No attempt will be made to give a detailed summary of all the findings of the present experiment. It is rather our purpose to draw attention to the main principles emerging.

1. The influence of extremes of high and low planes of nutrition during the first 16 weeks of post-natal life upon the growth in body proportions and in anatomical composition has been studied experimentally in six pairs of closely inbred pigs. Quantitative differences in nutrition operative from birth have resulted in an average live weight at 16 weeks of 113 lb. in the High-Plane and 37 lb. in the Low-Plane animals.

2. In body proportions, the head, ears, neck, legs, and body length are penalized relatively less by inadequate nutrition than are body depth, loin, and hindquarters. Conversely, good nutrition favours most the latter characters. These effects upon body form are similarly evident i n the gross weight of the different anatomical regions involved. Low-Plane animals to a large extent retain the proportions of the juvenile and High-Plane approach the conformation of the adult

Grass is a complex crop and its value for agriculture must be assessed in terms of the quantity and quality of downstream livestock products (milk, meat and wool). In addition to being a natural low-cost feed for ruminants, grassland protects soil and water resources and enhances the landscape. Temperate grasslands support a major share of the world's milk and beef production but now there is increasing emphasis on sustainability in livestock farming systems rather than maximizing outputs. The economic sustainability of livestock producers in many developed temperate regions is increasingly linked to production from fewer animals giving a higher quality product. A key element in the efficiency of all grassland systems is to optimize the protein/energy balance of forage and value it in a similar way to other livestock feeds. Grasses are rich in energy comprising structural and non-structural carbohydrates while forage legumes are rich in protein. The main forage legumes used in Europe are white and red clover, and lucerne, which form an essential part of sustainable farming systems because of their high nutritive value and ability to fix nitrogen. The productivity of grasslands containing legumes generally reflects the amount of N fixation, which is 65–280 kg/ha/year in W. Europe. Animal production from white clover-based pastures in Europe can be 0·8 that obtained from grass pastures fertilized with 400 kg N/ha/year, and that from lucerne and red clover can be equivalent to animal production from such pastures.

The widespread adoption by agronomists and researchers of handheld leaf chlorophyll meters stimulates enquiries on instrumental calibration issues, given the necessity, for some applications, of inferring actual chlorophyll concentrations from the readings provided. This is especially required for recently developed and more innovative devices such as the Dualex (Force-A, France), which unlike the more common SPAD-502 (Minolta, Japan) has not undergone extensive (published) calibration tests. Additionally, devices for spectral reflectance measurements are also becoming increasingly available. In the present paper, the calibration of SPAD on maize (Zea mays L.) and of Dualex on winter wheat (Triticum aestivum L.), durum wheat (Triticum durum Desf.), horse bean (Vicia faba L.) and maize, was compared to spectral reflectance indices and full spectral information (400–2500 nm) acquired by a spectroradiometer (ASD FieldSpec) equipped with a contact probe and leaf clip. Full spectral data were exploited using partial least squares regression (PLSR). The measurements were performed in the field at Maccarese (Central Italy) in 2012, gathering a specific experimental dataset. The calibration models obtained on experimental data for SPAD (on maize) and Dualex (on four crops) showed intermediate or high estimation accuracy with root-mean-square error (RMSE) values ranging between 7 and 11 μg/cm2 depending on the species. These results were slightly better than those achieved using spectral reflectance indices, which were inferior though to those provided by PLSR using full spectral resolution. A synthetic database, generated by the physically based PROSPECT model, simulating hemispherical leaf reflectance and transmittance, was used to compare the performances of the reflectance indices and the chlorophyll meters for a wider range of leaf properties. The results confirmed the substantial equivalence of reflectance-based and transmittance-based (i.e. simulated SPAD and Dualex) indices and the advantage of exploiting the full spectral information, e.g. through PLSR, if available.

It is unlikely that as a formulated problem any consideration of settled crop-husbandry is of greater antiquity than the cereal yield problem. In its broad form it embraces all the possible means of increasing the output of grain per unit area. The earliest civilizations of Mesopotamia and Egypt must have been compelled to explore these means as soon as they began to encounter the limitations to cultivable area which dwelling in fixed communities imposed. Wheat and barley were their principal food stuffs so that the cereal yield problem, the most comprehensive concern of present-day agriculture, goes back to the remotest antiquity. It must have evoked incessant effort along divers lines and the cumulative result is appreciable from a comparison of the best cereal races of to-day and the forms which like Hordeum spontaneum and Triticum dicoccum dicoccoides have been regarded as the progenitor types. Unfortunately it is not possible to trace back very far the sequence of the solution of the problem as constituted by improvements in husbandry and the utilization of better cereal forms. Fragments of information may be culled from the writings of various periods but they are of doubtful value. The author's reliability is often in question, the unit of measure uncertain, and even the identity of the crop a matter of doubt. Herodotus' well-known story, passed on from another, of increases of 200 and even 300 fold yielded by barley in Mesopotamia in 500 B.c. is possibly the oldest fragment. It is difficult to interpret but it gains colour from the further statement that the leaves of the plant were of the width of four fingers. Concerning progress in England, while reasonably precise information goes back no further than forty years, there are widely separated records of sufficient worth to indicate the historical trend. It has been deduced from the Manorial Records that at the time when that system had become established there was a flat rate of about ten bushels per acre for wheat. Much later, when Sir Charles Davenant compiled An Essay upon the Probable Methods of making a People Gainers in the Ballance of Trade (published 1699), he computed the “neat produce” of eight million acres of arable land to be 79 million bushels of grain.

Ewes. There was some variation from year to year in the times of onset and end of the breeding season; on the average it was evenly spaced on either side of the shortest day. Occasionally ewes were served and became pregnant at times well outside the normal limits of the breeding season. Lambs were allowed to suckle the ewes for as long as they would; when lambing occurred more than about 100 days from the start of the season there was no delay in onset of heat in the ewe. When lambing was later there was some delay, but the duration of the lactation anoestrum shortened to a minimum near the middle of the season and then lengthened again.

In the first half of the season the period of the oestrous cycle lengthened slowly and steadily; in the second part it became more variable, there was first a slight shortening, but upon the whole it continued to increase in length. From the start of the season the frequency of twinning increased quickly to a peak in about November and then declined for the rest of the season. At the end of the season there was a high proportion of services not fertile.

Lambs. Growth in the first 2 months was greatest in those born in May; in the fourth to sixth months it was greatest in the earliest born and least in the latest, the highest weight at 6 months old being reached by those earliest born.

Field experiments with the South American grain crop, quinoa, were carried out at two sites in Denmark in 1988–90 in order to study the effects of varying the nitrogen fertilization rate, seed rate, row spacing, harvesting method and harvest date. Although there was a significant yield increase when the amount of nitrogen fertilizer was increased from 40 to 160 kg N/ha, quinoa seems to be well adapted to poor soils. Yield decreased by 24–1% when the nitrogen supply was reduced from 160 to 40 kg N/ha, while the yield decrease was 120 and 2–7% when the nitrogen supply was reduced to 80 and 120 kg/ha, respectively.

A model expressing yield as a function of plant density, for three experiments analysed as one, showed an optimal plant density with respect to yield of 327 ± 220 plants/m2. This plant density was the top point of the curve relating yield to plant density. However, the large standard deviation indicates that apparently a rather wide range of plant densities would provide similar yields. When the row spacing was varied, it was shown that plots with a row spacing of 50 cm, which were hoed, gave a higher yield than plots with 25 or 12·5 cm row spacing, which were unhoed. There was an overall increase in yield when changing from combined harvesting to swathing; however, when comparing the yields from the optimal harvest dates for the two methods, no yield differences could be detected. The optimal harvest date for swathing was found to be the stage when the inflorescences start to turn brown, whereas for combining, the optimal harvest date was the stage when most of the inflorescences are already brown.

Some aspects of intervarietal crossing in Lolium perenne have been studied.

Using a number of experimental designs with non-red plants as the tester variety, results have been obtained as to the effects of isolation distance on intervarietal crossing.

In all cases contamination decreases rapidly, at first with increasing distance, but there is a progressive reduction in the rate of decrease produced by repeated increases in isolation distance. The actual rate of decrease varies with the number and arrangement of plots.

The effect of intravarietal pollen in reducing intervarietal crossing appears similar to that of distance in its mode of action. Within short distances from the contaminant, additional rows of intervening plants are highly effective in reducing contamination. This suggests that pollination within a population of plants occurs chiefly between neighbouring plants.

The flowering periods of the different strains of Lolium perenne and L. italicum overlap to varying degrees. Several early strains flower at the same time, e.g. British commercial, New Zealand Certified Mother Seed and Station-bred S24 perennial rye-grass; others, such as Kentish indigenous perennial ryegrass and strains of L. italicum, which are intermediate in date of flowering, overlap with both the early- and late-flowering strains.

Intervarietal crossing is considerably reduced when varieties which differ widely in date- of flowering are grown in close proximity to one another, but even in the case of extreme early and late strains some spatial isolation, or discarding of border rows, is necessary for maintaining varietal purity.

In certain instances when seed crops of early-flowering strains are endangered by late-flowering plants growing in adjoining leys, satisfactory isolation may be achieved through cutting back the contaminant crop just before flowering. When seed crops of late-flowering strains are grown alongside leys containing early-contaminant varieties, cutting back should be delayed until a few days prior to commencement of flowering in the seed crop.

The practical application of the results to grass seed production has been discussed. Existent isolation requirements appear not too great for grass seed crops intended for further seed multiplication, but for commercial seed crops the spatial isolation distance generally recommended may be reduced to 100, or even 50 yd., in the case of large fields.

A standard method is proposed for establishing the seasonal pattern of production for grasses. The procedure consists in recording the yield from grass swards cut every 4 weeks and from which limitations to growth from the supply of water or nutrients have been removed. Four series of plots are harvested in rotation, spaced a week apart so that there is a routine of harvesting a constant number of plots on the same day each week. A statistical analysis is also described enabling comparisons to be made between the grasses under test. An example is given to illustrate the method and the results obtained.

The soil nitrate content has been determined at fortnightly intervals on bare fallow plots and on plots under crops and natural vegetation in the forest and savannah regions of Ghana. Nitrifiable nitrogen, ammonium and soil moisture contents have also been determined. It has been found that the changes in nitrate content are related to changes in the content of nitrifiable nitrogen. During the dry season, a partial sterilization of the soil occurs and consequently the content of nitrifiable nitrogen rises. This nitrifiable nitrogen is slowly converted to nitrate in the dry season and rapidly converted once the rains commence. Nitrate is then lost from the soil by leaching and denitrification. Under bare fallow conditions leaching is the most important cause of nitrate loss, but it is probable that denitrification makes some contribution on cropped soils and those under permanent vegetation. There is no indication of microbial nitrate absorption under a crop. This is presumably due to the rapidity with which nitrate is lost by leaching and denitrification, and to the greater quantity of organic matter required in these free-draining tropical soils than in most temperate ones to produce an equivalent absorption of nitrate. The high levels of nitrate and nitrifiable nitrogen which are found under natural forest probably represent an equilibrium level typical of a cycle in which nitrogen fixation and nitrification as well as nitrate losses proceed very rapidly. Natural savannah grassland suppresses nitrogen mineralization in the field almost entirely, but the nitrifiable nitrogen content is at times high, in spite of the very high carbon/nitrogen ratio of the soil of over 20. This confirms the view that little nitrate absorption takes place in spite of the presence of what might be considered excess carbonaceous material. The suppression of mineralization under grass is considered due to an excretion of the plant roots which is toxic to the nitrification process. The failure of organic matter to build up in these savannah soils, although mineralization is suppressed, is most probably associated with their low general fertility.

Sixty Holstein/Friesian dairy cows, 28 of high genetic merit and 32 of medium genetic merit, were used in a continuous design, 2 (cow genotypes)×4 (concentrate proportion in diet) factorial experiment. High and medium merit animals had Predicted Transmitting Abilities for milk fat plus protein yield, calculated using 1995 as the base year (PTA95 fat plus protein), of 43·3 kg and 1·0 kg respectively. Concentrate proportions in the diet were 0·37, 0·48, 0·59 and 0·70 of total dry matter (DM), with the remainder of the diet being grass silage. During this milk production trial, 24 of these animals, 12 from each genetic merit, representing three animals from each concentrate treatment, were subject to ration digestibility, and nitrogen and energy utilization studies. In addition, the efficiency of energy utilization during the milk production trial was calculated.

There were no genotype×concentrate level interactions for any of the variables measured (P>0·05). Neither genetic merit nor concentrate proportion in the diet influenced the digestibility of either the DM or energy components of the ration (P>0·05). When expressed as a proportion of nitrogen intake, medium merit cows exhibited a higher urinary nitrogen output and a lower milk nitrogen output than the high merit cows. Methane energy output, when expressed as a proportion of gross energy intake, was higher for the medium than high merit cows (P<0·05), while urinary energy output tended to decrease with increasing proportion of concentrate in the diet (P<0·05). In the calorimetric studies, neither heat energy production, milk energy output and energy retained, when expressed as a proportion of metabolizable energy intake, nor the efficiency of lactation (kl), were affected by either cow genotype or concentrate proportion in the diet (P>0·05). However when kl was calculated using the production data from the milk production trial the high merit cows were found to have significantly higher kl values than the medium merit cows (0·64 v. 0·59, P<0·05) while k l tended to fall with increasing proportion of concentrate in the ration (P<0·05). However in view of the many assumptions which were used in these latter calculations, a cautious interpretation is required.

1. In an experiment with ninety-nine lambs the effects on the body composition of male and female lambs were examined when five diets containing different concentrations of crude protein (in the range 10–20%) were given at three levels of feeding and lambs were slaughtered at two live weights (27·5 and 40 kg).

2. With lambs slaughtered at 27·5 kg there were significant increases in the rate of both nitrogen and fat retention with increases in levels of feeding. There were also linear increases in the rate of protein deposition and decreases in fat deposition with increases in the concentration of crude protein. This effect was particularly marked at the high level of feeding.

3. With lambs slaughtered at 40 kg live weight there were also linear increases in fat and in nitrogen deposition with increasing feeding level but the effect of increasing the protein concentration on increases in nitrogen retention departed from linearity.

4. While at 27·5 kg there were no significant effects of feeding level on nitrogen and ether-extract content of the bodies at slaughter, with animals slaughtered at 40 kg there was a significant linear decrease in ether-extract content with increasing feeding level and a corresponding linear increase in nitrogen content with increased level of feeding.

5. Male lambs deposited more nitrogen and less fat than females. This was true of both rate of deposition and of carcass composition at 40 kg live weight.

The digestibilities of grass cell wall constituents determined in a digestion trial were compared with those obtained by suspending various isolated cell wall preparations in nylon bags in the rumen of a sheep. Particular attention was paid to acetyl groups and to individual sugars, which were determined in both cases by gas liquid chromatography.

For dried grass and hay in the digestion trial the cell wall constituents showed digestibilities decreasing in the following order: arabinose, galactose, glucose, xylose, acetyl, lignin.

For a leaf cell wall preparation derived from all cell types except mesophyll, the nylon bag technique allowed the same order of digestibilities; rhamnose and uronic acids were also measured and found to be rapidly digested. Mesophyll cell walls placed in nylon bags were more readily digested than non-mesophyll. All the sugars, and also acetyl groups, were digested to the same extent.

In a grass cell wall preparation isolated from sheep faeces, tested similarly, xylose and glucose were digested to the same extent, but acetyl groups were less digested.

Removal of acetyl groups, using sodium ethoxide, which left the sugar composition and lignin content unchanged, increased the digestibility particularly of the cell walls from faeces.

The results are discussed with reference to the relationship between cell wall composition and digestibility.

Winter oilseed rape (Brassica napus) is an important crop for human consumption and biofuel production and its production is increasing worldwide. It is generally assumed that cross-pollination by insects increases oilseed rape yield but testing of this has been restricted to a few rapeseed varieties and produced varying results. The present study determines whether cross-pollination benefits a number of oilseed rape varieties by comparing yield in the presence and absence of insects. Four rapeseed varieties (Sherlock, Traviata, Treffer and Visby) were used with ten individuals each in four pollination treatments: (1) supplementary hand-pollination, (2) open pollination with insects able to access the flowers, (3) wind pollination and (4) autonomous self-pollination. Across all four varieties, open and supplementary hand-pollination treatments resulted in higher fruit set, numbers of seeds per pod and seed yield compared with wind and self-pollination. The cross-pollination benefits, however, differed among rapeseed varieties: Treffer and Visby had a higher dependence on open (insects) and supplementary cross-pollination than Sherlock and Traviata. Across all four varieties, seed weight compensated for reduced fruit set and was highest when plants were self-pollinated. The present results highlight the importance of considering varietal differences in crop pollination research. Information on the pollination requirements of crop varieties is required by farmers to optimize management decisions in a world of increasing agropollination deficits.

This paper provides estimates of varieties × environments and plot error variances based on more than 1000 trials of varieties of oats, barley, wheat, perennial and Italian ryegrass, timothy, cocksfoot, potato, sugar beet, swedes, autumn kale, forage maize and field beans. Tables of critical differences and acceptance probabilities are presented to guide in planning future series of trials.

The importance of conducting studies on the behaviour of grazing animals has been stressed by several authors. Stapledon & Jones (1927) indicated the need for such work; while more recently Stapledon (1948, 1949) has made further reference to this need.

Adequate reviews of the work conducted prior to 1939 are to be found elsewhere (Castle, Foot & Halley, 1950; Tribe, 1950), and only the more important aspects need be considered here. The main weakness on the part of many of these earlier studies was that they were based on few observation periods, and that few animals were observed during each period. Many workers (Cory, 1927; Hodgson, 1933; Sheppard, 1921) carried out their observations during the daytime only, on the assumption that little or no grazing occurred after dark. In spite of this and the fact that the methods of study adopted varied considerably, some correlation exists between the results reported by the different workers.

1. Using blood plasma FFA and ketone values to assess the nutritional state of individual ewes, high (H), medium (M) and low (L) planes of nutrition were imposed on 3 groups of Blackface ewes during pregnancy. By this method, ewes bearing single or twin foetuses were equally well or severely undernourished within treatment groups. The effects of these planes of nutrition during pregnancy have been assessed in terms of milk production, lamb growth, and live-weight changes by the ewes duriug their subsequent lactation. Immediately after parturition all ewes were individually fed a pelleted food ad lib. and their voluntary food intakes recorded. From 5 weeks of age individual voluntary intakes of solid food by the lambs were also recorded. Because of insufficient pen accommodation group-M ewes and lambs were discarded after 5 weeks of lactation.

Some applications of near infra-red reflectance (NIR) analysis in plant breeding have been tested. Prediction of the nitrogen content of cereals, kale and beans, and nitrogen and oil in rapeseed was sufficiently accurate for screening purposes although wheat straw gave a less accurate result. The prediction of nitrogen content of wheat grain could be supplemented by the simultaneous estimation of grinding resistance and bran cleanliness, characters of importance for bread-making quality. Hagberg falling number, sodium dodecyl sulphate (SDS) sedimentation volume and loaf volume could not be accurately predicted by NIR. Encouraging results were obtained for predicting malting quality of barley and the digestibility of kale samples.

The largest yields of wheat and potatoes came from the combination of longer ley plus optimum fertilizer N but yields of winter beans were decreased where N had been given to the previous crops. Without fertilizer N, two year old leys significantly increased yields compared to one year leys and the effect of longer leys was small except for the first wheat, when grain yields were large and plateaued after the three year ley.

Exponential response curves were fitted to the wheat yields and an exponential plus linear trend to the potato yields after each of the leys. Maximum yields and maximum economic yields and their associated N dressings were then estimated. Maximum economic yields of wheat in 1987 ranged from 811 to 914 t/ha grain and the fertilizer N needed declined from 174 kg/ha after the one year ley to 48 kg/ha after the six year ley. For potatoes in 1988, yields ranged from 63 to 71 t/ha tubers but the N required (137–150 kg/ha) varied little with ley age. For winter wheat, in 1989 yields ranged from only 5·51 to 6·99 t/ha grain, because of drought but, as with the potatoes, the N required (203–218 kg/ha) varied little. For each crop the six individual N response curves could be shifted to bring them into coincidence, and the benefits of the ley estimated in terms of a quantity of fertilizer N applied in spring (horizontal shift) and effects other than spring N (vertical shift). The spring N effects relative to the one year ley varied with ley age; for the first wheat the range was from 6 to 126 kg N/ha for the two to six year leys respectively. Spring N effects were negligible, however, for potatoes (average 6 kg/ha) and also for wheat in the third year (6 kg/ha). Benefits other than those which could be ascribed to spring N increased yield of the first wheat, on average, by 0·94 t/ha grain for the two to five year leys; for potatoes they ranged from 3·5 to 8·1 t/ha tubers for the three to six year leys; for the third crop wheat they ranged from 0·86 to 1·49 t/ha grain for the three to six year leys.

On average, the first wheat recovered only 34% of the applied fertilizer N whilst potatoes and the following wheat recovered 55 and 56% respectively. There was a benefit from the longer leys which affected the efficiency with which fertilizer N was used.

Increasing ley age up to five years increased total soil carbon by a maximum of 0·17%C; 18% of the carbon content of the soil in the one year ley plots. This small increase in soil organic matter provided up to 230 kg/ha mineral N in the first autumn after ploughing. Between 17 October 1986 and 27 April 1987 the average loss of NO3-N from soils following three to six year leys was equivalent to 202 kg N/ha, whilst the average uptake of N by 11 May in the above-ground wheat was only 88 kg/ha; the net loss was 114 kg N/ha. A computer simulation, which included mineralization of organic N during this period together with N uptake and nitrate leaching losses, computed a loss of 250 kg N/ha following the six year ley, and this would have given 400 mg NO3/1 in the 275 mm through drainage that winter.

An experiment is described in which the possible yield benefits of mixing dwarf sorghum and beans were examined under intensive farming conditions. A ‘replacement series’ of pure sorghum, two-thirds sorghum/one-third beans, one-third sorghum/twothirds beans and pure beans was used at four plant populations. A high level of nitrogen was applied to the sorghum to eliminate the effects of nitrogen transfer from the beans.

Yields of the mixtures were up to 55% higher than could be achieved by growing the crops separately. As with some earlier maize/beans experiments (Willey & Osiru, 1972), it is concluded that these yield increases must have been due to a greater utilization of environmental resources. It is suggested that the main factors which made this possible were probably the different rooting depths of the two crops and their different growth cycles.

In agreement with the earlier experiments, mixtures which consisted of two-thirds sorghum/one -third beans gave greatest yield increases at high populations and also had a higher optimum population than the pure stands. However, no such trends were apparent in the mixtures which consisted of one-third sorghum/two-thirds beans.

For both species intra-specific competition was greater than inter-specific competition. In contrast to the earlier maize/beans experiments, the relative interspecific competitive abilities of the species changed with change in the initial proportions of species in the mixtures. In the two-thirds sorghum/one-third beans mixtures the sorghum was the more competitive species, whilst in the one-third sorghum/two-thirds beans mixtures the bean was the more competitive species. Also in contrast to the maize/beans experiments, these relative competitive abilities were not affected by change in theoverall plant population pressure.

Tritiated water (TOH) space was determined in sixty-one sheep of known age (3 days to 18 months). Representative samples of the minced carcass were subsequently analysed to determine body composition (water, fat, protein, ash and energy). The regressions of the weight of the various body components on TOH space and body weight reported here gave equations suitable for prediction. These were similar to equations derived from published results for adults. Combining data on young sheep and adults gave broadly based equations that could be used to predict the body composition of healthy sheep of all ages from 3 days to adults.