Silicon nutrition of rice is affected by soil pH,weathering and silicon fertilisation

Silicon (Si) is a beneficial element for tropical grasses such as rice (Oryza sativa) and responses to applications of Si are common on highly weathered soils. However, the importance of pH (and hence Si speciation), weathering and fertilisation on Si uptake is still poorly understood. The responses of rice to Si fertilisation were studied in two variably weathered basalt soils (Red Ferrosol, Grey Vertosol) adjusted at different pH values (5.5–9.5) with three levels of acidulated wollastonite. Soil Si was extracted using deionised water (H₂O), 0.01 M CaCl₂, or 0.5 M NH₄OAc. Significant increases in Si uptake and rice biomass were observed in the Red Ferrosol following fertilisation (p < 0.01). Greater biomass production was observed at lower pH, due to decreased Si sorption and higher solution Si concentrations. Silicon uptake by rice was greater at low pH, despite similar extractable Si concentrations; suggesting a relationship between Si speciation and uptake. In contrast, Si uptake and rice shoot dry matter in the less weathered Grey Vertosol were unaffected by Si fertilisation (p > 0.05) except at the highest rate and lowest pH (5.5). Solution Si concentrations were controlled by precipitation/polymerisation reactions in equilibrium with specific soil pH values rather than adsorption processes. Silicon speciation effects (monosilicic acid vs. silicate ions) were unable to be measured due to an induced phosphorus deficiency in both soils at pH values > 8.5. In conclusion, weathered soils are more responsive to Si fertilisation and Si uptake is increased at low pH.     

Calcium efficiency among tomato strains depends on nitrogen regimes 1

Two Ca‐efficient and 3 Ca‐inefficient tomato strains were grown for 18 days in nutrient solutions with NH₄‐N:NO₃‐N ratios (%) of 0:100, 50:50, or 90:10 and with 40 mg of total Ca⁺⁺. When NH₄‐N nutrition was used, efficient strains exhibited Ca‐deficiency symptoms sooner or produced less dry matter than inefficient strains. The greatest reductions in dry weight production occurred between 50 and 90% NH₄‐N nutrition. The greatest reduction in solution pH and in % of Ca in plant tissues occurred between 0 and 50% NH₄‐N nutrition. Ratings of Ca efficiency varied according to the proportion of NH₄‐N in the nutrient solutions.     

Growth and mineral composition of tomato under various regimes of nitrogen nutrition 1

Five‐week‐old tomato plants were transplanted into pots containing 10 kg of potting compost which was amended with 0, 0.1, or 0.3 g of nitrapyrin and 4 g of N from KNO₃, (NH₄)₂SO₄ or sewage sludge and were grown in a greenhouse. After 2 to 3 weeks, leaves of the plants grown on any nitrapyrin x N source combination were curled with reduced laminae. Symptoms were most severe with the nitrapyrin x sludge regimes and least severe with the nitrapyrin x KNO₃ treatments. With (NH₄)₂SO₄ and sludge, growth was depressed linearly by nitrapyrin additions but was unaffected with KNO₃ fertilization. The concentrations of Ca and Mg in the shoots were lowered linearly or curvilinearly by nitrapyrin combination with any fertilizer whereas that of K was unaffected. Levels of Mn in leaves rose with nitrapyrin additions to the (NH₄)₂SO₄ or sludge treatment but were stable with any of the nitrapyrin x KNO₃ combinations. Cation antagonism among NH₄ ⁺, Ca⁺⁺, and Mg⁺⁺ is suggested as affecting the concentrations of these ions in tissues, whereas acidification of the medium and a restriction in dry matter production may account for the elevated levels of Mn in the tomato shoots grown in the presence of nitrapyrin.     

A COMPARISON OF URINARY SPECIFIC GRAVITY AND OSMOLALITY IN SHEEP

Urinary specific gravity and osmolality were determined on urine samples collected from three categories of sheep -- animals that were normal, in diuresis or had nephron numbers reduced surgically. Values for specific gravity and osmolality were compared and regression coefficients calculated for each category of sheep. In this study, specific gravity was found to be a relatively reliable indicator of osmolality, the correlation being highest in the urine from the sheep with reduced nephron numbers.     

Bacteroides ruminicola as a possible cause of “lumpy-jaw” in Bennett's wallabies

Bacteroides ruminicola subspecies brevis was isolated from the jaw lesions of three Bennett's wallabies with “lumpy-jaw”. Nocardia was not isolated from any of the three animals. It is suggested that Bacteroides ruminicola subspecies brevis is the causal organism of “lumpy-jaw” and was one of the organisms noted in this condition by Fox in 1923. As far as we are aware this subspecies has not previously been reported as a pathogen in animals or human beings. The results of antibiotic sensitivity tests are given and therapy with metronidazole or clindamycin is suggested.     

Pharmacokinetics of cefotaxime in the dog

Each of five dogs was given cefotaxime at a dose rate of 50 mg/kg by intravenous, intramuscular and subcutaneous routes, in three separate treatments. Plasma concentration time profiles were characterised by a linear two-compartment model after the intravenous administration. After intravenous, intramuscular and subcutaneous injections the mean biological half-lives were 0.74, 0.83 and 1.71 hours, respectively. The apparent steady state volume of distribution was 0.48 litre/kg and body clearance after intravenous injection was approximately 0.63 litre/hour/kg. After intramuscular and subcutaneous injections peak plasma cefotaxime concentrations were 47 +/- 15 and 29.6 +/- 16 micrograms/ml at 0.5 and 0.8 hours, respectively. The average bioavailability of cefotaxime given by intramuscular injection was 86.5 per cent and for cefotaxime given subcutaneously it was approximately 100 per cent. After two hours, the cefotaxime plasma concentration remained higher after subcutaneous than after intramuscular administration.