bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soil moisture changes under grassland as measured by neutron probe in midland England
Authors: Hall D. G. M. , Jones R. J. A. 
Published: March 2009

SUMMARYThe moisture regimes of three soils under grassland in midland England were investigated using a neutron probe moisture meter from May 1976 until August 1978. The main aim of the experiments was to compare the differential build-up of moisture deficits in the three soils of different texture by monitoring moisture extraction down to 1·50 m depth. The moisture deficits measured by neutron probe were also compared with those predicted from meteorological data using the Grindley (1970) model.The sandy (Newport) soil dried out more quickly and more completely than the clayey (Worcester) or fine loamy over clayey stagnogley (Salop) soil, particularly in 1976. This reflected the fact that the former had the smallest available water, most of which is held at low suctions, whereas the Salop soil, with much of its water bound at high suctions, continued to supply small amounts to plant roots when the available water in both the other soils was exhausted.The soil moisture deficits determined from neutron probe measurements were much larger at all three sites in 1976 than in the following 2 years. The deficit increased more slowly in the Salop soil than in the other two in the early part of 1976 and more slowly than predicted by the Grindley model. However, during July and August of the same year, deficits in the Salop and Worcester soils increased more quickly than predicted and maximum deficits were in proportion to the available water capacities of the three soils. Deficits in 1978 were very small (less than 70 mm) in all three soils because of the wetter weather.The results of this neutron probe study clearly show that the patterns of moisture extraction and the maximum deficits which developed in the three soils, particularly in 1976, are closely related to their physical properties, as determined from undisturbed soil cores.
Accumulated day-degrees as a measure of physiological age and the relationships with growth and yield in early potato varieties
Authors: O'Brien P. J. , Allen E. J. , Bean J. N. , Griffith R. L. , Jones Susan A. , Jones J. L. 
Published: March 2009

SUMMARYData from nine experiments from 1973 to 1981 which examined the effects of physiological age on sprout and field growth of early potato varieties are reported. Length of longest sprout per tuber and all aspects of field growth were related to number of daydegrees > 4 °C experienced by the seed after onset of sprout growth (measured as the appearance of a 3 mm sprout). It is, therefore, suggested that this scale is an effective measure of physiological age. In Home Guard and Maris Bard, increasing age of seed tubers resulted in earlier emergence and tuber initiation, larger early leaf areas and increased early tuber yields. As growth proceeded young seed produced the largest and most persistent leaf areas and the yields surpassed those of older seed and in some experiments yields decreased with increasing age at the final harvests.Optimum ages for specific harvesting periods were determined from regressions of tuber yield on age. In both varieties, they decreased with delay in harvesting. However, optimum ages differed in the two varieties and the implications for production and storage of seed and testing of varieties are discussed.
The comparison of five response curves for representing the relationship between the annual dry-matter yield of grass herbage and fertilizer nitrogen
Authors: Sparrow P. E. 
Published: March 2009

SUMMARYThe results of 84 experiments with six levels of nitrogen were used to investigateresponse curves relating the dry-matter yield of grass herbage to fertilizer nitrogen. Of the five curves tested, the inverse quadratic represented the relationship well, although no one curve fitted best on all experiments.
A simple technique to evaluate the effect of mechanical stress on root growth
Authors: Chaudhary M. R. , Aggarwal G. C. 
Published: March 2009

SummaryA simple technique to evaluate accurately the effect of mechanical stress on root growth has been developed. The roots are allowed to grow against a predetermined pressure in the chamber of a pressure-plate apparatus. The root growth was studied against the applied pressures of 0, 2, 4, 6, 8 and 10 bar. A relationship of the form Y = aXb was observed between the rate of root elongation (Y) and applied pressure (X).
Dry-matter distribution and seasonal yield changes in five contrasting genotypes of white clover
Authors: Haycock R. 
Published: March 2009

SummaryA field trial of five contrasting types of white clover grown in monoculture was established in August 1978. Measurements commenced in October and continued for 12 months during which time no additional treatments were applied.Seasonal trends of dry-matter accumulation and distribution were recorded and particular reference was made to the components of harvestable yields, which showed a strong seasonal trend. During the summer the density of growing points decreased in all types except D while the number of leaves per growing point and mean dry weight per leaf increased. The principal component of yield, mean dry weight per leaf, increased later than number of leaves per growing point. Stolons did not show the same cyclical pattern and produced an overall increase during the experiment. The five genotypes also showed large variation in the distribution of dry matter between leaves, flowers, stolons and roots.
Grazing studies on the Guadalcanal Plains, Solomon Islands
Authors: Smith M. A. , Whiteman P. C. 
Published: March 2009

SummaryPastures of a mixture of Brachiaria mutica(para) and B. decumbens(signal) grown with Gentrosema pubescens(centro) and Macroptilium atropurpureumcv. Siratro and grazed at three stocking rates 1·8, 2·1 and 3·6 animals/ha for 5 and 6 years of grazing were compared with B. humidicolacv. Tully (Koronivia) oversown with centro and siratro and grazed at 3·0, 3·6 and 4·5 animals/ha and native pastures of Themedaaustralis and Pennisetum polystachyon oversown with Stylosanthes guianensis cv. Schofield after burning, and grazed at 1·3, 2·0 and 2·7 animals/ha. All pastures were given 20 kg/ha of sulphur.The para and centro pasture gave the highest live-weight gain with 731 kg/ha/year when stocked at 3·6 animals/ha in 1979–80. and 592 kg/ha/year in 1980–1. Signal grass gave 621 and 493 kg/ha/year in 1979–80 and 1980–1 at 3·6 animals/ha. Koronivia grass gave similar production as signal: 639, 466 and 406 kg/ha/year at 3·6 animals/ha stocking rate from 1979 to 1982. On the natural pastures 1st year gains were high, 412 kg/ha/year at 2·7 animals/ha, but declined to 224 kg/ha/year at 2·0 animals/ha in year 2.In the para pastures, centro increased up to 50%, while with signal it increased to 25% of the botanical composition, owing to a decline in grass dry matter. In koronivia pastures, centro and siratro declined, inversely with stocking rate, and M.pudica increased in the high stocking rate. In the natural pastures T. triandra declined with increasing stocking, to 1% at 2·7 animals/ha. P. polystachyon remained approximately stable. M. pudica became important as grazing increased, and weeds also increased. Para grass was high in N, P, S and Na. N was low in signal, koronivia and T. triandra while the concentration of Na (0·41%) was high in koronivia, but it was extremely low in signal and T. triandra(0·02%).The trials suggest that landholders could commence grazing of existing natural pastures for up to 2 years at about 2·0 animals/ha in the 1st year and 1·3 animals/ha in subsequent years to obtain 350 kg LWG/ha in year 1 and the 200 kg LWG/ha thereafter. With cultivated pastures much higher yield can be obtained using para plus centro on the low-lying aieas, and signal plus centro plus siratro on non-flooded areas. Koronivia can be used in occasionally intensively stocked areas. All pastures require S fertilizer every 2 years.
The productivity of native grasslands oversown with legumes and grazed at five stocking rates in north-east Thailand
Authors: Gutteridge R. C. 
Published: March 2009

SummaryStylosanthes humilis cv. Lawson, S. hamatacv. Verano, S. guianensis cv. Endeavour and Macroptilium atropurpureum cv. Siratro were oversown into native grassland dominated by Arundinaria ciliata and grazed by cattle at 2·5, 3·5, 4·5, 5·5 and 6·5 animal units/ha per half-year during the wet season for 4 years.Siratro was the most persistent of the legumes but its susceptibility to heavy grazing pressure limited its contribution at the higher stocking rates. At the start of grazing its mean yield was 1420 kg/ha representing 40 % of total pasture yield while at the end of 4 years in the lowest stocking rate treatment it comprised 18% of total yield at 460 kg/ha.The long-term productivity of the three Stylosanthes species was poor and their percentage contribution to the pastures was either zero or very low by the end of 4 years. Yield of Verano, the most successful of the three, declined from 5000 kg/ha in 1977 to 20 kg/ha in 1980. The main factor contributing to the poor performance of these species was the strongly competitive nature of A. ciliata. Percentage composition, height and yield of this tall, rhizomatous grass increased with time independent of stocking rate, and the illuminance of the Verano canopy was reduced to 0·38–0·65 full sunlight. Cattle showed negative selection for bamboo grass and consumed leaf but not stem; leaf to stem ratio was negatively (and unusually) related to stocking rate.Stocking rate effects were reduced by the intervening dry season resting periods and the over-riding influence of other factors such as the prevailing climatic conditions, disease occurrence and plant interference.
Studies on thiaminase I activity in ruminant faeces and rumen bacteria
Authors: Boyd J. W. 
Published: March 2009

SummaryKinetic studies of thiaminase I in extracts of ruminant faeces showed that the affinity for one substrate varied with the concentration of the other substrate in the manner of a two-step transfer mechanism. When the alternate substrate concentration was optimal, the apparent Michaelis constant (Km) for thiamine was 176 μΜ and the apparent Km for aniline was 3·19 mΜ. It is recommended that in routine thiaminase assays, the thiamine and aniline concentrations should be at least 1·5 and 25 mΜ, respectively. When non-saturating concentrations of thiamine are used in thiaminase assays the results should be reported as unimolecular reaction constants since the enzyme activity can be calculated only if suitable Km data have been determined.Improved radioactive and colorimetric thiaminase assays with saturating substrate concentrations gave similar results. The analytical variation of the colorimetric method was rather high but this method may be useful for laboratories which lack radioactive isotope facilities.Thiaminase assays were performed on cultures of 14 species of rumen bacteria. Only Megasphaera elsdenii had thiaminase activity and its cosubstrate specificity was different from the rumen thiaminase associated with cerebrocortical necrosis in ruminants. It was concluded that the source of rumen thiaminase in that disease has yet to be identified.
The teart pastures of Somerset: III. Reducing the teartness of pasture herbage
Authors: Lewis A. H. 
Published: March 2009

1. Clovers and Yorkshire fog are outstanding among pasture plants in their ability to absorb molybdenum from teart soils. Many teart pastures contain a fair amount of clover, but Yorkshire fog is only a very minor component of the herbage. Other grasses as well as Yorkshire fog often contain enough molybdenum to cause scouring.2. Acidic nitrogenous fertilizers decrease teartness by suppressing clovers and by reducing molybdenum uptake by grasses.3. Acidification of the soil by regular applications of sulphur would reduce the availability of molybdenum in the soil.4. Basic materials, such as lime and slag, increase molybdenum uptake by grasses on acid soils which contain a fair amount of molybdenum. They also encourage clovers and should, therefore, be used only with the greatest discretion on such soils.5. The percentage molybdenum content of newlysown grasses is low, but it increases with age. A system of short leys consisting largely of grasses would give an increased output of material of low molybdenum content.
Effects on wool growth of the infusion of mixtures of amino acids into the abomasum of sheep
Authors: Reis P. J. , Tunks D. A. 
Published: March 2009

SUMMARYMerino sheep were given abomasal infusions of either mixtures of amino acids or protein during periods of 8 or 12 days. Effects on wool growth were measured using autoradiography and a clipping procedure which allowed time for the emergence of the wool fibres. Estimates of volume growth rate, from the autoradiographic measurements, and of mass of wool grown, from clipping, were in good agreement.An infusion of a standard mixture of 13 amino acids, which included ten essential amino acids in approximately the proportions in casein, consistently stimulated wool growth. The mean increases in volume and mass of wool grown, during 30 infusions, were 66 and 67% respectively. A mixture of ten essential amino acids alone appeared to be as effective as the standard mixture for stimulating wool growth, and there were no significant differences between the effects on wool growth of casein and the standard mixture of amino acids.The omission of methionine from an infusion of the standard mixture of amino acids, or from a mixture of essential amino acids only, inhibited wool growth rate; both fibre diameter and length of wool grown per day were reduced to below the control values. In addition, the strength of the fibres was considerably reduced.Infusions of zein and of an amino acid mixture simulating the essential amino acid composition of zein both inhibited wool growth rate, due to a reduction in fibre diameter. Similar effects on wool growth were observed when any one of three essential amino acids (lysine, isoleucine or leucine) was omitted from an infusion of the standard mixture of amino acids. The omission of five other essential amino acids (arginine, histidine, phenylalanine, threonine or valine) from the infusion, or variations in the proportions of leucine, lysine or methionine, had no appreciable effects on wool growth.
On the validity of Fisher'sztest when applied to an actual example of non-normal data. (With five text-figures.)
Authors: Eden T. , Yates F. 
Published: March 2009

Summary1. Previous work on the validity of thetandztests on non-normal distributions is described. The question as to whether these tests, which are all on small samples from theoretical distributions, are really apposite is discussed.2. The necessity of making a practical test with actual data which shall comply with the usual conditions obtaining in agricultural experiments is urged.3. A practical test has been made on a skew distribution obtained from the observation of 256 height measurements on wheat. The distribution of the values of R. A. Fisher'szfrom a thousand random samples has been obtained and found to agree satisfactorily with the theoretical distribution.
The study of the conditions and factors affecting hair growth in the guinea-Pig (With Plates II and III and seven text-figures.)
Authors: Strangeways D. H. 
Published: March 2009

Summary1. A method for the weekly determination of the amount of hair produced on defined areas of skin is described.2. The normal hair growth in adult male and female guinea-pigs has been determined. It is shown that the amount of hair produced on a defined area of skin in equal intervals of time is not constant. The fluctuations are mainly due to variations in the number of follicles which are active.3. There seem to be two periods during the year when an increased production occurs in most animals, in late spring and autumn. The times of increased hair growth correspond approximately to the occurrence of the moult.4. Measurements have been made of the length of the fibres at the end of a week's growth. It is found that fibres of all lengths are present and that the maximum length at the end of any week in any stage of the cycle is 5 mm.
Lamb birthcoat relationship to the adult fleece in Merino, coarse wool Barki and Merino × Barki sheep crosses
Authors: Guirgis R. A. 
Published: March 2009

SUMMARYThe present study was carried out on adult fleeces, of Merino, coarse wool Barki and five of their crosses, of known birthcoats. The adult fleece traits studied were clean fleece weight, mean fibre diameter and its variability and mean staple length and its variability.Birthcoat-adult fleece relationship was dependent on the breed studied. In Barki, plateau array in the birthcoat developed to adult fleeces with higher values of mean fibre diameter and its variability, mean staple length and clean fleece weight than those with saddle array. In ⅝ Merino there was a gradient in staple length, running from plateau, via saddle, to ravine, with higher values of the coarser arrays. Differences occurred in variability of fibre diameter between plateau and saddle arrays in ⅜ and ⅝ Merino and between saddle and ravine in ½, ⅝ and ¾ Merino.Differences occurred where birthcoats, with plateau array with precipice, in the curly-tip group, grew into adult fleeces with longer mean staple than those with transition in Barki sheep. In the other breed groups differences observed in saddle array, with different features, precipice or transition, at the birthcoat level, did not contribute differences in their adult fleeces.Selection of Barki lambs with plateau fibre type array in their birthcoats would result in higher clean adult fleece weights that have coarser fibre diameter, with higher variability, and longer staple than those with saddle array. Within saddle array, selection of those with reduced SK% would develop into adult fleeces with higher clean fleece weight and those with reduced CT% would grow into adult fleeces with finer diameter.Selection of lambs that have birthcoat ravine array in f, ⅜, ½, ⅝ and ¾ Merino would reduce the within-staple variability in their adult fleece fibre diameter.
The effects of plane of nutrition, genotype and sex on growth, body composition and wool production in grazing sheep
Authors: Kellaway R. C. 
Published: March 2009

SummaryGrowth rates, chemical composition of the body and wool production were measured with wethers and ewes from two genotypes of sheep grazing at two planes of nutrition. The nutritional treatments were applied after weaning at 12 kg live weight. Animals were slaughtered at 6 kg intervals between 12 and 54 kg live weight.Dorset Horn × (Border Leicester × Merino) lambs grew 57% faster than South Australian Merino lambs before weaning, produced 22% more wool and contained more fat at weaning.Post-weaning growth rates on the high and low planes of nutrition were 168 and 78g/day for Merinos and 183 and 116 g/day for Cross-breds. Despite these differences, there was virtually no effect on body composition. Sheep which were starved and re-grown also had a similar body composition to sheep grown continuously.There was, however, a nutritional effect on wool production. On the high plane of nutrition the rate of wool production was 22% higher than on the low plane of nutrition.After weaning there were only small differences in the growth rate of the two genotypes but the Merinos grew 30% more wool than Cross-breds on the high plane of nutrition and 39% more wool on the low plane of nutrition. Genotype differences in the fat and protein content of the empty body were small, but Merinos contained more ash, Ca, P and Mg.After weaning the normal pattern of allometric growth was reversed; at 18 kg live weight the sheep contained a lower proportion of fat and higher proportion of water than at 12 kg live weight. Above 18 kg live weight normal allometric growth was resumed. The fat-free empty body became progressively less hydrated but the ratio of protein: ash remained constant at 79:21 for Merinos and 81:19 for Cross-breds.There was a trend towards ewes being fatter than wethers, but this was only significant with Merinos. Other sex differences in body composition, body growth and wool growth were not significant.
Effects of seed covering treatments on the emergence and seedling growth of crisp lettuce drilled with an experimental dibber drill
Authors: Wurr D. C. E. , Fellows Jane R. , Bufton L. P. 
Published: March 2009

SUMMARYPelleted seed of the crisp lettuce variety Pennlake was sown on five occasions with units from either the experimental dibber drill designed by the National Institute of Agricultural Engineering or a Stanhay S870 drill. There were three dibber-drill treatments: seeds left in open holes or covered with peat–vermiculite or perlite. Seedling emergence and growth from each sowing of the four drill treatments were compared under different moisture regimes.There were large differences between drill treatments in emergence percentage, time to emergence of 50% of the seedlings which emerged (t50) and seedling weight at all sowings but there was a significant effect of drill treatment on the standard deviation of seedling emergence times at only one sowing. Of the dibber-drill treatments, only very occasionally did open holes or perlite cover give significantly better emergence than peat-vermiculite cover, which gave the most consistent results. In general, the dibber drill with peat-vermiculite cover gave significantly faster and higher emergence and heavier seedlings than the Stanhay drill. Differences in percentage seedling emergence tended to be greater under dry conditions.