bluuebunny/crossref_metadata_2025_split huggingface dataset:
Competition for plant nutrients in soil; a theoretical approach
Authors: Baldwin J. P. 
Published: March 2009

SummaryA mathematical model of whole plant growth in soil is presented. Particular emphasis is given to those factors which relate to the absorption of nutrients and water by the root system. There are two basic premises; that a plant is made up of two pools, structural material and precursors to structural material, and that structural material is produced by a reaction between a given ratio of precursors. The precursors are soluble carbohydrate and unbound nitrogen, probably nitrate. Increase in leaf area and root length is a consequence of absorbed nitrogen combining with photosynthate.The absorbing power and the distribution throughout the soil of the roots is controlled, through feedback mechanisms, by the ratio of the precursors, within the plant. The description of plant growth is interfaced with a model of one-dimensional flow of water and solutes in soil, and gives a model for investigating plant growth, or competition between root systems of more than one plant. The results of a number of simulations are presented. A sensitivity coefficient is defined to compare the effect of various properties on overall growth. Its value is calculated for 11 plant properties. It is some measure of the competitive advantage conferred on the plant by a change in the value of each property. The results of the competition experiments are given as replacement diagrams.The model has weaknesses. Because it is explicit, it defines in precise detail the experiments which would support the hypotheses, or suggest modifications to them. As a holistic analysis, it brings together ideas from different disciplines into one comprehensible framework.
The reaction of two spring wheat varieties exposed to epidemics of Septoria nodorum and S. tritici of varying intensity and duration
Authors: Jones D. G. , Rowling R. D. W. 
Published: March 2009

SummaryTwo spring wheat varieties, Cardinal and Kolibri, were inoculated with Septoria nodorum Berk and S. tritici Rob. & Desm. at Growth Stages 3, 7, 10.1 and 10.5 of the Feekes' scale. The treatments included single inoculations at each growth stage and multiple inoculations at 2, 3 and 4 of the above growth stages.Thousand-grain weights of both varieties were reduced by inoculation with either pathogen, S. nodorum causing the largest reduction. Numbers of grain per head in Cardinal were severely reduced by S. nodorum, particularly after the multiple inoculations. In Kolibri, there was evidence of increases in numbers of grain with S. tritici inoculation which nullified the grain size reductions. The results are discussed in relation to compensatory mechanisms and disease tolerance.
Genetic variation amongst swede varieties and their hybrids and their response to soil fertility
Authors: Denton O. A. , Whittington W. J. 
Published: March 2009

SummaryThe mean total yield and mean fresh weight of seven swede varieties and theirF1hybrids was increased primarily by nitrogen and also by phosphorus fertilizer. There was no evidence of genotype × environment interaction for characters concerned with yield except for dry-matter content where two varieties, Best-of-All and Reform, were less stable to fertility environments than the others. Heterosis was common amongstF1hybrids and this suggests their use in swede improvement: the inheritance pattern of root weight showed overdominance, shoot weight showed partial dominance and drymatter content showed additivity, with no evidence of gene interaction. Segregation for root fresh weight and dry-matter content occurred inF2populations and although an overall negative correlation was found there was evidence that progeny from certain crosses gave reasonable prospects of combining both characters.
Growth and yield of determinate and indeterminate cowpeas in dryland agriculture
Authors: Chaturvedi G. S. , Aggarwal P. K. , Sinha S. K. 
Published: March 2009

SummaryCowpea is an important food legume crop of arid and semi-arid regions of the tropics. In such climates whether a determinate or indeterminate type of growth habit would be more useful is not clear. In the present study a determinate and indeterminate cultivar of cowpea were grown at two population densities under rainfed conditions for 2 years. Grain yield was higher in the indeterminate variety for both years. At higher density more dry matter was produced but it had no effect on grain yield. Nitrogen analysis showed that it moved from leaves to developing pods. However, a large amount of nitrogen was still left in vegetative parts in contrast to cereals. Pod development was completed in 19 days and the rate of dry-matter accumulation during the peak period of growth was as high as 120 mg/day per fruit. It was difficult for the plant to cope with this high demand for photosynthates. It is suggested that more pods can develop on a plant provided the growth rate of individual pods is slower and extended to a longer period.
Selection indices using plant type characteristics in Navy beans (Phaseolus vulgaris L.)
Authors: Davis J. H. C. , Evans Alice M. 
Published: March 2009

SummaryA replicated trial of 18 families of Navy-bean breeding lines in the F4 generation was grown at Cambridge. The selection-index technique was used to investigate means of improving the efficiency of simultaneous selection for four criteria, namely yield, seed shape (numerical scores from ‘good’ to ‘poor’), early maturity and increased height of pod tips. Relative economic weights were chosen. The yield components and a range of characters describing plant type were measured making 15 characters in all, and combinations of these were included in 32 indices.It was predicted that simultaneous selection would be limited by adverse correlations between some of the four selection criteria, especially early maturity and height. The estimated efficiency of selection would hardly be improved by including information on the yield components. Combinations of the plant type characters, on the other hand, were predicted to provide considerable additional advance amounting to a 10% improvement when information on total number of nodes and inflorescences and hypocotyl diameter was included.It was concluded that the time involved in collecting yield component data would be better spent collecting information on a limited number of plant type characteristics in future trials, and that an ideal plant was one with reduced branching and a few heavily podded inflorescences borne on a tall plant with a strong base.
Effect of feeding a lupin grain supplement on reproductive performance of maiden and mature ewes
Authors: Brien F. D. , Cumming I. A. , Baxter R. W. 
Published: March 2009

SummaryA study was made of reproductive performance in 183 maiden and 218 mature ewes from a single Merino flock either with or without lupin grain supplement (Lupinus angustifolius cv. Uniwhite) at 500 g/head/day from 14 days prior to the introduction of the rams until 12 days post coitus. The ewes were grazed either on irrigated perennial pasture or hay fed on a fallow area. Ovulation rates increased (P < 0·01) in ewes which received the supplement. Insemination rates were not affected by the supplement, although embryo survival was reduced (P < 0·05). Feeding the lupin grain supplement did not increase the number of embryos present at days 28·31 post coitus. Ovulation rate and embryo survival were not influenced by diets of irrigated pasture or hay, although insemination rates of ewes tended to be lower when ewes grazed the irrigated pasture rather than hay.
Response by sugar beet to irrigation, 1965–75
Authors: Draycott A. P. , Messem A. B. 
Published: March 2009

SummarySugar yield increases from irrigation in 19 experiments on a sandy-loam soil at Broom's Barn over an 11-year period were examined in relation to rainfall and to both potential and measured soil moisture deficit. Irrigation increased average yield from 7·6 to 8·3 t sugar/ha and in six of the years significantly increased yield by more than 1 t sugar/ha (15%). The experiments also tested plant density, nitrogen, harvest date and time and amount of irrigation. Without irrigation, maximum sugar yield was from a density of 74000 plants/ha but larger densities gave slightly more yield when irrigated. Irrigation affected the magnitude of response to nitrogen but 100 kg N/ha gave the most profitable yield increase, both with and without irrigation. Yield increases of about 1 t sugar/ha (15%) between early and late harvesting were also independent of irrigation. Early irrigation of 25 mm and 50 mm in June and July respectively increased yield in 4 of the 5 years but in all years applications in late summer did not increase sugar yield. The main factors controlling the yield response to irrigation were period and size of deficit. The soil type and summer rainfall at Broom's Barn were compared with those in 36 other experiments at five localities between 1947 and 1973; yield increases at Broom's Barn were smaller, probably because the others were on lighter soils.
Systematic mixed stands of spring wheat cultivars
Authors: Prasad R. , Sharma S. N. 
Published: March 2009

SummaryHeight variability in spring wheat (Triticum aestivum L.) cultivars permits growing them in systematic mixed stands and such mixtures are reported to lead to better utilization of solar radiation. Studies on such wheat mixtures are limited. A field experiment was therefore conducted for two wheat seasons (1974–5 and 1975–6) at the Indian Agricultural Research Institute, New Delhi, to compare the yield potentials of the mixed and pure stands of three spring wheat cultivars varying in plant height. Two kinds of canopy stands, namely, pyramidal and columnar, were created by making appropriate row arrangements of the cultivars while seeding. Mixed stands gave significantly higher straw yields and the grain yield was also significantly higher than the highest yielding cultivar in its pure stand at a high rate of nitrogen application (120 kg N/ha).
Growth and nutrition of Hibiscus cannabinus L.
Authors: Sinha A. K. , Saha S. 
Published: March 2009

SummaryIn a field study, the effect of N, P, K and their combinations on the growth, yield and nutrient uptake pattern by mesta (Hibiscus cannabinus L.) was studied. No effect of N, P, K on growth characteristics like plant height and base diameter occurred up to 60 days. Effect of fertilizer treatments on plant growth was observed only after 90 days. The effect of N was more pronounced than P and K. Initially, growth of leaves was higher than both the bark and the wood. Nutrient concentration was at a maximum in the early stages of growth but declined with age and became steady at about 60 days. The quality of fibre obtained after 120 days of growth was assessed and the effect of nutrients on quality is discussed.
Photosynthesis and growth of spring barley: some effects of drought
Authors: Leach J. E. 
Published: March 2009

SummaryDuring the dry summer of 1976, measurements were made of the photosynthesis, transpiration, respiration, and growth of irrigated (I) and non-irrigated (NI) spring barley growing in large field plots. Using a field enclosure, the photosynthesis of the irrigated barley was measured on 19 separate days during the latter two-thirds of the growing season when the plants were large enough to have measurable gas exchanges. The response of photosynthesis to water stress was determined from 3 days' comparative measurements on the I and NI crops, using both the field enclosure and, on 2 days only, a single-leaf photosynthesis chamber.Water stress in the NI crop caused large decreases in yield: the dry-matter yields of grain and straw were respectively reduced by 19 and 27%; number of grains (but not grain mass) was also reduced. Field enclosure measurements, which were in good agreement both with values for canopy net photosynthesis derived from the leaf chamber measurements and with estimates of dry-matter production derived from plant weighings, indicated that the net CO2 uptake per unit leaf area was little affected by water stress. Results from the plant weighings and mensurations showed that, during the growing season, the main effect of water stress, mediated by the survival of fewer tillers and the premature senescence of leaves, was a reduction of leaf area (by 40%).
Comparative response of groundnut and wheat to phosphorus in a groundnut–wheat rotation
Authors: Pasricha N. S. , Aulakh M. S. , Sahota N. S. , Baddesha H. S. 
Published: March 2009

SummaryPod yield of groundnut and grain yield of wheat grown in that sequence was compared as affected by date of sowing and response to direct, residual and cumulative P application over 3 years in a field experiment. Total yield of groundnut and wheat was higher when groundnut was sown on 22 June and the following wheat on 1 November than when groundnut was sown on 6 July, followed by wheat sown on 16 November. Limited P requirement of groundnut was indicated by the small and inconsistent response to applied P on soil low in available P. Wheat responded to the second increment of P and direct application to wheat proved more effective than residual effects of previous application. Differential response of wheat to direct and residual P application in the groundnut-wheat cropping sequence indicates that P applications are more effective for wheat than groundnut, and groundnut can grow well on the residual P that remained in the soil.
Hybrid necrosis as a problem in handling hexaploid × tetraploid wheat crosses
Authors: Gregory R. S. 
Published: March 2009

SummaryA tetraploid wheat breeding programme was initiated at the Plant Breeding Institute in 1970. Hexaploid × tetraploid wheat crosses were expected to contribute to the improvement of the tetraploid wheats but severe hybrid necrosis caused the death of the pentaploidFxhybrid plants in most crosses. The genotypes of tetraploid wheat selections derived from crosses involving Rampton Rivet, a non-carrier ofNeuwere determined by test crossing to hexaploid wheat varieties which were known to carry theNeimallele. Similarly, hexaploid wheat selections which did not carryNe2were identified from crosses involving Maris Ranger by test crossing to durum selections which carried theNefallele. By the careful choice of one parent, hexaploid x tetraploid wheat crosses were then made which avoided the hybrid necrosis problem. Segregation of theNe%gene was as expected but selection for agronomic characters appeared to favour the retention of the dominant allele of theNe1gene. Nevertheless, test crossing on a relatively small scale still identified many non-carriers.
The use of radiography in studies of pod growth in oil-seed rape (Brassica napus L.)
Authors: Pechan P. M. , Bashford J. A. , Morgan D. G. 
Published: March 2009

SummaryThe technique of radiography has been used successfully to provide permanent records of mature and developing pods in oil-seed rape. X-ray films and photographs of the pods show clearly the shape and size of the pods as well as the numbers, positions and to some extent the size of the seeds within them.
A study of growth in swards of timothy and meadow fescue II. The effects of cutting treatments
Authors: Langer R. H. M. 
Published: March 2009

1. Pure swards of S. 48 timothy and S. 215 meadow fescue were cut (a) after ear emergence, (b) before ear emergence and in the aftermath to prevent flowering, and (c) every 4 weeks. The number and weight of tillers and leaves were determined.2. Tiller numbers declined considerably from early spring to the middle of summer. This fall was reduced by a system of frequent defoliation in the wet summer of 1956, especially in timothy.3. Leaf weight per unit area of sward increased rapidly from early spring until about the time of ear emergence; no further significant gains were recorded after ears had appeared, when the plots were cut for hay.4. The weight per leaf also increased in the spring and was similar in both species. In the regrowth following a cut meadow fescue produced considerably heavier leaves than timothy.5. As both grasses approached the flowering stage, their leaf canopy was increasingly raised above ground level. Variable proportions of foliage were thus removed by cutting according to the developmental stage of the plant. Crop growth rates following a cut appeared to be related to the amount of leaf material remaining in the sward.6. Relative growth rates during uninterrupted growth were greatest around the time of ear emergence.
Acclimatization of calves to a hot humid environment
Authors: Bianca W. 
Published: March 2009

1. Three calves were exposed in a climatic room to an environment of 40° C. dry-bulb and 38° C. wet-bulb temperature for up to 110 min. each day for 1-2 weeks.2. These exposures produced progressive changes in the physiological reactions of the animals to heat:(a) Rectal temperature and skin temperature (for a given time of exposure) declined. In consequence there was a marked increase in the tolerance time, i.e. in the time for which the animals could withstand the hot environment before reaching a rectal temperature of 42° C.(b) Respiratory rate rose earlier and assumed higher levels (for given levels of body temperature).(c) Heart rate decreased markedly.3. These changes are discussed in relation to heat loss and heat production and have been interpreted as reflecting chiefly a reduction in the metabolic heat production of the animals.
The development of the digestive system of the young animal I. Tissue weights, dry matter of tissues, total acidity and chloride content of stomach contents in the young pig
Authors: Walker D. M. 
Published: March 2009

1. A total of forty pigs (four litters) were slaughtered at weekly intervals from birth to 5 weeks of age.2. Results are given for the changes in weight of different parts of the digestive organs and their contents with increasing age, and for the content of NaCl and of total acidity in the stomach contents.3. Stomach pH was on average more alkaline than pH 3.4 at all ages up to 5 weeks; the average pH of the duodenum was 6.5 and of the small intestine 6.4.4. Total NaCl and total acidity in stomach contents remained roughly constant from birth up to 5 weeks of age. No free HCl was detected in any of the stomach contents of the pigs.5. The consistency of the stomach contents varied with the age of the pig; the hard milk clot which was characteristic of the contents at 2–3 weeks of age appeared softer and more broken in older pigs.
Bloat investigations
Authors: Alder F. E. , Davies William 
Published: March 2009

A series of seven experiments were carried out between May and September 1954 at the Grassland Research Institute as part of a co-operative study of bloat, which the Agricultural Research Council had helped to organize.Hereford colour-marked steers were grazed or fed on legume-dominant herbage in an endeavour to produce pasture bloat. Observations were made to determine patterns of animal behaviour and bloat incidence. Heart rates were determined both before and during the experiments and jugular blood samples were taken for determination of cholin-esterase levels. Herbage samples were analysed botanically in order to determine the type of material eaten, and chemically for nitrogen content. Other herbage samples were placed in cold storage.In the seven experiments (375 cattle feeding or grazing days) only twenty-seven cases of mild bloat and five cases of moderate bloat were recorded. This is surprising, because pains had been taken to provide feed that would by all normal standards be regarded as likely to induce bloat in cattle.
Effect of daily infection withOstertagia circumcinctalarvae on food intake, milk production and wool growth in sheep
Authors: Leyva V. , Henderson A. E. , Sykes A. R. 
Published: March 2009

SUMMARYForty pregnant sheep were allocated to four groups and maintained indoors in individual pens on a pelleted diet. During the last 6 weeks of pregnancy and the first 6 weeks of lactation groups were infected daily with 4000 larvae ofOstertagia circumcinctaor remained as controls in a cross-over design. Thus groups were either not infected (CC), infected only during pregnancy (IC), during lactation (CI) or during both pregnancy and lactation (II). Food was offered on the basis of body weight at the beginning of pregnancy and lactation. Food intake, body-weight change, faecal egg counts, plasma pepsinogen and milk production were measured weekly, wool growth and fibre diameter during 21-day periods and tensile strength of wool over the whole experimental period.Eggs were seen in faeces of only three sheep infected during pregnancy, but in all sheep infected during lactation; maximum mean values were 467 ± 144 and 222 ± 58 eggs/g fresh faeces in CI and II sheep, respectively. Pepsinogen concentrations rose after 1 week of infection during pregnancy and lactation; peak values were 868 + 57 and 1104 ± 146 m-u/l, respectively.Infection reduced food intake by 16% during lactation but had no effect during pregnancy. There were significant interactions between pregnancy and lactational treatments on intake during lactation. Infection during lactation increased bodyweight loss; mean values were 57, 40, 114 and 78 g/day for groups CC, IC, CI and II respectively. Milk production was decreased during weeks 4–6 of lactation, mean values being 1·59 and 1·32 kg/day in control and infected groups, respectively.Infection reduced wool growth and wool fibre diameter by 20 and 7%, respectively, during the final 3 weeks of infection during lactation. The staple strength of wool grown during the experiment was reduced by 14, 45 and 23% in IC, CI and II groups, respectively. Infection moved the point of greatest wool tenderness from parturition in control sheep to a time during the period of infection, particularly when infection occurred during lactation.
A comparison of three ultrasonic machines (Scanogram, Danscan and AIDD (NZ)) and visual estimates for predicting carcass composition of live cattle
Authors: Bass J. J. , Winn G. , Paulsen W. D. 
Published: March 2009

SUMMARYVery experienced livestock judges and three ultrasonic machines were compared for accuracy in predicting carcass composition.Sixty-four steers of mixed breed were visually scored for fatness and meat yield by seven judges. Subcutaneous fat depths over the eye muscle at the 13th rib were measured with three different ultrasonic devices prior to slaughter. There was little difference between the ultrasonic machines and the best visual estimates of fatness for predicting weight of commercial trimmed or total dissected fat. Visual estimates of meat yield were not as accurate as the judges' fat scores for predicting carcass composition.Subcutaneous fat depths measured by ultrasonics were shown to be as well related to carcass composition as the best judge's fat scores.
Competition in utero between twin lambs
Authors: Donald H. P. , Purser A. F. 
Published: March 2009

1. The weights at birth of 822 pairs of twin lambs have been studied with respect to the differences between males and females. Data were obtained during five lambing seasons from various breeds and crosses in five flocks.2. The sex distribution of twin pairs came close to the ratio .3. Analyses made within season and within the major breed categories showed that sex differences were small relative to other sources of variation, but that there was a significant effect of sex of co-twin on birth weight. The following average differences were found (the sex of co-twin being indicated in brackets):These differences had an average S.E. of 0·078 lb. (Table 3). The sex difference in litters of mixed sex was twice as large as that obtained from like-sexed litters.4. The data for particular flocks and seasons suggest that in addition to these average effects, there may be some interaction between sex and breed or season which can cause deviations from the averages.5. These results are interpreted to mean that there is competition between twins for some element of growth in limited supply; and that in twins of mixed sex, the result tends to favour the male.