THE NATURE OF THE NITROGEN COMPOUNDS IN SOIL ORGANIC MATTER EXTRACTED BY ANHYDROUS FORMIC ACID

Organic matter extracted with 9 : 1 formic acid : acetylacetone from twenty-five soils of widely varying organic content and precipitated with excess di-isopropyl ether was hydrolysed with 6N HC1. The relationships between the proportions of acid-soluble N, acid-insoluble N, amino-N, and ammonium-N thus produced, and the properties of the original soil were examined. The distribution of N in acid hydrolysates was similar to that reported in the literature for material isolated by neutral and alkaline extractants. The relatively large proportion of N released as ammonium-N from organic matter obtained from soils of high pH and low C : N ratio may derive from organically fixed ammonia. The low levels of amino-N in organic matter extracted by formic acid from soils of high clay content imply the existence of clay-amino complexes that resist extraction although formation of such complexes during extraction cannot be ruled out.     

The effect of the duration of regrowth on photosynthesis, leaf death and the average rate of growth in a rotationally grazed sward

A study was made to characterize the effect of the duration of regrowth on the pattern of changes in the major physiological processes involved in the net accumulation of herbage, and so to provide a rational basis for optimizing production under rotational grazing.
During regrowth following a severe defoliation, rates of canopy photosynthesis, and so the rate of production of new leaves, increased rapidly but there was a delay before there was a corresponding increase in the rate of leaf death. Although the amount available for harvest (crop live dry weight, W ) continued to increase as the duration of regrowth was extended from 'short' (12–13 days), through 'medium' (19–23 days) to 'long' (30-34 days), there was not a continued increase in the average growth rate – the increase in the weight of the crop, ( W – W_o ), divided by the duration of regrowth, t , In this study, the average growth rate (based on changes in the weight of lamina alone) increased as the duration of regrowth was extended from 12-13 to 19-23 days but changed little as the duration of regrowth was extended from 19-23 days to 30-34 days. In spring and summer, elongating stems increased the average growth rate (of lamina plus stem) up to 30-34 days but the accumulated stem material could not reliably be harvested by sheep.
A mathematical model was used to explain why the average growth rate is characteristically insensitive to the duration of regrowth beyond a given minimum duration. For practical purposes, we suggest from the results of this study that regrowths of at least 14 days but less than 28 days will be effective in achieving not only close to the maximum average growth rate of highly digestible material, but also in sustaining a densely tillered, leafy sward which regrows rapidly from severe defoliation and is more reliably harvested (utilized) by sheep.     

Enhancement of transdermal delivery of phenylbutazone from liposomal gel formulations through deer skin

Phenylbutazone (PBZ) is a nonsteroidal anti‐inflammatory drug used in the treatment of chronic pain and arthritis. Topical and transdermal administration of PBZ would be beneficial in large animals in terms of minimizing gastro‐intestinal ulcerations and other side effects, easy administration to legs and joints and minimizing the dose to reduce systemic toxicity of the drug. A topical liposomal preparation with different concentrations of a mono‐substituted alkyl amide (MSA) and PBZ was formulated. The formulations were evaluated by in vitro skin‐permeation kinetics through deer skin using Franz diffusion cells. By increasing drug loading from 1% to 5% w/w, the steady‐state flux (μg/cm²/h) of PBZ was increased twofold (P < 0.001). Similarly, by increasing the MSA concentration from 0% to 4%, the steady‐state flux (μg/cm²/h) of PBZ was increased twofold (P < 0.001). Overall, by increasing the drug load and the use of an appropriate amount of the penetration enhancer, the steady‐state flux of PBZ through skin was increased fourfold (P < 0.001). MSA at both 2% and 4% w/w concentrations significantly increased the skin levels of PBZ as compared with control (P < 0.05). In conclusion, MSA served as an effective skin‐penetration enhancer in the liposomal gel of PBZ for deer.     

有机物-金属相互作用对重金属负载土柱中粘土矿物吸附剂再生的影响

Natural clay minerals can play an important role in crude remediation of wastewater polluted with the heavy metals (HMs) Cu,Zn and Ni.The presence and timing of addition of natural dissolved organic matter (DOM) have a significant effect on the HM removal by clay mineral sorbents.However,the influence of the presence of DOM on the remediation of the used clay mineral sorbents once saturated with HMs is largely unknown.To resolve this,clay mineral-rich soil column of varying composition,loaded (i) with Cu,Zn and Ni only,(ii) first with DOM followed by Cu,Zn and Ni,or (iii) with DOM,Cu,Zn and Ni simultaneously,was used in a set of desorption experiments.The soil columns were leached with 0.001 mol L-1 CaCl2 dissolved in water as control eluent and 0.001 mol L-1 CaCl2 dissolved in DOM as treatment eluent.During the preceding loading phase of the sorbent,the timing of DOM addition (sequential or concurrent with HMs) was found to have a significant influence on the subsequent removal of the HMs.In particular when the column was loaded with DOM and HMs simultaneously,largely irreversible co-precipitation took place.Our results indicate that the regeneration potential of clay mineral sorbents in wastewater treatment will be significantly reduced when the treated water is rich in DOM.In contrast,in manured agricultural fields (where HMs enter together with DOM),HM mobility will be lower than expected from interaction dynamics of HMs and clay minerals.     

Use of a model to optimize the interaction between frequency and severity of intermittent defoliation and to provide a fundamental comparison of the continuous and intermittent defoliation of grass

A previously described model of grass growth was used to analyse the effect of the severity of defoliation and the duration of the subsequent regrowth on the overall balance between photosynthesis, gross tissue production and leaf death and so on the amount that could be harvested/consumed per hectare under intermittent defoliation. Maximum yield per hectare was shown to be achieved whenever the fluctuations in LAI during regrowth and defoliation led lo the same low average LAI that was previously shown to give maximum yield (amount harvested/consumed per hectare) under continuous grazing. Thus, it is suggested that production under both continuous and intermittent defoliation may best be characterized, and diverse managements may be rationalized, on the basis of the average sward state, the average achieved. The analysis leads us to reconsider some widely held concepts of the growth and utilization of grass applied in both agronomic and ecological theory, and the provision of practical guidelines for management.     

Comparison of the residual virulence of Newcastle disease vaccine strains V4, Hitchner Bl and La Sota

The clinical response of 7-day-old chickens to Newcastle disease vaccine strains V4, B1 and La Sota administered by the aerosol method was used to study the residual virulence of the strains. Parameters used to assess the severity of the clinical response were the number of sneezes recorded and the weight gain of chickens in the 10 day test period. The demeanour of the chickens was also observed.
Strain V4 was less pathogenic for chickens than strain B1 which was less virulent than strain La Sota. Statistically significent differences were recorded in weight gain and the number of sneezes detected in each group. An unexpected mild respiratory disease recorded in chickens dosed with strain V4 may have been associated with administration of virus as a fine particle aerosol. Aust. vet. J. 61: 47–49     

Order of amino acid limitation in poultry by-product meal

1. Two chick assays (from 8 to 17 d posthatching) were conducted to determine the order of amino acid (AA) limitation in poultry by-product meal (PBPM) using AA deletion and addition assays. 2. In the deletion assay, the basal diet contained 155 g/kg crude protein (provided solely by PBPM) and was fortified with cystine, tryptophan, threonine, lysine, valine, isoleucine, histidine, methionine and phenylalanine to meet the Illinois ideal AA Pattern. Each AA was then deleted individually from the basal diet and its effect on growth assessed. 3. In the addition assay, various individual or combined additions of nine AAs were made to an unfortified 155 g/kg crude protein diet containing PBPM as the sole source of dietary crude protein. 4. The results from the deletion assay were in general agreement with those from the addition assay. Based on the combined results of the deletion and addition assays, the order of AA limitation in PBPM was 1) cystine, 2) tryptophan, 3) threonine and lysine, 5) valine, and 6) isoleucine and histidine with the degree of deficiency of valine, isoleucine and histidine being similar. The results also suggested that methionine may be slightly limiting in PBPM protein.     

The Current State of Solar Modeling

Data from the Global Oscillation Network Group (GONG) project and other helioseismic experiments provide a test for models of stellar interiors and for the thermodynamic and radiative properties, on which the models depend, of matter under the extreme conditions found in the sun. Current models are in agreement with the helioseismic inferences, which suggests, for example, that the disagreement between the predicted and observed fluxes of neutrinos from the sun is not caused by errors in the models. However, the GONG data reveal subtle errors in the models, such as an excess in sound speed just beneath the convection zone. These discrepancies indicate effects that have so far not been correctly accounted for; for example, it is plausible that the sound-speed differences reflect weak mixing in stellar interiors, of potential importance to the overall evolution of stars and ultimately to estimates of the age of the galaxy based on stellar evolution calculations.