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Nutrients and antiquality factors in different morphological parts of the Moringa oleifera tree
- H. P. S. MAKKAR, K. BECKER
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- 01 May 1997, pp. 311-322
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Moringa oleifera grows throughout most of the tropics and has several industrial and medicinal uses. The objective of this study was to evaluate the potential of different morphological parts of this tree as animal feed. The crude protein (CP) content of leaves, soft twigs and stems was 260, 70 and 60 g kg−1 respectively. About 64, 79 and 67% of the total CP present in the leaves, twigs and stems respectively was found to be degradable after 24 h in the rumen. The protein insoluble in acid detergent fibre (ADIP), considered unavailable to animals, in these samples was 30, 150 and 170 g kg−1 respectively. About 87% of the total CP was in the form of true protein in the leaves (60 and 53% in twigs and stems respectively). The leaves had negligible amounts of tannins (12 g kg−1), and trypsin and amylase inhibitors, lectins, cyanogenic glucosides and glucosinolates were not detected. The saponin content of the leaves was 80 g kg−1 as diosgenin equivalent, which did not show any haemolytic activity. The phytate content of the leaves was 21 g kg−1. Tannins, saponins, cyanogenic glucosides and glucosinolates were detected in twigs and stems but the concentrations were negligible. Trypsin and amylase inhibitors were not detected in twigs and stems. Phytate contents of both twigs and stems were c. 30 g k−1. In leaves, amounts of all the essential amino acids were higher than the amino acid pattern of the FAO reference protein and comparable to those in soyabeans. The CP and lipid contents of the kernel were 370 and 420 g kg−1 respectively, and the CP of the meal (fat-free) was 610 g kg−1. The kernels and meal are extracted with water and the extract is used for the purification of water in some developing countries. The residues left after water extraction of kernels and meal (designated as extracted-kernel and extracted-meal) had a CP content of 350 and 700 g kg−1 respectively and all of this CP was in the form of true protein. After taking into account the ADIP contents in these samples, c. 38 and 69% of the total protein was calculated to be available in the post-rumen in extracted-kernel and extracted-meal respectively. The pepsin digestibility of these samples was 91 and 84% respectively. The sulphur-containing amino acids in kernel proteins were present at higher concentrations than those specified in the amino acid pattern of the FAO reference protein but other essential amino acids were deficient. Amongst the antinutritional factors mentioned above, glucosinolates and phytate were present in appreciable amounts (65·5 μmol/g and 41 g kg−1 respectively) in meal. Haemagglutination activity was also detected in the meal. The extracted-meal was virtually free of all the antinutritional factors examined except for phytate (67 g kg−1). The leaves of Moringa oleifera and the residue obtained after the recovery of oil and coagulants can be good sources of proteins for animal feeds.
- Cited by 216
The breeding season of the sheep with particular reference to its modification by artificial means using light
- N. T. M. Yeates
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- 27 March 2009, pp. 1-43
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At the beginning of the present century Heape (1900), describing the sexual season of mammals, pointed out that sheep in the British Isles are sexually active during only a portion of the year.
- Cited by 216
Nutritional and immunological importance of colostrum for the new-born pig
- J. LE DIVIDICH, J. A. ROOKE, P. HERPIN
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- 31 October 2005, pp. 469-485
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The nutritional and immunological importance of colostrum for the survival and development of the neonatal pig are reviewed. The pig is born with low body energy stores and devoid of serum immunoglobulins. Colostrum provides the piglet with both energy and maternal antibodies but its fat and protein composition is very variable. Colostrum is very digestible, and both colostral energy and nitrogen (N) are retained with a very high efficiency. Colostrum production by the sow assessed from the weight gain of the litter from birth to 24 h of age is very variable (from 1900 to 5300 g). There is no clear effect of litter size or parity, suggesting that colostrum production is a characteristic of the sow. Within a litter, colostrum consumption by the individual piglets varies considerably. It is independent of birth order, but related positively to birth weight and negatively to litter size. Other factors influencing colostrum consumption, including cold stress, premature birth and birth hypoxia, are discussed. Because of the epitheliochorial nature of the porcine placenta, the new-born piglet must acquire maternal immunoglobulin G (IgG) from ingested colostrum for passive immune protection until the immune system of the piglet becomes fully developed. Colostrum IgG concentrations in milk vary widely between individual sows both in initial concentration and in the rate at which concentrations decline during the first 24 h of life. The piglet can only absorb intact IgG prior to gut closure, which occurs in the first 24 h of life and is induced by intakes of colostrum which are insufficient to maintain piglet live-weight. As a result, the amounts of intact IgG absorbed by the piglet vary widely. The effects of colostrum consumption on neonatal survival are discussed. Consumption of colostrum in amounts sufficient to meet the energy requirement of the piglet is a major determinant for survival. Since most neonatal losses occur in the first 2 days of life, before acquisition of a maternal IgG for immune protection becomes important for survival, piglet serum IgG concentration does not correlate well with early survival but is important in later resistance to disease challenge. It is concluded that colostrum production is a good marker for the maternal quality of the sow. Future research should focus on the ability of the sow to produce more colostrum and on the possible delayed effects of passive immunisation on the health and performance of piglet at weaning and later in life.
- Cited by 214
Denitrification in soil. II. Factors affecting denitrification
- J. M. Bremner, K. Shaw
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- 27 March 2009, pp. 40-52
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1. The factors affecting denitrification in soil have been studied by determining loss of nitrogen from soil under various conditions by total-N analysis.
2. It was found that the rate of denitrification of nitrate in soil was dependent upon various factors such as the pH, temperature and water content of the soil and that, under conditions conducive to denitrification, 80–86% of nitrate-N added to Rothamsted soils was lost by denitrification in 5 days.
3. The rate of denitrification was greatly affected by the pH of the soil. It was very slow at low pH (below 4·8), increased with rise in soil pH and was very rapid at pH 8·0–8·6.
4. The rate of denitrification increased rapidly with rise in temperature from 2° to 25° C. The optimum temperature for denitrification was about 60° C.
5. The degree of water saturation of the soil had a profound influence on the rate of denitrification. Below a certain moisture level practically no denitrification occurred; above this level denitrification increased rapidly with increase in moisture content. The critical moisture level was about 60% of the water-holding capacity of the soil.
- Cited by 212
The effect of protein infusion on urinary excretion of purine derivatives in ruminants nourished by intragastric nutrition
- T. Fujihara, E. R. Ørskov, P. J. Reeds, D. J. Kyle
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- 27 March 2009, pp. 7-12
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Two experiments were carried out to determine endogenous excretion of purine derivatives in steers and lambs, and to investigate the relationship between microbial nucleic acid input and urinary excretion of purine nitrogen.
The endogenous excretion of allantoin after conversion of hypoxanthine, xanthine and uric acid to allantoin, was calculated to be 72 and 26 mg/kg W0·75 per day in steers and lambs, respectively, when the dietary protein contained no nucleic acid nitrogen.
The excretion of purine derivatives increased linearly with increasing microbial nucleic acid input in lambs. The excretion of purine derivatives in excess of endogenous contribution was closely related to the theoretically expected values. The average recovery was calculated as 0·96 for one sheep and 1·0 for the other.
- Cited by 211
Impact of high-temperature stress on rice plant and its traits related to tolerance
- F. SHAH, J. HUANG, K. CUI, L. NIE, T. SHAH, C. CHEN, K. WANG
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- 27 April 2011, pp. 545-556
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The predicted 2–4°C increment in temperature by the end of the 21st Century poses a threat to rice production. The impact of high temperatures at night is more devastating than day-time or mean daily temperatures. Booting and flowering are the stages most sensitive to high temperature, which may sometimes lead to complete sterility. Humidity also plays a vital role in increasing the spikelet sterility at increased temperature. Significant variation exists among rice germplasms in response to temperature stress. Flowering at cooler times of day, more pollen viability, larger anthers, longer basal dehiscence and presence of long basal pores are some of the phenotypic markers for high-temperature tolerance. Protection of structural proteins, enzymes and membranes and expression of heat shock proteins (HSPs) are some of the biochemical processes that can impart thermo-tolerance. All these traits should be actively exploited in future breeding programmes for developing heat-resistant cultivars. Replacement of heat-sensitive cultivars with heat-tolerant ones, adjustment of sowing time, choice of varieties with a growth duration allowing avoidance of peak stress periods, and exogenous application of plant hormones are some of the adaptive measures that will help in the mitigation of forecast yield reduction due to global warming.
- Cited by 210
The effects of fatty acids on pure cultures of rumen bacteria
- C. Henderson
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- 27 March 2009, pp. 107-112
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The effects of fatty acids, at low concentrations (0–005-O5 g/1), on the growth of seven species of rumen bacteria were examined. Anaerovibrio lipolytica(strain 5 S), Peptostreptococcus elsdenii(type 2), Bacteroides ruminicola46/52 and Selenomonas ruminantium(strain 17) were unaffected by addition of oleic acid to the medium. Growth of ButyrivibrioB 835 was stimulated by low concentrations of oleic (< 0–01 g/1), lauric (< 0–1 g/1) or capric (< 0–1 g/1) acids while higher concentrations of these acids were inhibitory. Myristic, palmitic and stearic acids were inhibitory at all concentrations tested. Ruminococcus4263/1 was inhibited at all concentrations of the six acids. Production of methane by pure cultures of Methanobacterium ruminantiumwas also inhibited by the additions of long-chain fatty acids. Oleic acid was the most inhibitory of the series of acids. These results are consistent with the reported effects of lipids on rumen function.
- Cited by 210
A century of fungicide evolution
- P. E. RUSSELL
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- 28 June 2005, pp. 11-25
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Up until the 1940s chemical disease control relied upon inorganic chemical preparations, frequently prepared by the user. Key areas of use were horticulture and vegetable production with key targets being diseases that caused easily recognized damage. After this era and as the damaging effects of more crop diseases became obvious by the use of chemical control, the crop protection industry expanded rapidly and research to discover new active materials began in earnest. As new areas of chemistry were introduced, each one aiming to offer advantages over the previous ones, chemical families were born with research-based companies frequently adopting patent-busting strategies in order to capitalize on the developing fungicides market. Systemic fungicides offered new opportunities in disease control. The rise in Research and Development (R & D) and the increase in the number and quantity of chemicals being applied led to the introduction of regulation in the 1950s, initially on a voluntary basis, but now strictly controlled by legal obligations. In the 1960s, the market switched from horticulture and vegetables to one in which the main agricultural crops dominated. The cereal market, initially based on barley, moved to the current dominant market of wheat. The costs of R & D have risen dramatically in recent years and have become dominated not by the discovery process per se but by the provision of all the extra data needed to obtain registration. These rising costs happened at a time when markets showed little growth and are currently showing some decline. This has resulted in an industry that is continually striving to cut costs, normally by mergers and take-overs. As a consequence, many plant disease problems are not now being targeted by the industry and special measures have been introduced to ensure adequate disease control is available for these minor markets. Plant disease control will remain a necessity and fungicides will remain as a key factor in such control, although it is predicted that integrated control using chemicals, biological controls and biotechnology approaches will begin to dominate.
- Cited by 209
The growth of lambs before and after birth in relation to the level of nutrition
- L. R. Wallace
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- 27 March 2009, pp. 93-153
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In presenting the results of these investigations, we have attempted to discuss in each section the findings that have been described, and here we will merely be concerned with summarizing the major points that have emerged.
- Cited by 208
Growth and development in the pig, with special reference to carcass quality characters. I1
- C. P. McMeekan
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- 27 March 2009, pp. 276-343
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1. With the object of establishing the general order of development during post-natal life of the body proportions, tissues, and anatomical units, the relative changes with age in these characters have been studied in a series of male pigs killed at monthly intervals from birth to 7 months. The study is to be regarded in the light of a preliminary investigation, providing a background to experimental studies on the influence of nutrition on the growth and development of the pig.
2. Growth in body proportions, when measured both photographically and by the weight of the individual anatomical regions, conforms to the law of developmental direction, exhibiting a well-defined anterior-posterior gradient from earlier to later developing regions. The limbs appear as relatively early developing parts with the fore limbs slightly earlier developing than the hind.
3. The major body tissues exhibit marked differential growth behaviour; skeleton, muscle, and fat develop in that order. This situation has its origin in the differential rates of growth of the three tissues, in consequence of which the earlier developing skeleton makes a greater proportion of its growth earlier in life than does muscle, while the latter makes a greater proportion of its growth earlier than does the still later developing fat.
4. Within any one tissue, the individual anatomical units or regions of the body similarly show well-defined differential growth relationships. Thus, the skeletal units of the head and trunk exhibit an anterior-posterior gradient in their order of development, while the bones of each limb show a centripetal gradient, the upper units being later developing than the lower units. To an even more marked degree, both the muscle and the fat surrounding these skeletal units afford evidence of similar gradients in these tissues.
- Cited by 206
Studies on mixtures of maize and beans (Phaseolus vulgaris) with particular reference to plant population
- R. W. Willey, D. S. O. Osiru
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- 27 March 2009, pp. 517-529
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Two experiments are described in which the possible yield benefits of mixing maize and beans were examined under intensive farming conditions. A ‘replacement series’ of pure maize, two-thirds maize/one-third beans, one-third maize/two-thirds beans and pure beans was used at four plant populations. A high level of nitrogen was applied on the maize to eliminate the effects of nitrogen transfer from the beans.
Yields of the mixtures were up to 38% higher than could be achieved by growing the crops separately. It is concluded that this occurred because the mixtures achieved a greater utilization of environmental resources; it is suggested that, because of the marked height differences of the two crops, an increased utilization of light was probably a major contributing factor. The need for high populations in mixtures is indicated, partly because the largest yield increases were achieved at high populations and partly because the mixtures required a higher population pressure to produce their maximum yield.
The maize was found to have the higher relative competitive ability, and this increased with increase in plant population pressure. It is suggested that this was probably due to the shading effect which the maize had on the beans. The effects of a change in relative competitive abilities, or in relative selling prices, on the optimum proportion of two species in a mixture are also considered.
- Cited by 205
Effects of temperature, wind speed and air humidity on ammonia volatilization from surface applied cattle slurry
- S. G. Sommer, J. E. Olesen, B. T. Christensen
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- 27 March 2009, pp. 91-100
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Ammonia losses from surface-applied cattle slurry were measured under field conditions using a wind tunnel system that allows variables affecting ammonia loss to be examined under controlled conditions. The experiments were carried out on a sandy soil with seven different surface covers. This report considers the effect of wind speed, temperature and water vapour deficit on the ammonia loss over a series of 6-day periods. During October 1986 to November 1989 42 treatments were examined, using slurries taken from the same slurry tank to provide slurries of similar chemical composition.
When temperatures were near zero, the rate of ammonia loss was generally low. The accumulated loss over 6 days was high, however, because the rate of loss was constant throughout the period. In these experiments the soil was saturated with water and partly frozen, and the infiltration of slurry into the soil reduced. At 19 °C initial loss rates were high but, after 12 h, almost no further loss occurred. Apart from these extremes, the ammonia loss rates within the initial 24 h were significantly affected by temperature and wind speed.
Ammonia volatilization after 6 h was exponentially related to temperature (r2 = 0·841) but the correlation weakened with time after slurry application. An increase in ammonia volatilization with increasing water vapour pressure deficit was considered to be an effect of temperature.
The ammonia loss rate increased when wind speeds increased up to 2·5 m/s. No consistent increase in ammonia volatilization was found when the wind speed increased from 2·5 to 4 m/s. Ammonia loss after 24 h increased with increasing initial pH of the slurry.
A two-stage pattern for ammonia volatilization from slurry is proposed. During the first stage (the initial 24 h) ammonia loss rate is high due to an elevated pH at the slurry surface followingv application, and temperature significantly affects the loss rate. In the next stage, pH declines and the rate of ammonia volatilization decreases. During this stage other factors, including the dry matter content of the slurry, control the rate of ammonia loss.
- Cited by 203
A comparison of the organic matter, biomass, adenosine triphosphate and mineralizable nitrogen contents of ploughed and direct-drilled soils
- D. S. Powlson, D. S. Jenkinson
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- 27 March 2009, pp. 713-721
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Soil samples were taken from four field experiments on the growth of cereals in direct-drilled and in mouldboard-ploughed soil. When sampled, one of the experiments had run for 5 years, one for 6, one for 8 and one for 10 years. Sampling was to just below plough depth and was done on an ‘equivalent depth’ basis, i.e. the more compact direct-drilled plots were sampled more shallowly than the ploughed plots in such a way that both samples represented the same weight of soil per unit area. No significant differences in total nitrogen or in total organic carbon were observed between cultivation treatments at any of the four sites.
In three of the four sites, there was no significant difference in microbial biomass carbon, adenosine 5'-triphosphate (ATP), or mineralizable nitrogen between directdrilled and ploughed soils. In the fourth, which contained more clay than the others, there was slightly more biomass carbon and ATP in the direct-drilled soil. As microbial biomass carbon (or ATP, which is closely correlated with microbial biomass carbon) responds more rapidly to changes in management than do total carbon and nitrogen, a change in biomass carbon should provide early warning of changes in soil organic matter, long before changes in total carbon and nitrogen become measurable. That no such change was observed, with one partial exception, is evidence that a change from traditional methods of cultivation to direct drilling has little effect on soil organic matter other than altering its distribution in the soil profile.
- Cited by 203
Synergies between the mitigation of, and adaptation to, climate change in agriculture
- P. SMITH, J. E. OLESEN
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- 07 June 2010, pp. 543-552
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There is a very significant, cost effective greenhouse gas (GHG) mitigation potential in agriculture. The annual mitigation potential in agriculture is estimated to be 4200, 2600 and 1600 Mt CO2 equiv/yr at C prices of 100, 50 and 20 US$/t CO2 equiv, respectively. The value of GHG mitigated each year is equivalent to 420 000, 130 000 and 32 000 million US$/yr for C prices of 100, 50 and 20 US$/t CO2 equiv, respectively. From both the mitigation and economic perspectives, we cannot afford to miss out on this mitigation potential.
The challenge of agriculture within the climate change context is two-fold, both to reduce emissions and to adapt to a changing and more variable climate. The primary aim of the mitigation options is to reduce emissions of methane or nitrous oxide or to increase soil carbon storage. All the mitigation options, therefore, affect the carbon and/or nitrogen cycle of the agroecosystem in some way. This often not only affects the GHG emissions but also the soil properties and nutrient cycling. Adaptation to increased variability of temperature and rainfall involves increasing the resilience of the production systems. This may be done by improving soil water holding capacities through adding crop residues and manure to arable soils or by adding diversity to the crop rotations.
Though some mitigation measures may have negative impacts on the adaptive capacity of farming systems, most categories of adaptation options for climate change have positive impacts on mitigation. These include: (1) measures that reduce soil erosion, (2) measures that reduce leaching of nitrogen and phosphorus, (3) measures for conserving soil moisture, (4) increasing the diversity of crop rotations by choices of species or varieties, (5) modification of microclimate to reduce temperature extremes and provide shelter, (6) land use change involving abandonment or extensification of existing agricultural land, or avoidance of the cultivation of new land. These adaptation measures will in general, if properly applied, reduce GHG emissions, by improving nitrogen use efficiencies and improving soil carbon storage.
There appears to be a large potential for synergies between mitigation and adaptation within agriculture. This needs to be incorporated into economic analyses of the mitigation costs. The inter-linkages between mitigation and adaptation are, however, not very well explored and further studies are warranted to better quantify short- and long-term effects on suitability for mitigation and adaptation to climate change. In order to realize the full potential for agriculture in a climate change context, new agricultural production systems need to be developed that integrate bioenergy and food and feed production systems. This may possibly be obtained with perennial crops having low-environmental impacts, and deliver feedstocks for biorefineries for the production of biofuels, biomaterials and feed for livestock.
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The volume-changes associated with variations of water content in soil
- William B. Haines
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- 27 March 2009, pp. 296-310
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(1) A new and simple method of measuring the shrinkage of moist soil on drying is described, which at the same time gives values for the pore space and specific gravity of the soil.
(2) Diagrams for a number of diverse soils are given, illustrating the character of soil shrinkage.
(3) The shrinkage is shown to take place in two stages in both of which there is a linear relationship to the moisture content.
(4) Tentative explanations of these two stages are advanced, based on the well-known colloidal-coating hypothesis, and confirmatory experiments described.
(5) By means of the method the effect of alternate wetting and drying of soil in producing a good tilth is illustrated.
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PAPER PRESENTED AT INTERNATIONAL WORKSHOP ON INCREASING WHEAT YIELD POTENTIAL, CIMMYT, OBREGON, MEXICO, 20–24 MARCH 2006 Understanding the physiological basis of yield potential in wheat
- R. A. FISCHER
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- 12 February 2007, pp. 99-113
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The present paper focuses on the physiology of yield potential in wheat (Triticum aestivum L.), because breeding progress in yield potential has overtaken farm yield progress. The paper examines developments largely in the last 10 years seeking routes to higher yield potential. Lately this subject has come under pressure from two new imperatives: perceived slowing of genetic progress and ambitious functional genomics. Analysis of trials between 1996 and 2005 at the CIANO research centre in northwest Mexico suggests that yield potential progress in CIMMYT spring wheats has slowed to around 0·50% per year, but has not ceased there nor in winter wheats elsewhere. Meanwhile, in the last 10 years or so, physiological understanding has advanced somewhat. Increased kernel number/m2 remains strongly associated with genetic progress in grain yield, and new research reinforces the importance of spike dry weight (g/m2) at anthesis in its determination. Lengthening the spike growth period through manipulation of sensitivity to photoperiod looks promising, but more attention to kernels per unit of spike weight is also urged. With respect to plant height, an optimum somewhere between 0·7 and 1·0 m is accepted and we are moving away from infatuation with the Norin 10 dwarfing genes as a way of reaching that. What has not been achieved is good lodging resistance in all short spring wheats, nor a complete understanding of its physiological basis. New information is coming to light on the possible role of stored stem reserves at anthesis, for these reserves appear to have increased as yield potential has increased. Part of the benefit may be related to assimilate supply per kernel around anthesis, which new understanding suggests is important for maximum potential kernel weight. Nevertheless, results continue to suggest that despite more kernels/m2, the most recent wheats are still largely sink-limited during grain filling. Growing evidence from spring and winter wheat (and from rice and maize) now points to the importance of increased photosynthetic activity before and around flowering for recent genetic increases in yield potential. This opens up new possibilities for selection in field plots. Finally, attention is given to effects of weather on yield potential and recent advances in techniques for elucidating the physiological basis of genotype by year interactions. From physiological understanding such as described, traits can be suggested as possible selection criteria for yield potential. However, apart from the ACIAR/CIMMYT project looking at stomatal aperture-related traits as well as source and sink traits (Condon et al., in press; Reynolds et al., in press; van Ginkel et al., in press), there appear to have been few attempts to validate physiological (or morphological) selection criteria for wheat yield potential in the last decade, but recent promising results with spectral reflection indices could foreshadow more validation work. This contrasts with efforts to improve the performance of wheat (and maize) under water-limited conditions, and with the new plant type and super rice approaches of IRRI and China, respectively. Such research could be mapped out for wheat yield potential improvement, and could lead to more efficient breeding for yield potential and/or faster progress, but it requires a multidisciplinary team, including, nowadays, molecular biologists. It also needs suitable controlled and field environments and substantial long-term support. All this may no longer be available in the public sector, at least at a single location.
- Cited by 191
Nitrogen inputs and losses from clover/grass pastures grazed by dairy cows, as affected by nitrogen fertilizer application
- S. F. LEDGARD, J. W. PENNO, M. S. SPROSEN
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- 01 March 1999, pp. 215-225
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Nitrogen (N) inputs and outputs were measured over 3 years in a trial with four farmlets (each with 16 randomly-allocated 0·4 ha paddocks) on permanent white clover/ryegrass pastures which were grazed throughout the year by dairy cows near Hamilton, New Zealand. Three farmlets were stocked at 3·3 cows/ha and received nominal rates of N fertilizer (urea in 8–10 split applications) of 0, 200 or 400 kg N/ha per year. A fourth farmlet with 4·4 cows/ha received 400 kg N/ha per year and was supplemented with maize grain during the first two years.
Nitrogen balances were calculated, with [sum ]N inputs[ape ][sum ]N outputs. Annual inputs from N2 fixation were 99–231 kg N/ha in the 0 N farmlet, but declined to 15–44 kg N/ha in the 400 N farmlets. The main N outputs (in kg N/ha per year) were in milk (72–126), nitrate leaching (20–204), and transfer of N via cow excreta from pastures to lanes and milking shed (54–92). Gaseous losses by denitrification (3–34) and volatilization (15–78) were smaller than the other N outputs but increased significantly with N fertilizer application. In the maize-supplemented farmlet, N outputs in milk were 31% higher than in the corresponding non-supplemented 400 N farmlet, whereas leaching losses averaged 17% lower during the 2 years of supplementation.
In the N-fertilized farmlets, estimated N balances were influenced by inclusion of the transitional N processes of immobilization of fertilizer N into the soil organic N pool (estimated using 15N at 42–94 kg N/ha per year) and the contribution from mineralization of residual clover-fixed N in soil not accounted for in the current estimates of N2 fixation (estimated at up to 70% of measured N2 fixation or 46 kg N/ha per year). However, these processes were counteracting and together were calculated to have only a small net effect on total N balances.
The output of N in products (milk, meat and feed) relative to the total N input averaged 26% in the 400 N farmlets, and is compared to that measured for commercial intensively-managed dairy farms in England and the Netherlands (14–20%). The 0 N farmlet, which was reliant on N2 fixation as the sole N input, was relatively very N-efficient with the milk production being 83% of that in the 400 N farmlet (at 3·3 cows/ha) and the N output in products relative to total N input averaging 52%.
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Cell membrane stability, an indicator of drought tolerance, as affected by applied nitrogen in soyabean
- G. S. Premachandra, H. Saneoka, S. Ogata
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- 27 March 2009, pp. 63-66
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Four soyabean cultivars were grown with two N application rates (50 and 300 kg N/ha) in the field at Hiroshima University, Japan, from June to August 1988. Cell membrane stability (CMS) by the polyethylene glycol (PEG) test, leaf water relations and nutrient concentrations in cell sap and leaf tissues were measured when the plants were 50 days old, in the uppermost fully expanded leaves.
Cell membrane stability was higher at the higher N rate, the increase over the lower rate being greater in the cultivars Lee+ and Lee–than in Tamahomare and T201. Leaf water potential was not affected by the higher rate of N application. Osmotic adjustment, which was independent of water stress, was observed with the higher rate of N and it was higher in Lee + and Lee–than in Tamahomare and T201. It is suggested that osmotic potential in leaf tissues may influence CMS measured by the PEG test. Solute concentrations in cell sap and leaf tissues were higher at the higher N rate. Sugar and K were the major contributors to osmotic potential.
- Cited by 188
Effect of synchronizing the rate of dietary energy and nitrogen release on rumen fermentation and microbial protein synthesis in sheep
- L. A. Sinclair, P. C. Garnsworth, J. R. Newbold, P. J. Buttery
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- 27 March 2009, pp. 251-263
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The effects of two diets formulated to be either synchronous or asynchronous with respect to the hourly supply of energy and nitrogen on rumen fermentation and microbial protein synthesis were studied in sheep.
In Expt 1, the in situ degradation characteristics of nitrogen (N), organic matter (OM) and carbohydrate (CHO) fractions were determined in winter wheat straw, winter barley, malt distillers dark grains rapeseed meal and fishmeal. The feeds exhibited a large range in degradability characteristics of the nitrogen and energy-yielding fractions.
A computer program was developed based upon the raw material degradation characteristics obtained from the above studies. The program was used to formulate two diets with similar metabolizable energy (9·5 MJ/kg DM) and rumen degradable protein contents (96 g/kg DM) but to be either synchronous (diet A) or asynchronous (diet B) with respect to the hourly rate of release of N and energy. The program was used to predict the hourly release of N, OM and CHO and the molar production of volatile fatty acids (VFA).
In Expt 2, the two diets were fed to four cannulated sheep at the rate of 1 kg/day in four equal portions, in two periods, using a change-over design. Rumen ammonia concentrations followed the predicted rate of N degradation. A maximum concentration of 10·5 and 7 mM for diets A and B respectively was achieved within the first hour of feeding which then fell to 7 and 3 mM respectively. Rumen VFA proportions were more stable for the synchronous diet (A) than the asynchronous diet (B) and were more stable than predicted for both diets. True ruminal degradation of OM and CHO was similar for both diets and close to that predicted, although fibre degradability in diet A was 30% lower than predicted due to a reduction in both cellulose and hemicellulose digested. Microbial protein production was estimated simultaneously with L-[4,5–3H]leucine and a technique based on cytosine. Estimates varied with marker but mean values indicated a 27% greater production of microbial N (g N/kg DM I) with the synchronous diet (A) and an average improvement in microbial protein efficiency (g N/kg OM truly degraded or CHO apparently degraded) of 13%, although neither difference was significant. There was evidence of a greater recycling of N in the animals and a significantly lower content of rumen degradable protein when the sheep were fed the asynchronous diet (B).
The results are consistent with the view that synchronizing the rate of supply of N and energyyielding substrates to the rumen micro-organisms based upon ingredient in situ degradation data can improve microbial protein flow at the duodenum and the efficiency of microbial protein synthesis.
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Modelling the fate of nitrogen in crop and soil in the years following application of 15N-labelled fertilizer to winter wheat
- N. J. Bradbury, A. P. Whitmore, P. B. S. Hart, D. S. Jenkinson
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- Published online by Cambridge University Press:
- 27 March 2009, pp. 363-379
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A computer model is presented that describes the flow of nitrogen between crop and soil on the field scale. The model has a compartmental structure and runs on a weekly time-step. Nitrogen enters via atmospheric deposition and by application of fertilizer or organic manures, and is lost through denitrification, leaching, volatilization and removal in the crop at harvest. Organic nitrogen is contained within three of the model compartments – crop residues (including plant material dying off through the growing season), soil microbial biomass and humus. Inorganic nitrogen is held in two pools as NH4+ or NO3-. Nitrogen flows in and out of these inorganic pools as a result of mineralization, immobilization, nitrification, leaching, denitrification and plant uptake. The model requires a description of the soil and the meteorological records for the site – mean weekly air temperature, weekly rainfall and weekly evapotranspiration. The model is designed to be used in a ‘carry forward’ mode – one year's run providing the input for the next, and so on. The model also allows the addition of 15N as labelled fertilizer, and follows its progress through crop and soil. Data from a Rothamsted field experiment in which the fate of a single pulse of labelled N was followed over several years were used to set the model parameters. The model, thus tuned, was then tested against other data from this and two contrasting sites in south-east England. Over a period of 4 years, the root mean square (R.M.S.) difference between modelled and measured quantities of labelled N remaining in the soil of all three sites was c. 7·5 kg N/ha, on average. The root mean square error in the measurements was c. 2·5 kg/ha. Similarly, the R.M.S. difference between modelled and measured recovery of labelled N by the crop was 0·6, compared with 0·3 kg/ha in the measurements themselves.