ALBERT

Description: Radiometric and AMS radiocarbon dating of a 6-m sediment core from Loch Ness, Scotland, indicates that it represents perhaps the very end of the Late Pleistocene, and the first ca. 7500 yr of the Holocene. Counts of laminations observed in the Holocene section of the core suggest that they are present in sufficient number to constitute annual laminations (varves), an hypothesis consistent with the pollen record, which contains a sequence of zones representative of the Early, Middle and part of the Late Holocene regional vegetation history. On the basis of BSEM and X-ray studies of sediments, and modern seston trap data, the laminations are believed to be produced by winter floods, which introduce increased silt loading into the Loch. Sediment for the rest of the year is mostly composed of clay-sized material. This hypothesis is being further tested, however, by continuing sedimentological and microfossil studies.Time-depth relations for the core based on calibrated 14C dates and lamination counts, respectively, illustrate the close correspondence between the two sets of data. The latter are therefore now being used to develop a varve chronology for the Holocene for Loch Ness. This will then in turn be used for further chronological studies, and for investigations of palaeoclimatic variations over the eastern North Atlantic, to which the signal of lamination thickness in the sediments is thought to be particularly sensitive. They may also eventually be used for calibration studies, employing 14C dating of specific carbon compounds, or groups of compounds extracted from the sediment using modern organic geochemical methods.

Description: Ice at depth in ice sheets can be softer in bed-parallel shear than Glen’s flow law predicts. For example, at Dye 3, Greenland, enhancement factors of 3 4 are needed in order to explain the rate of borehole tilting Previous authors have identified crystal fabric as the dominant contributor, but the role of impurities and crystal size is still incompletely resolved. Here we use two formulations of anisotropic flow laws for ice (Azuma’s and Sachs’ models) to account for the effects of anisotropy, and show that the measured anisotropy of the ice at Dye 3 cannot explain all the detailed variations in the measured strain rates, the jump in enhancement across the Holocene–Wisconsin boundary is larger than expected from the measured fabrics alone. Dust and soluble-ion concentration divided by crystal size correlates well with the residual enhancement, indicating that most of the “excess deformation” may be due to impurities or crystal size. While the major features of the deformation at Dye 3 are explained by anisotropy and temperature, results also suggest that further research into the role of impurities and crystal size is warranted.

Description: SUMMARYDisposal methods for straw from continuous winter wheat were tested on two soil types, a flinty silty clay loam and a sandy loam, over 7 years (1985–91). The methods tested were burnt or chopped straw in full factorial combination with four cultivation methods (tined to 10 cm, tined to 10 cm then to 20 cm; ploughed to 20 cm; tined to 10 cm then ploughed to 20 cm). Measurements were taken to determine the effects on crop establishment and growth, pest and disease incidence, and the consequent effects on yield. Another experiment (1985–91) on the flinty silty clay loam site, investigated the interactions between straw treatments (burnt, baled or chopped in plots that were all shallow cultivated to 10 cm) and five other factors; namely, time of cultivation, insecticides, molluscicides, fungicides and autumn nitrogen. All the straw x cultivation systems allowed satisfactory crops to be established but repeated incorporation of straw using shallow, non-inversion cultivations resulted in very severe grass-weed problems. Early crop growth, as measured by above-ground dry matter production, was frequently decreased by straw residues, but the effect rarely persisted beyond anthesis. Pests were not a problem and their numbers were not greatly affected either by straw or cultivation treatments, apart from yellow cereal fly which, especially on the heavier soil, was decreased by treatments which left much straw debris on the soil surface. Incorporating straw also caused no serious increases in the incidence of diseases. Indeed, averaged over all sites and years, eyespot and sharp eyespot were both slightly but significantly less severe where straw was incorporated than where it was burnt. Eyespot, and even more consistently sharp eyespot, were often more severe after ploughing than after shallow, non-inversion cultivations. Effects on take-all were complex but straw residues had much smaller effects than cultivations. Initially the disease increased most rapidly in the shallow cultivated plots but these also tended to go into the decline phase more quickly so that in the fourth year (fifth cereal crop) take-all was greater in the ploughed than in the shallow cultivated plots. On average, yields did not differ greatly with straw or cultivation systems, although there were clear effects of take-all in those years when the disease was most severe. In the last 2 years, yields were limited by the presence of grass weeds in the plots testing chopped straw incorporated by tining to 10 cm.

Description: Ten daylit, controlled-environment cabinets were used to investigate the possible impacts of global rises in atmospheric CO2 concentration and temperature on beetroot (Beta vulgaris L.), carrot (Daucus carota L.) and bulb onion (Allium cepa L.) plants. Their responses to CO2 concentrations of 350, 450, 550, 650 and 750 vpm and temperatures of 12, 13·5, 15, 16·5 and 18°C were examined by using a fractional factorial design for the two treatment factors. Use of the daylit cabinets allowed the plants to be grown in natural light, common atmospheric humidities (vpd 0·7 kPa) and non-limiting supplies of water and mineral nutrients.Polynomial models were used to summarize the whole plant dry weight and fresh weight yield responses and to indicate the potential impact of climate change. Additionally, the models were used to generate predictions of the percentage change in whole plant dry weight and plant fresh weight yield for the years 2025 and 2050 relative to 1992. Baseline values of 350 vpm for CO2 and a mean temperature of 13·5°C for 1992 together with forecast CO2 values of 407 and 442 vpm and temperature increases of 0·7 and 1·1 C for 2025 and 2050 respectively were used. For 2025, fresh weight yield changes of +19%, +9% and +13% were obtained for beetroot, carrot and onion crops respectively, while for 2050 the respective changes were +32%, +13% and +21%.Measurements of the ratio of the maximum diameter of the bulb to the minimum diameter of the neck for onions showed that there was little or no influence of CO2, whereas the effect of temperature was substantial. Bulbing was accelerated by high temperature and was greatly delayed at low temperature. At temperatures

Description: SUMMARYThe effects of overwinter cover cropping, delayed ploughing and method of straw disposal on the quantities of nitrate leached (averaged over three winters during 1989–93) from a chalk loam in Eastern England were examined. The recovery of ‘retained’ nitrogen (retained through cover crop uptake, delayed ploughing and immobilization by straw) in a following spring crop was also assessed. In the first two winters, the rye cover crop decreased nitrate leaching by 〉 90% (28 kg N/ha per year), as compared with bare fallow treatments. In 1992/93 this decrease was only 23% (10 kg/ha), due to the early onset of drainage before cover was well established. Delayed ploughing on bare treatments, to decrease autumn N mineralization and subsequent nitrate leaching, was ineffectual in 1989/90 but had substantial effects in 1990/91 and 1992/93; N mineralization, inferred from soil mineral nitrogen content, and nitrate leaching were decreased by 31 and 35% in 1990/91 and by 36 and 61% in 1992/93, respectively. Nitrate leaching (averaged over three winters) was unaffected by straw incorporation. There was no evidence of recovery of cover crop N in the spring sown test crops (barley or sugarbeet). In the low soil N input situation encountered in this experiment, it was unnecessary to sow cover crops before early September in years of average or below average rainfall to ensure that the average soil solution concentrations remained below the EU drinking water limit of 11 mg NO3-N/1. However, in wetter seasons substantial N leaching occurred before cover had taken up much N. In 1992/93 N retained against leaching by a rye cover crop in previous years was apparently being remobilized and lost through leaching, although if cover was grown again there was less leaching than from bare land. In the future, an increase in the extent of cover cropping might increase transpiration rates and therefore lead to a decrease in aquifer recharge.

Description: Thirty-two N'Dama heifers were offered ad libitum Andropogon hay plus 10·2 g/kg liveweight (LW) groundnut hay (GNH) (L) or 10·2 g/kg LW GNH and 3·9 g/kg LW groundnut cake (GNC) (H). After 4 weeks on the diets, half of each group were infected intradermally with Trypanosoma congolense clone (ITC 50) (LI and HI). Peak parasitaemia occurred 6–8 days after infection and started to decrease c. 56 days later. No differences in parasitaemia were observed between LI and HI animals. Packed cell volume (PCV) fell in all treatments (by 5·4, 13·8, 3·7 and 9·4 units after 49–63 days post-infection (p.i.) for the L, LI, H and HI groups respectively) and significant effects of infection and diet were observed. GNH and GNC intakes were maintained during the trial; however, infected animals had a decreased intake of Andropogon hay. LI animals lost significantly more weight during the experimental period than the non-infected controls (−71·4 v. −13·7 g/day). Meanwhile, HI animals gained less weight compared with the H group (52·2 v. 167·6 g/day). Weight losses appeared to be due to decreased food intake. In the period 54–68 days p.i., plasma concentrations of albumin were lower and plasma protein was higher in infected animals. Plasma cholesterol concentrations were also lower in infected animals 54–68 days p.i. Plasma urea concentrations were higher in supplemented animals but were not affected by infection. The results showed that animals on a higher plane of nutrition showed less severe clinical signs of infection. However, for all the parameters considered, the magnitude of the difference between groups on different diets was similar for both infected and control animals, suggesting that mechanisms of resistance were not affected by the planes of nutrition considered.

Description: SUMMARYThe idea that the addition of compound feed to grass at ensilage can result in adequate preservation of the crop without the need for an acid additive, and that less compound feed would then need to be given when the silage is subsequently fed, was tested with dairy cows. Two diets were compared: (1) a conventional grass silage, to which acid had been added at the time of ensiling, plus concentrates supplied at the time of feeding, and (2) grass silage, to which a compound feed had been added at the time of ensiling, plus a lower rate of concentrates. Each diet was fed to 12 lactating cows for 82 days.The total intake of dry matter was 17·3 kg per cow per day on diet 1 and 18·3 kg on diet 2. Daily milk yields per cow were 24·5 and 26·1 kg, respectively, with similar milk composition. The estimated diet costs per kg of milk were 9·3 p on (1) and 8·3 p on (2). It is concluded that the addition of compound feed to grass at ensilage is worth considering on dairy farms as an alternative to conventional grass silage, but that a more comprehensive study is needed.

Description: SUMMARYA multifactorial experiment sown to winter wheat cv. Hustler in autumn 1978 tested the effects of combinations of the following eight factors, each at two levels: drill type, sowing date, amount of nitrogen, division of nitrogen, irrigation, autumn pesticide (aldicarb), summer aphicide (pirimicarb), and fungicide (carbendazim, maneb and tridemorph).The mean grain yield of all plots was 9·7 t/ha and the best eight-plot treatment mean was 11·3 t/ha. The factors that had the greatest effect on yield were aphicide and fungicide, mainly from the control of Metopolophium dirhodum and Septoria spp. respectively. Both factors increased grain size and their effects were more than additive and greater with 250 than with 160 kg N/ha. Aphicide and fungicide also temporarily decreased the numbers of microbes on the developing ears. Autumn pesticide gave good control of aphids in the winter and some control in the summer: it also decreased nematode populations and slightly increased yields.Precision sowing compared with random distribution of seeds along the row had little effect on growth or yield. Sowing on 21 September compared with 13 October greatly increased growth early in the season but had less effect after anthesis; it was the only factor that increased yield when aphicide and fungicide were applied. There was negligible infection by barley yellow dwarf virus in crops sown on either date. The amount and division of N fertilizer affected N uptake early in the season and had small effects on the production and survival of tillers. Three N applications instead of one slightly increased grain yields but did not affect total N uptake by grains plus straw, which averaged 190 kg N/ha. The larger amount of N always increased N uptake but decreased yield in the absence of aphicide and fungicide. Irrigation slightly decreased yield despite prolonging the duration of green leaf area.

Description: Ice at depth in ice sheets can be softer in bed-parallel shear than Glen’s flow law predicts. For example, at Dye 3, Greenland, enhancement factors of 3 4 are needed in order to explain the rate of borehole tilting Previous authors have identified crystal fabric as the dominant contributor, but the role of impurities and crystal size is still incompletely resolved. Here we use two formulations of anisotropic flow laws for ice (Azuma’s and Sachs’ models) to account for the effects of anisotropy, and show that the measured anisotropy of the ice at Dye 3 cannot explain all the detailed variations in the measured strain rates, the jump in enhancement across the Holocene–Wisconsin boundary is larger than expected from the measured fabrics alone. Dust and soluble-ion concentration divided by crystal size correlates well with the residual enhancement, indicating that most of the “excess deformation” may be due to impurities or crystal size. While the major features of the deformation at Dye 3 are explained by anisotropy and temperature, results also suggest that further research into the role of impurities and crystal size is warranted.

Description: Neoproterozoic–Cambrian rocks of the Zavkhan Basin (Govi-Altay, western Mongolia) comprise large-scale alternations of siliciclastic- and carbonate-dominated units (cf. ‘Grand Cycles’). Analysis of such depositional sequences near the base of the Cambrian confirms that the distribution of trace fossils, small shelly fossils and calcimicrobial structures was strongly controlled by ecology and taphonomy, corresponding to specific points in a sea-level cycle. Evolution of the Cambrian biota is thus viewed through aseries of narrow time windows, once only for each depositional cycle. Correlation of the Precambrian–Cambrian boundary level on the basis of the first appearance of the Phycodes pedum assemblage is also fraught with difficulty, since stratigraphic resolution may be limited to a single sea-level cycle(c. 1–5 Ma). It is suggested that, in many cases, basin analysis will need to be undertaken before this boundary can be drawn.