ALBERT

Description: The horseshoe vortex formed around the base of a cylinder by a separating laminar boundary layer has been investigated experimentally. Smoke flow visualization shows that both steady and unsteady vortex systems exist. Pressure distributions beneath both types of vortex system have been measured and the variation of the horseshoe vortex position on the plane of symmetry upstream of the cylinder has been determined. Unsteady horseshoe vortex systems are shown to have a complex oscillatory behaviour and the nature of this oscillatory behaviour is described. Using smoke flow visualization techniques some measurements have been made of the velocity distributions within horseshoe vortex systems. © 1979, Cambridge University Press

Description: 1. Studies were made during the 1951 and 1952 seasons of the oxalate contents of the leaves of mangolds, sugar mangolds and fodder sugar beet.2. In all varieties greater concentrations of total oxalates were found during the summer months, the amounts diminishing gradually as the season advanced. Up to 12% was found in the dry-matter of mangold leaves and 9% in fodder sugar-beet leaves in July, these levels falling to 3% by mid-winter. There is some evidence that these changes are due in part to loss of outer leaves.3. Roughly one-third of the oxalates are present in water-soluble form. The addition of 1 part of chalk to 1000 parts of leaves, as has been generally recommended, is theoretically sufficient to render unavailable the soluble oxalates present during winter, but insufficient for leaves fed earlier hi the season.4. A number of observations showed small reductions in the soluble oxalate contents of the leaves due to wilting, but there were exceptions to this, and these appear to be related to sampling periods rather than to varieties.5. Insoluble oxalates appear to be unaffected by wilting and may show apparent increases in amount due to respiration losses of labile leaf constituents. The insoluble/soluble oxalate ratio is thus changed by wilting.6. It is suggested that the undesirable effects sometimes resulting from the feeding of beet leaves to livestock may not be due to oxalates, but that other factors present, which are labile during wilting, may be involved.

Description: 1. Studies were made of the effects of varying ground water-levels upon the productivity and composition of Italian Ryegrass grown on a calcareous light peat in the Fenland area. Six cuts were taken throughout the season at 3 to 4-weekly intervals.2. High ground water-level (approximately 15in. below ground surface) had a very deleterious effect on the total yield of fresh grass and of dry matter. Yields were little more than half of those obtained at medium and low water-levels (24 and 38 in. below ground surface, respectively).3. High water-level apparently interfered with nitrogen metabolism in the soil, and considerably lower percentages of crude protein were found in the grass growing on the high water-level plots than at the other levels. On the other hand, the percentage of crude fibre remained fairly constant for all levels of ground water.4. High water-level also had a depressing effect on the percentage of potassium, magnesium and chlorine in the grass. It had no obvious effect upon the calcium and phosphorus levels in the plants. The silica content of the grass rose steadily as the season advanced, this being most marked on the high water-level plots.5. Physical examination of typical plants showed the effect of the various ground water-levels upon the development of the root systems, with consequent effect upon the chemical composition of the grass.6. The composition of hay and aftermath showed similar changes to those reported for the green herbage.7. The findings are discussed in relation to grassdrying policies in Fenland areas.

Description: SUMMARYA scheme was developed to describe how the rate at which apical primordia are initiated in cereals depends on temperature and photoperiod. It was used to analyse initiation in field crops of winter wheat (Triticum aestivum L., cv. Maris Huntsman).For the initiation of leaves and spikelets, a straightforward linear regression of initiation rate R against mean air temperature (Ta) gave base temperatures (Tb) close to 0 °C for leaves and for spikelets. However, initiation rate was also correlated with mean photoperiod (P) and base photoperiods (Pb) of –0·5 h and 4h were established for leaf and spikelet initiation. When R was correlated with the index (T – Tb) (P – Pb), r2 was 0·62 for both leaves and spikelets.

Description: SummaryAn experiment to measure the variation in the phenological and apical development ofwinter wheat (cv. Avalon) in England and Scotland is described. Ten sites which ranged from Aberdeen (57·2° N), the most northerly, to Newton Abbot (50·6° N), the most southerly, were included in the survey, and at each site seed was hand-sown in mid-September, October and November 1983. Developmental stages and sampling procedures were precisely defined to ensure uniformity in scoring by the observers at each site. Temperatures during the growing season were in line with the long-term means, though spring was cooler at all sites and summer warmer at most. The range of monthly-mean temperatures between sites was about the same as the difference between consecutive months. The method of analysis of development rates and durations was in terms of thermal time, modified by sensitivity to photoperiod and a vernalization requirement that slowed early development until a number of days of low temperatures had been experienced. In general, crops at northern sites developed more slowly than those in the south and particularly the south-west of England. There was less variation in the timing of apical stages for later sowings. Developmental rates responded linearly to temperature and photoperiod, with the base temperature increasing for later phases of development. The effect of photoperiod in modifying the rate of development was apparent for all developmental phases from emergence to anthesis, longer days accelerating development, but there was no effect on the duration of the grain-filling period. Vernalization exerted its effect solely within the phase from emergence to double ridge, and had a major influence on the variation between sites only for the first sowing.

Description: SummaryThe initiation of leaf and spikelet primordia was studied at sites ranging in latitude from Newton Abbot (50·6°N) to Aberdeen (57·2°N) in crops sown in the middle of September, October and November 1983. The rate of primordium initiation tended to decrease from south to north but there were also marked differences between quite close sites.The rate of leaf initiation increased with temperature but photoperiod had little effect; the rate of spikelet initiation was affected both by temperature and by photoperiod. There were differences in the total number of leaves initiated which were only partlyexplained by differences in vernalization.Expressing leaf and spikelet initiation rates in terms of thermal and photo-thermal time respectively showed a constant rate of leaf initiation and a constant and more rapid rate of spikelet initiation.

Description: SUMMARYMain-stem apical development and its inter-relations with other aspects of plant morphology were studied in seven field crops of winter wheat (Triticum aestivum L., cv. Maris Huntsman).Apical primordia were produced slowly in autumn and winter, then faster in spring as the weather became warmer. Spikelets were initiated about three times as fast as leaves. Leaf initiation ended at around the time that tiller bud initiation stopped. Apical dome length and diameter both increased during leaf initiation, reached a maximum at double ridges and then decreased. Double ridges appeared when very nearly 50% (range 49–52%) of the final number of spikelets was present. Spikelet initiation ended a few days after the first florets were initiated and when stem extension began, but usually before the stem apex rose above the soil. Floret initiation finished at about the time that the flag leaf appeared. Throughout tillering there was a strong association between tiller emergence and leaf appearance.There were considerable differences between seasons in the timing of developmental events on the apices of main stems, but a difference in sowing date of 5 months was reduced to little more than 1 month in the timing of anthesis and the maximum numbers of organs varied only slightly with sowing date.

Description: 1. Studies were made of the composition of Giant sainfoin cut successively at different stages of growth in two seasons under contrasting conditions of weather and soil.2. Cuts were taken at preflowering, early- and full-flowering stages of growth. Yields of both fresh material and dry matter substantiated the usual farming practice of taking two cuts at full flower in one season, and indicate that cutting sainfoin before it comes into bloom has a seriously depressing effect on productivity.3. Like most green fodder crops, sainfoin has a lower content of crude protein and nitrogen-free extractives, and a higher content of crude fibre as the plant increases in maturity. The mineral content is somewhat variable, and in particular the potassium content appears to reflect the status of this element in the soil.4. The ratio of leaf dry matter to total dry matter of the plant decreases with advancing maturity. The leaf composition is fairly constant, irrespective of stage of growth, number of cuts and season, the fibre content being remarkably constant in contrast with that of stem, where it increases with advancing maturity. Leaf is richer than stem in crude protein, ether extract and total mineral matter, particularly calcium. Thus changes which do occur in the composition of the plant are due to variations in stem composition and leaf-stem ratio.5. Analyses of sainfoin hay, made under both experimental and commercial conditions, are discussed, and the range of variation in the main constituents of thirty-five commercial samples is commented upon.6. The present investigations into the composition of sainfoin, both as green fodder and as hay, show figures that differ appreciably from those derived from earlier German work. Examination of the data available for the nutritive value of fresh and conserved sainfoin reveal anomalies which suggest that such data are not typical of the crop as grown in this country, and also suggest the need for more modern data.

Description: 1. Further studies were carried out during 1950 on the effects of different ground water-levels upon the productivity and composition of Italian ryegrass grown on a calcareous light peat soil. The season was an unusually wet one, in contrast with the dry season experienced in 1949.2. Seven successive cuts were taken during the season from each of two crops of ryegrass, one following a crop of marrow-stem kale, and the other a crop of celery. Different amounts of a general compound fertilizer had been applied.3. Generally, the findings confirmed those of the previous year's investigation. High ground waterlevel (approximately 18 in. below ground surface) had a deleterious effect upon the yield and quality of ryegrass as reflected by its protein content, compared with the medium and low water-levels (23 and 30 in. below ground surface, respectively).4. The high water-level also had a depressing effect upon the percentage of potassium and magnesium in the grass, but had no consistent effect upon calcium and phosphorus. The silica content rose steadily in all cases as the season advanced, as occurred in the previous year.5. Residual manuring effects were well marked in the crop following celery. The total yields of dry matter from the medium and low water-levels considerably exceeded those of similar plots following kale, and the protein contents were also appreciably higher. This demonstrates the advantages of a high soil nutrient status, under conditions of suitable water-levels, for a crop of fenland grass.6. A high water-level inhibited growth and quality, irrespective of the nutrient status of the soil.