Instability of PR toxin in blue cheese.

PR toxin was unstable in solvent extracts of blue cheese and in strongly acidic solutions. However, it was appreciably stable over a 2.5 hr period in moderately acidic methanol-water extracts (pH 2--3) of blue cheese. Using this extraction mixture, it was determined that PR toxin was not stable in blue cheese itself. PR toxin reacted with model neutral and basic amino acids and the formation of PR imine from PR toxin in the presence of blue cheese was demonstrated. While PR imine added to blue cheese could be recovered on analysis after 5 min, over a 2--5 day period it too was unstable in the cheese.     

The effects of the severe drought of 1976 on the vegetation of some moorland pools in The Netherlands

The effect of the extreme drough of 1976 has been studied to obtain information on the reaction of the vegetation of moorland pools following a fall in the ground water level. The degree of change appeared to be dependent on the nutrient status of water and soil and on the relief. The vegetation of metatrophic and guanotrophic moorland pools showed the most drastic change.     

Effect of strains of Rhizobium trifolii on the establishment of oversown white clover (Trifolium repens)

Strains of Rhizobium trifolii incorporated into commercial peat inoculants were compared for their effect on the establishment and growth of oversown white clover (Trifolium repens) on soils devoid of infective rhizobia.There were marked differences in numbers of seedlings establishing and clover dry matter production per hectare with the various strains. However, when adjusted to a constant number of established seedlings, dry matter production from all strains, apart from one strain at one site, were similar indicating that the strains did not appear to influence the growth of individual clover plants.The marked differences in establishment of clover inoculated with the various strains could not be accounted for by differences in the number of rhizobia in the peat inoculant.Selecting strains of rhizobia for ability to increase establishment is considered important where clover is oversown onto soils devoid of rhizobia.     

A comparison of methods of recovering oesophageal extrusa from grazing sheep

Extrusa samples were collected from two groups of oesophageally fistulated sheep grazing together. One group had foam plastic oesophageal plugs fitted below the fistula to assist in the complete collection of extrusa; the second group grazed without plugs. The extrusa were collected in four periods chosen to cover as wide a range of herbage conditions as possible varying from herbage with a high proportion of green leaves to predominantly dry material with a high proportion of dead leaves and stems. The plant components of the extrusa were determined and there was no evidence that stems or any other plant component preferentially by-pass the fistula in grazing sheep. It was concluded that it is not necessary to insert foam plastic plugs in the oesophagus of grazing sheep to obtain representative samples of ingested herbage.     

The effect of propionic acid on the storage losses of hay

Storage losses in moist hay treated with propionic acid were compared with those occurring in untreated moist hay in two experiments and with field-cured hay in three experiments. Dry matter losses in treated hays ranged from 41 to 8.6% and from 1.7 to 12.6% in untreated hays. Digestible organic matter losses in both treated and untreated hays were generally greater than dry matter losses. Only in one experiment did propionic acid application significantly reduce nutrient losses in moist hays. Nutrient losses, and water-soluble carbohydrate losses in particular, were shown to be correlated with maximum and cumulative bale temperatures during storage in two of the experiments. The rise in hale temperatures during storage was reduced in all three experiments, to a greater or lesser extent, by application of the additive. Loss of propionic acid from the hay during and after application was very large. In the three experiments 86.2, 85.3 and 85.6% of the acid applied was lost by the end of the storage period. Acid distribution studies indicated that variation in acid concentration within bales was as great as between bales. It was concluded that more research is needed into applicator design and position on the baler and into alternative application methods if the benefits of propionic acid as a moist hay preservative are to be fully exploited.     

A comparison of continuous grazing systems for milk production

In two experiments conducted with Ayrshire dairy cows in 1974 and 1975 on swards of S23 perennial ryegrass, four systems of continuous grazing were investigated. The leys received 345 and 370 kg ha^-1 fertilizer nitrogen in 1974 and 1975 respectively and were stocked at the rate of five cows per ha. In 1974, a comparison was made between two systems which either integrated silage making with, or separated it from, the continuous grazing. The provision of a silage aftermath in late July increased milk yield after that time, but had no significant effect on milk yield over the 19-week experimental period. In 1975, a comparison between weekly and monthly applications of fertilizer N showed no significant differences between milk yields in a 20-week period. The feeding of supplementary concentrates from late July onwards significantly increased milk yield. The treatments in both years had only small and mainly non-significant effects on milk composition. On average, excluding the concentrate treatment, the annual output of milk was 10,800 kg ha^-1 using spring-calved cows.     

Inoculation of pines with mycorrhizal fungi in natural soils—III: Effect of soil fumigation on rate of infection and response to inoculum density

Pinus radiata seedlings were inoculated with basidiospores of Rhizopogon roseolas and Suillus granulatus, and with chlamylospores of two unidentified but highly effective mycorrhizal fungi in undisturbed cores of natural soil fumigated with methyl bromide. Fumigation stimulated mycorrhizal infection rate and enhanced the response of seedlings to increasing concentrations of both inoculum types, but the effect of chlamydospore inoculum was more favoured by fumigation than that of basidio-spores. Chlamydospore inocula appear more sensitive to competitive and antagonistic soil microorganisms than basidiospores. Soil fumigation appears a necessary adjunct to the use of chlamydospores as inoculants in nurseries and is discussed in relation to nursery culture of pines.     

In vitro experiments simulating the possible fates of aphid honeydew sugars in soil

In vitro intact soil cores were treated with sugar amendments at a rate equivalent to that of honeydew produced by a population of tree dwelling aphids. The priming action induced by such amendments was dependent upon the soil type, nature of sugar added and degree of repetition of amendment. A hypothesis has been proposed to explain the presence of a positive priming effect in a woodland soil and a negative priming effect in a grassland soil after equivalent sucrose additions.