Assessing water quality for cropping management practices: A new approach for dissolved inorganic nitrogen discharged to the Great Barrier Reef

Applications of nitrogen (N) fertiliser to agricultural lands impact many marine and aquatic ecosystems, and improved N fertiliser management is needed to reduce these water quality impacts. Government policies need information on water quality and risk associated with improved practices to evaluate the benefits of their adoption. Policies protecting Great Barrier Reef (GBR) ecosystems are an example of this situation. We developed a simple metric for assessing the risk of N discharge from sugarcane cropping, the biggest contributor of dissolved inorganic N to the GBR. The metric, termed NiLRI, is the ratio of N fertiliser applied to crops and the cane yield achieved (i.e. kg N (t cane)^-1). We defined seven classes of water quality risk using NiLRI values derived from first principles reasoning. NiLRI values calculated from (1) results of historical field experiments and (2) survey data on the management of 170,177 ha (or 53%) of commercial sugarcane cropping were compared to the classes. The NiLRI values in both the experiments and commercial crops fell into all seven classes, showing that the classes were both biophysically sensible (c.f. the experiments) and relevant to farmers' experience. We then used machine learning to explore the association between crop management practices recorded in the surveys and associated NiLRI values. Practices that most influenced NiLRI values had little apparent direct impact on N management. They included improving fallow management and reducing tillage and compaction, practices that have been promoted for production rather than N discharge benefits. The study not only provides a metric for the change in N water quality risk resulting from adoption of improved practices, it also gives the first clear empirical evidence of the agronomic practices that could be promoted to reduce water quality risk while maintaining or improving yields of sugarcane crops grown in catchments adjacent to the GBR. Our approach has relevance to assessing the environmental risk of N fertiliser management in other countries and cropping systems.

The potential for refining nitrogen fertiliser management through accounting for climate impacts: An exploratory study for the Tully region

Increasing the precision of nitrogen (N) fertiliser management in cropping systems is integral to increasing the environmental and economic sustainability of cropping. In a simulation study, we found that natural variability in year-to-year climate had a major effect on optimum N fertiliser rates for sugarcane in the Tully region of north-eastern Australia, where N discharges pose high risks to Great Barrier Reef ecosystems. There were interactions between climate and other factors affecting crop growth that made optimum N rates field-specific. The regional average optimum N fertiliser rate was substantially lower than current industry guidelines. Likewise, simulated N losses to the environment at optimum N fertiliser rates were substantially lower than the simulated losses at current industry fertiliser guidelines. Dissolved N discharged from rivers is related to fertiliser applications. If the reductions in N applications identified in the study occurred in the Tully region, the reduction in dissolved N discharges from rivers in the region would almost meet current water quality improvement targets. Whilst there were many assumptions made in this exploratory study, and there are many steps between the study and a practically implemented dynamic N fertiliser recommendation system, the potential environmental benefits justify field validation and further development of the concepts identified in the study.

Prioritizing Crop Management to Increase Nitrogen Use Efficiency in Australian Sugarcane Crops

Sugarcane production relies on the application of large amounts of nitrogen (N) fertilizer. However, application of N in excess of crop needs can lead to loss of N to the environment, which can negatively impact ecosystems. This is of particular concern in Australia where the majority of sugarcane is grown within catchments that drain directly into the World Heritage listed Great Barrier Reef Marine Park. Multiple factors that impact crop yield and N inputs of sugarcane production systems can affect N use efficiency (NUE), yet the efficacy many of these factors have not been examined in detail. We undertook an extensive simulation analysis of NUE in Australian sugarcane production systems to investigate (1) the impacts of climate on factors determining NUE, (2) the range and drivers of NUE, and (3) regional variation in sugarcane N requirements. We found that the interactions between climate, soils, and management produced a wide range of simulated NUE, ranging from ∼0.3 Mg cane (kg N)^-1, where yields were low (i.e., <50 Mg ha^-1) and N inputs were high, to >5 Mg cane (kg N)^-1 in plant crops where yields were high and N inputs low. Of the management practices simulated (N fertilizer rate, timing, and splitting; fallow management; tillage intensity; and in-field traffic management), the only practice that significantly influenced NUE in ratoon crops was N fertilizer application rate. N rate also influenced NUE in plant crops together with the management of the preceding fallow. In addition, there is regional variation in N fertilizer requirement that could make N fertilizer recommendations more specific. While our results show that complex interrelationships exist between climate, crop growth, N fertilizer rates and N losses to the environment, they highlight the priority that should be placed on optimizing N application rate and fallow management to improve NUE in Australian sugarcane production systems. New initiatives in seasonal climate forecasting, decisions support systems and enhanced efficiency fertilizers have potential for making N fertilizer management more site specific, an action that should facilitate increased NUE.

Nitrogen Cycling from Increased Soil Organic Carbon Contributes Both Positively and Negatively to Ecosystem Services in Wheat Agro-Ecosystems

Soil organic carbon (SOC) is an important and manageable property of soils that impacts on multiple ecosystem services through its effect on soil processes such as nitrogen (N) cycling and soil physical properties. There is considerable interest in increasing SOC concentration in agro-ecosystems worldwide. In some agro-ecosystems, increased SOC has been found to enhance the provision of ecosystem services such as the provision of food. However, increased SOC may increase the environmental footprint of some agro-ecosystems, for example by increasing nitrous oxide emissions. Given this uncertainty, progress is needed in quantifying the impact of increased SOC concentration on agro-ecosystems. Increased SOC concentration affects both N cycling and soil physical properties (i.e., water holding capacity). Thus, the aim of this study was to quantify the contribution, both positive and negative, of increased SOC concentration on ecosystem services provided by wheat agro-ecosystems. We used the Agricultural Production Systems sIMulator (APSIM) to represent the effect of increased SOC concentration on N cycling and soil physical properties, and used model outputs as proxies for multiple ecosystem services from wheat production agro-ecosystems at seven locations around the world. Under increased SOC, we found that N cycling had a larger effect on a range of ecosystem services (food provision, filtering of N, and nitrous oxide regulation) than soil physical properties. We predicted that food provision in these agro-ecosystems could be significantly increased by increased SOC concentration when N supply is limiting. Conversely, we predicted no significant benefit to food production from increasing SOC when soil N supply (from fertiliser and soil N stocks) is not limiting. The effect of increasing SOC on N cycling also led to significantly higher nitrous oxide emissions, although the relative increase was small. We also found that N losses via deep drainage were minimally affected by increased SOC in the dryland agro-ecosystems studied, but increased in the irrigated agro-ecosystem. Therefore, we show that under increased SOC concentration, N cycling contributes both positively and negatively to ecosystem services depending on supply, while the effects on soil physical properties are negligible.

Understanding the Impacts of Soil, Climate, and Farming Practices on Soil Organic Carbon Sequestration: A Simulation Study in Australia

Carbon sequestration in agricultural soils has the capacity to mitigate greenhouse gas emissions, as well as to improve soil biological, physical, and chemical properties. The review of literature pertaining to soil organic carbon (SOC) dynamics within Australian grain farming systems does not enable us to conclude on the best farming practices to increase or maintain SOC for a specific combination of soil and climate. This study aimed to further explore the complex interactions of soil, climate, and farming practices on SOC. We undertook a modeling study with the Agricultural Production Systems sIMulator modeling framework, by combining contrasting Australian soils, climates, and farming practices (crop rotations, and management within rotations, such as fertilization, tillage, and residue management) in a factorial design. This design resulted in the transposition of contrasting soils and climates in our simulations, giving soil-climate combinations that do not occur in the study area to help provide insights into the importance of the climate constraints on SOC. We statistically analyzed the model's outputs to determinate the relative contributions of soil parameters, climate, and farming practices on SOC. The initial SOC content had the largest impact on the value of SOC, followed by the climate and the fertilization practices. These factors explained 66, 18, and 15% of SOC variations, respectively, after 80 years of constant farming practices in the simulation. Tillage and stubble management had the lowest impacts on SOC. This study highlighted the possible negative impact on SOC of a chickpea phase in a wheat-chickpea rotation and the potential positive impact of a cover crop in a sub-tropical climate (QLD, Australia) on SOC. It also showed the complexities in managing to achieve increased SOC, while simultaneously aiming to minimize nitrous oxide (N2O) emissions and nitrate leaching in farming systems. The transposition of contrasting soils and climates in our simulations revealed the importance of the climate constraints on SOC.

Training for visiting registrars: experience in East Anglia, UK

A questionnaire was sent to 24 visiting registrars in East Anglia to obtain information on their perceptions of their training experiences. The results suggest that the needs of overseas doctors and the requirements of training authorities would benefit from organisational changes aimed at improving selection and training programmes. Formal training programmes are needed, tailored to an individual's requirement, with identification of educational supervisors for each trainee. An improved system of introduction to the National Health Service is also required.

Training for medical teachers: a UK survey, 1993

Opportunities and resources for training of medical teachers have been criticized in recent UK reports. A survey of undergraduate and postgraduate medical deans showed that training courses were available at most institutions, though only a few were specifically designed for medical teachers. Many new and specific courses are being planned and many new appointments are being made in medical education at both medical school and postgraduate levels. While the outcome of greater resources for training of medical education cannot yet be determined, we conclude that criticisms are being speedily addressed.

Undergraduate obstetrics and gynaecology in the United Kingdom and the Republic of Ireland, 1989

Undergraduate obstetrics and gynaecology has given rise to concern at a time when the community has become increasingly sensitive about genital structure and function and human reproduction. A survey of clinical schools in the United Kingdom and the Republic of Ireland shows that an average of 11 weeks is available for undergraduate learning in the discipline. Nearly all schools provide written aims and objectives for clinical students. Pelvic examination is taught in what is concluded to be a sensible and responsible manner; students are expected to conduct an average minimum of eight deliveries. Family planning instruction is seen as generally inadequate. Comparison of clinical courses with those in Australia and New Zealand shows striking similarities. Undergraduate courses need to be under constant review and revision so that the best students are encouraged to see obstetrics and gynaecology as a desirable career path.

Mature-age entrants to medical school: a controlled study of sociodemographic characteristics, career choice and job satisfaction

A comparison of 121 mature-age and 270 normal-age entrants who graduated from the University of Queensland Medical School between 1972 and 1987 shows that mature-age entrants are some 7 years older, are more likely to come from public (state) schools and less likely to have parents in professional/technical occupations. Otherwise, the two groups were similar in terms of gender, marital status, number of children, ethnic background and current practice location. The educational background of mature-age entrants prior to admission includes 44.6% with degrees in health-science areas and 31.4% with degrees in non-health areas. Reasons for delayed entry of mature-age entrants include late consideration of medicine as a career (34.7%), financial problems (31.4%), dissatisfaction with previous career (30.6%), poor academic results (19.8%), or a combination of the above factors. Motivations to study medicine include family influences (more so in normal-age entrants), altruistic reasons (more so in mature-age entrants) and a variety of personal/social factors such as intellectual satisfaction, prestige and financial security (similar for both groups) and parental expectations (more so in normal-age entrants). Mature-age entrants experienced greater stress throughout the medical course, especially with regard to financial difficulties, loneliness/isolation from the students and family problems (a greater proportion were married with children). While whole-course grades were similar in both groups, normal-age entrants tended to win more undergraduate honours/prizes and postgraduate diplomas/degrees, including specialist qualifications. Practice settings were similar in terms of group private practice, hospital/clinic practice or medical administration, but there was a greater proportion of mature-age entrants in solo private practice, and a smaller proportion in teaching/research. If given the time over, some two-thirds of both groups would choose medicine as a career. Reasons for job satisfaction include helping patients, intellectual stimulation and financial rewards. Reasons for dissatisfaction include pressure of work, red-tape/paperwork, 'doctor-bashing', long working hours, emotional strain, financial pressure, unfulfilled career expectations and irritation with trivial medical complaints.

Undergraduate education in obstetrics and gynaecology in Australia and New Zealand, 1989

Medical schools in Australia and New Zealand provide an average of 10.7 weeks for instruction in obstetrics abd gynaecology. The stated aims and objectives in 14 clinical schools vary from none at all to those which establish the programme with great clarity. The learning exercises provided vary from the conventional, ward and clinic-based to those with an accent on observing closely a mother, her baby and her family. Newer methods for learning about pelvic examination have not been widely adopted. Schools expect students to gain experience in an average of 9 vaginal deliveries. Competition with midwives for available deliveries was described by 9 clinical schools. The survey shows a need for greater emphasis in text books on communication skills and psychological aspects of patient care.

Ultrasound imaging in the management of ovulation stimulation

The present role of ultrasound imaging in the assessment of ovarian response to gonadotrophin therapy was assessed by comparing a group of patients in whom ultrasound was used to determine suitability of follicles for induction of ovulation with a group in whom ultrasound was not available. Ultrasound provides new and useful information, and may allow a reduction in the incidence of multiple pregnancies.

The rise of the caesarean section: a review

Caesarean section is of recent development as a credible procedure. A rapidly increasing incidence in many countries has led to a far-ranging concern. Proposed causes for the increase include insistence on repeat operations and a resultant cumulative effect, more frequent diagnoses of disproportion and ineffective labour, the use of fetal heart monitoring, and a steady trend away from vaginal breech delivery. Increased perinatal morbidity is seen in Caesarean section, together with a qualified increase in perinatal mortality. Maternal morbidity is greater and maternal death rates are reportedly 2-4 times greater in Caesarean section births. More work is needed on the psychosocial sequelae of abdominal delivery.

Effects of prolactin on steroid production by human luteal cells in vitro

The effects of prolactin on steroidogenesis were studied in dispersed luteal cells prepared from human corpora lutea of the menstrual cycle. Prolactin, at concentrations of 0.1-1000 ng/ml, had no effect on progesterone production by luteal cells during short-term incubation (3 h). However, in two out of five corpora lutea, higher concentrations of prolactin (100 and 1000 ng/ml) significantly reduced the oestradiol-17 beta production induced by human chorionic gonadotrophin (hCG; 10 i.u./ml); lower doses of prolactin had little effect. In the remaining corpora lutea, prolactin failed to affect either basal or hCG-induced production of oestradiol-17 beta. These results are discussed in relation to the mechanism by which prolactin influences human ovarian function.

Oxytocin may play a role in the control of the human corpus luteum

The effects of oxytocin on dispersed luteal cells from human corpora lutea of the menstrual cycle were studied. Oxytocin at a concentration of 4 mi.u./ml produced a slight increase in basal progesterone production. However, higher oxytocin concentrations (400 and 800 mi.u./ml) markedly inhibited both basal and human chorionic gonadotrophin-induced progesterone production. These data provide evidence for an effect of oxytocin on the human corpus luteum. In view of the inhibitory action of oxytocin, increased secretion of this hormone may be important in the demise of the corpus luteum at the end of the menstrual cycle.

Recognition of the 'at risk' pregnancy

Every pregnancy is associated with risks but a number of factors denoting 'high risk' have been identified. Scoring systems devised to assess cumulative risk levels have limited application. Of greater value is recognition of specific risk factors such as the hazards associated with maternal age, parity, social status, alcohol consumption and place of delivery. New risk factors are those associated with certain methods of pregnancy management.

Trends in adolescent pregnancies

Pregnancies in adolescents aged under 17 years constitute about 1.3% of all births in Queensland. A study of 189 adolescent pregnancies at the Royal Women's Hospital, Brisbane in 1977-1979 showed adequate antenatal care, and antenatal complications similar to those of a control group. There were greater incidences of unplanned Caesarean section, postpartum haemorrhage and puerperal infection. The major difference in the adolescent group was a perinatal mortality more than double that for the overall hospital population. The role of inadequate education in reproduction in the genesis of many adolescent pregnancies is stressed.

Sites of steroid production in the polycystic ovary

Tissue culture of slices of polycystic ovaries shows that androstenedione and oestradiol are mostly produced by the cortical, cyst-containing portions, with little steroid production in vitro by medullary stromal tissues.

Blood pressure changes when uterine stimulants are used after normal delivery

Use of an automatic sphygmomanometer showed that intravenous ergometrine given immediately after delivery caused significant elevation of diastolic blood pressure in all 10 normotensive women studied. Blood pressure was also raised in some patients following the use of intramuscular oxytocin and ergometrine (Syntometrine). Uterine stimulants for use after delivery must be chosen with care.

Control chart for urinary oestriol excretion during pregnancy

Calculations to define the distribution of normal urinary oestriol excretion values during pregnancy are presented. The values had a normal distribution, uniform variance and increased linearly with time after logarithmic conversion. The variance could, therefore, be partitioned and a control chart constructed.

Bromocriptine, methyl testosterone and placebo for inhibition of physiological lactation: a controlled study

Lactation occurs when the fully developed breast is released from the inhibitory influence which oestrogen and progesterone exert upon the action of prolactin. The use of oestrogens to suppress lactation depends on a continuation of the peripheral, that is, mammary, inhibition of prolactin. Androgens are also believed to act by inhibition of the action of prolactin on the mammary gland epithelium. Bromocriptine, when compared in a double-blind trial with orally administered methyl testosterone and placebo, gave almost complete relief of breast discomfort and congestion, though a small amount of milk production was seen. Methyl testosterone, in the dosage used in this study, was quite ineffective in suppressing lactation or breast symptoms.

Hormone production by the intact human corpus luteum in vitro

Human CL removed during the menstrual cycle were cultured for up to 5 days. Production of progesterone, measured by radioimmunoassay of the culture fluid, continued throughout each experiment. Addition of hCG to the culture medium stimulated progesterone production in a biphasic manner.

Oestradiol production by human graafian follicles cultured in vitro

Intact human Graafian follicles recovered during the preovulatory phase of the menstrual cycle and cultured in vitro, gave a mean oestradiol production of 33 ng/hour over periods of 4 to 92 hours. Treatment of follicles with human pituitary gonadotrophin or human chorionic gonadotrophin resulted in an increased production of oestradiol.

Estrogen excretion patterns in induced ovulation

Observation of response to gonadotropins in the treatment of anovulation has allowed us to define the estrogen excretion pattern which leads to a successful single pregnancy. The typical pattern shows a low pretreatment urinary total estrogen excretion; treatment with gonadotropins, of human pituitary origin, is continued for about 14 days. There is a predictable rate of rise of preovulatory estrogen excretion (30 microgram/24 hr2). Human choronic gonadotropin--about 4000 IU--should be given when an estrogen excretion of 75-100 microgram/24 hr has been obtained. The use of this pattern of ovarian response is put forward as a useful guide in the planning of gonadotropin therapy.

Burkitt's lymphoma in Australia

An Australian case of Burkitt's lymphoma is reported. The clinical features of large ovarian masses and subsequent bone marrow invasion, as well as the results of investigations related to the Epstein-Barr virus, were more consistent with the American than the African type of Burkitt's lymphoma. After a good initial response to cyclophosphamide and vincristine, the tumour rapidly became resistant to these and other therapeutic measures and the patient died 10 months after diagnosis.

A rapid method for the estimation of estriol in plasma during pregnancy

A rapid, reliable fluorimetric method for the determination of estriol (E3) in plasma is described. The method is eminently suitable for use in hospital laboratories and provides results within 5 hours of the reception of samples. It has several features not found in other methods. As little as 0.2 ml of plasma is required, all additions and aliquoting procedures are semi-automated an no special technical skill is necessary. A technician can carry out 20 determinations per day. Average recoveries of 70% are routinely achieved, and the accuracy (2.4%) and the precision (4.0%) of the method are remarkably good for an assay of this type. A spectrofluorometer of high sensitivity, counting equipment and a high temperature oven are the essential major pieces of equipment.

Progress in fetal assessment

The growth areas in fetal assessment in late pregnancy have been studied by making a quantitative review of the papers in four obstetric journals. Of the 130 relevant papers published, in 1973, the most common subject treated was the phospholipid test of fetal lung maturity. Other important tests reviewed were estrogen assays, ultrasonic studies, human placental lactogen and alpha-fetoprotein measurements. The clinical value of phospholipid tests was demonstrated; liquor creatinine assays are much inferior in assessing fetal maturity. Plasma estriol assays are likely to be of increasing importance in clinical practice. Some caution should be applied in the interpretation of ultrasonic measurements of biparietal diameter as a test of fetal development and well-being.