The case of the forgotten toothbrush

INTRODUCTION

Although foreign body ingestion is relatively common, toothbrush swallowing is rare. A diagnosis of small-bowel perforation, caused by a sharp or pointed foreign body, is rarely made preoperatively because the clinical symptoms are usually nonspecific and can mimic other surgical conditions, such as appendicitis and diverticulitis.

PRESENTATION OF CASE

We report a case of a swallowed toothbrush which passed past the pylorus and perforated the terminal ileum. The patient however presented with a fluctuant mass in the left iliac fossa, pyrexia and generalised tenderness mimicking a diverticular abscess.

DISCUSSION

Ingestion of a foreign body is commonly encountered in the clinic among children, adults with intellectual impairment, psychiatric illness or alcoholism, and dental prosthetic-wearing elderly subjects. However, toothbrush swallowing is rare, with only approximately 40 reported cases.

CONCLUSION

Bowel perforation by foreign bodies can mimic acute appendicitis and should be considered in differential diagnoses. Clinically, patients often do not recall ingesting the foreign body, which makes the clinical diagnosis more challenging, and a correct diagnosis is frequently delayed. Several radiological investigations, such as small-bowel series, ultrasonography, and computed tomography scans, may lead to the correct diagnosis, but in most patients, the diagnosis is not confirmed until the surgical intervention has been performed.

Water use by annual crops. 1. Role of dry matter production

In southern Australia, expanding dryland salinity is the result of increased deep drainage associated with widespread replacement of native perennial vegetation by annual agricultural crops and pastures. Although perennial pastures have been shown to assist in slowing salinisation, their adoption has been slow, and annual crops and pastures are likely to remain as the dominant land use for the foreseeable future. Therefore, understanding the water balance of annual crops and pastures, and how it can be manipulated, is important in trying to manage salinity. In this research we investigate the effect of varying levels of dry matter production on components of the water balance (soil evaporation, transpiration, soil water storage, and drainage) for annual crops at contrasting sites and soil types in south-western Australia. Dry matter production was controlled by fertiliser addition and crop rotation, and varied by a factor of up to 2, depending on seasonal conditions. Deep drainage was zero for most sites and years, but where it was greater than zero, there was no discernible effect due to production level. Out of a total of 14 site/year comparisons, the difference in soil water extraction associated with greater dry matter production averaged 5 mm, and was greater than 20 mm on only 1 occasion. However, high dry matter production was associated with greater transpiration, at the expense of soil evaporation. Manipulating dry matter production is unlikely to have a substantial effect on deep drainage and the expansion of dryland salinity in south-western Australia.

Unusual presentation of blunt laryngeal injury with cricotracheal disruption by attempted hanging: a case report

The management of a patient with traumatic disruption of the cricotracheal junction in an attempted suicide by hanging is described. Such injury is uncommon, and many patients die at the scene; detailed radiologic imaging is rare because of the urgency of airway management. The delayed complete disruption of the major airway in this patient allowed adequate imaging and corrective management. Associated soft-tissue injuries of the great vessels of the neck are also described.

Incidence of Campylobacter and Salmonella isolated from retail chicken and associated packaging in South Wales

AIMS

To investigate the incidence of Campylobacter and Salmonella contamination associated with supermarket and butchers' shop chicken and related packaging.

METHOD AND RESULTS

Three hundred raw samples (whole chicken, chicken breast with skin or chicken pieces) were purchased on a monthly basis for seven months. Packaging associated with the chicken was also sampled to provide isolation data for external and whole packaging. Campylobacter and Salmonella were isolated from 68% and 29% of retail chicken, respectively. Campylobacter was isolated from 3% of external and 34% of whole packaging overall. Salmonella was absent from external packaging but was isolated from 11% of whole packaging. No significant trends in isolation rates of the organisms were obtained during the period of sampling.

CONCLUSIONS

The food industry and consumers should be made aware of the potential risk of Campylobacter and Salmonella on both the external and internal surfaces of packaging in addition to chicken itself.

SIGNIFICANCE AND IMPACT OF THE STUDY

Chicken and chicken packaging is a potential vehicle for the introduction of pathogens in retail and domestic kitchens and in particular for the cross-contamination of Campylobacter and Salmonella.

Potential deep drainage under wheat crops in a Mediterranean climate. II. Management opportunities to control drainage

High rates of deep drainage in Western Australia are contributing to groundwater recharge and secondary salinity. Strategies are being sought to increase water use in cropping systems and to reduce deep drainage. Quantifying potential drainage through measurements is hampered by the high degree of complexity of these systems as a result of diverse soil types, a range of crops, and in particular the inherent seasonal variability. Simulation models can provide the appropriate means to extrapolate across time and space. The Agricultural Production Systems Simulator (APSIM) was used to explore the effect of alternative agronomic practices on wheat production and deep drainage for representative soils and rainfall regions of the central wheatbelt of Western Australia. Soil water profiles were reset each year to the lower limit of plant-available water, assuming maximum water use in the previous crop. The long-term simulation studies showed that management practices with N fertiliser directed at yield increase were most effective in achieving these aims in the medium to high rainfall regions. The corresponding effect for drainage reduction was marginal. The small effect on drainage control associated with production increase can be traced to the effect of rainfall distribution with major occurrences of both rainfall and drainage during winter (June–August) coinciding with the lowest potential atmospheric demand for evapotranspiration, in combination with low water-holding capacity soils. Nitrogen-induced increases in crop transpiration were in conjunction with reduced soil evaporation, which increased water use efficiency and occurred mostly after the main drainage period, but had little effect on deep drainage within the season. Similar outcomes of enhanced productivity with minor impact on deep drainage were noted with crops sown at different times and with a hypothetical wheat crop having a deeper rooting system. Simulations without resetting soil water each year enabled the quantification of potential carryover effects on long-term average deep drainage. The carry-over of soil water left behind at crop harvest reduced the water storage capacity of the soil in a subsequent year and could increase long-term deep drainage substantially, depending on soil type. Improved management increased late water use in the high rainfall region, in particular on better water-holding soils, and could largely reduce this carry-over effect. The current wheat-based cropping systems, even with alternative management practices, continue to be a major threat to sustainability on the low water-holding soils in the wheatbelt of Western Australia, as a main cause of secondary salinity.

Soft X-ray microscopy with a cryo scanning transmission X-ray microscope: I. Instrumentation, imaging and spectroscopy

We have developed a cryo scanning transmission X-ray microscope which uses soft X-rays from the National Synchrotron Light Source. The system is capable of imaging frozen hydrated specimens with a thickness of up to 10 microm at temperatures of around 100 K. We show images and spectra from frozen hydrated eukaryotic cells, and a demonstration that biological specimens do not suffer mass loss or morphological changes at radiation doses up to about 1010 Gray. This makes possible studies where multiple images of the same specimen area are needed, such as tomography (Wang et al. (2000) Soft X-ray microscopy with a cryo scanning transmission X-ray microscope: II. Tomography. J. Microsc. 197, 80-93) or spectroscopic analysis.

Towards internationally acceptable standards for food additives and contaminants based on the use of risk analysis

Internationally acceptable norms need to incorporate sound science and consistent risk management principles in an open and transparent manner, as set out in the Agreement on the Application of Sanitary and Phytosanitary Measures (the SPS Agreement). The process of risk analysis provides a procedure to reach these goals. The interaction between risk assessors and risk managers is considered vital to this procedure. This paper reports the outcome of a meeting of risk assessors and risk managers on specific aspects of risk analysis and its application to international standard setting for food additives and contaminants. Case studies on aflatoxins and aspartame were used to identify the key steps of the interaction process which ensure scientific justification for risk management decisions. A series of recommendations were proposed in order to enhance the scientific transparency in these critical phases of the standard setting procedure.

Adaptation of lentil (Lens culinaris Medik.) to Mediterranean-type environments: effect of time of sowing on growth, yield, and water use

This study examined the adaptation of lentil (Lens culinaris Medik. cv. Digger) to dryland Mediterranean-type environments of southern Australia and determined the effect of time of sowing on growth, yield, and water use. Phenology, canopy development, radiation absorption, dry matter production and partitioning, seed yield, and water use were measured from a range of sowing times at a number of field locations in south-western Australia in 1994, 1995, and 1996. Contrary to previous results with poorly adapted cultivars, our study showed that lentil is well adapted to low to medium rainfall regions (300-500 mm/year) of south-western Australia and that seed yields greater than 1·0 t/ha and up to 2·5 t/ha can be achieved when sown early. Even in the dry season of 1994 when May-October rainfall was <200 mm, yields of approximately 1·0 t/ha were produced from early sowings. Seed yields were reduced with delayed sowing at rates of 4-29 kg/ha · day. Sowing in late April or early May allowed a longer period for vegetative and reproductive growth, rapid canopy development, greater absorption of photosynthetically active radiation, more water use, and, hence, greater dry matter production, seed yield, and water use efficiency than when sowing was delayed. Early-sown lentils began flowering and filling seeds earlier in the growing season, at a time when vapour pressure deficits and air temperatures were lower, and used more water in the post-flowering period when compared to those treatments where sowing was delayed. The values of water use efficiency for dry matter and grain production, and transpiration efficiency, for early-sown lentil (up to 30 kg/ha · mm, 11 kg/ha · mm, and 20 kg/ha · mm, respectively) were comparable to those reported for cereal and other grain legume crops in similar environments. The development of earlier flowering cultivars than Digger with greater dry matter production together with improved agronomic packages will increase and stabilise lentil yields in low rainfall environments of southern Australia.

Grain yield and water use efficiency of early maturing wheat in low rainfall Mediterranean environments

Wheat cultivars with very early maturities appropriate for late sowings in low-rainfall (<325 mm) short-season environments are currently unavailable to wheat growers in the eastern margin of the cropping region of Western Australia. A demonstration that very early-maturing genotypes can out-perform current commercial cultivars would open new opportunities for breeding programs to select very early-maturing, high- and stable-yielding cultivars for these environments. Six field experiments were conducted over 4 seasons at 2 low-rainfall sites in Western Australia to investigate crop growth, grain yield, and water use efficiency of very early-maturing genotypes compared with current commercial cultivars when sown after 1 June. Very early-maturing genotypes reached anthesis up to 24 days (328 degree-days) earlier than the current cultivars, produced less leaves, had similar yields and dry matter, and maintained high water use efficiencies. On average across seasons and locations the very early-maturing genotypes (W87–022–511, W87–114–549, W87–410–509) yielded more than the later maturing cultivars Gamenya and Spear (190 v. 160 g/m2) but they were similar to the early-maturing commercial cultivars Kulin and Wilgoyne (191 g/m2). Very early-maturing genotypes generally had a higher harvest index and produced fewer spikelets, but heavier and more grains, than Kulin and Wilgoyne. There were only small differences in total water use between very early-maturing genotypes and commercial cultivars; however, very early-maturing genotypes used less water in the pre-anthesis period and more water in the post-anthesis period than the later maturing genotypes, and hence, experienced less water deficit during the grain-filling period. This study indicates that there is a role for very early-maturing genotypes in low-rainfall short-season environments, when the first autumn rains arrive late (after 1 June).

The Effect of Magmatic Activity on Hydrothermal Venting Along the Superfast-Spreading East Pacific Rise

A survey of hydrothermal activity along the superfast-spreading (approximately 150 millimeters per year) East Pacific Rise shows that hydrothermal plumes overlay approximately 60 percent of the ridge crest between 13 degrees 50' and 18 degrees 40'S, a plume abundance nearly twice that known from any other rige portion of comparable length. Plumes were most abundant where the axial cross section is inflated and an axial magma chamber is present. Plumes with high ratios of volatile ((3)He, CH(4), and H(2)S) to nonvolatile (Mn and Fe) species marked where hydrothermal circulation has been perturbed by recent magmatic activity. The high proportion of volatile-rich plumes observed implies that such episodes are more frequent here than on slower spreading ridges.

Effect of different direct drilling and conventional sowing techniques on soil strength, root growth and grain yield of wheat on sandplain soils in Western Australia

Experiments were conducted to compare different direct drilling and conventional sowing techniques, and describe the effects of these techniques on soil strength, root growth and grain yield of wheat on sandplain soils in the northern wheat-belt of Western Australia. Soil strength was identified as a critical factor affecting root growth; increasing the depth of soil loosening beneath seeding depth with a modified direct drill reduced soil strength relative to that found in the traditional direct drill treatments, and increased rooting density beyond the 10 cm soil depth. As loosening depth increased, there were increases in both shoot growth and grain yields, and water use efficiency also improved. Maximizing the depth of soil disturbance by deep ripping after sowing resulted in the highest grain yields, but the time and cost penalties associated with this tillage operation are substantial and likely to deter its routine use. Modifying a direct drill to loosen soil beneath sowing depth therefore combined the advantages of conventional direct drilling (timeliness, moisture conservation and lower risk of erosion), with those obtained by sowing after cultivation (improved root growth and yield) without the yield penalties associated either with direct drilling or delayed sowing on these soils.

The place of the family in mental health nursing: past, present and future

The importance of the family system has, in recent years, been de-emphasized in the planning and delivery of mental health services. A sample of the psychiatric nursing literature over the last 4 decades is reviewed to reveal that this is not a new phenomenon with regard to psychiatric nursing practice. The shortcomings of such a de-emphasis are discussed, some exceptions to the rule are described and some suggestions for future development of family interventions by mental health nurses are made.

Row spacing fails to modify soil evaporation and grain yield in spring wheat in a dry Mediterranean environment

The loss of moisture by evaporation from soil under crop canopies (Esc) has been recognized as a major cause of poor water use efficiency (WUE), and hence poor grain yield, in crops grown in environments with limited rainfall. Agronomic approaches to restrain Esc aim to reduce the transmission of solar radiation to the soil beneath the crop by improving ground cover by the crop canopy. However, the sparse canopies produced in these environments have a limited effect on evaporation during the energy dependent first stage (Es1); much of the evaporation is independent of energy at the soilsurface (Es2), and therefore less sensitive to the influence of the crop canopy. Manipulating plant arrangement, primarily by changing row spacing, may provide a simple approach for improving ground cover and restraining E,, without changing GAI, and thus improving WUE and grain yield. To explore the potential benefit of variable row spacing on Esc and grain yield in the dry (300 mm) Mediterranean environment of the eastern wheatbelt of Western Australia, spring wheat was grown in 0.09, 0.18, 0.27 and 0.36 m row spacings on coarse textured and fine textured soil types at Merredin in 1989. Esc was determined with an empirical model and measured with microlysimeters. Row spacing had no significant effect on the development of green area index (GAI), dry matter (DM) accumulation and evapotranspiration (ET) throughout the season. However, in mid-season, the proportion of ground covered by the canopy was higher and transmission of solar radiation was reduced in the 0.09 m row spacing compared with the 0.36 m row spacing. These effects did not restrain E,,, which was similar in all treatments. Esc was not restrained even when the plant density was doubled in the 0.09 m row spacing treatment. Esc during the season averaged 88 mm across all row spacings on both soils; this accounted for 56% and 48% of the mean seasonal ET on the coarse textured and fine textured soils respectively. Consequently, neither water use efficiency nor grain yield were affected by variation in row spacing; water use efficiency averaged 25 kg DM ha-1 mm-1 on both soil types. For dry Mediterranean environments of Western Australia, it was concluded on the basis of these results, and yield data from other row spacing trials in the same districts, that there are no significant yield benefits to be obtained by reducing the row spacing from the current spacing of 0.18 m.

Components of the water balance on duplex soils in Western Australia

The water balance of soils is of interest both in terms of crop productivity and of sustainability, because water that is not used by crops contributes not only to loss of yield but also to the processes of land degradation. Land clearance for agriculture in Western Australia has changed the hydrological balance resulting in greater drainage and increased secondary salinisation. The relative importance of components of the water balance changes with rainfall. In the drier, eastern wheatbelt, evapotranspiration dominates the balance and there is little drainage, except through narrow, preferred pathways. In contrast, in the wetter region of the Darling Peneplain up to 40% of rainfall may be lost by pathways other than evaporation. Movement of water at the interface of the sand and clay layers (throughflow) has been poorly quantified. The dominant direction of flow is vertical, but substantial lateral flow may occur during winter storms on sloping sites. For example, measurements at a site near Narrogin showed up to 15 mm of throughflow during the cropping season. Drainage using interceptor drains provides a practical means of removing the throughflow and reducing the incidence of waterlogging. Yields of wheat on duplex soils are poorly related to the amount of evapotranspiration. At low rainfall, the relationship is poor, because rainfall is rarely uniformly distributed throughout the season, and lack of water during grain-filling may depress yields. In high rainfall areas, there are few detailed studies of water use, but yields may be lower than anticipated because of waterlogging, low inputs of fertiliser, and disease.

Limitations to growth and yield of cereal and lupin crops on duplex soils

The combination of soil physical and chemical properties in duplex soils can depress crop growth and yield, and cause considerable variability in yield within a paddock and from year to year. At an intensively monitored site at East Beverley, Western Australia, the sandy A horizon was found to be nutrient deficient, low in pH, and contained hard layers which impeded root growth. The clayey B horizon had a higher pH, and variable permeability which influenced waterlogging in winter, and root growth and water availability from the subsoil in spring. Growth of wheat and lupin crops reflected response to these stresses. Wheat yields in particular were very variable (0.7-4.2 t/ha in 1988), and as all components of yield were affected, this suggests that the crop in low yielding areas experienced stress throughout the growing season. Lupin yields varied more widely from year to year than wheat yields, but were less variable within a year, possibly because of a more limited exploration of the subsoil by roots. Treatments to overcome the chemical constraints to growth raised yields and reduced variability; wheat and lupin yields were increased by about 25% after application of potassium, and wheat yields increased by about 10% after application of lime. Ripping lowered soil strength in the A horizon, but had little effect on yield, suggesting that the subsoil plays a larger role in determining yield on this soil. Attempts to improve the permeability of the subsoil using gypsum were inconclusive in the year of application. Similar physical and chemical problems have been identified on other duplex soils throughout Australia. Responses to ameliorative treatments have been variable, and there have often been interactions between treatments. Further improvements in yield on these difficult soils requires a better understanding of the interaction of soil physical, chemical and biological properties, and their interactions with crop physiology.

Physical and chemical characteristics of duplex soils and their distribution in the south-west of Western Australia

Duplex soils are widespread in Western Australia and occupy about 60% of the south-west agricultural area. The physical and chemical properties of these soils reflect their origin as erosional surfaces of old laterite profiles and the predominance of underlying, quartz-rich, granitic materials. The resulting combination of high contents of quartz sand, kaolin clay, and iron and aluminium oxides has important consequences on water-holding capacity, fertility, nutrient leaching, phosphate fixation, anion and cation exchange capacity, and buffering capacity. These soils are generally held to have a number of physical and chemical problems. Among these, low fertility and low permeability of the clay B horizon have greatest effect. While data on the chemical properties of these soils are limited, significant data sets on the physical properties of duplex soils are available from several studies of catchment hydrology. These studies reflect concern with runoff, waterlogging, and the development of secondary salinisation. Depth to clay varies from 5 to >100 cm. The shallower depths (10-40 cm) predominate and, in medium and high rainfall areas, combine with low permeability in the clay to result in widespread waterlogging. Commonly, the sand surface can be hardsetting and can have high strength from structural decline, from the presence of cementing agents, and from traffic effects. Sodicity is widespread and has effects on hardsetting in the A horizon and on permeability of the B horizon. Management strategies are available to treat some of these problems, but generally, much has yet to be done to develop sustainable agricultural systems on these soils.

Root and shoot growth, and water and light use efficiency of barley and wheat crops grown on a shallow duplex soil in a mediterranean-type environment

Growth, interception of radiation and water use of three genotypes of barley (Beecher, O'Connor and Syrian) and one of wheat (Gutha) were measured on a duplex soil at East Beverley, W.A. All crops received 11 kg P ha-1 with the seed but no nitrogen fertilizer. Growth was initially slow until 69 days after sowing (das) with only small and inconsistent differences between crops. Thereafter, Beecher and O'Connor grew faster than Syrian and Gutha, maintained growth for longer, and at harvest weighed about 7.5 t ha-1 shoot dry matter, while Syrian and Gutha were about 5.0 t ha-1. Total root weight and length of Gutha increased until anthesis but reached their maxima at 83 das in all barley crops. Root weight as a percentage of total plant weight was about 40% during the winter decreasing to about 15% by anthesis. Root distributions of Beecher and O'Connor were similar but different from those of Syrian and Gutha; the former had up to 25% of the total root length at anthesis below 40 cm, but the latter had only about 5%. Dry matter production was linearly related to the amount of photosynthetically active radiation (PAR) intercepted, although the relations showed a break at about the time of flag leaf emergence, and efficiencies of conversion of PAR to dry matter were higher prior to this than after. Efficiencies for the barley crops were similar (about 2 g total dry weight MJ-1 before flag leaf emergence) and about 20% greater than for Gutha. Despite the large differences in dry matter production between crops, evapotranspiration (ET) was similar. For Beecher and O'Connor, evaporation E was about 40% of seasonal ET but for Syrian and Gutha it was about 50%. Values of water use efficiency (about 30 kg shoot ha-1 mm-1 for Beecher and OIConnor and 20 kg ha-1 mm-1 for Syrian and Gutha) were similar to other cereal crops and the amount of shoot dry matter per unit of water transpired for barley crops grown in W.A., U.K. and Syria was nearly constant; the value of the 'crop specific constant' was 3.0 Pa.

A new approach to percutaneous transluminal angioplasty of profunda femoris origin stenosis

We describe 3 patients in whom percutaneous transluminal angioplasty (PTA) of a stenosis at the origin of the profunda femoris artery was carried out successfully using a retrograde approach. Unfavorable anatomy precluded profunda femoris PTA via either the ipsilateral antegrade or the contralateral approach. Retrograde profunda femoris PTA offers an alternative approach when other percutaneous routes of access are precluded.

Water use and water use efficiency of old and modern wheat cultivars in a Mediterranean-type environment

Water use and water use efficiency of old and modern wheat cultivars and one barley cultivar were measured in a Mediterranean environment at Merredin, W.A. Water use efficiency for grain increased substantially from old to modern cultivars, with little difference among modern cultivars. Water use efficiency for dry matter was similar between cultivars. Barley had the highest water use efficiency of both grain and dry matter. Improved water use efficiency for grain in modern cultivars was associated with faster development, earlier flowering, improved canopy structure and higher harvest index. Modern cultivars used slightly less water than old cultivars. The pattern of water use was also different, with late-maturing old cultivars using more water in the pre- than the post-anthesis period. The ratio of pre- to post-anthesis water use was highest with the late-maturing, old cultivar Purple Straw (5.2:1) and lowest with early-maturing, modern cultivar Gutha (3.0:1). Soil evaporation estimates showed that modern cultivars had lower rates of soil evaporation in the early part of the growing season. This was associated with their faster leaf area development and improved light interception. About 40% of the total water use was lost by soil evaporation with very little difference between wheat cultivars. Barley had 15% less soil evaporation than wheat. Water use efficiency for grain based on transpiration (transpiration efficiency) for the four modern cultivars was 15.8 kg ha-1 mm-1, similar to other studies in comparable environments. Some further improvement in water use efficiency appears possible through improvement in crop biomass and harvest index. However, given the frequent and severe limitations of total water supply at low rainfall sites such as Merredin, there appears to be more scope for improvement in yield and water use efficiency in the medium and high rainfall areas of the wheatbelt.

Growth, development and light interception of old and modern wheat cultivars in a Mediterranean-type environment

A field experiment was conducted at Merredin in the eastern wheat belt of Western Australia, comparing 10 wheat cultivars representing old and modern wheats. The aim of the study was to identify any morphological and physiological characters associated with higher grain yield of modern wheat cultivars.The modern cultivars reached double ridge, terminal spikelet, anthesis and maturity earlier than the old cultivars, but modern cultivars had a longer duration between double ridge and terminal spikelet stage. The number of leaves on the main stem generally decreased from old, Purple Straw (14) to modern cultivars like Kulin (8). The modern cultivars had a shorter phyllochron interval than the old cultivars. The old cultivars also produced more tillers per plant (7.3) and had a lower percentage (35%) of ear bearing tillers, as compared with 3.9 and 51% for modern cultivars.The green area index and ground cover was higher in old than modern cultivars. However, the efficiency of conversion of photosynthetically active radiation to dry matter was slightly greater for modern cultivars. Although dry matter at final harvest was similar between cultivars, there was a trend for higher dry matter production with modern cultivars. The post-anthesis green area duration was longer with modern cultivars and grain yield increased with increase in post-anthesis green area duration.Grain yield and HI increased consistently from old to modern cultivars. The most recent cultivar Kulin had the highest yield and second highest harvest index, which were 63% and 48% respectively higher than the oldest cultivar, Purple Straw. Increases in grain yield in the modern cultivars were associated with increased grains spikelet-1 and grains ear-1. Mean grain weight showed a slight reduction with modern cultivars. The results are discussed in relation to future improvement in yield.

Root length density and water uptake in cereals and grain legumes: how well are they correlated

Total root length per unit ground area (La) is often considered to be directly related to the amount and rate of water uptake. Experiments were conducted to compare the water use of spring wheat, barley, lupin (L. angustifolius) and field pea on four differing soil types in drought-stressed conditions. The La values of cereals were consistently five to ten times as large as those of grain legumes, whereas the aboveground biomass was sim~iar and never greater than twice that of the grain legumes. Growing-season water loss (WL) from the soil profile was very similar for wheat and lupins, despite this big difference in root length. Soil evaporation may have been greater under lupins, but when crop water uptake was compared for the period when leaf area was greatest, rates of change in soil water content within the root zone were still similar and were not well correlated with La. Specific root water uptake (Ur) was consistently greater for lupin than wheat. Maximum rooting depth was better correlated with WL than was La in all cases. Higher Ur values in lupin and pea may be related to their large and abundant metaxylem vessels, which give much lower axial resistance than in cereals. These results provide strong evidence for genotypic variation in root morphology, density and root extension between dicotyledenous and monocotyledenous species. They also indicate that La is not necessarily the root morphological characteristic most responsible for efficiency of water uptake in drought-stressed environments.

Tillage and growth of a wheat crop in a loamy sand

In the fourth consecutive year of a long-term tillage trial in a loamy sand in Western Australia above- and below-ground growth of a wheat crop (cv. Gamenya) was monitored. The grain yield was nearly 20% greater in the crop sown after ploughing than in those crops sown by direct drilling. A similar trend had been noted in each preceding year. Cumulative water use was 15 and 9 mm less with zero and minimum tillage than with ploughing. The ploughed treatment had lower soil strengths, not only in the seedbed but also to 50 cm in the subsoil, until 8 weeks after seeding. These lower soil strengths coincided with more-rapid wetting of the subsoil under ploughing, and faster root extension rates. Dry matter production was significantly greater in the ploughed crop from the initial sampling date, and direct-drilled crops were not able to compensate in the later part of the season, despite using slightly more water during that period. The slower wetting of the profile under direct drilling was a persistent feature over several seasons in this soil type. It was considered responsible for the increased soil strength and slower root extension rates. The implications of direct-drilled sandy soils for crop productivity, and drainage control of recharge soils in saline catchments, are discussed.

Wheat root penetration and total available water on a range of soil types

Depth of root penetration was examined over three years on a range of soil types in Western Australia. A consistent pattern was recognized. Roots penetrated rapidly to 5 to 10 cm from the soil surface within the first week from planting. Subsequent penetration was slow to 6 weeks, at which stage, depending on soil types, depth of root penetration was 15 to 30 cm. Rates of root penetration increased after 6 weeks from planting with greatest penetration occurring between 8 to 13 weeks. Respective maximum depths of root penetration in the deep sand, sandy loam, grey clay and sand over clay soils investigated were 169, 173, 31 and 73 cm. These depths were reached between 10 to 14 weeks after planting. Potential available soil water to maximum depths of root penetration were 2.6, 20.1, 5.6 and 8.1 cm for the deep sand, sandy loam, grey clay and sand over clay respectively. More than half of this available soil water was accessible for crop exploitation over the 9 to 14 week period after planting, except with shallow water and root penetration in the grey clay.

Root growth of wheat. I. Early patterns of multiplication and extension of wheat roots including effects of levels of nitrogen, phosphorus and potassium

Wheat root growth was followed to 30 days from planting in wheat supplied with standard, twofold, half and nil levels of nitrogen, phosphorus and potassium. Root numbers and lengths followed consistent patterns of increase in the seminal and nodal root systems of all treatments. Most root components demonstrated their highest rates of relative increase in length and number immediately after first appearance. Within a few days this decreased to a constant rate of increase which continued until the end of the experiment. Rates during the stages of constant relative increase were higher with increasing order of lateral, and the same for all treatments, except when nutrient deficiency seriously suppressed root growth. Potassium deficiency stopped root growth completely within 10–12 days of planting. Nitrogen and phosphorus deficiencies gave increasing delays in root component appearance with increasing order of lateral. Increasing suppression of seminal lateral numbers and a severe suppression of nodal root growth followed. Lower root numbers caused by nitrogen deficiency were compensated by greater lateral lengths in the seminal but not the nodal root systems. Some reduction in root growth resulted from application of the half and twofold levels of nitrogen, phosphorus and potassium. All responses to applied nutrient levels were more obvious with increasing order of lateral and with the nodal rather than seminal root systems. The nodal root system reflected plant response better than the seminal root system.