Plant growth responses to biochar addition: an Australian soils perspective

The use of biochar as an agricultural amendment has attracted much attention owing to its potential to improve soil condition and plant growth; however, production outcomes are often uncertain. Although soil type is a major driver of plant productivity, there are relatively few biochar studies that directly compare plant growth responses across a range of soil types. We tested the wheat growth response to biochar derived from poultry litter and from wheat straw applied at 1, 5 and 10 t ha^?1 (approximately 0.13, 0.67 and 1.33 % w/w) in four soils representing major agricultural regions in Australia: an acidic arenosol (Western Australian cereal belt), an acidic rhodic ferralsol (Northern New South Wales), a neutral vertisol (Queensland cropping) and an alkaline haplic calcisol (Eyre Peninsula in South Australia). In the neutral vertisol, where plant growth was vigorous in the control treatments, biochar had little impact, whereas in the alkaline calcisol, there was a small significant increase in shoot biomass at high (10 t ha^?1) application rates. Plant growth responses in the acidic soils were most evident but demonstrated a strong contrast to one another. In the acidic arenosol, negative growth impact correlated with increasing electrical conductivity, while in the acidic ferralsol a small rate-dependent increase in pH correlated with relatively large gains in biomass, possibly due to improved phosphorus nutrition and alleviated Al toxicity. Moving towards effective integration of biochar as a management tool will not only require stratification based on soil types, but wider consideration of the main plant production constraints, such as pH, pertinent to a particular system.     

Biochar and fertiliser applications influence phosphorus fractionation and wheat yield

The use of biochar in agriculture to achieve the dual benefits of improving soil quality whilst sequestering carbon (C) has received much attention. However, in low-intensity broadacre agricultural systems where yield is constrained by rainfall and costs associated with phosphorus (P) fertiliser, the application of biochar at rates commonly reported (>10 t ha^?1) are likely to be prohibitively expensive where yield benefits cannot be guaranteed. In marginal areas where calcareous soils dominate, biochar application has no liming effect, reducing its value compared to application in acidic soils. In the present study, we use a field experiment to investigate the interaction between P fertilisation and biochar banding at low application rates (<1 t ha^?1) on wheat yield and soil P fractionation (assessed by a modified Hedley method) in a highly alkaline Haplic Calcisol in a dryland broadacre cropping system. Our results demonstrate no statistically significant effect of low rate biochar banding on wheat yield in this highly P-constrained soil, but a significant effect of both biochar and fertiliser on P fractionation in both years of the study. Higher P fertiliser rates significantly increased wheat yield in all biochar treatments. The interactions between biochar, P fertiliser and P fractionation indicate shifts in potential P availability both as a result of P fertilisation and also biochar application. Further work is required in low productivity calcareous systems such as that studied here to elucidate the potential for biochar amendment to improve productivity and sequester C.     

Vancomycin for the treatment of methicillin-resistant staphylococcal and enterococcal infections in 15 horses

We retrospectively reviewed the cases of 15 foals and adult horses in which vancomycin was used, alone or in combination with an aminoglycoside, to treat methicillin-resistant staphylococcal and enterococcal infections. Signalment, presenting complaint, history (including history of treatment for the current complaint), results of bacterial culture and antimicrobial susceptibility testing, treatment, and outcome were reviewed. The average vancomycin dosage was 7.5 mg/kg q8h, administered by intravenous infusion over 30 min. The infection resolved in all 7 horses with soft tissue infections and in 6 of the 8 horses with infections involving a bone or a joint, or both. No adverse effects of vancomycin therapy were noted. Although the number of cases is small, our findings suggest that vancomycin, alone or in combination with an aminoglycoside, is safe and effective for the treatment of resistant staphylococcal and enterococcal infections in horses and foals. However, owing to the importance of staphylococci and enterococci in human medicine and the problems with emerging resistance, we recommend that the use of vancomycin in horses be limited to cases in which culture and susceptibility results clearly indicate that this agent is likely to be effective and in which there is no reasonable alternative.     

Glycine,nitrate, and ammonium uptake by classic and modern wheat varieties in a short-term microcosm study

Plants take up nitrogen principally in the form of nitrate and ammonium; however, evidence is growing that they can also use organic N in the form of amino acids. Selecting varieties that better use organic N could be important in maximizing productivity in organic and low-input systems because these varieties may access a wider pool of available nutrients. We tested amino acid-N uptake by wheat (Triticum aestivum L.) seedlings over 24 h over a range of soil glycine concentrations. Wheat was grown in 5 ml pipette tips for 10 days prior to labeling with ¹⁴C-labeled glycine. In a second experiment, uptake of amino acid-N relative to nitrate and ammonium was tested in three pre-1940 wheat varieties (Arco, Idaed, and Red Fife), three modern varieties (Alpowa, Madsen, and Zak), and one perennial wheat variety (unreleased). Glycine-N was detected in all shoots (with the exception of the lowest soil concentration) and increased with increasing soil concentration. There were few differences in uptake between individual varieties tested but seedlings of modern varieties were more efficient at capturing organic N than classic varieties. Glycine-N constituted between 3.9% and 8.1% of total N uptake over 24 h and constituted a significantly greater proportion of total N in perennial wheat than annual wheat varieties. These results show that there may be sufficient varietal differences in organic N uptake in wheat to warrant selection for this trait in breeding programs targeted to improving N use efficiency.     

The genome of the sea urchin Strongylocentrotus purpuratus

We report the sequence and analysis of the 814-megabase genome of the sea urchin Strongylocentrotus purpuratus, a model for developmental and systems biology. The sequencing strategy combined whole-genome shotgun and bacterial artificial chromosome (BAC) sequences. This use of BAC clones, aided by a pooling strategy, overcame difficulties associated with high heterozygosity of the genome. The genome encodes about 23,300 genes, including many previously thought to be vertebrate innovations or known only outside the deuterostomes. This echinoderm genome provides an evolutionary outgroup for the chordates and yields insights into the evolution of deuterostomes.     

The Acute Hemodynamic Effects of Milrinone in Dogs With Severe Idiopathic Myocardial Failure

To examine the effects of acute oral milrinone administration (0.75 mg/kg) on dogs with severe idiopathic myocardial failure and the effect of prolonged milrinone administration on survival time, we measured hemodynamics before and 2 hours after drug administration and recorded survival time and cause of death in 13 dogs with dilated cardiomyopathy. Hemodynamics were measured using a Swan-Ganz catheter and femoral artery puncture along with recording an M-mode echocardiogram. Cardiac index increased from 1.92 +/- 0.54 to 3.06 +/- 0.81 L/min/m2, stroke volume index increased from 11.3 +/- 4.3 to 16.7 +/- 6.3 ml/beat/m2, and pulmonary capillary wedge pressure decreased from 23 +/- 8 to 12 +/- 8 mmHg. A clinically significant increase in heart rate was observed in seven dogs, resulting in a statistically significant increase in heart rate for the group from 174 +/- 34 to 194 +/- 44 beats/minute. Mean arterial blood pressure did not change significantly for the group but did decrease more than 20 mmHg in three dogs, suggesting a predominant primary vasodilating effect of milrinone in these dogs. An increase in contractility appeared to be the predominant reason for the improved hemodynamics in seven dogs. Eight dogs died of causes other than worsening heart failure, including four of eight Doberman pinschers that died suddenly, presumably from an acute tachyarrhythmia. Two dogs that had the greatest increase in an index of contractility are alive more than 2 years after the initiation of milrinone administration.