bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of ‘adequate’ and ‘low’ sodium intake on reproductive performance of Scottish Blackface ewes and growth of their lambs
Authors: Vincent Isobel C. , Williams H. Ll. , Michell A. R. , Hill R.
Published: March 2009

A low sodium diet was given to Scottish Blackface ewes over two reproductive seasons. It provided a total of 3–7 mmol sodium per day, except during lactation when the intake was about 11 mmol sodium per day. Control ewes were given the same diet supplemented with sodium chloride to Agricultural Research Council recommended concentration which was about ten times greater than that in the experimental diet.

The ewes remained clinically healthy throughout the experiment. The length of gestation and the birth weight of lambs were unaffected by diet. The number of lambs born alive per ewe lambing was unaffected by year or diet.

The percentage of ewes producing twins was similar in control ewes in both years at about 64; in treatment ewes this was 70% in year 1, and 50% in year 2. Lamb mortality was higher in both years in the treatment ewes than in control ewes. None of these differences reached significance.
Amounts of NO3-N and NH4-N in soil, from autumn to spring, under winter wheat and their relationship to soil type, sowing date, previous crop and N uptake at Rothamsted, Woburn and Saxmundham, 1979–85
Authors: Widdowson F. V. , Penny A. , Darby R. J. , Bird E. , Hewitt M. V.
Published: March 2009

Soil NO3-N and NH4-N were measured to 90 cm depth in autumn and again in spring, under several sets of winter wheat experiments, on contrasting sites. Crop samples were taken throughout the growing season, both before and after the fertilizer N was applied, to measure N uptake. The amount of NO3-N in soil at the outset of growth in autumn was related to the uptake of N by wheat not given any fertilizer N until April.

The effect of sowing date (September v. October) on both crop and soil N was compared, as also was the effect of soil type (retentive of NO3-N v. readily leached) and previous crop (potatoes v. oats and wheat v. beans).

The amounts of NO3-N in the soils in autumn related well with previous crop and declined gradually during winter on the heavier soils, but rapidly on the sandy soil, in the latter case as a consequence of leaching. On the heavier soils, where little leaching occurred, the decline in soil NO3-N related well with the amount of N taken up by September-sown wheat during autumn and winter, but not with that taken up by October-sown wheat, where NO3-N accumulated in the soil during winter, because uptake was so small. Hence delayed sowing enhanced the likelihood of losses of NO3-N by leaching or by denitrification. On the sandy soil at Woburn, whilst the September-sown wheat removed more N than the October-sown, losses of NO3-N by leaching were severe, so that late winter growth was restricted by shortage of N in soil, and the amount of N taken up was far smaller than at Rothamsted.

The soil measurements distinguished between the NO3-N residues remaining after beans or wheat in the same field and between residues after oats or potatoes on soils of the same soil series, but in different fields on the same farm.

The amount of NO3-N in soil and the N taken up by wheat in February-March were together used to adjust the amount of fertilizer N applied in April, using a balance sheet approach to meet a specific yield objective. Some of the N uptake data from these experiments are presented. This should aid the calculation of N requirement during specific growth periods and thus help improve the prediction of fertilizer N dressings in spring.
Biodegradability of mature grass cell walls in relation to chemical composition and rumen microbial activity
Authors: Ford C. W. , Elliott R.
Published: March 2009

Cell walls from mature stems of three tropical grass species (Digitaria decumbens(pangola),Setaria anceps(cv. Kazangula) and sugar cane), and temperate barley straw, were analysed for lignin, carbohydrate, and the maj or acyl groups ferulate, ρ-coumarate and acetate. Samples were incubated in nylon bags in the rumen of sheep in a 4 x 4 latin-square design, and rates of disappearance of cellulose, hemicellulose, xylose, arabinose, ferulate, ρ-coumarate and acetate were determined during 60 h incubation. Interspecies differences in cell-wall chemistry appeared largely in the variable degree of acylation with p-coumaric acid (1·0–3·3%) and acetate (0·5–3·6%), and the high glucose concentration in the hemicellulose from pangola (17%) andSetaria(9%). Barley had much lower concentrations of these components than the tropical species. After 24 h incubation, losses of cellulose and acyl groups were greatest from pangola, whereas hemicellulose and its major components xylose and arabinose were degraded to the greatest degree from barley straw.Setariacell-wall components were generally more resistant to degradation than the other species. No relationship was found between the concentration of any cell-wall constituent and degradability measurements. Nor were changes in microbial population, indicated by measuring the accumulation of cystine on the fibres, related to the rate or degree of degradation of any of the measured cell-wall constituents. Lignin was fractionated with alkali into insoluble and soluble fractions. The latter (25–50% of original lignin) gave high interspecies correlations with the degradability of total hemicellulose and its component monosaccharides. It was concluded that variability in the biodegradability of the cell walls was more likely due toin situstructural features, such as cross-linking between polymers, than to the concentration of any particular cell-wall constituent.
The relative importance of cluster size, sowing depth, time of seedling emergence and between-plant spacing on variation in plant size in red beet (Beta vulgaris L.) crops
Authors: Benjamin L. R.
Published: March 2009

Beets with a coefficient of variation (c.v.) of weight of only 36–46% were produced by reducing the variation in cluster size, sowing depth, time of seedling emergence, proximity and size of neighbours to as low a value as practicable. The relative importance of these different sources of variation in plant size was examined in two experiments sown in contrasting conditions.

Variation in time of seedling emergence was a major source of variation in plant size and was partially caused by variation in the environment around the clusters. Variation in true seed size and between-plant spacing was achieved by use of clusters of different sizes, but these factors were associated with only a negligible variation in root size. Similarly, local interactions between plants, brought about by variation in plant-to-plant spacing, accounted for only a small proportion of the variation in root weight.
Varietal differences in growth characteristics in sugar cane
Authors: Singh S. , Rao P. N. Gururaja
Published: March 2009

In sugar cane, investigations made earlier (Singh & Gururaja Rao, 1985) have shown that high-yielding varieties have higher net assimilation rate than low-yielding types. Similarly, differences in progeny means for relative growth rate and net assimilation rate have been reported by George (1965). In other crops also, varietal differences in leaf area index and net assimilation rate have been reported (Watson, 1947). It appears that in this crop, limited attempts have been made to study all the growth characteristics. This paper describes the differences in most of the growth characteristics in six sugar-cane varieties.
Selection for height of nectar in the corolla tube of English singlecut Red Clover
Authors: Hawkins R. P.
Published: March 2009

Pollination of red clover by honey bees would be expected to increase if varieties could be produced in which the nectar is within 7 mm of the mouth of the corolla tube and so within the bee's reach.

Pollination by honey bees in a small glasshouse increased the height of nectar in the resulting stock of red clover but when this was again pollinated by honey bees there was no further increase.

Selection of plants with above average nectar height ultimately produced a stock in which the nectar height was 0·76 mm higher than in the original; a difference which was significant. There was also a considerable and significant increase in the proportion of florets with nectar within 7 mm of the mouth of the corolla tube.

It was concluded that the height of nectar can be increased by selection; this would be of particular value for the pollination of red clover varieties with long corolla tubes grown for seed where there are insufficient numbers of bumble bees.
Plant population and shading studies in barley
Authors: Willey R. W. , Holliday R.
Published: March 2009

Two barley experiments are described in which a range of plant populations were shaded during different periods of development. Shading during the ear development period caused considerable reductions in grain yield, largely by reducing the number of grains per ear. Shading during the grain-filling period caused no reduction in grain yield. It is suggested that under conditions of these experiments there was probably a potential surplus of carbohydrate available for grain filling and that grain yield was largely determined by the storage capacity of the ears. The importance of the number of grains per ear as an indicator of individual ear capacity is emphasized.

The effects of plant population on grain yield and its components are also examined. It is concluded that the number of grains per ear is the component having greatest influence on the decrease in grain yield at above-optimum populations and attention is again drawn to the possible importance of ear capacity. It is argued that on an area basis the number of grains per unit area may give a good indication of ear capacity. Examination of this parameter shows a close relationship with grain yield per unit area for both the shading and population treatments. It is particularly evident that a decrease in grain yield at high populations was associated with a comparable decrease in the number of grains per unit area. It is suggested that this decrease in grain number may be due to a lower production of total dry matter during ear development rather than an unfavourable partitioning of this dry matter between the ear and the rest of the plant. This lower production of total dry matter is attributed to the crop growth rates of the higher populations having reached their peak and then having declined before the end of the ear development period. This crop growth rate pattern, through its effect on grain number per unit area, is put forward as the basic reason why, in the final crop, grain yield per unit area decreases at above-optimum populations.
Plant population, shading and thinning studies in wheat
Authors: Willey R. W. , Holliday R.
Published: March 2009

Three wheat experiments are described in which a range of plant populations were shaded during different periods of development; in two of the experiments plant thinning was also carried out at a number of growth stages. Shading during the period of ear development caused an appreciable decrease in grain yield by decreasing the number of grains per ear. Shading during the grain filling period also reduced grain yield, this being brought about by decreased grain size. Thus in contrast to the barley experiments reported earlier (Willey & Holhday, 1971), these particular results gave no indication of a potential surplus of carbohydrate for grain filling and an associated limited ear capacity. However, when plant thinning was carried out at anthesis to make more carbohydrate available for grain filling in the remaining ears, grain yield per ear did not increase. It is argued, therefore, that grain yield probably was determined at least partly by a limited ear capacity. Plant thinning at earlier stages showed how the development of competition during the ear development period progressively reduced the potential capacity of the ear; the greater competition of higher plant populations accelerated this reduction in ear potential.

From an examination of the effects of plant population, it is suggested that the number of grains per ear is the component having greatest influence on the decline in grain yield at above-optimum populations. The possible importance of the number of grains per unit area as an indicator of ear capacity on an area basis, and as a determinant of grain yield per unit area, is emphasized. A close relationship between grain yield per unit area and number of grains per unit area is illustrated for a number of plant-population response curves, and it is suggested that the decrease in grain yield at high populations is probably determined by a decrease in the number of grains per unit area. Evidence is presented to substantiate the idea put forward in the barley paper that this decrease in the number of grains per unit area may be attributable more to a lower production of total dry matter by the high populations during the later stages of ear development, than to an unfavourable partitioning of such dry matter between the ear and the rest of the plant.
Inter-varietal competion and its possible consequences for the production of F1 hybrid wheat
Authors: Sage G. C. M.
Published: March 2009

The graphical and statistical analyses of competition diallels devised by Durrant were applied to an experiment investigating competition between four spring-wheat varieties. The results indicated that at low seed rates mixtures between varieties having a wide phenotypic difference between them in competitive characters, such as height and early maturity, could significantly outyield pure-stands of the component varieties. However, the results of a second experiment, in which these mixtures were grown at a range of seed rates, indicated that the yield advantage of mixtures over pure-stands was unlikely to occur at normal seed rates.

It is suggested that, at the low seed rates likely to be used in growing F1 hybrid wheat crops, mixtures of F1 hybrids and male parental lines might achieve very nearly the same yield as the pure F1 hybrid variety with a seed bulk that was cheaper to produce.
The voluntary intake of silage by sheep:I. Interrelationships between silage composition and intake
Authors: Wilkins R. J. , Hutchinson K. J. , Wilson R. F. , Harris C. E.
Published: March 2009

The voluntary intake by sheep of seventy silages was measured in experiments in several years. Linear and multiple regression analyses were made between these voluntary intakes and the contents of dry matter, various acids and nitrogen and the digestibility value determined in vivo. There were some differences in these relationships for silages made from different groups of species, particularly those made from legumes. Voluntary intake was positively correlated with the contents of dry matter, nitrogen, lactic acid as a percentage of total acids and with the Flieg index. Voluntary intake was negatively correlated with the contents of acetic acid and ammonia as a percentage of total N. Although pH alone did not account for a significant part of the variation in intake, multiple regressions in which pH and one of the measurements of fermentation quality were included were significant, with pH positively related to intake. When all silages were considered, the correlation between voluntary intake and the apparent digestibility of dry matter was not significant. However, for legumes this correlation was significant and positive and for grasses other than ryegrass the correlation was significant and negative.
The voluntary intake of silage by sheep:III. The effects of post-ruminal infusions of casein on the intake and nitrogen retention of sheep given silage ad libitum
Authors: Hutchinson K. J. , Wilkins R. J. , Osbourn D. F.
Published: March 2009

Isocaloric quantities of casein, and glucose were infused into the abomasum and duodenum of sheep given perennial ryegrass silage ad libitum. Casein infusion significantly increased nitrogen retention but failed to affect silage consumption, suggesting that the positive relationship found between silage intake and silage nitrogen content is unlikely to be due to a low nitrogen status in sheep fed all-silage rations.
Controlling soil pH with different N-fertilizers in experiments with ryegrass in pots
Authors: Bolton J.
Published: March 2009

The pH of soil cropped with ryegrass increased with calcium nitrate as a fertilizer and decreased with ammonium nitrate, especially in the mid-range of pH. Changes above pH 7·2 and below pH 4·5 were small.

Yields of 4 cuts of grass given either N-fertilizer were similar over a pH range (in 0·01M-CaCl2) from 4·3 to 7·4. However, the composition of the grass and nutrient uptakes were affected by both soil pH and form of N-fertilizer.
Cation-anion relationships in crop nutrition
Authors: Cunningham R. K. , Karim A.
Published: March 2009

Italian rye-grass was grown in the greenhouse in clay loam soil in winter 1962 with several rates of a nutrient solution containing NO3-N and P, K, Ca and Mg to see whether the grass had maximum values for sums of the cations and anions (σ cations, σ anions). Two other experiments were done in summer 1962 with a similar nutrient solution containing either NO3-N alone or NO3-N plus NH4-N.

At the same level of added nutrients summer yields of grass were about twice those in winter and there was little difference when nutrient mixtures with NO3-N+NH4-N or with NO3-N alone were used. The sum of the cations (m-equiv./lOO g. dry matter) in the grass was positively correlated
The grazing feed intake of Hereford and Brahman cross cattle in a cool temperate environment
Authors: Moran J. B.
Published: March 2009

The grazing feed intake of four ¾ Brahman and four purebred Hereford steers was measured on four occasions during 12 months while they grazed improved pastures in a cool temperate environment. When pen fed roughage diets, the excretion pattern of chromic oxide and faecal nitrogen–digestibility relationships were also investigated in these animals.

There were no breed differences in the relative recovery of Cr2O3 in the faeces when bulking 10.00 and 17.00 h samples nor were there breed differences in the faecal nitrogen–digestibility regression obtained. However, although there were large discrepancies between feed intake and live-weight change when measured in different seasons, the Herefords had the higher feed intake on each occasion while breed differences in live-weight change were non-significant.
Effect of harvesting stage on cereal and legume forage production in low rainfall regions
Authors: Hadjichristodoulou A.
Published: March 2009

The effect of stage of harvesting on dry-matter (D.M.) yield and chemical composition of barley, wheat and the legumes common vetch (F. sativa), woollypod vetch (F. dasycarpa) and fodder peas (P. sativum) were studied in Cyprus under low rainfall conditions in a series of trials sown in four successive years. Cereals were harvested at the beginning of heading, 50% heading and the milk stage of grain, and legumes at three stages from preflowering to full pod formation, D.M., protein and digestible D.M. yields and percentage D.M. content increased with age, whereas percentage protein content and D.M. digestibility declined. Under moisture stress conditions before and during the harvesting period D.M. yields did not increase significantly with age. Protein content of cereals under low rainfall conditions was higher than that of cereals grown in the U.K. under higher N fertilization levels. Rainfall conditions affected drastically the performance of both cereals and legumes. However, average yields were satisfactory; the barley variety 628 gave 8·98 t/ha, the highest D.M. yield among all cereal and legume varieties.
Evaluation of the performance of sweet potato genotypes by joint regression analysis
Authors: Ngeve J. M.
Published: March 2009

Two experiments, each involving a set of six sweet potato clones, the first set developed in sites differing in altitude, and the second in sites differing in soil type, were done at three locations in 4 years in Cameroon. Data obtained were subjected to analyses of variance to determine the presence of genotype × environment (G × E) interactions, and to joint regression analyses to measure the performance of clones across environments. The first experiment produced higher yields and contained more stable clones than the second. In both experiments, mean yields were almost twice as high in 1984 (21·1 t/ha) as in each of the other years (c. 11·0 t/ha), and highest at Nyombe (18·0 t/ha). In Expt 1, the G × E interaction mainly concerned interaction with location, whereas in Expt 2 it concerned interaction with years.

Clones 1611 (Expt 1) and 048 (Expt 2) yielded above average and gave linear regressions significantly above unity (b> 1·0) for most traits, indicating specific adaptation to high-yielding environments and hence below average stability. Clones 1112, 1639 and TIbl (Expt I) yielded above average and had regression slopes equal to unity (b= 1·0), indicating average stability and thus general adaptability. Clones TIb2 (Expt 1) and 1487 (Expt 2) produced below average yields (b< 1·0), indicating specific adaptation to low-yielding environments. Since sweet potato is grown mainly for human consumption in Cameroon, a preferred clone must have stable marketable yields. Only clones 1112, TIbl and 1639 could be considered desirable for release to growers.
Comparative studies of upland and swamp rice varieties (Oryza sativaL. ). I. Effect of soil moisture on growth and nutrient uptake
Authors: Enyi B. A. C.
Published: March 2009

Growth and nutrient uptake by an upland rice variety, Agbede and a swamp rice variety, BG 79, were studied under four different soil moisture regimes (60, 80, 100% soil moisture saturation and flooding).

BG 79 (Swamp rice) ultimately attained greater mean total dry weight than Agbede (Upland rice), except in the flooding treatment, where the reverse applied. For both, 100% soil moisture saturation gave the greatest total dry weight increase, whereas the driest soil depressed dry-matter production: plants grown on soil maintained at 80% moisture saturation ultimately attained greater mean total dry weight than those grown on flooded soil. Flooded plants of the swamp rice outyielded plants grown on soil maintained at 80% moisture saturation, but the reverse applied to the upland rice.

Total leaf numbers were usually greater in BG 79 than in Agbede during the tillering and mid-vegetative stages. Increase in the soil moisture up to complete saturation increased the total leaf number in both varieties.

Mean leaf area was greater in Agbede than in BG 79 during the tillering and midvegetative stages. During these two periods of growth the 100% saturation treatment produced plants with the greatest leaf area, whereas 60% soil moisture saturation produced plants with the smallest leaf area in both varieties.

BG 79 had more shoots than Agbede. During tillering saturated and flooded soil encouraged the production of shoots in both varieties, but the driest soil prolonged the tillering period, especially in BG 79. Final shoot number tended to decrease with decreasing soil moisture. The percentage shoot mortality in Agbede was not significantly affected by soil moisture regimes, but BG 79 plants grown on the driest and saturated soil had significantly greater percentages of shoot mortality than flooded plants. In both varieties, plants grown on the driest soil had significantly greater percentage shoot mortality than those grown on soil maintained at 80% moisture saturation.

Mean Relative Leaf Growth Rate and Net Assimilation Rate were significantly faster in BG 79 than in Agbede variety, but the reverse applied with regard to Leaf Weight Ratio.

In both varieties flooded plants had the lowest concentration of manganese, especially during tillering. The small adsorption of Mn with flooding is attributed to a probable antagonism between iron and manganese.
Variation in the host-parasite relationship of a crop disease
Authors: Arnold M. H. , Brown S. J.
Published: March 2009

Variations in the host–parasite relationship of bacterial blight of cotton, caused by Xanthomonas malvacearum, E. F. Smith (Dowson), axe elucidated in terms of the three main components of variation, namely, genetic variation in the host, genetic variation in the parasite and variations in environment.

Although the relative resistance shown by host varieties differed both with the culture of the pathogen used for inoculation and with the environmental conditions, over-riding patterns of host resistance could be detected, showing that certain varieties maintained their resistance over a wide range of conditions.

It was found that phage type in X. malvacearum was not related to virulence. Moreover, none of the cultures of the pathogen which had been isolated from different sources, could be shown to be identical when inoculated into a range of host varieties under a range of environmental conditions. It was concluded that the pathogen showed continuous variation in virulence and that it would be difficult and of little value to attempt to define races.

Some success was achieved in relating observed variations in the host–parasite relationship to easily measured components of the environment, by using multiple regression analyses. It is suggested that this might provide a means of characterizing the complex variations observed and that the host–parasite relationship could be regarded as a dynamic system, in which disease expression is a function of the interactions of environmental factors and two polygenic systems, that of the host and that of the parasite.

Intrapopulation variances were also studied in the host varieties. A population which showed little variation for resistance under one set of conditions might show considerable variation in a different environment or when inoculated with a different culture. It is suggested that selection for resistance under conditions which favour the expression of variation can lead, by repeated selection and inbreeding, to the production of resistant populations which retain their resistance under conditions in which the parental stocks showed no worthwhile resistance. These conclusions are discussed in relation to problems in resistance breeding and genetics.
Serum protein concentrations in 2-day-old Finnish Landrace, Scottish Blackface, Merino and Merino × Cheviot lambs
Authors: Halliday R.
Published: March 2009

The micro-Kjeldahl technique and paper electrophoresis were used to measure the total protein and γ-globulin concentrations in the sera of 423 2-day-old Finnish Landrace, Scottish Blackface, Merino and Merino × Cheviot lambs, and the total protein concentrations in the sera and colostra of their mothers. The concentrations were higher in Finnish lambs than in lambs of other breeds. The interbreed variations between single lambs were not significant, but the variations between lambs from larger litters were highly significant, because the concentrations in Finnish twins and triplets were as high as in single lambs, whereas the concentrations in Blackface and Merino × Cheviot lambs were negatively correlated with litter size. The differences between the breeds were attributable to the particularly high protein concentrations in the colostra from the Finnish ewes, to the small size of their lambs, and, probably, to a higher rate of production of colostrum by Finnish than by other ewes. There was some evidence of a positive correlation between the lengths of the gestation periods and the γ-globulin concentrations of the lambs.
Potassium reserves in British soils. I. The Rothamsted Classical Experiments
Authors: Talibudeen O. , Dey S. K.
Published: March 2009

Thirty-four soils from the Rothamsted Experiments were exhaustively cropped with ryegrass in the glasshouse. The concentration and yield of potassium in ryegrass tops and the potassium intensity in the soil were measured every 4 weeks, after harvesting the grass.

The change in K-intensity of soils, rich in potassium, with exhaustion differed from that of ‘poor’ soils. This change was related to the rate of change of the cumulative K-yield. The rate of change of soil K-intensity demarcated periods of intense and limited exhaustion and partial recovery of the soil during cropping.

The cumulative K-yield of ryegrass was very significantly related to the K-intensity of the uncropped soil; the ‘16-week’ yield was slightly better related than the ‘60-week’ yield. For Park Grass soils, the relationship was improved by allowing for variations in soil pH.

The K-intensity of all soils, with or without manuring, decreased to nearly 10-3(M)½in (AR)0units after 16 weeks cropping, although large differences in K-yield persisted until much later.

K-buffer capacityper unit clay contentof the soil, measured by a laboratory method, was inversely related to the K-intensity of the uncropped soil. The K-buffer capacities of soils rich in potassium, measured in laboratory and glasshouse experiments, were significantly related, but were unrelated for ‘poor’ soils. The K-buffer capacity (laboratory method) of Rothamsted soils with different manurial treatments was only very approximately related to the cumulative K-yield.

Less K was taken up from all Rothamsted soils given nitrogen fertilizer in the field and their K intensities were also smaller than the corresponding soils without ‘N’. Field liming of acid soils decreased their K-intensity and increased their K-buffer capacity, presumably because more potassium was removed by the field crop.

A rapid method is suggested for measuring potassium intensities of soils.
Variation between tetraploid red clover plants in corolla tube length and height of nectar
Authors: Bond D. A.
Published: March 2009

Crosses between eelworm-resistant tetraploid red clover plants varied significantly in corolla tube length and in the distance between the top of the nectar and mouth of the corolla tube. Variability between plants in height of nectar above the base of the corolla was positively correlated with corolla tube length but a significant residual variance in nectar height was independent of corolla tube length.

Tetraploids had higher nectar but longer corolla tubes and greater distances for bees to reach than those in related diploids which were previously reported.

The implications of the findings are discussed in relation to the improvement by breeding of the attractiveness of tetraploid red clover to honey-bees.
A comparison of the yield of three grass species at various levels of nitrogenous fertilizer sown alone or in a mixture
Authors: Cowling D. W. , Lockyer D. R.
Published: March 2009

The production of herbage dry matter harvested from a mixture of S. 24 perennial ryegrass, S. 37 cocksfoot and S. 48 timothy is compared with the yields of the same species sown alone. Various levels of fertilizer nitrogen were applied to the grasses which were harvested by cutting fourteen times over a 3-year period.

The possibility that the mixture produced a greater yield than swards of pure species (after taking into account that the three species are not present in equal proportions in herbage harvested from the mixture) was examined using the concept of ‘the sum of the relative yields’. There was no evidence of a beneficial or antagonistic effect of one species on another; rather, the species seemed to be ‘mutually exclusive’ (de Wit & van den Bergh, 1965).

The botanical composition of the mixture changed through the course of the experiment, e.g. cocksfoot became increasingly dominant, particularly at the highest level of nitrogen. Changes in composition accounted for any tendency for the yield of the mixture to deviate from the mean of the pure-sown swards.

Some of the advantages and disadvantages of using mixtures are discussed and it is concluded that a rational approach to grassland husbandry should be based on swards sown to a single grass variety.
Prediction of leaf area indices and yields of wheat
Authors: Benbi D. K.
Published: March 2009

Changes in leaf area index (LAI) of wheat are predicted by using information on daily heat units, atmospheric evaporative demand, water supply and nitrogen. The results of experiments on two different soils at Punjab Agricultural University Farm, Ludhiana, India from 1987 to 1990 showed that the rate and extent of leaf area development and its decline were dependent on the amount and pattern of water supply. Maximum leaf area index (LAImax) during the three years was found to depend on a combined effect of NO3-N in the 180 cm soil profile at sowing plus fertilizer N added. A relative growth factor (RGF) to scale cumulative water supply commensurate with crop growth was computed, which takes into account the combined effect of crop demand and supply of water and nitrogen from the soil. For adequately irrigated wheat, leaf area senescence could be predicted from cumulative potential evapotranspiration (PET). However, under droughted conditions, water supply, along with PET, also affected leaf area senescence. The dependence of wheat grain yield on LAImaxin conjunction with water supply subsequent to attainment of LAImaxwas almost linear. It is concluded that, for adequately irrigated wheat, N availability at sowing and cumulative PET determines LAImaxand the pattern of leaf development. Wheat grain yield is determined by LAImaxand cumulative water supply from LAImax to maturity.
The effect of bacterial inoculants on kikuyu silage quality
Authors: Figueiredo M. De , Marais J. P.
Published: March 2009

Two commercial bacterial inoculants (Lacto-flora and Ecosyl) were added to kikuyu grass (Pennisetum clandestinum) at ensiling, in 1985 and 1988 respectively, at Cedara, South Africa, using laboratory silos. In 1985 (Expt 1), Lacto-flora was added on its own and in combination with the enzymes Celluclast or SP249. In 1988 (Expt 2), Ecosyl was added on its own and in combination with molasses, at two levels of addition.

The addition of Lacto-flora alone did not significantly increase the lactic acid bacteria or the lactic acid content of the treated silage. However, treated silage contained 53·6% less iso-butyric acid and 53·7% less ammonia than the control silage. Kikuyu silage supplemented with a combination of Lacto-flora and Celluclast or SP249 had higher numbers of lactic acid bacteria at ensiling (0·231 × 108/ml) than the control silage or silage receiving Lacto-flora alone. However, only silage supplemented with the combination of Lacto-flora and Celluclast had a significantly higher lactic acid content (2·23 compared with 0·04, 0·18 and 0·13% DM for the control silage, silages with Lactoflora and with a combination of Lacto-flora +SP249, respectively). Nevertheless, this silage contained 19·78% more acetic than lactic acid.

Silage supplemented with Ecosyl on its own did not differ significantly in digestibility, loss of dry matter, ammonia, total non-structural carbohydrates, lactic acid and crude protein, from the untreated silage. A significant decrease in silage pH (from 5·08 to 4·70) was observed when Ecosyl was added together with molasses at the higher level of addition only. However, no other benefit was obtained by the addition of Ecosyl in combination with molasses.
Effect of green manuring on the physical properties of soil under a rice–wheat cropping system
Authors: Joshi R. C. , Haokip D. D. , Singh K. N.
Published: March 2009

The effects of green manuring withSesbania aculeata, or withLeucaena leucocephalaleaves and of weed incorporation on the physical properties of a clay loam soil under a rice–wheat rotation were compared at New Delhi, India, in 1986–87. Under puddled conditions, the volumetric moisture content of the saturated topsoils varied from 0·400 cm3/cm3in theSesbania-treated plots to 0·425 cm3/cm3in plots receiving no green manure, but in the unsaturated soils at rice harvest the corresponding values were 0·317 and 0·271 cm3/cm3. The effects of the green manures on the water content of the soils were still evident after a subsequent wheat crop. Other soil physical properties affected by the treatments were the following (data refer to topsoils measured after the rice harvest): settling index (cm/cm), an estimate of structural instability, which ranged from 25·5% (Sesbania-treated plots), to 28·6% (weed incorporation), 29·7% (Leucaena-treated plots) and to 33·5% (NPK-fertilizer only). Soil dispersion increased from 6·0 to 10·0 g/100g through the same treatment sequence. Hydraulic conductivity in the NPK-fertilizer only plots was 31 cm/day, but increased to 4·8 cm/day in theSesbania-trealed plots.Sesbaniawas superior to the other green manures for improving soil physical properties after its incorporation.
Intake and digestibility of low quality roughages when supplemented with leguminous browse
Authors: Goodchild A. V. , McMeniman N. P.
Published: March 2009

In the first two of four experiments, sheep were fed,ad libitum, sorghum stover supplemented with graded levels of foliage of the shrub leucaena (Leucaena leucocephald) or mulga (Acacia aneura), which provided between 0 and 0·34 or between 0 and 0·43 of the dietary dry matter (DM) respectively. A second treatment (with or without urea) was superimposed in a factorial design. The effect of treatments on liveweight (LW) was explainable by their effects on voluntary intake of apparently digestible organic matter (DOMI). D0M1 was increased by mulga, largely due to an increase in the total voluntary intake of organic matter (OM). Leucaena increased DOMI by increasing the ration OM digestibility and, at low levels of inclusion, intake of the basal diet. Roughage intake was greatest when leucaena provided 0·15–0·20 of the dietary DM. Leucaena increased rumen ammonia, and whenever roughage intake was increased by urea, leucaena also increased it.

In the third experiment, when diets were made isonitrogenous with urea, roughage intake was slightly greater when leucaena, rather than its ash or a mineral mixture, was supplemented. Total OM intake and DOMI were greatest when leucaena was fed.

In the final experiment, sheep were fed one of ten treatments: three basal diets (two of sorghum stover and the third of native pasture hay) each supplemented with legumes (leucaena to the hay and one stover diet and cowpea straw to the second stover diet), ash of the respective legume and formaldehyde-treated casein. The tenth treatment was sorghum stover plus urea. For sorghum stover diets with leucaena-based or cowpea straw-based supplements, DOMI responded linearly to the nonurea nitrogen concentration of the diet. On the other hand, for native hay with leucaena-based supplements, the response of DOMI to non-urea N was negligible. It was noted that the native hay (predominantly Flinders grass,Iseilema vaginiflorum), contained lower concentrations of polyphenols than sorghum stover.

It was concluded that browse foliage can increase the voluntary DOMI of sheep consuming low quality roughages by providing nitrogen and sometimes minerals and OM of greater digestibility. The slowly-degradable proteins in leucaena, cowpea straw or formaldehyde-treated casein are more effective with polyphenol-rich sorghum stover than with native hay of otherwise similar composition.
Nutritional evaluation of kale (Brassica oleracea) diets:1. Growth of grazing lambs as affected by time after introduction to the crop, feed allowance and intraperitoneal amino acid supplementation
Authors: Barry T. N. , McDonald R. C. , Reid T. C.
Published: March 2009

Three successive sowings of marrow-stemmed kale (cv. Maris Kestrel) were grazed with lambs (initial weight 22·5 kg) for two consecutive 6-week periods, so that crop yield at the time of grazing was kept relatively constant at 6·5 t D.M./ha. Three crop allowances, 3·9 (H), 2·6 (M) and 1·3 (L) kg D.M./animal/day were imposed in a replicated design. Halfof the 32 lambs grazing each allowance received intraperitoneal injections of L-methionine + L-threonine three times per week. Twelve lambs were slaughtered at the start of the experiment and 48 at the end of each period.

Leaf tissue, the diet of the H groups, contained 0·5% D.M. as S-methylcysteine sulphoxide (SMCO) and 0·7–1·5% total N as nitrate. Whole plants, the diet of the L groups, contained 0·75% D.M. as SMCO and 4·0–7·5% total N asnitrate. The diet of the M groups was intermediate.

Rates of live-weight gain (LWG), empty-body weight gain (EBWG) and carcassweight gain (CWG) were lower in period 1 than in period 2 for animals grazing at all three allowances. A Heinz-Ehrlich body anaemia developed that was more severe in the first period, but did not differ between groups receiving the different allowances. Methaemoglobin was only detected in significant quantities at the time of peak Heinz body formation in period 1. CWG/EBWG was increased by the amino acid supplementation during period 1 but not period 2, showing that there was a temporary amino acid deficiency corresponding to the time when tho anaemia was most severe and body growth most depressed.

In both periods animals grazing at L allowance had lower rates of LWG, EBWG and CWG than M and H animals, who performed similarly. Most of the differences in EBWG between feed allowance treatments and between periods could be explained by changes in estimated intake. Wool growth rates increased with increasing feed allowance and were slightly stimulated by amino acid supplementation.

Copper true availability was calculated to be 1·6–2·7% with the lowest values for leaf tissue due to its high sulphur content. Truly available Cu/kg plant D.M. was below the minimum requirement for lamb growth, thus leading to a reduction in total liver Cu as the experiment progressed. Some indication was obtained that this could have been depressing LWG in the second period, especially in H lambs. Slight increases in thyroid gland weight were observed as the experiment progressed, but these were considered unlikely to have depressed body growth. It was concluded that the major factor limiting the feeding value of B. oleracea was its high content of nonprotein sulphur compounds, especially SMCO.
Genotype-environment interactions in tea (Camellia sinensis L.) and their implications in tea breeding and selection
Authors: Wickramaratne M. Rupa T.
Published: March 2009

An analysis of yield data from 31 tea clones grown in replicated trials at four locations revealed the presence of significant genotype-environment interactions. Joint regression analysisshowed that a significant proportion of these interactions could be attributed to differences in the linear response of each genotype (clone) to the range of environments. However, estimates of the deviations from regression were also significant, indicating the presence of some unpredictable variation.

The response of each individual clone was estimated by computing the regression coefficient of individual yield on environmental mean yield at each location. The clones used in this study had regression values ranging from 0·19 to 2·08, indicating considerable genotypic difference in response to environmental change. Genetic variation in adaptation was also found to be present. Clones of the Assam type were found to possess general adaptation whereas the one clone of Indo-Chinese origin was specifically adapted to low-yielding environments.

Some known features of several tea clones are explained on the basis of the linear regression model and a more scientific basis is provided for the recommendations of clones for differentdistricts. The implications of genotype-environment interactions in practical tea breeding and selection are also discussed.
Performance of different Scottish Blackface stocks and their crosses
Authors: Al-Nakib F. M. S. , Findlay R. H. , Smith C.
Published: March 2009

The performance of different stocks of Scottish Blackface sheep and their crosses was compared on a harsh Scottish hill experimental farm. The strains were the Stanhope farm stock (a control flock, closed for 30 years), stock from local Breeders, and first crosses and back-crosses of Stanhope stock with stocks represented by rams purchased at Lanark market. Some 3892 ewe records were available with 1837 lamb performance records. Estimated effects for the three types of stock and of heterosis in the Stanhope and Lanark cross were derived statistically. The local Breeders' stock had the heaviest lambs at weaning and the Stanhope stock the lightest. The local Breeders' stock also had the heaviest ewes and higher litter size but had lower fertility and lower lamb survival. Output expressed relative to ewe weight was highest for the cross-bred stock. Heterosis was positive for all traits studied except survival but was statistically significant only for ewe weight and lamb birth weight. If the Stanhope stock was representative of Scottish Blackface sheep of 30 years ago, breeding by Scottish Blackface breeders has led to an estimated improvement of 9% in the output per ewe exposed, and 5% in efficiency of production.
Trends in herbage yields over the last century on the Rothamsted Long-term Continuous Hay Experiment
Authors: Jenkinson D. S. , Potts J. M. , Perry J. N. , Barnett V. , Coleman K. , Johnston A. E.
Published: March 2009

Yields from five of the plots on the Park Grass Continuous Hay experiment at Rothamsted, started in 1856, were examined to see if any long-term trends could be detected over the last 100 years. Three of the plots examined are unfertilized; two receive inorganic nutrients every year; all are harvested twice a year. In 1959 the harvesting procedure was changed: yields for the periods before and after this change were examined separately and together. On none of the three unfertilized plots was the slope of the regression of total yield (i.e. first and second cutscombined) on time significantly (P< 0·05) different from zero in either the 1891–1958 or 1960–1992 periods. On both the fertilized plots, there were significant declines in yield with time over the 1960–92 period, assuming that the effects of autocorrelation are sufficiently small to be ignored; there were no consistent changes between 1891 and 1958. There were some significant trends on the five plots when the two cuts were considered separately.

A linear regression model was fitted to the data in an attempt to separate the effects of meteorological variables (rainfall and sunshine hours over selected parts of the year) on total yield from possible long-term effects brought about, for example, by the increasing concentration of CO2in the atmosphere. On four of the five plots this model accounted for between 12 and 21% of the yield variance in the pre-1959 period and between 45 and 63% after 1960. On the fifth plot, which received the highest level of N, the model accounted for 29% of the variance in the first period but only for 16% in the second period. When a linear trend with time was included in the model, this was not significant on any of the plots over the entire 1891–1992 period, although some significant trends appeared when the two periods were considered separately. The model was also fitted with the atmospheric CO2concentration in place of the linear trend with time: again there were no consistent trends.

Neither changes in the concentration of CO2in the atmosphere over the last century nor increasing inputs of combined N in rainfall or in dry deposition have had any detectable effects on yield in these plots.