ALBERT

Description: Field trials were conducted at six sites throughout Ireland in 1992, 1993 and 1994, to assess the efficiency of utilization of N in cattle slurry treated with nitric acid. Slurries were left untreated or were acidified to pH 5·5 with 12 m nitric acid immediately prior to spreading. Slurries were either band-spread or splashplate-spread using an automated tanker system. The efficiency of N (NH+4-N+NO−3-N) in slurry for grass production (Eff-N%) was measured by comparing N offtake values with those from a range of rates of inorganic fertilizer N (ammonium nitrate/calcium carbonate) treatments. Slurry was applied at rates (13–28 m3/ha) which supplied N (NH+4-N+NO−3-N) below the highest inorganic fertilizer treatment. In all experiments, untreated cattle slurry was compared with nitric acid-treated cattle slurry at the same rate of application. The Eff-N% values for unacidified or acidified slurries were highly variable by both spreading methods. The effect of spreading method depended on whether or not the slurry was acidified. On average the Eff-N% value of the band-spread unacidified slurry (59%) was significantly higher than the Eff-N% value of the splashplate-spread slurry (37%). For acidified slurry, the average Eff-N% value of the band-spread slurry (85%) was not significantly different from the Eff-N% value of the splashplate-spread slurry (81%). The overall average Eff-N% value of the acidified slurry was 83% which was significantly less than 100%. Cattle slurry acidified with nitric acid to pH 5·5 was more variable and less efficient than inorganic fertilizer N under the soil and climatic conditions tested.

Description: Detailed information on the timing of terminal spikelet formation, anthesis, maturity and the rate of leaf appearance is crucial to the predictive accuracy of the AFRCWHEAT2 growth simulation model for wheat. To obtain appropriate data under different growing conditions for two spring wheat (Triticum aestivum L.) cultivars (cvs Minaret and Canon), a main field experiment was conducted comprising eight sowing dates between mid-March and late June 1994; data from single sowings of Minaret in 1992 and 1995 were also included in the analysis. Minaret is the focus of a major European study of the impact of climate change factors on the growth and development of wheat, and data of the type reported here were essential to support the modelling aspects of the project involving AFRCWHEAT2.The accumulated thermal time from emergence to critical developmental stages was similar for all sowings of both cultivars, even though biomass was greatly reduced in the later sowings. Although final leaf numbers were comparable for all sowing dates, the rate of leaf appearance was correlated with the rate of change of day length at crop emergence in Minaret. The unmodified AFRCWHEAT2 model did not predict the timing of critical growth stages and leaf numbers well, but removal of the vernalization and photoperiod factors from the developmental sub-model greatly improved the accuracy of such predictions. These results strongly suggest that fixed quantities of thermal time may be employed successfully to predict the timing of critical developmental stages of these spring wheat cultivars over a range of sowing dates, geographic locations and climatic conditions, since development appeared to be a linear function of temperature.Despite removing the photoperiod and vernalization functions, the model consistently over-predicted final leaf number because leaf production by the model continued until 1·8 phyllochrons before anthesis, as compared to the three phyllochrons actually recorded for Minaret. AFRCWHEAT2 could therefore be further modified to reproduce more accurately the smaller number of leaves typical of these spring cultivars.

Description: SummaryEleven single-rearing and 14 twin-rearing Greyface (Border-Leicester × Scottish Blackface) ewes which had previously been individually fed indoors on three nutritional treatments (treatment 1, adequately nourished; treatment 2, moderately undernourished; treatment 3, severely undernourished) during the final 6 weeks of pregnancy, were subsequently grazed with eight non-lactating Greyface ewes on a ryegrass–white clover pasture for the first 14 weeks of lactation.Herbage organic matter (OM) intakes and milk yields of ewes were measured weekly and the herbage OM intakes of lambs from week 7 of lactation.Mean daily OM intakes were 36·6 (± 1·09), 38·9 (± 0·99) and 26·4 (± 0·93) g OM/kg body-weight for single- and twin-rearing, and non-lactating ewes respectively. Prepartum nutrition had no effect on intake. Maximum intakes were achieved in week 5 for twin-rearing ewes (53 g OM/kg) and week 4 for single and non-lactating ewes (54 and 38 g OM/kg respectively).Mean daily weight gains over the period for single-, twin-rearing and non-lactating ewes were 89 (±22·2), 73 (±16·1) and 182 (±22·5)g respectively. There were no differences due to prepartum treatment.There were significant differences (P 〈 0·05) in milk production between singleand twin-rearing ewes in the first 5 weeks of lactation. Twin-rearing ewes of prepartum treatment 1 produced consistently more milk in weeks 2, 3 and 4 of lactation, whereas ewes from treatment 3 tended to produce more milk than ewes from the other treatment groups thereafter.Milk intakes of single lambs were always significantly greater than individual twin lambs, and single lambs ate significantly less grass during the herbage OM intake measurement period from week 7; their growth rates up to week 7 were also significantly greater.No differences in the intake or growth rate of lambs could be attributed to the prepartum nutritional treatment of their dams.Ewe maintenance requirements during lactation were estimated to be 242 (± 35·1) kJ ME/kg body weight/day; the efficiency with which ME was used for milk production to be 59%; and the efficiency with which ME was used for body-weight gain, 53%.Lamb maintenance requirements were estimated to be 427 (± 143) kJ ME/kg W in weeks 1 and 2 of lactation and 287 (± 44·2) kJ/kg from week 7. Efficiency of utilization of energy for body-weight gain in each period was estimated to be 71 and 80% respectively.

Description: For very small samples, it is difficult to prepare graphitic targets that will yield a useful and steady sputtered ion beam. Working with materials separated by preparative capillary gas chromatography, we have succeeded with amounts as small as 20 μg C. This seems to be a practical limit, as it involves 1) multiple chromatographic runs with trapping of effluent fractions, 2) recovery and combustion of the fractions, 3) graphitization and 4) compression of the resultant graphite/cobalt matrix into a good sputter target. Through such slow and intricate work, radiocarbon ages of lignin derivatives and hydrocarbons from coastal sediments have been determined. If this could be accomplished as an “online” measurement by flowing the analytes directly into a microwave gas ion source, with a carrier gas, then the number of processing steps could be minimized. Such a system would be useful not just for chromatographic effluents, but for any gaseous material, such as CO2 produced from carbonates. We describe tests using such an ion source.

Description: Layers of volcanic ash, or tephra form widespread chronostratigraphic marker horizons which are important because of their distinctive characteristics and rapid deposition over large areas. Absolute dating of prehistoric layers effectively depends upon 14C analysis. We focus here on Icelandic tephra layers at both proximal and distal sites and consider three strategies to obtain age estimates: 1) the conventional dating of individual profiles; 2) high-precision multisample techniques or “wiggle-matching” using stratigraphic sequences of peat; and 3) a combination of routine analyses from multiple sites. The first approach is illustrated by the dating of a peat profile in Scotland containing tephra from the ad 1510 eruption of Hekla. This produced a 14C age compatible with ad 1510, independently derived by geochemical correlation with historically dated Icelandic deposits. In addition, the ca. 2100 bp date for the Glen Garry tephra in Scotland, determined by a series of dates on a peat profile in Caithness, is supported by its stratigraphic position within 14C dated profiles in Sutherland, and may be applied over a very large area of Scotland. More precise dates for individual tephras may be produced by “wiggle-matching”, although this approach could be biased by changes in peat-bog stratigraphy close to the position of the tephra fall. As appropriate sites for “wiggle-match” exercises may be found only for a few Icelandic tephras, we also consider the results of a spatial approach to 14C dating tephra layers. We combined dates on peat underlying the same layer at several sites to estimate the age of the tephra: 3826 ± 12 bp for the Hekla-4 tephra and 2879 ± 34 bp for the Hekla-3 tephra. This approach is effective in terms of cost, the need for widespread applicability to Icelandic tephra stratigraphy and the production of ages of a useful resolution. We stress the need for accurate identification of tephra deposits without which the conclusions drawn from subsequent 14C dating will be fundamentally flawed.

Description: SummaryA radiography unit was developed with which two technicians and two assistants were able to diagnose number of foetuses in 400–600 ewes per day on farms. Diagnoses made between 100 and 120 days of gestation in flocks where weekly mating records were made were 95–98% accurate as judged by lambing records. In most flocks more than 90% of twin pregnancies were correctly diagnosed. Agreement between diagnoses and lambing records was reduced when weekly mating records were not available. The radiographic examination had no detrimental effects on ewes or lambs.

Description: SUMMARYData on ovulation rate and numbers of ova and transferable embryos recovered from superovulated cattle and sheep were analysed using generalized linear models, quasi-likelihood, restricted maximum likelihood (REML) and generalized linear mixed models (GLMMS). The data pertained to the operation of nucleus breeding schemes in cattle and the commercial application of embryo transfer in sheep.Results of the analyses showed that generalized linear models involving Poisson and Binomial distributions were inappropriate because of over-dispersion, and that analyses using quasi-likelihood to model negative binomial and β-binomial distributions were more suitable. Factors identified as important in determining the results in cattle were the number of previous superovulations (a higher proportion of transferable embryos were obtained in the initial flush compared to subsequent recoveries in two out of three sets of data), the donor (significant in all analyses with repeated recoveries) and its mate (significant in some analyses). In sheep, the use of pFSH or hMG for superovulation increased embryo yields above those obtained with PMSG + GnRH. Analyses of a further data set for sheep showed the effect of breed was ambiguous.The effects of donors and their mates were treated as random effects in analyses involving REML and GLMMS. Results showed that the repeatability of the number of transferable embryos produced per donor ranged between 0·13 and 0·23 in three sets of data and was significant in all cases. In these analyses the variance among mates was not significantly different from zero.The results of analyses were used to develop a random generator to simulate the numbers of ova and embryos recovered from a cow following superovulation. By sampling from negative binomial distributions where the scale factor used for each cow was a normally distributed deviate, distributions were obtained which had the same mean, variance and repeatability as those observed.

Description: SUMMARYThe effect of water stress on nitrogen fixation in seven common bean (Phaseolus vulgaris L.) genotypes was investigated in Celaya, Gto., Mexico, in 1991. Beans were grown under four moisture regimes: (1) well-irrigated, control, (2) with water stress during the vegetative stage, (3) with water stress during the reproductive stage and (4) with water stress during the whole growing cycle. Biological nitrogen fixation was measured by 15N-isotope dilution using sorghum as a reference crop. Nodulation and N2-fixation data showed genotypic differences in response to water stress. Under non-stressed conditions, cv. Bayocel fixed the most nitrogen (85 kg/ha) and cultivar Flor de Mayo Baji'o the least (33 kg/ha). Under water stress at the reproductive stage, these cultivars fixed 9 and 6 kg N/ha, respectively. Water stress during the reproductive stage reduced nodulation by an average of 43% with no recovery after rewatering. Water stress during the reproductive stage had a greater effect on N2-fixation than on grain yield; in comparison to the control, N2-fixation was reduced to one sixth while grain yield was only reduced by 50%.

Description: Growth, shoot water relations and root hydraulic conductivity were studied in tomato plants (Lycopersicon esculentum cv. INCA9) subjected to different salt concentrations in the root medium. Two experiments were carried out at Instituto Nacional de Ciencias Agrícolas (INCA), Cuba, during May and June 1995. In the first experiment, plants were grown for 13 days in a nutrient solution with 0 or 100 mM NaCl. In the second experiment, the hydraulic conductivity was measured on roots submerged in nine different concentrations of NaCl up to 200 mM. The effect of temperature treatments between 0 and 50 °C on root hydraulic conductivity was also examined. Shoot growth, leaf water potential, leaf stomatal conductance, leaf relative water content and root hydraulic conductivity values decreased more rapidly in the treated plants than in control plants. A strong correlation was found between the root hydraulic conductivity and leaf water parameters, indicating that water flow through the roots was the main factor controlling shoot water relations.

Description: SUMMARYA model is derived that relates yield to levels of applied fertilizer in terms of parameters that have direct physical meaning. N8, P8, and K8 define the contribution of the soil to the supply of nitrogen, phosphorus and potassium for plant growth; BN, BP and BK define the responses to nitrogen, phosphorus and potassium fertilizer at low nutrient levels and aN is the level of nitrogen required to raise the osmotic pressure sufficiently to prevent growth.To test the model, field experiments were carried out on French beans and summer cabbage in which 125 different combinations of levels of nitrogen, phosphate and potassium fertilizers were applied. The yield data from each block of each experiment fitted the model very well. Fitted values differed from block to block but these differences could be attributed to the fact that for each block equally good fits were often obtained with widely differing parameter values. Estimates of N8 were made from chemical analysis of the (NH4 + NO3) — N of soil samples from the field plots, and P8, and K8 from chemical studies of the adsorption of phosphate and potassium on untreated soil. They were in substantial agreement with the average values obtained by the entirely different procedure of fitting the model to the yield data. Also estimated values for BN, BP and BK and aN from other chemical studies were consistent with those obtained by model fitting.It is concluded that although the theory has limitations it is broadly in accord with the results of the detailed field experiments.