1. Three species of grass, rye-grass (two varieties, S 23 and S 24) cocksfoot (variety S 37) and timothy (variety S 48) were cut at various stages of maturity, dried and given at several planes of nutrition to sheep in respiration chambers. The detailed chemical composition of the grasses and the apparent digestibility of the constituents were studied.

1. The volume of rumen liquor in milk-fed calves at different ages up to 32 weeks was estimated by injecting polyethylene glycol into the rumen and subsequently determining its concentration in the rumen liquor. This volume increased progressively with age in relation to unit body weight. The increase xswas approximately fourfold between 4–8 weeks on the one hand and 28–32 weeks on the other.

2. The amount of milk entering the rumen during a feed was estimated at different ages up to 32 weeks by the subsequent determination of the volume and fat content of the rumen liquor. In the majority of cases less than 5% of the milk fed entered the rumen. There did not appear to be any increase in the quantities of milk entering the rumen as the calves got older.

3. An estimate of the rate of flow of fluid into and out of the rumen (other than milk at feeding) was made by measuring the rate of disappearance of polyethylene glycol from the rumen. A mean figure of 255 ml./hr./100 kg. body weight s.d. ± 50 was obtained in this way. It is suggested that this value probably represents the rate of flow of saliva.

4. Magnesium, in a concentration up to about 8 mg./100 ml. in the rumen liquor, did not appear to be absorbed to more than a small extent through the rumen wall.

Experiments investigating effects of foliar disease control on wheat grain protein concentration (GPC) are reviewed. Fungicidal control of rusts (Puccinia spp.) and powdery mildew (Erysiphe graminis) increased or had no significant effect on GPC in almost all cases, whilst control of the Septoria spp. often resulted in reduced GPC, but with exceptions. Reasons for these differences are discussed with reference to host pathogen interactions. Irrespective of infection strategy (biotrophic or necrotrophic), controlling severe infection increased nitrogen yield and the proportion of above-ground crop nitrogen that was partitioned to the grain. Similar effects are recorded for above-ground biomass and dry matter harvest index. The relationships between fungicide effects on green flag leaf area duration (GFLAD) and GPC were examined and shown to be unaffected by mode of action of the fungicide. Interactions between fungicide use and cultivar, nitrogen and growing season are related to the amount and type of pathogen present, and environment. An economic analysis demonstrated that fungicide effects on GPC should not affect the choice of fungicide or application programme, but that applications of foliar urea at the start of grain filling can deliver a cost-effective method of eliminating GPC reductions that may occasionally result from fungicide use.

Increasing crop competitiveness using higher seeding rates is a possible technique for weed management in low input and organic farming systems or when herbicide resistance develops in weeds. A range of wheat seeding rates were sown and resulted in crop densities between 50–400 plants/m2 (current recommendations are 100–150 plants/m2) in the presence and absence of annual ryegrass (Lolium rigidum Gaud.) in three wheat cultivars at nine experiments in southern Australia. Wheat densities of at least 200 plants/m2 were required to suppress L. rigidum and to a lesser extent increase crop yield across a wide range of environments (seasonal rainfall between 200–420 mm) and weed densities (50–450 L. rigidum plants/m2). Doubling crop density of all cultivars from 100 to 200 plants/m2 halved L. rigidum dry weight (averaged over all experiments) from 100 g/m2 to about 50 g/m2. Higher crop densities gave diminishing marginal reductions in weed biomass, while cultivar differences in weed suppression were small. Grain yields ranged from 0·5 t/ha to over 5 t/ha depending on site and season. Maximum yields in the weed-free plots (averaged over environments and cultivars) were at 200 crop plants/m2, and yield declined only slightly by 4–5% at densities up to 425 plants/m2. In the weedy plots grain yield continued to increase up to the highest density but at a slower rate. The percentage yield loss from weed competition was of a smaller magnitude than the suppression of L. rigidum by wheat. For example, 100 wheat plants/m2 led to an average 23% yield loss compared with 17% at 200 plants/m2, and the probability of reduced crop grain size and increased proportion of small seeds was negligible at these densities. Cultivar differences in yield loss from weed competition were small compared with differences due to crop density. Adoption of higher wheat seed rates as part of integrated weed management is now strongly promoted to farmers.

1. The results are presented of an investigation in which the growth and development of forty single male sheep foetuses was examined. The material, obtained from slaughterhouses, included seventeen specimens of known age, while further details of the remainder were lacking. For these reasons, and the fact that the specimens were preserved in 10% formalin prior to dissection, relative, rather than absolute, trends were discussed. This had been achieved by expressing all values as percentages of those obtained from four single male lambs dissected at birth.

2. In order to age the experimental material with the greatest possible accuracy, data were collected from the literature on foetal weights and crownrump lengths of specimens of known age. Mean values were computed and normographs established for the pre-natal period between 18 days and fullterm. By employing the method of least squares, it was not possible to fit single curves to the data; in the case of both weight and crown-rump length the curves had to be divided into five segments in order to establish the relationships with age. Apart from a rather marked change in the rate of growth and development between the 109th and 110th days of gestation, the apparent ‘breaks’ in the curves were not considered important. It would seem that lack of data at certain stages, together with the heterogeneity of the population studied, were greatly responsible for the differential rates of growth and development recorded.

3. The data were inadequate to examine fully the effect of fixation on foetal weight; however, it would appear that whereas specimens weighing less than 200 g. and over 1200 g. lost weight during the course of preservation, foetuses intermediate between the above values gained weight. Since the causes could not be satisfactorily explained, the need for further investigation was emphasized.

4. Of the foetal measurements recorded, head length and, particularly, head width were shown to be earlier maturing than chest circumference and chest depth, while crown-rump length made even greater proportional increases during pre-natal life. In general, the results supported accepted theory that the retardation of rate of development proceeds in an anterior-posterior direction prior to birth.

5. By dissecting the head from the body and weighing each unit separately, it was shown that the head decreases in relative size throughout foetal life. Head:body ratio, however, was found to be unsuitable as a criterion of pre-natal age, since foetuses of equal age may differ appreciably in this respect. It was shown, for example, that a lamb at birth, though above the average in terms of absolute weight, may possess the conformation of a 120-day-old foetus on the basis of head: body ratio.

6. Dissections of the major constituent parts of the foetal body indicated the skinned head to be the earliest maturing, followed in order by the organs (weighed en masse), dressed carcass, total skin and, finally, the skinned feet and tail, which were latest maturing. The order in which these parts grow before birth appeared explicable primarily upon a basis of functional necessity.

7. The skull was shown to develop to a relatively lesser degree during foetal life than the mandibles, while skull measurements indicated the cranial portion to be earlier maturing than the facial. Linear measurements of the various vertebral regions at different stages of development did not yield entirely satisfactory results, but it was evident that the anterior cervical vertebrae are earlier maturing than those of the posterior extremity (caudal vertebrae).

8. Weights of the major units of both thoracic and pelvic limbs indicated the former to be slightly earlier maturing. In contrast to the direction of retardation of growth during post-natal life, in the foetus the gradient followed a proximo-distal direction; scapula and pelvis, for example, being earlier maturing than metacarpus and metatarsus.

9. Linear development of individual bones was shown to be earlier maturing than growth in weight. However, on the basis of length measurements, the course of development proceeded in a similar direction as the trends established in terms of weight, i.e. proximo-distally. Width of pelvis, on the contrary, was shown to be earlier maturing than width of scapula; this was explained in terms, particularly, of earlier developing cartilage in the former bone.

10. In terms of weight, m. longissimus dorsi appeared to be earlier maturing than m. rectus femoris and m. gastrocnemius lateralis; between the latter two muscles no marked difference in rate of growth could be established. The results indicated that these three muscles develop at much the same rate in respect of length and depth during pre-natal life, but m. longissimus dorsi showed relatively less development in width over the same period of time than the other muscles.

11. Of each of the above-mentioned muscles, the cross-diameter of fifty individual fibres was measured by means of an ocular micrometer. Again, a tendency was observed for fibres of m. longissimus dorsi to be earlier maturing than those of m. rectus femoris or m. gastrocnemius.

12. Development of muscle-fibre diameter during foetal life was examined further on the overall mean for the three muscles studied, i.e. the mean of 150 measurements per foetus. The results showed that whereas muscle-fibre diameter increased but slightly (approximately 19·5%) during the first two-thirds of pre-natal life, the increase thereafter was substantial; on the basis of a linear regression, the increase amounted to 113·2% from about 108 days to full-term. The data thus appears to support the accepted view that muscular growth occurs initially by an increase in the number of fibres, and in late foetal life primarily by hypertrophy.

13. The dispersion of muscle-fibre sizes, in absolute measure, was shown to increase with advancing foetal age, the range at birth being considerable. In accord with the results of other investigators, a small proportion of small fibres was observed between approximate ages of 61 and 68 days which, apparently, were not present at either earlier or later stages.

14. Measurement of fibres from muscles situated in different anatomical regions of the body indicated that the muscles of the head were earlier maturing than those of the trunk, and muscles of the thoracic limb earlier maturing than those of the pelvic limb. In agreement with the results obtained on bone weights and measurements, the retardation appeared to proceed in a proximo-distal direction, particularly in the case of the pelvic limb.

The Broadbalk Wheat Experiment at Rothamsted (UK) includes plots given the same annual applications of inorganic nitrogen (N) fertilizer each year since 1852 (48, 96 and 144 kg N/ha, termed N1 N2 and N3 respectively). These very long-term N treatments have increased total soil N content, relative to the plot never receiving fertilizer N (N0), due to the greater return of organic N to the soil in roots, root exudates, stubble, etc (the straw is not incorporated). The application of 144 kg N/ha for 135 years has increased total soil N content by 21%, or 570 kg/ha (0–23 cm). Other plots given smaller applications of N for the same time show smaller increases; these differences were established within 30 years. Increases in total soil N content have been detected after 20 years in the plot given 192 kg N/ha since 1968 (N4).

There was a proportionally greater increase in N mineralization. Crop uptake of mineralized N was typically 12–30 kg N/ha greater from the N3 and N4 treatments than the uptake of c. 30 kg N/ha from the N0 treatment. Results from laboratory incubations show the importance of recently added residues (roots, stubble, etc) on N mineralization. In short-term (2–3 week) incubations, with soil sampled at harvest, N mineralization was up to 60% greater from the N3 treatment than from N0. In long-term incubations, or in soil without recently added residues, differences between long-term fertilizer treatments were much less marked. Inputs of organic N to the soil from weeds (principally Equisetum arvense L.) to the N0–N2 plots over the last few years may have partially obscured any underlying differences in mineralization.

The long-term fertilizer treatments appeared to have had no effect on soil microbial biomass N or carbon (C) content, but have increased the specific mineralization rate of the biomass (defined as N mineralized per unit of biomass).

Greater N mineralization will also increase losses of N from the system, via leaching and gaseous emissions. In December 1988 the N3 and N4 plots contained respectively 14 and 23 kg/ha more inorganic N in the profile (0–100 cm) than the N0 plot, due to greater N mineralization. These small differences are important as it only requires 23 kg N/ha to be leached from Broadbalk to increase the nitrate concentration of percolating water above the 1980 EC Drinking Water Quality Directive limit of 11·3mgN/l.

The use of fertilizer N has increased N mineralization due to the build-up of soil organic N. In addition, much of the organic N in Broadbalk topsoil is now derived from fertilizer N. A computer model of N mineralization on Broadbalk estimated that after applying 144 kg N/ha for 140 years, up to half of the N mineralized each year was originally derived from fertilizer N.

In the short-term, the amount of fertilizer N applied usually has little direct effect on losses of N over winter. In most years little fertilizer-derived N remains in Broadbalk soil in inorganic form at harvest from applications of up to 192 kg N/ha. However, in two very dry years (1989 and 1990) large inorganic N residues remained at harvest where 144 and 192 kg N/ha had been applied, even though the crop continued to respond to fertilizer N, up to at least 240 kg N/ha.

Grasslands are one of the world's major ecosystems groups and over the last century their use has changed from being volunteer leys, or a resource on non-arable land, to a productive resource equal to any crop and managed as such. Many grasslands are now being acknowledged as having a multifunctional role in producing food and rehabilitating crop lands, in environmental management and cultural heritage. However, grasslands across the globe are under increasing pressure from increasing human populations, reduced areas with increasing livestock numbers, and declining terms of trade for livestock production, and they are managed to varying degrees of effectiveness. The complexity of grassland uses and the many aspects of grassy ecosystems require a framework wherein solutions for better management can be developed. The present paper discusses a generic approach to grassland management to satisfy these multiple objectives. A focus on ecosystem functionality, i.e. on water, nutrient and energy cycling and on the biodiversity required to sustain those functions, provides a means of resolving the dilemmas faced, through the intermediary, management-related, criteria of herbage mass, which also relates directly to animal production. Emphasis is placed on the opportunities to satisfy multiple objectives. A consideration of the basic relationships between stocking rate and animal production shows that the longer-term, economically optimal stocking rate is associated with improved environmental outcomes. There may be environmental objectives that go beyond economically sustainable limits for livestock producers and in those cases direct payments from the government or others will be needed. These are likely to be where degradation is clearly apparent. The achievement of desirable outcomes in grassland management that satisfy multiple objectives will require new areas of research that seek viable solutions for farmers and society.

Pests and diseases impact on crop yield and quality, and also reduce resource-use efficiency. Improved crop protection strategies to prevent such damage and loss can increase production and make a substantial contribution to food security. DNA-based technologies are likely to greatly increase the speed, sensitivity and accuracy of pest and pathogen detection and diagnosis. Rapid sequencing of nucleic acids from infected plants will aid identification of novel disease agents. Biomarkers of disease or crop damage such as volatile chemicals or blends may also be used to detect pest outbreaks. Biosensors coupled to information networks will provide real-time monitoring and surveillance of crops or stored produce and hence early warning of emerging problems and new invasive species. Challenges remain in the dissemination of new technologies and information to resource poor farmers in developing countries, although the rapid extension of the internet, mobile phones and other communication networks will provide new opportunities. Defining the genetic and molecular basis of innate plant immunity has been a major advance in plant biology with the potential to identify new targets for intervention via novel chemistry or genetic modification (GM). Identification of regulatory genes, signal molecules, pathways and networks controlling induced plant defence should lead to the development of a new generation of defence modulators, delivered either as crop protection products, or via biological agents on seeds or in the root zone. There should also be opportunities to select more responsive crop genotypes, or to develop transgenic crops tailored to respond to specific chemical cues or molecular patterns diagnostic for particular biotic threats. Sequencing of the genomes of the major crop species and their wild relatives will expand enormously the known gene pool and diversity of genetic resources available for plant breeders to access. It should be possible to identify genomic regions and genes conferring more durable, quantitative resistance to pathogens. The breeding cycle will be accelerated by high-throughput phenotyping and more efficient selection of resistance traits using within-gene markers. GM approaches will facilitate pyramiding (combining) resistance genes with different specificities and modes of action, thereby reducing the risk of directional selection for virulence. Analysis of the genomes of plant pathogens and invertebrate pests is already providing new information on genes, gene families and processes involved in host colonization and pathogenicity. Comparative genomics of species with diverse host ranges, contrasting feeding habits and different pathogenic lifestyles will identify new targets for inhibiting pest attack and aid the development of novel antimicrobial drugs and pesticides. Understanding the natural ecology of pests and pathogens, such as the factors determining host location, resource exploitation and interactions with other organisms, will improve our ability to manipulate behaviour, or exploit natural enemies or other antagonists of pest species. Volatile signals, either from natural plant sources, or engineered in transgenic crops, will be more widely used to modify pest behaviour. It may also be possible to manipulate microbial communities regulating pathogen populations and activity, and thereby recruit and retain more effective biocontrol agents. Insights into the natural diversity and activity of soil and microbial populations in the zones surrounding roots and seeds will provide new information on mechanisms of suppression regulating pest species. Fully effective interventions are unlikely, due to the complexity and diversity of the soil system, but there should be progress towards integrated control regimes combining more resistant crop genotypes (either selected or GM) with targeted management of natural suppressive processes. Harnessing new technologies and knowledge to create more durable resistant crops and sustainable disease and pest management systems will require improved understanding of the factors driving pest and pathogen adaptation and evolution. There must also be an increased emphasis on translational research and delivery, and developing strategies appropriate for lower-input production systems, if the second ‘green revolution’ is to become a reality.

1. The acid hydrolysis of six soils with nitrogen contents ranging from 0·1 to 2·38% has been studied by determining the amounts of ammonia-, humin- and α-amino-N present in the soil hydrolysates after various periods of hydrolysis.

2. Under the conditions of hydrolysis employed (3 ml. of 6N-HCl/g. soil) the period required for maximum liberation of amino-acids from the soils was about 12 hr. 24·2–37·1% of the total-nitrogen of the soils examined was liberated as α-amino-N in this period. Further hydrolysis led to destruction of amino-acids. Similar amounts of α-amino-N were liberated by hydrolysis of the soils with alkali (5N-NaOH).

3. From 69 to 87% of the total-nitrogen of the soils was brought into solution by acid hydrolysis; the amount dissolved by hydrolysing with alkali or with alkali under reducing conditions (alkalistannite) was not significantly different. It is concluded that most of the insoluble-nitrogen found after acid hydrolysis is not derived from protein material, and it is suggested that some of this nitrogen is in the form of heterocyclic nitrogen compounds.

The free-acid content of grass silages was reduced by the addition of sodium bicarbonate to the silage and increased by additions of lactic acid. In each of four comparisons the addition of sodium bicarbonate to increase pH from about 4·0 to about 5·4 resulted in significant increases in intake of dry matter which ranged from 9·7 to 20·7%. Intake of organic matter was consistently increased by this partial neutralization treatment, but the increases were not significant in all experiments. The addition of sodium as sodium chloride rather than sodium bicarbonate did not alter the intake of a highly acid silage. Addition of lactic acid to reduce the pH of a silage feed from 5·4 to 3·8 resulted in a decrease in dry-matter intake of 22%. The correlation between dry-matter intake and the silage characteristics: titratable acidity, total organic-acid content, lactic-acid content and pH were all significant.

It is concluded that the acids produced during the normal silage fermentation can limit the intake of the silage and it is suggested that chemical treatments to preserve wet grass without the presence or formation of large quantities of acids be investigated.

Gaseous NH3 losses from pig and cattle slurry stored in eight storage tanks were measured simultaneously using wind-tunnels. The slurry was either stirred weekly (uncovered), or was allowed to develop a natural surface crust. Oil, peat, chopped cereal straw, PVC foil, leca® (pebbles of burned montmorillonitic clay) and a lid were tested as additional covers. Convective transport of ammonium to the surface layers caused NH3 volatilization losses of 3–5 g NH3-N/m2 per day from the stirred, uncovered tanks. The loss of NH3 from the stirred slurry was related to air temperature. The development of a natural surface crust reduced NH3 losses to 20% of those from stirred slurry. NH3 losses from slurry not developing a natural surface crust layer and left undisturbed were similar to the losses from stirred slurry. A 15 cm layer of straw was as effective as a surface crust layer in reducing NH3 losses. In one experiment, cracks developed in the oil cover and losses were therefore only reduced to 50% of those of uncovered slurry. Apart from this experiment, NH3 losses from slurry covered with oil, leca®, peat and foil were small.

Soil close to roots generally has chemical, physical and biological properties which are significantly different from those of soil located some distance away (Jenny & Grossenbacher 1963; Hawes & Pueppke 1986; Young 1995). The root–soil interface is defined as soil near to or adhered to the root surface to some small distance into the soil matrix. This distance may vary between <1 mm and c. 10 mm. Working definitions include rhizosphere, where ‘zones of influence’ are inferred, and rhizosheath, when soil adhered to the root is discussed. Most work carried out at the root–soil interface has concentrated on biological or chemical processes, due both to the fact that the relevant techniques required to examine these processes have been more advanced than the physical techniques, and also because the farmer is generally offered either biological or chemical solutions to his everyday problems, as these are readily accessible, easy to use and cheap. The main manipulation of soil physical conditions occurs during cultivations, and the addition or removal of water from the soil profile. Intensive cultivations are a regular occurrence in many farming systems, despite the potential drawbacks: damage of the soil structure, leading to reduced crop yields and an increased risk of erosion.

The main aim of this review is not to cover all the complex issues related to the root–soil interface. Instead, it concentrates on the biophysical processes which, compared with conventional plant physiological and soil microbiological research, have attracted relatively limited attention (e.g. see Waisel et al. 1996). The review examines small-scale (μm-mm) interactions and, where possible, links their impact to the larger scale. Three interacting areas are investigated: the physical structure of the soil and root growth, water dynamics and microbial dynamics.

Global warming has accelerated in recent decades and the years 1995–2006 were the warmest ever recorded. Also, in Finland, the last decade has been exceptionally warm. Hence, this study examines how current field crop cultivars, adapted to northern long-day conditions and short growing seasons, have responded to the elevated temperatures, especially with regard to determination of yield potential and quality. These comparisons were carried out with spring and winter wheat (Triticum aestivum L.), oats (Avena sativa L.), barley (Hordeum vulgare L.), winter rye (Secale cereale L.), pea (Pisum sativum L.) and rapeseed (turnip rape, Brassica rapa L. and oilseed rape, B. napus L.). Long-term data sets of MTT Official Variety Trials and the Finnish Meteorological Institute were used to study crop responses to precipitation and elevated temperatures at different growth phases. The MTT data sets were also grouped into experiments that could be considered typical of the temperature conditions in the period 1971–2000 seasons (termed ‘1985’ conditions) or typical of the period 2010–39 (termed ‘2025’). At elevated temperatures, yields generally declined in these relatively cool growing conditions of northern Europe, except for pea. Elevated temperatures tended to have negative effects both in the pre- and post-anthesis phases, but the response depended on species. The response was probably associated with reduced water availability, which limited yield determination, especially in early growth phases. For example, in spring cereals a decrease in early summer precipitation by 10 mm decreased yields by 45–75 kg/ha. As warmer conditions also typically hastened development and growth in such generally cool growing conditions of Finland, it is essential that breeding programmes produce cultivars that are less sensitive to elevated temperatures, which are likely to become more frequent in future.

Automatic mobile shelters were used to keep rain off a barley crop in a drought experiment. The treatments ranged from no water during the growing season to regular weekly irrigation. This paper reports the effect of drought on the harvest yield and its components, on water use and nutrient uptake.

Drought caused large decreases in yield, and affected each component of the grain yield. The magnitude of each component varied by up to 25% between treatments, and much of the variation could be accounted for by linear regression against the mean soil water deficit in one of three periods. For the number of grains per ear, the relevant period included tillering and ear formation; for the number of ears per unit ground area, the period included stem extension and tiller death; for grain mass, the period included grain filling.

The harvest yields were linearly related to water use, with no indication of a critical period of drought sensitivity. The relation of grain yield to the maximum potential soil water deficit did show that a prolonged early drought had an exceptionally large effect on both yield and water use.

Two unsheltered irrigation experiments, also on barley, were made in the same year on a nearby site. The effects of drought on yield in these experiments were in good agreement with the effects observed on the mobile shelter site.

When fully irrigated, the small plots under the mobile shelters used water 11% faster than larger areas of crop, because of advection. The maximum depth from which water was extracted was unaffected by the drought treatment. When 50% of the available soil water had been used the uptake rate decreased, but the maximum depth of uptake continued to increase.

Measurements of crop nutrients at harvest showed that nitrogen uptake was large, because of site history, and that phosphate uptake was decreased by drought to such an extent that phosphate shortage may have limited yield.

An algorithm to fit boundary lines, using cubic smoothing splines, was written and used to identify yield responses to changes in soil properties. This method involves fitting a curve that represents the maximum yield response to each predictor value, which represents the yield potential at each soil property value. Boundary-line yield responses to individual soil properties were found to differ from responses found by fitting curves through the data scatter. The effects of correlated variables appeared to be lessened using the boundary line approach. Multivariate boundary-line models, based on the Law of the Minimum, were found to be useful for the identification of site-specific causes of yield variation and yield potentials. The boundary line was found to be a useful complement to more traditional data analysis techniques.

15N-labelled fertilizer was applied, in spring, to winter wheat crops in nine experiments in eastern England over a period of 4 years. Five were on Batcombe Series silty clay loam, two on Beccles Series sandy clay loam (with a mole-drained clay subsoil) and two on Cottenham Series sandy loam. In three of the experiments, different rates of fertilizer N were applied (up to 234 kg N/ha); in the others, a single rate (between 140 and 230 kg/ha) was used.

Recovery of fertilizer N in the above-ground crop (grain, chaff, straw and stubble) ranged from 46 to 87% (mean 68%). The quantity of fertilizer N retained in the soil at harvest was remarkably constant between different experiments, averaging 18% where labelled N was applied as 15NH415NO3, but less (7–14%) where K16NO3 was applied. Of the labelled N present in soil to a depth of 70 cm, 84–88% was within the cultivated layer (0–23 cm).

L70 = 5(± 1 63) + 0·264(±00352) R3

accounted for 73% of the variation in the data where: L70 = percentage loss of fertilizer N from the crop: soil system, defined as percentage of labelled N not recovered in crop or in soil to a depth of 70 cm at the time of harvest; R3 = rainfall (in mm) in the 3 weeks following application of N fertilizer.

There was a tendency for percentage loss of fertilizer N to be greater when a quantity of N in excess of that required for maximum grain yield was applied. However, a multiple regression relating loss both to rainfall and to quantity of N applied accounted for no more variance than the regression involving rainfall alone. In one experiment, early and late sowing were compared on the first wheat crop that followed oats. The loss of N from the early-sown crop, given fertilizer N late in spring, was only 4% compared with 26 % from the later-sown crop given N at the same time, so that sowing date had a marked effect on the loss of spring-applied fertilizer N.

Uptake of unlabelled N, derived from mineralization of organic N in soil, autumn-applied N (where given) and from atmospheric inputs, was < 30 kg/ha on a low organic matter (0·08% total N) sandy soil but > 130 kg/ha when wheat followed potatoes or beans on soil containing c. 0·15 % total N. Unlabelled N accounted for 20–50% of the total N content of fertilized crops at harvest. About 50% of this unlabelled N had already been taken up by the time of fertilizer application in spring and the final quantity was closely correlated with the amount present in the crop at this time. Applications of labelled fertilizer N tended to increase uptake of unlabelled N by 10–20 kg/ha, compared to controls receiving no N fertilizer. This was probably due to pool substitution, i.e. labelled inorganic N standing proxy for unlabelled inorganic N that would otherwise have been immobilized or denitrified.

1. The recommencement of the sexual rhythm from deep anoestrus, is described in barren pony mares. Follicular development and oestrus follow after an interval of preliminary changes in the ovaries and accessory reproductive organs.

2. The onset of oestrus can be accelerated by general irradiation with strong artificial light. Local irradiation with a mercury vapour lamp has no effect on the ovaries.

3. Pregnant matings will result from such artificially induced heat periods provided that ovulation is induced.

4. Doses of less than 10 c.c. of sperm injected will cause fertilization when ovulation is so induced.

5. There is a close connexion between the shedding of the coat and renewed ovarian activity.

6. The stimulus to the ovaries probably passes through the eyes as in the ferret.

Despite the importance of selection for quality characteristics in plant improvement programmes, literature on experimental design and statistical analysis for these traits is scarce. Most quality traits are obtained from multi-phase experiments in which plant varieties are first grown in a field trial then further processed in the laboratory. In the present paper a general mixed model approach for the analysis of multi-phase data is described, with particular emphasis on quality trait data that are often highly unbalanced and involve substantial sources of non-genetic variation and correlation. Also detailed is a new approach for experimental design that employs partial replication in all phases. The motivation for this was the high cost of obtaining quality trait data, thus the need to limit the total number of samples tested, but still allow use of the mixed model analysis. A simulation study is used to show that the combined use of the new designs and mixed model analysis has substantial benefits in terms of the genetic gain from selection.

The objective of the present study was to compare the performance of seven different, widely applied crop models in predicting heat and drought stress effects. The study was part of a recent suite of model inter-comparisons initiated at European level and constitutes a component that has been lacking in the analysis of sources of uncertainties in crop models used to study the impacts of climate change. There was a specific focus on the sensitivity of models for winter wheat and maize to extreme weather conditions (heat and drought) during the short but critical period of 2 weeks after the start of flowering. Two locations in Austria, representing different agro-climatic zones and soil conditions, were included in the simulations over 2 years, 2003 and 2004, exhibiting contrasting weather conditions. In addition, soil management was modified at both sites by following either ploughing or minimum tillage. Since no comprehensive field experimental data sets were available, a relative comparison of simulated grain yields and soil moisture contents under defined weather scenarios with modified temperatures and precipitation was performed for a 2-week period after flowering. The results may help to reduce the uncertainty of simulated crop yields to extreme weather conditions through better understanding of the models’ behaviour. Although the crop models considered (DSSAT, EPIC, WOFOST, AQUACROP, FASSET, HERMES and CROPSYST) mostly showed similar trends in simulated grain yields for the different weather scenarios, it was obvious that heat and drought stress caused by changes in temperature and/or precipitation for a short period of 2 weeks resulted in different grain yields simulated by different models. The present study also revealed that the models responded differently to changes in soil tillage practices, which affected soil water storage capacity.

1. An analysis of pre-weaning mortality in inbred Large White pigs showed that the over-all mortality in ten generations of sows was 47·3%. During the first four generations mortality fluctuated between 30 and 45%; from the 5th to the 9th it fluctuated between 50 and 68% and in the 10th rose to 88%.

2. 70·2% of all deaths occurred in the first 3 days post-parturition and the average birth weight of pigs which died within 3 days was only 1003·5 g. compared with 1258·5 g. for those which survived. 83·0% of pigs weighing less than 900 g. at birth died within 3 days, whereas only 18·5% of pigs weighing more than 1400 g. died within the same period.

3. There were marked seasonal variations in mortality, this being highest during the winter months. Mortality was highest in litters of under 5 and over 15, but between 5 and 15 there was no increase in mortality with litter size. There was no difference in mortality between males and females.

4. Foetal growth was studied in 80 outbred sows of various breeds. Foetal weight was affected not only by age but also by litter size. The withinlitter variation in foetal weight increased with litter size but no increase in between-litter variation with litter size could be demonstrated statistically. Male foetuses were slightly heavier than females at all stages of pregnancy investigated.

5. The growth of the inbred Large White foetus was also studied at an early and late stage of inbreeding, and the reduced birth weight in the latter was shown to be reflected in slower growth of the foetus from mid-pregnancy onwards.

6. The anatomical composition of inbred Large White foetuses at a late stage of inbreeding has been compared with that of similar foetuses at an earlier stage and also with normal outbred Essex foetuses, at 51, 74, 97 and 108 days of pregnancy. The chemical composition of inbred Large White foetuses of a later stage of inbreeding was compared with that of outbred Essex foetuses at 51, 74, 97 and 108 days. The differences in anatomical composition between the smallest and largest foetuses within litters are comparable with those found postnatally in pigs fed on a high or low plane of nutrition, but this was not reflected in a very definite way in the chemical composition. X-ray photographs showed that ossification was more advanced in the largest foetus within a litter than in the smallest but the appearance of the ossification centres was not delayed in the latter.

7. Attempts to make reciprocal ovum transfers between inbred Large White and outbred Essex sows met with little success, probably due to the low fertility of the Large Whites, the prolonged exposure of the ovum during transference and the necessity of effecting the transfer of the ova at the 2-cell stage. The latter was conditioned by the rate of passage of the ova through the tube and the fact that they enter the uterus in the 4-cell stage.