Risk assessment of unsuitable winter conditions for manure and nutrient application across Ontario.

Practical guidelines addressing the timing of manure and nutrient application must consider the concerns of the farm operators while ensuring the protection of the environment. An approach was developed and analyzed through case studies to determine the first recommended day in the spring, and the last in the fall, for manure and nutrient application based on probability analysis. Since most manure and nutrient application guidelines recommend avoiding adverse conditions, the three criteria established to perform a risk assessment were: (i) a frost depth greater than 0.05 m; (ii) a snow accumulation of greater than 0.05 m; and (iii) a soil volumetric water content greater than or equal to that of the plastic limit for the soil. Climatic data and typical soil information for seven locations in Ontario were used to model volumetric soil water contents, frost depths, and snow accumulation from the simultaneous heat and water (SHAW) model for a 48-yr period (1954-2001). Applying the three criteria to the modeled output, the average range between the least limiting probability (0.1, or one in ten year occurrence) and the greatest limiting probability (0.001, or one in one thousand year occurrence) analyzed among the locations was 16 d in the spring as compared to 29 d in the fall. Although geographical location affected the predicted spring start and fall end recommended manure and nutrient application dates, local climate and soil hydraulic properties also played an important part in the determination of these days. Overall the prediction method developed performed reasonably well and provided insight into the environmental factors influencing manure and nutrient application timing.

Seasonal leaching and biodegradation of dicamba in turfgrass.

The leaching of surface-applied herbicides, such as dicamba (2methoxy-3,6-dichlorobenzoic acid), to ground water is an environmental concern. Seasonal changes in soil temperature and water content, affecting infiltration and biodegradation, may control leaching. The objectives of this study were to (i) investigate the leaching of dicamba applied to turfgrass, (ii) measure the degradation rate of dicamba in soil and thatch in the laboratory under simulated field conditions, and (iii) test the ability of the model EXPRES (containing LEACHM) to simulate the field transport and degradation processes. Four field lysimeters, packed with sandy loam soil and topped with Kentucky bluegrass (Poa pratensis L.) sod, were monitored after receiving three applications (May, September, November) of dicamba. Concentrations of dicamba greater than 1 mg L(-1) were detected in soil water. Although drying of the soil during the summer prevented deep transport, greater leaching occurred in late autumn due to increased infiltration. From the batch experiment, the degradation rate for dicamba in thatch was 5.9 to 8.4 times greater than for soil, with a calculated half-life as low as 5.5 d. Computer modeling indicated that the soil and climatic conditions would influence the effectiveness of greater degradation in thatch for reducing dicamba leaching. In general, EXPRES predictions were similar to observed concentration profiles, though peak dicamba concentrations at the 10-cm depth tended to be higher than predicted in May and November. Differences between predictions and observations are probably a result of minor inaccuracies in the water-flow simulation and the model's inability to modify degradation rates with changing climatic conditions.

Cardiac surgery in the very elderly.

OBJECTIVE: To determine the results of cardiac surgery in the very elderly. DESIGN AND SUBJECTS: A retrospective study of 56 very elderly patients (mean age 82 years, range 79-89 years) undergoing open heart surgery between 1988 and 1991. Thirty-three patients had coronary artery bypass grafting, 12 had valve replacement alone and 11 had valve replacement with an associated procedure. SETTING: St Francis Xavier Cabrini Hospital, Melbourne--a large private hospital. RESULTS: There were four in-hospital deaths (7%). The one-year actuarial survival rate was 88%. Of the 49 survivors, 92% were in New York Heart Association (NYHA) Class III or IV before operation, whereas 96% were in NYHA Class I or II a mean of 15 months after operation. CONCLUSION: In very elderly patients with medically refractory cardiac symptoms, cardiac surgery has a tolerable mortality and provides excellent relief of symptoms.

The treatment of paracetamol overdose with charcoal haemoperfusion and cysteamine.

A 53-year-old female was admitted to hospital one hour after taking an overdose of 60 g of paracetamol and 960 mg of codeine. Two hours after ingestion of the drug, the plasma concentration of paracetamol was 3040 mumol/l. In view of the enormous, and potentially fatal, plasma concentration of the drug, charcoal haemoperfusion was undertaken as well as cysteamine therapy. Charcoal haemoperfusion and cysteamine therapy led to the rapid removal of the paracetamol from the body and consequently prevented the development of severe hepatic necrosis. It is suggested that charcoal haemoperfusion as well as cysteamine has a role in the management of severe overdosage with paracetamol. This is the first report on the use of charcoal haemoperfusion for acute poisoning in Australia.