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- Cited by 137
Studies in crop variation. I. An examination of the yield of dressed grain from Broadbalk
- R. A. Fisher
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- 27 March 2009, pp. 107-135
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In Part I is given a survey of the results of a statistical examination of the yield of the plots of Broadbalk “Wheat field during 67 years. The main features of the comparison of mean yields are well known; the comparative rates of decrement, shown in Section 5, supply a class of facts well worthy of further study. Particularly striking are the relatively slow rates of decrement of plots 2b and 8, compared with plot 7, which would seem to show a permanent advantage in very high nitrogenous dressings, and to emphasise the need for caution in the application of the principle of diminishing returns. The evidence of the influence of potassium sulphate and its substitutes, sodium sulphate and magnesium sulphate, shown in Table V, is also very striking. An unsuspected feature of the changes of mean yields, which precludes the possibility of obtaining from these data true curves of exhaustion has appeared in the slow changes which have taken place in all the plots in a similar manner. In Part II the mathematical methods by which the variation has been analysed has been discussed, partly as a justification of novel procedure, partly, to make clear that the three types of variations found have been genuinely distinguished. In Part III such evidence as is available has been presented, in order to throw light upon the possibility that the changes in mean yield have been caused by variations in the prevalence of weeds at different periods.
One point of importance which should be emphasised is that average wheat yields, even over long periods, from different fields or for different seasons cannot approach in accuracy the comparison of plots of the same field in the same seasons. The advantage of the method adopted by Lawes in the permanent experiments which he instituted is very evident. The effects of weather clearly require that the seasons should be identical, unless the series be very long, but the slow changes in mean yield show that even comparatively long series of different years from the same field cannot be accurately compared. Within the same field, however, the slow changes have almost proportional effects, and comparison between the mean yields of neighbouring plots may be made with great accuracy. The only case in which changes in mean yield sensibly affect the comparison of averages is that of plots 17 and 18. In comparing these with plots 3 and 4, 5, 7, and 10, it would be more accurate to confine attention to high yielding periods, at which the disturbing causes are at their minimum.
It is believed that the deviations from the smooth curves, which have been freed, for the most part, from the effects of exhaustion and weeds, form statistically homogeneous material for the study of meteorological effects.
- Cited by 136
Practical application of induced resistance to plant diseases: an appraisal of effectiveness under field conditions
- D. R. WALTERS, J. M. FOUNTAINE
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- 23 June 2009, pp. 523-535
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Plants resist pathogen attack through a combination of constitutive and inducible defences. Different types of induced resistance have been defined based on differences in signalling pathways and spectra of effectiveness. Systemic acquired resistance (SAR) occurs in distal plant parts following localized infection by a necrotizing pathogen. It is controlled by a signalling pathway that depends upon the accumulation of salicylic acid (SA) and the regulatory protein NPR1. In contrast, induced systemic resistance (ISR) is promoted by selected strains of non-pathogenic plant growth-promoting rhizobacteria (PGPR). ISR functions independently of SA, but requires NPR1 and is regulated by jasmonic acid (JA) and ethylene (ET).
Resistance can be induced by treatment with a variety of biotic and abiotic inducers. The resistance induced is broad spectrum and can be long-lasting, but is rarely complete, with most inducing agents providing between 0·20 and 0·85 disease control. In the field, expression of induced resistance is likely to be influenced by the environment, genotype, crop nutrition and the extent to which plants are already induced. Unfortunately, understanding of the impact of these influences on the expression of induced resistance is rudimentary. So too is understanding of how best to use induced resistance in practical crop protection. This situation will need to change if induced resistance is to fulfil its potential in crop protection.
- Cited by 136
The fortune of a botanical curiosity – Triticale: past, present and future
- G. OETTLER
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- 30 September 2005, pp. 329-346
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Triticale (×Triticosecale Wittmack) is the intergeneric hybrid between the female parent wheat (Triticum ssp.) and the male parent rye (Secale ssp.). The early work identifying and then producing primary and secondary triticales is described. Early wheat–rye hybrids were characterized by reproductive disorders and the cytology and meiotic characteristics have received much attention. Chromosome constitution has been studied particularly in relation to R-D substitution. Triticale has always been bred as a self-pollinating crop, although outcrossing can occur, and current cultivars are all nearly homozygous and homogeneous lines. Hybrid breeding (using cytoplasmic male sterility) makes the optimum exploitation of heterosis possible and, with the aid of molecular markers, triticale germplasm is presently being investigated to establish genetically diverse heterotic groups.
The first released spring and winter cultivars were generally characterized by good disease resistance, but low grain yield, shrivelled grain, high protein content, excessive height, lodging and preharvest sprouting. Breeding effort has increased yield, reduced shrivelling and improved test weight but at the expense of protein content, which is now comparable to wheat and rye. Plant height and lodging are also now comparable to wheat and rye. Progress in reducing preharvest sprouting by genetic selection is proving difficult and slow. Triticale may be suitable for grain production and for dual purpose usage for forage and grain.
The role of biotechnology in triticale improvement is described. The future of the crop, especially in low-input systems, and as raw material for industrial uses is considered.
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Effects of the plane of nutrition on growth and the development of carcass quality in lambs Part I. The effects of High and Low planes of nutrition at different ages
- H. Pálsson, Juan B. Vergés
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- 27 March 2009, pp. 1-92
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1. Two series of half-brother-sister lambs of balanced sexes have been reared on widely different (High and Low) planes of nutrition from the end of the third month of foetal life to 41 weeks of age. The effect of this on the growth in live weight and relative development of the body proportions has been studied.
2. The feeding of the mothers of the experimental lambs during the last 2 months of pregnancy was such that the High-Plane mothers gained 39·5 lb. live weight during pregnancy as compared with a gain of 1 lb. only in the Low-Plane group. The single lambs from both groups were of equal weight at birth, while on the average each individual twin was 47% heavier in the High-Plane than in the Low-Plane group.
3. In post-natal life the High-Plane lambs were fed so as to allow them to grow at their maximum rate and the feeding of the Low-Plane ones was controlled so as to allow them to grow at a slow but uniform rate. Lambs from both groups were killed at birth, at 9 weeks old and at 41 weeks old. At 9 weeks old the Low-Plane lambs killed had an average live weight of 14·3 lb. and the High-Plane ones 61·5 lb.; at 41 weeks old the respective weights were 69·5 and 180 lb.
4. The study of the age changes in the High-Plane lambs further proved the theory put forward by Hammond (1932) that in the sheep in post-natal life the different anatomical regions and tissues of the body grow differentially and in a definite order of development. The dressed carcass is later maturing than the organs and offal parts as a whole.
5. Of all the organs in the body the brain is the earliest developing, followed closely by the eyes. The thoracic organs as a whole are earlier maturing than the abdominal organs. Of the former, the thyroids, lungs and trachea and the heart are the earliest maturing in that order, while the thymus glands are later maturing. Of the alimentary tract, the oesophagus and the abomasum are the earliest developing parts, while the rumen and reticulum are much later maturing, growing at nearly twice the rate of muscle in the carcass from birth to 41 weeks. Of the other abdominal organs, the kidneys are earliest maturing, growing at approximately similar rate as the lungs and trachea, and slower than the heart in post-natal life. The abdominal fats are the latest maturing of all the organs, and of these kidney fat is the earliest maturing and the caul fat the latest.
6. The marked heterogonic growth of the organs appears to be related to their function. Those organs of most vital function to the life of the animal like the brain, eyes, lungs, kidneys, heart, oesophagus, abomasum and small intestines, are relatively well developed at birth, and consequently grow proportionately less in post-natal life than organs like the rumen and reticulum, which have an unimportant function until after the lamb begins to consume fibrous foods, or those whose function is largely that of storage of nutrients, which develop mainly in the later stages of growth.
7. The development of the different joints or body regions exhibits a marked gradient of increasing growth rate from the head and feet to the loin region, the feet and head growing least and the loin most in post-natal life, while the legs, neck and shoulders are in an intermediate position, the legs being earlier maturing than the shoulders.
8. The major tissues of the body exhibit marked differential growth rates in post-natal life. The order of increasing growth rate with age follows an outward trend from the central nervous system to bone, tendon, muscle, intermuscular fat and subcutaneous fat. Consequently, the early maturing nervous tissue and the skeleton make a greater proportion of their growth earlier in life than does muscle and fat; the latter, particularly subcutaneous fat, does not develop to any great extent until late in the growing period.
9. Within any of the major tissues, bone, muscle and fat, well-defined growth gradients are observed. Within the skeleton, in post-natal life, waves of increasing growth intensity pass from centres of early (even foetal) maximum rate of growth near the extremities, towards the central region of the body. As regards the axial skeleton, the skull, or rather the cranium, is the earliest part to develop, and from it waves of increasing growth intensity pass backwards to the lumbar region and downwards to the nose and lower jaw. In each limb, similar growth waves pass with age from the early developing metacarpals and metatarsals (cannon bones) down to the distal bones and up towards the lumbar region of the body, the pelvis and scapula being later developing than the femur and the humerus. The ribs appear to be the latest developing bones of the body, while the sternum situated further down in the body, though late maturing, is, however, earlier maturing than the scapula and the ribs. The bones of the fore-limb appear somewhat later maturing than those of the hind-limb.
10. As regards growth in length and thickness of the long bones of the limbs, a similar wave of increasing growth intensity passes from the cannons up the limbs. The upper bones increase relatively more both in length and thickness than the cannons after birth, and growth rate in length is at its maximum at an earlier age than growth rate in thickness.
11. In the case of muscle and fat, gradients have been demonstrated in their order of development from the head and neck backwards, and from the lower parts of the limbs (arms and legs) upwards to the loin region.
12. Changes in carcass measurements are of the same order as the changes in weight and/or shape of the tissues and parts measured, thus confirming their values as indices of carcass composition as well as conformation.
13. Marked differences between the sexes are apparent. The High-Plane males were on the average 15% heavier at birth than the females, which was found to be significant at the 5% level. At 41 weeks the wethers weighed 215·5 lb. and the ewes only 144·75 lb. This great difference appears to be principally caused by a longer span of growth in the wethers and by their higher rate of growth during the latter part of the growing period, rather than being due to their higher birth weight, for the females grow at a faster rate immediately after birth, and at 2 weeks of age have reached a greater average live weight than the males.
14. At 9 weeks of age the ewes were in a more advanced stage of development in respect of all characteristics than the wethers. The latter were proportionally less developed in all the late maturing characters such as dressed carcass percentage, had less fat and more bone, and each tissue was proportionately less developed in the late maturing joints in the wethers than in the ewes.
15. At 41 weeks the picture was completely reversed in every respect. The wethers at that age had not only reached 50% greater weight than the ewes but all their tissues and body proportions were in a more advanced stage of development, i.e. the later maturing tissues and anatomical regions were proportionately better developed in the wethers than in the ewes. At both ages these differences were reflected in photographs of the carcasses and the limb bones as well as in the carcass measurements.
16. The vastly different quantitative planes of nutrition of the High- and the Low-Plane lambs did not affect all the parts and tissues of the body equally, so that the Low-Plane lambs were not miniature images of the High-Plane lambs at the same age. On the contrary, the restricted nutrition of the Low- Plane lambs affected the different anatomical regions, organs and tissues of the body differentially and in an orderly manner. With but few minor exceptions, the different organs, tissues and anatomical regions of the body have been retarded in development by the restricted nutrition, in the direct order of their growth intensity. At any stage, an organ, part or tissue of high natural growth intensity at that stage was proportionately more retarded in development than organs, parts or tissues of lower growth intensity at that age. Over the whole experimental period the later developing parts or tissues were proportionately more affected than the earlier developing ones, which can only be explained in the same way as McMeekan (1940,1941) did in the pig, that the earlier maturing parts or tissues have a priority claim for the limited nutrients available in the blood stream when the growing animal is insufficiently fed to provide all parts or tissues of the body with an adequate nutritive supply for normal (maximum) growth. This holds at any stage of development, but at birth the differential effects of the restricted nutrition were much less pronounced than at 9 and 41 weeks.
17. The dressed carcass is more affected by the restricted nutrition in post-natal life than the organs and offal parts with the exception of the abdominal fats.
18. Of all the organs, the earliest developing brain and eyes are least affected in the Low-Plane lambs. At 41 weeks the brain is only 5% heavier in the Highthan the Low-Plane lambs, which is statistically insignificant for the available degrees of freedom; as the difference was proportionately greater at birth, poor nutrition in post-natal life appears to have no effect on the brain weight, while it may do so to some extent in foetal life. The ewes have a significantly lighter brain than the wethers (corresponding to their smaller live weight at birth). The eyes, though but slightly affected compared with other organs and body parts, are significantly lighter in the Low-Plane series at 41 weeks.
19. The restricted nutrition in foetal life did not have any effect on the weight of the lungs at birth and but little on the weight of the heart, while it greatly depressed the development of the thymus glands and that of the oesophagus, abomasum, spleen and somewhat less that of the liver, pancreas and kidneys. The development of the digestive tract and the abdominal organs was more retarded than that of the thoracic organs at birth in the Low-Plane lambs. In post-natal life the earlier maturing organs are in general less affected by the restricted nutrition than the later developing ones, the only important exception being the alimentary tract, which though growing at a relatively faster rate in post-natal life than the thoracic organs as a group, is less depressed by the low level of nutrition.
20. An organ of great growth intensity at any particular age interval is much more affected by the restricted nutrition during that interval than at other ages, i.e. the abomasum before birth, the rumen and the thymus glands from birth to 9 weeks, and the caul and kidney fat from 9 to 41 weeks old.
21. At birth the restricted nutrition in foetal life has had but small effect on proportional development of the different body regions. The head, however, is least and the legs most affected. In post-natal life the various joints are affected by the poor nutrition to a very different extent, and at each age interval they are, with minor exceptions, affected in the direct order of their growth intensity. At 41 weeks the head is 1·6 and the feet 1·8 times as compared with the thorax 4 and loin 4·4 times heavier in the High- than the Low-Plane lambs.
22. At birth the major tissues of the carcass are differentially affected by the restricted nutrition, the brain being least affected followed by the skeleton, muscle, tendon and fat. In post-natal life these tissues are affected in the order of increasing growth intensity, with age; the brain is least affected, followed by the skeleton, muscle, intermuscular fat, kidney fat and subcutaneous fat.
23. Restricted nutrition produces also differential effects on the relative development of the different anatomical units within each of the three major tissues, bone, muscle and fat. As regards the skeleton, individual bones or skeletal parts are retarded in development in direct relation to their growth intensity at each age interval. At birth the earliest maturing bones, i.e. those with high growth rate in foetal life, are relatively less developed than the other bones in the Low-Plane lambs, while at later ages the development of the late maturing bones is proportionately much more affected.
24. Not only does the plane of nutrition affect the weight of the individual skeletal units differentially, but it also affects the form of the bones in a comparable way. The late developing growth in thickness is retarded by poor nutrition to a much greater extent than the earlier developing length growth in postnatal life, while in foetal life the length growth of the early maturing cannon is more affected than its late maturing growth in thickness, the latter having very low growth intensity in foetal life as compared with the length growth. The differential effect on the form of the metacarpals over the whole experimental period is so great that those of the Low-Plane lambs at 41 weeks resemble bones of semi-wild or unimproved late maturing breeds, being very thin and round, while the cannon bones of the High-Plane lambs at 9 weeks and much more so at 41 weeks, have the thick flattened shaft characteristic of early maturing improved breeds.
25. The effect of the Low Plane of nutrition on the development of muscle, intermuscular fat and subcutaneous fat, as in the skeleton, exhibits a gradient from the early to the late maturing regions of the body in each case, i.e. the latest maturing parts are most and the earliest developing least affected.
26. Marbling or intermuscular fat as measured by chemical analysis of a sample of the longissimus dorsi muscle is affected by the Low Plane of nutrition to a greater extent than intermuscular fat, but less than subcutaneous fat. The plane of nutrition also affects the water content of the muscle, it being 3% higher at 9 weeks and 2% higher at 41 weeks in the Lowthan the High-Plane lambs.
27. The resultant effects of the plane of nutrition upon the body conformation and composition in terms of its major tissues is clearly reflected by the various carcass measurements taken.
28. The wethers appear to be more sensitive to restricted nutrition than the ewes and more so in the late maturing tissues and anatomical regions of the body. The proportionately more advanced development of the High-Plane wethers at 41 weeks as compared with the ewes is more than completely suppressed by the restricted nutrition of the Low-Plane wethers, the latter being in a less advanced stage of development than the ewes of the same treatment group at the same age.
29. Though an animal which has been retarded in its development by restricted nutrition retains more of the juvenile form than another of the same age which has been growing to its full inherent capacity, it is, however, not merely anatomically younger, corresponding to the weight difference, because of the differential effects of the restricted nutrition on the different organs, parts and tissues of the body. That even within a tissue some parts are penalized proportionately more than others by restricted nutrition during a period of active growth, has been tested statistically in the skeleton and found to be true.
30. Practical applications of some of the results are discussed.
- Cited by 131
Emission of greenhouse gases during composting of deep litter from pig production – effect of straw content
- S. G. SOMMER, H. B. MØLLER
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- 01 May 2000, pp. 327-335
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Of the anthropogenic greenhouse gas emission in Denmark animal manure contributes an estimated 40% of methane (CH4) and 20% of nitrous oxide (N2O). Livestock production systems undergo changes for the purpose of increasing animal welfare, and such changes often include increasing the amounts of bedding manure. Emission of greenhouse gases from composting pig deep litter was studied during a 4-month period. Effects of increasing the amount of straw used in deep litter (reducing litter density) were included in the study. Methane was produced at a high rate in the centre of the heap at high density during the thermophilic phase of composting, and CH4 emission was only measured during this phase. In this treatment N2O was also produced in the centre both initially and after the temperature of the compost had dropped to below 45 °C. Emissions of N2O were only significant in the low temperature phases. Production of N2O was probably restricted to the surface layers during the thermophilic phase of composting. Total carbon dioxide (CO2) emissions were 7·37 and 0·09 kg C/t fresh weight from the heaps with bulk densities of 0·44 and 0·23 kg/l, respectively. Methane emission from the high density compost heap was 191 g C/t and N2O emission was 58 g N/t. Emissions of CH4 and N2O from the low density heap were not detected. The greenhouse effect of gas emission from the high density compost heap was calculated by multiplying the climate force efficiencies and the cumulated gas emission. This calculation showed that CH4 contributes almost as much to the global warming potential as CO2, and N2O contributed twice as much as CO2.
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The relation between the clay content and certain physical properties of a soil
- Bernard A. Keen, Henry Raczkowski
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- 27 March 2009, pp. 441-449
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A simple experimental method has been described for measuring certain physical constants of soil, using small brass boxes into which soil passing a sieve of 100 meshes to the inch has been packed by hand. The quantities determined are:
(1) The weight of unit volume (100 c.c.s.) of air-dry soil, or the apparent specific gravity.
(2) Amount of water taken up by unit weight of soil.
(3) Pore space.
(4) Specific gravity of the soil.
(5) The volume expansion of unit volume (100 c.c.) of soil when saturated.
The results for one soil only are given, and discussed, to illustrate the method. With the co-operation of the Science Masters Association it is being applied to a number of soils by various schools.
The particular soil used was obtained in six depths as follows: 0–6–12″, 12–18″, 18–24″, 2–3′, 3–4′, and the above constants were determined on each depth. It was shown that (1) and (4) varied inversely with the percentage of clay in the soil, while (2), (3), and (5) varied directly with the clay percentage. The effect on the constants of the larger quantities of organic, matter present in the top two layers of soil was, weight for weight, approximately equal to that of the clay, except in the volume expansion results where the effect if any was within experimental error.
It is possible that the fraction fine silt II, whose upper limit of diameter is ·005 mm., has similar effects to the clay fraction.
- Cited by 130
The teart pastures of Somerset: I. The cause and cure of teartness
- W. S. Ferguson, A. H. Lewis, S. J. Watson
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- 27 March 2009, pp. 44-51
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The scouring of cattle and sheep caused by the teart pastures of central Somerset is due to the presence of molybdenum in the herbage in amounts varying from about 20 to 100 parts per million in the dry matter.
The scouring can be prevented and cured by feeding or drenching with copper sulphate. A daily dose of 2 g. copper sulphate for cows and 1 g. for young stock, is sufficient to cure and prevent the scouring on very teart land. Less copper sulphate may be enough on mildly teart land.
- Cited by 129
Stem and root characteristics associated with lodging resistance in four winter wheat cultivars
- M. J. Crook, A. R. Ennos
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- 27 March 2009, pp. 167-174
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The effects of root and shoot characteristics on the lodging resistance of four cultivars of winter wheat were investigated by combining results from a field trial (set up at Manchester University's Experimental Grounds, Jodrell Bank, in mid-September 1991) with morphological and mechanical measurements on their stems and anchorage systems. Cultivars showed contrasting lodging resistance: Widgeon was most susceptible, followed by Galahad, Riband and Hereward which, alone, did not lodge. Lodging resistance was not related to the strength and stiffness of the stems, which were usually adequate to withstand the forces to which they were subjected. Most plants instead failed in their root system which rotated through the soil. Resistance was associated with short and light stems (and hence on the force applied to the plants by wind and gravity) and with high values of the anchorage strength of the root system (and hence on the force resisting lodging). Lodging occurred during grain filling when the ears were heaviest and when the soil was wet. The anchorage strength of a plant depended on two characteristics of the root system: the bending strength and the angle of spread of the basal coronal roots. Plants with stronger, more widely spread coronal roots produced larger soil cones during anchorage failure and resisted larger forces. Future breeding for lodging resistance, therefore, should continue to select for plants with shorter stems and with stiffer, more widely spread, coronal roots.
- Cited by 128
The nitrogen cycle in the Broadbalk Wheat Experiment: recovery and losses of 15N-labelled fertilizer applied in spring and inputs of nitrogen from the atmosphere
- D. S. Powlson, The Late G. Pruden, A. E. Johnston, D. S. Jenkinson
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- 27 March 2009, pp. 591-609
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15N-labelled nitrogen fertilizer (containing equal quantities of ammonium-N and nitrate-N) was applied in 4 consecutive years (1980–3) to different microplots located within the Broadbalk Wheat Experiment at Rothamsted, an experiment which has carried winter wheat continuously since 1843. Plots receiving 48, 96, 144 and 192 kg N/ha every year were given labelled fertilizer in mid-April at (nominally) these rates.
Grain yields ranged from 1–2 t/ha on plots given no N fertilizer since 1843 to a maximum of 7·3 t/ha with 196 kg N/ha. On plots given adequate P and K fertilizer, between 51 and 68% of the labelled N was recovered in the above-ground crop; only about 40% was recovered where P deficiency limited crop growth. In 1981 fertilizerderived N retained in soil (0–70 cm) at harvest increased from 16 kg/ha, where 48 kg/ha was applied, to 38 kg/ha, where 192 kg/ha was applied. More than 80% of this retained N was in the plough layer (0–23 cm).
Overall recovery of fertilizer N in crop plus soil ranged from 70 % to more than 90 % over the 4 years of the experiments. Losses of N were larger in years when spring rainfall was above average and when soil moisture deficits shortly after application were small.
Crop uptake of unlabelled N derived from soil increased from 28 kg N/ha on the plot given no fertilizer N to 67 kg N/ha on the plot given 144 kg N/ha. The extra uptake of unlabelled N was mainly, if not entirely, due to greater mineralization of soil N in the plots that had been given N fertilizer for many years. Presumably fertilizer N increased the annual return of crop residues, which in turn led to an accumulation of mineralizable organic N, although there was only a small increase in total soil N content.
Wheat given NH4-N grew less well and took up less N than wheat given N08-N in the relatively dry spring of 1980; there was little difference between the two forms of N in the wetter spring of 1981. In both years more fertilizer N was retained in the soil at harvest when fertilizer was applied as NH4-N than as N03-N.
The N content of the soil in several plots of the experiment has been constant for many years, so that the annual removal of N is balanced by the annual input. A nitrogen balance for the plot given 144 kg fertilizer N/ha showed an average annual input of non-fertilizer N of at least 48 kg/ha, of which N in rain and seed accounts for about 14 kg/ha. The remainder may come from biological fixation of atmospheric N2 by blue-green algae, or from dry deposition of oxides of nitrogen and/or NH3 onto crop and soil. The overall annual loss of N from the crop–soil system on this particular plot was 54 kg N/ha per year, 28% of the total annual input from fertilizer and nonfertilizer N.
- Cited by 128
Blood-urea concentration in relation to protein utilization in the ruminant
- D. Lewis
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- 27 March 2009, pp. 438-446
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1. It has been shown that under a given feeding régime the concentration of blood urea in the sheep is constant.
2. Changes in the diet lead to different levels of blood-urea concentration which can be correlated with different rumen-ammonia concentrations; the change in blood-urea concentration follows increases or decreases in rumen ammonia after a delay period of 4–8 hr.
3. Fluctuations in blood-urea concentration in the sheep are not primarily due to changes in the overall nitrogen intake.
4. It is suggested that these findings might form the basis of a supplementary test in assessing the value of the protein in a foodstuff for ruminants.
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Environmental temperature, energy metabolism and heat regulation in sheep. I. Energy metabolism in closely clipped sheep
- N. McC. Graham, F. W. Wainman, K. L. Blaxter, D. G. Armstrong
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- 27 March 2009, pp. 13-24
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1. The energy exchange of two sheep closely clipped at weekly intervals was determined at three feeding levels and seven environmental temperatures, using a respiration apparatus in which radiant temperature was equal to ambient temperature. All measurements were made under conditions in which the animal was in equilibrium with its environment and heat storage was zero.
2. Body weight and fleece growth were both markedly reduced at the lowest feeding level. Weight losses were most marked at the lowest temperatures.
3. The energy lost in faeces decreased slightly as environmental temperature increased from 8 to 38° C. Urine energy losses also fell. Losses of energy as methane were maximal in the temperature range 23–28° C. As a result of these changes, the metabolizable energy of food increased with environmental temperature by 7 Cal./24 hr./° C.
4. The environmental temperature of the sheep at which their heat production was minimal, i.e. the ‘critical’ temperature was 39–40° C. for the lowest feeding level, 33° C. for the medium feeding level and 24–27° C. for the highest feeding level.
- Cited by 127
The feeding value of chicory (Cichorium intybus) for ruminant livestock
- T. N. BARRY
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- 01 November 1998, pp. 251-257
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Chicory (Cichorium intybus) is perhaps best known for the extract of its roots used as an ingredient in ‘coffee substitute’ beverages. It is less well known as a grazed forage for ruminants. Thomas et al. (1952) reported the high content of some major and minor trace minerals in chicory grown in the UK, and commented on its use in pasture mixtures as a source of these minerals. Chicory was first mentioned in New Zealand (NZ) literature as an animal forage by Cockayne (1915), but a long period then elapsed before Lancashire (1978) reported its excellent value for forage production under rotational grazing in dry summer conditions. Plant selection then followed and the cultivar ‘Grasslands Puna’ was approved for commercial release as a grazed forage plant in 1985 (Rumball 1986). The use of Puna chicory has now spread throughout NZ and the variety is also being used commercially in Australia, North America and South America and is being evaluated in parts of Europe and Asia (W. Green, personal communication). Chicory is a herb, whereas other temperate forages used for ruminant production are either grasses or legumes. This paper reviews work on the chemical composition, nutritive value and feeding value of chicory relative to perennial ryegrass (Lolium perenne) and to red clover (Trifolium pratense), a legume that, like chicory, is used as a forage for dry summer conditions. Throughout this paper, feeding value is defined as the animal production response to grazing a forage under unrestricted conditions (Ulyatt 1973), with its components being voluntary feed intake (VFI), the digestive process and the efficiency of utilization of digested nutrients; the latter two comprise nutritive value/dry matter (DM) eaten.
- Cited by 126
PAPER PRESENTED AT INTERNATIONAL WORKSHOP ON INCREASING WHEAT YIELD POTENTIAL, CIMMYT, OBREGON, MEXICO, 20–24 MARCH 2006 Genetic progress in yield potential in wheat: recent advances and future prospects
- M. J. FOULKES, J. W. SNAPE, V. J. SHEARMAN, M. P. REYNOLDS, O. GAJU, R. SYLVESTER-BRADLEY
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- Published online by Cambridge University Press:
- 25 January 2007, pp. 17-29
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Knowledge of the changes in physiological traits associated with genetic gains in yield potential is essential to improve understanding of yield-limiting factors and to inform future breeding strategies. Recent advances in genetic yield potential and associated physiological changes in wheat (Triticum aestivum L.) are reviewed. Genetic gains in yield potential worldwide have been both positively correlated with harvest index (HI) and above-ground dry matter (AGDM), with more frequent reports of yield progress associated with biomass since about 1990. It is concluded that an important aim of future breeding will be the increase of biomass production while maintaining the present values of HI. In winter wheat recent biomass progress has been positively associated with pre-anthesis radiation-use efficiency (RUE) and water-soluble carbohydrate (WSC) content of stems at anthesis. Present results in two doubled-haploid (DH) populations show a positive linear relationship between stem WSC and grain yield in the UK environment. Results from various investigations worldwide in recent years have demonstrated that biomass increases have been associated with particular introductions of alien genes into wheat germplasm, e.g. the 1BL.1RS wheat-rye translocation and the 7DL.7Ag wheat-Agropyron elongatum translocation. Present results confirm a positive effect of 1BL.1RS on harvest biomass in two DH populations in the UK. The future prospects for identifying physiological traits to raise yield potential are considered with particular reference to winter wheat grown in northwestern Europe. It is proposed that optimized rooting traits, an extended stem-elongation phase, greater RUE, greater stem WSC storage and optimized ear morphology will be important for breeding progress in yield potential in future years.
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Effect of temperature and carpel size during pre-anthesis on potential grain weight in wheat
- D. F. CALDERINI, L. G. ABELEDO, R. SAVIN, G. A. SLAFER
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- Published online by Cambridge University Press:
- 01 June 1999, pp. 453-459
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The effect of environmental conditions immediately before anthesis on potential grain weight was investigated in wheat at the experimental field of the Faculty of Agronomy (University of Buenos Aires, Argentina) during 1995 and 1996. Plants of two cultivars of wheat were grown in two environments (two contrasting sowing dates) to provide different background temperature conditions. In these environments, transparent boxes were installed covering the spikes in order to increase spike temperature for a short period (c. 6 days) immediately before anthesis, i.e. between ear emergence and anthesis. In both environments, transparent boxes increased mean temperatures by at least 3·8 °C. These increases were almost entirely due to the changes in maximum temperatures because minimum temperatures were little affected. Final grain weight was significantly reduced by higher temperature during the ear emergence–anthesis period. It is possible that this reduction could be mediated by the effect of the heat treatment on carpel weight at anthesis because a curvilinear association between final grain weight and carpel weight at anthesis was found. This curvilinear association may also indicate a threshold carpel weight for maximizing grain weight.
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PAPER PRESENTED AT INTERNATIONAL WORKSHOP ON INCREASING WHEAT YIELD POTENTIAL, CIMMYT, OBREGON, MEXICO, 20–24 MARCH 2006 Prospects for increasing photosynthesis by overcoming the limitations of Rubisco
- M. A. J. PARRY, P. J. MADGWICK, J. F. C. CARVALHO, P. J. ANDRALOJC
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- Published online by Cambridge University Press:
- 19 December 2006, pp. 31-43
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The low activity and the competing reactions catalysed by Rubisco are major limitations to photosynthetic carbon assimilation in C3 plants; the present paper considers how these limitations can be overcome. The limitations could be most effectively addressed by introducing Rubisco with a higher catalytic rate and/or better able to discriminate between gaseous substrates. Although enzymes with desirable characteristics are available, technical advances are required before their potential can be realized in major crop plants. Significant improvements could be achieved also by increasing the concentrations of the productive substrates, CO2 and RuBP, at the active site of Rubisco. Critically, it is essential that other environmental and genotype constraints are minimized, to realize the highest photosynthetic potential.
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Determination of ammonia and nitrate in soil
- J. M. Bremner, K. Shaw
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- Published online by Cambridge University Press:
- 27 March 2009, pp. 320-328
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1. Methods for the determination of ammonia and nitrate in soil are described. The ammonia and nitrate are extracted at pH 1·0–1·5 with a mixture of potassium sulphate and sulphuric acid, and the ammonia is determined by distillation with magnesium oxide at 25° C. in a modified Conway microdiffusion unit. Ammonia plus nitrate is determined on a separate sample of the same extract by reduction of the nitrate to ammonia with titanous hydroxide and subsequent distillation with magnesium oxide, both the reduction and distillation being carried out in a modified microdiffusion unit at 25° C.
2. The methods are applicable to coloured extracts and are not affected by substances found to interfere with other methods of determining ammonia and nitrate.
3. It is suggested that the methods may also prove useful for the determination of ammonia and nitrate in plant materials.
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Thiomolybdates and the copper–molybdenum–sulphur interaction in ruminant nutrition
- A. T. Dick, D. W. Dewey, J. M. Gawthorne
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- 27 March 2009, pp. 567-568
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In 1945 we reported (Dick & Bull, 1945) the first observations on the effects of molybdenum in the diet of ruminants in limiting the accumulation of copper in their tissues.
Further observations (Dick, 1952) indicated that there was a third factor which materially altered the control by molybdenum of copper accumulation and this factor, present in lucerne hay, was identified as inorganic sulphate (Dick, 1953a). It was also shown that sulphate regulated molybdenum excretion (Dick, 1953b) in the urine and hence the level of molybdenum in circulating blood (Dick, 1953c).
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Cell wall characteristics in relation to forage digestion by ruminants
- J. R. Wilson
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- 27 March 2009, pp. 173-182
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Prediction of intake and digestion in ruminants by a model of rumen kinetics integrating animal size and plant characteristics
- A. W. Illius, I. J. Gordon
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- 27 March 2009, pp. 145-157
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Simulation modelling was used to investigate interactions between forage degradation characteristics, rumen processes and body weight, and to predict the voluntary food intake and digestion of a range of forages. Predicted voluntary intake and digestion agreed well with empirical data, explaining 61 and 70%, respectively, of variance in observed values. Since the data covered a wide range of animal weights and forage qualities, these results suggest that the model is a useful means of integrating the effects of animal and forage variables. Interactions were examined between animal weight and diet quality, as defined by the proportion of potentially digestible cell contents and cell walls and their rates of digestion. Retention time of food in the digestive tract was shown by regression to scale with W0·27. The time taken to comminute large fibre particles also scaled with W0·27. Longer retention of digesta by large ruminants increases digestive efficiency compared with small animals and would permit them to survive on lower-quality foods. The model showed that maximum intake of metabolizable energy scales with c. W0·87, greater than the scaling of maintenance with W0·73.
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Nitrogen and organic matter losses during storage of cattle and pig manure
- S. O. PETERSEN, A.-M. LIND, S. G. SOMMER
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- 01 February 1998, pp. 69-79
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Solid pig manure (240 g kg1 DM) and solid cattle manure (150-180 g kg1 DM) were stored in an open storage facility during spring-summer and autumn conditions for periods of 9-14 weeks during 1994 and 1995. Concentrations of C, N, P and K were determined prior to and after storage, corrected for dry matter losses and distance from the surface. Temperature and, in experiments with pig manure, gas phase composition inside the manure heap were monitored during storage. Nitrogen losses as ammonia volatilization, nitrous oxide emission and leaching were measured, while total denitrification was estimated from mass balance calculations. For both cattle and pig manure there was little difference between seasons with respect to the pattern of decomposition, as reflected in temperature dynamics and C/N turnover. In contrast, there was a distinct difference between manure types. Pig manure was characterized by maximum temperatures of 60-70°C, although the concentrations of oxygen and methane clearly demonstrated that anaerobic conditions dominated the interior parts of the heap for several weeks. Losses of C and N from pig manure both amounted to c. 50%. In contrast, the temperature of cattle manure remained close to the air temperature throughout the storage period and cattle manure had lower, not significant losses of C and N. Leaching losses of N constituted 1-4% with both manure types. Ammonia volatilization from cattle manure constituted 4-5% of total N, and from pig manure 23-24%. In pig manure a similar amount of N (23-33%) could not be accounted for after storage, a loss that was attributed to denitrification. Nitrous oxide emissions amounted to <2% of estimated denitrification losses.