ALBERT

Notes: The effect of annually switching sward management between cutting regimes that simulated rotational grazing and those for forage conservation vs. maintaining a constant management regime was studied by testing for ranking-order changes between six perennial ryegrass varieties.Total dry-matter (DM) yields were found to change in response to an annual switch in management. When under a conservation management and switched in the next year to simulated grazing, all six varieties yielded more in that year than when they were maintained constantly under simulated grazing. Similarly, when under a simulated grazing management and switched in the next year to conservation, all six varieties yielded less than when maintained constantly under a conservation management. These yield differences were largely expressed in spring of the year following the management switch.Differences in the ranking order of varieties were observed between the constant sward management treatments and the alternating managements. However, in these changes in variety ranking, no variety was consistently favoured or disadvartaged by the annual switch in management. Therefore, no clear evidence was produced that an alternating management system had any consistent effect on variety ranking and the observed changes were possibly due to the normal year-to-year variation frequently recorded in variety performance trials.

Notes: We report the characterization of high- and low-sodium-transporting lines developed by intravarietal selection within a cultivar, IR36, of rice (Oryza sativa L.). The purpose was to investigate the mechanistic basis of sodium uptake in material in which differences in salt uptake could be isolated from the many other morphological and physiological characteristics that affect the phenotypic expression of salt tolerance. The lines differed in mean sodium transport by a factor of 2. They differed in vigour and water use efficiency, which are characters that modify the effects of salt transport, by only 12% or 13%. The lines did not differ significantly in other physiological traits that are components of salt resistance: compartmentalization at the leaf and cellular levels. There was a strong correlation between the transport of sodium and a tracer for apoplastic pathways (trisodium, 3-hydroxy-5,8,10-pyrene trisulphonic acid, PTS) in both lines. The regression coefficient for sodium transport on PTS transport was the same in both lines. The individual variation in PTS transport was similar to that in sodium transport, and the variation in the transport of both was very much greater than the variation in any other character studied. The high-sodium-transporting line took up proportionately more PTS than the low-sodium-transporting line. It is concluded that the transpirational bypass flow is of major importance in sodium uptake by rice and that selection for differences in sodium transport has been brought about by selection for heritable differences in the bypass flow.

Notes: During three consecutive summers, forty spring-calving beef cows and their calves grazed perennial ryegrass-dominant swards receiving 250 kg N ha−1 at one of two annual stocking rates [2.0 (SR 2.0) or 2.5 (SR 2.5) cows ha−1] and one of two sward heights [4–5 (LS) or 7–8 (HS) cm] in a 2 × 2-factorial experiment, replicated twice. Sward heights were maintained from turn-out in spring by weekly adjustment of the area grazed and herbage was cut for silage in June and again in August from the areas not grazed. After the second cut of silage there was no control of sward height. Calves were weaned in early October and cows removed from pasture and housed when sward heights fell to 4 cm in autumn. Cows were fed in groups a variable but measured quantity of silage during winter to achieve a body condition score of 2.0–2.25 at turn-out the following spring.During the period of sward height control the cows on the HS treatment gained more live weight than those on the LS treatment (0.841 vs. 0.496 kg day−1; P〈0.01) as did the calves (1.167 vs. 1.105; P〈0.05). but the stocking rate treatment had no effect. From the time of second-cut silage to the time of weaning and housing respectively, calves and cows gained more live weight on the SR 2.0 treatment because sward heights were higher. Reproductive performance of cows was not affected by treatment.The quantity of silage produced and consumed per cow was not affected by sward height treatment, but the SR 2.0 treatment produced significantly (P〈0.001) more silage (1559 kg dry matter per cow) than the SR 2.5 treatment (833 kg dry matter per cow) and had higher winter silage requirements (1249 vs. 1153 kg dry matter per cow: P〈0.05). The overall mean stocking rate at which winter fodder production and requirements would be in balance was calculated as 2.25 cows ha−1 but values were 1.86, 2.60 and 2.28 in each of the three years of the experiment.The results showed that it was possible to control sward height in temperate beef cow systems by adjusting the area available for grazing. Body condition score can be used as a means of determining the feeding levels required to manipulate body condition of cows over winter to achieve prescribed levels of body condition. The experimental approach allows the identification of the stocking rate at which self-sufficiency in winter fodder can be achieved and the year-to-year variation associated with that stocking rate. This approach could be generalized if information on herbage growth rate were available, either from direct measurement or from predictive models.

Notes: Biochemical and tissue-composition indices were used to determine the impacts of temporary feeding reductions on juvenile Atlantic salmon (4.2g initial weight). Three levels of food reduction (fasting, 20% of control, 50% of control) lasting for 2, 4 or 8 days were compared to a control group (constant feeding at 2.75% of body weight day−1). Ornithine decarboxylase (ODC) activity and RNA concentrations were used to measure changes in protein synthesis; condition factor (K), liver-somatic index (LSI), visceral-somatic index (VSI), and gut index (GI)were used to provide information on stored energy levels. Results showed that physiological adjustments to decreases or increases in feeding occur very quickly. The most rapid responses were changes in ODC activity (within 2 days) and LSI (2–4 days). Changes in RNA concentrations and K required 4–8 days. There was no apparent effect of the treatments on VSI or GI. Temporary reductions of feeding lasting 2 days or less would not be detected by any index except ODC activity. Changes in the indices are discussed with respect to short-term changes in rates of protein synthesis and energy storage.

Notes: The paper describes (a) the research into substances with oestrogenic properties in river systems, (b) the background on why and how these substances are present in river systems, (c) the potential harm which they have through endocrine disruption, and (d) the different techniques for their detection. Results are presented form a preliminary study on the overall oestrogenic potential of sewage effluent being discharged into a river. These results show high levels of oestrogenic potential in the effluent and also in stream water upstream from any sewage-treatment works. The implications for the management of rivers which contain recycled water and possible future research directions in this field are discussed.

Notes: This paper addresses the issues of scale and appropriate model complexity for large-scale hydrological models. A grid-based hydrological model, which employs the UK Meteorological Office Rainfall and Evaporation Calculation System, is applied to the Severn and Thames catchments using a grid scale of 40 km, and is shown to reproduce the observed mean annual runoff over a 10-year period to within 6% with no prior calibration. The variation in the model performance is strongly correlated with the linearity of the annual rainfall/runoff relationship and a climate index. At the monthly scale, runoff routing becomes significant, and the introduction of a two-parameter routeing algorithm significantly improves the monthly runoff simulations giving efficiencies of 90% and 88% for the Severn and Thames respectively. The results provide guidance to climate modellers looking for efficient and robust land-surface parameterizations, and indicate the potential application of such a modelling scheme to water resource managers.

Notes: The mechanism of “475°C embrittlement” in age-hardened ferritic stainless steel, E-Brite and A129-4, is investigated. Experimental results for smooth tensile and notched bending fracture tests are interpreted using a finite element simulation of the stresses at fracture. Yield is characterised by profuse slip band formation. Transgranular fracture initiation is observed at slip band intersections with grain boundaries. Deformation twinning occurs during brittle fracture. Slip bands and deformation twins are identified using lattice rotations measured with electron back-scatter diffraction patterns. Mechanisms for the ductile-to-brittle transition are discussed.