied water uniformity using catch cans and the soil moisture uniformity using gravimetric water content measurements. The study also took into consideration variables that could affect the soil physical and hydrological properties including the field slope, the soil texture, the infiltration rate, the salt content and the soil organic matter content of the two fields. Since the soils were cracking clay Vertisols, further analyses were conducted on the crack dynamics, size and distribution using image analysis techniques. The research findings demonstrated that the cracks were the main contributors to water drainage below 250 mm soil depth due to the micro-run off from the crust surface to the cracks. The cracks ranged from a few millimeters to more than 40 mm in width. It was observed that the cracks which were wider than 15 mm remained open after irrigation for the specified application rates. Improving the irrigation system application uniformity did not always result in higher uniformity of the surface SMC (0-250 mm). The event that best enhanced soil moisture distribution and thus improved soil moisture recharging was observed after the sixth irrigation event when the field received 32 mm water application. The soil was at a relatively high initial SMC of 25%, (which represented 43.3% of the plant available water range) and the sprinkler water uniformity was rather high above 87% Christiansen coefficient of uniformity (CUc). At this SMC, the extent of soil cracking is limited.

This study reports on the use of naturally occurring F-specific coliphages, as well as spiked MS-2 phage, to evaluate a land-based effluent treatment/reuse system and an effluent irrigation scheme. Both the natural phages and the spiked MS-2 phage indicated that the effluent treatment/reuse system (FILTER - Filtration and Irrigated cropping for Land Treatment and Effluent Reuse) achieved a reduction in phage levels over the treatment system by one to two log10. FILTER reduced natural F-specific phage numbers from around 10(3) to below 10(2) 100-ml(-1) and the spiked phage from 10(5) to around 10(4) 100-ml(-1) (incoming compared with outgoing water). In the effluent irrigation scheme, phage spiked into the holding ponds dropped from 10(6) to 10(2) 100-ml(-1) after 168 h (with no detectable levels of natural F-specific phage being found prior to spiking). Only low levels of the spiked phage (10(2) gm(-1)) could be recovered from soil irrigated with phage-spiked effluent (at 10(6) phage 100 ml(-1)) or from fruits (around 10(2) phage per fruit) that had direct contact with soil which had been freshly irrigated with the same phage-spiked effluent.