The actual transpiration of Mexipak wheat (Triticum aestivium L.) was determined by the inflow-outflow method and by soil moisture determination by the use of a neutron probe and gravimetrically. Three irrigation treatments were used during the 1969 season, wet, medium and dry. Amounts of water given were 370, 310 and 255 mm for wet, medium and dry treatments respectively. One irrigation treatment was used during the 1971 and 1972 seasons in which 620 and 700 mm of water respectively was given. However, during the 1973 season, two wet irrigation treatments of 560 and 670 mm of water were used. Values of Et measured by different methods were closely related. Seasonal averages of Et were 2·55, 1·99 and 1·62 mm/day for wet, medium and dry treatments respectively. The empirical coefficient (f = Et/Eo) under wet treatment, was found to be higher than that given by Penman (1956) for short grasses and higher than that obtained by Boumans et al. (1963) for wheat and barley in Iraq. The empirical coefficient Kb in the Blaney-Criddle formula was less than the value given by Blaney & Criddle (1950) for an arid climate and less than the value obtained by Boumans et al. (1963) for wheat in Iraq. The water use efficiency for grain production was greater under dry than under wet treatment.

In North West Pembrokeshire, sulphur was determined in soils sampled at 268 sites, and in pasture plants sampled at 172 sites. The sulphur contents of the topsoils ranged from 199 to 3392 mg/kg, with a mean of 710 mg/kg; and the S contents of the subsoils from 115 to 1344 mg/kg, with a mean of 356 mg/kg. Sulphur was concentrated in soils containing much organic matter. There was no clear relationship between plant and soil sulphur contents, though soil drainage influenced both. Poorly drained soils were richer in S than well-drained soils, whereas herbage on poorly drained soils accumulated less S than herbage growing on well-drained soils. Herbage S contents ranged from 0·180 to 0·560%, with a mean of 0·310%. If other factors, e.g. soil N, are not limiting, 14% of the herbage sampled in Pembrokeshire had less than the critical S level recommended by other workers for maximum dry matter yield.

Seeds of wild safflower, Carthamus oxyacantha Bieb., collected from the Bajgah area, Iran, were subjected to chilling and/or scarification and their germination and emergence characteristics and seedling growth were studied in two laboratory experiments. Seeds of Arak 2811 variety of cultivated safflower, C. tinctorius L., harvested from the same area at the same time was used for comparison.

In the first experiment, the untreated, scarified, chilled at 0 °C for 1 month, and chilled and scarified wild seed and seed of the variety Arak 2811 were incubated at six different temperatures (5, 10, 15, 20, 25 and 30 °C) and their germination percentage and seedling lengths were recorded. In the second experiment, the seeds of the above five treatments were planted in a silty clay loam at room temperature (23 ± 2 °C) and their emergence and seedling heights were noted.

In all cases, the cultivated variety, Arak 2811, had higher germination and emergence percentages and seedling heights than the wild type. Germination of both strains was greatly reduced at the two extreme temperatures (5 and 30 °C). The optimum temperatures for germination of the wild and the cultivated strains were between 15 and 20 °C.

Scarification of the wild seed did not improve the germination or emergence percentages and chilling of the seed for a month at 0 °C reduced the emergence of the wild seed. Temperature of germination, however, seemed to be an important factor affecting germination and seedling growth of wild safflower.

Six hybrids, either pure dent or flint x dent crosses, together with two open-pollinated flint varieties of early maturity, were grown at Oxford, England, and the yield of grain determined over a range of 15 densities (5.30.8 plants/m2). The relationship of yield to density was studied by fitting mathematical functions to the observed yields. Only two functions, (1) the inverse quadratic on yield per unit area, and (2) the linear regression between density and the logarithm of grain yield per plant, were satisfactory fits. The linear regression was preferred because of its ease of calculation and interpretation. Between genotypes the largest differences in grain yield per unit area were found at densities either above or below those which are employed in normal practice.

The ranking of the genotypes for grain production depended upon the density. Whereas at the lowest density a very short, early-maturing flint genotype, GaspéFlint, yielded least, and a tall, full season dent hybrid, 0X324, yielded most, this position was reversed at the higher densities. Maximal levels of yields of the open-pollinated flint varieties were low, and it is apparent that the incorporation of this source of germplasm in hybrids is limited if commercially acceptable yields are to be attained. Maximal yields of 600 g/m2 were produced by three hybrids, but the optimal densities were markedly divergent. They ranged from 6.2 plants/m2 for 0X324 to 9.7 and 10.8 plants/m2 for INRA 270 and INRA 200. Possible reasons for such differences are discussed in terms of the interactions of density and genotype on the components of yield.

The proportions of bacterial and dietary protein entering the duodenum of sheep fed fresh herbage were assessed using 2,6-diaminopimelic acid as a marker. The herbages fed were Lolium perenne L., ‘Grasslands Ruanui’ perennial ryegrass; L. (perenne × multiflorum), ‘Grasslands Manawa’ short-rotation ryegrass; Trifolium repens L., ‘Grasslands 4700’ white clover.

The dietary protein degraded in the stomach was approximately 70% for all herbages. The bacterial contribution to protein entering the duodenum was 43·1, 57·1 and 52·9% for Ruanui, Manawa and white clover respectively. Protein entering the duodenum contained only a small amount of protozoal protein.

Bacterial protein synthesis in the stomach was different for all three herbages, averaging 16·2, 30·7 and 19·8 g/100 g organic matter apparently digested for Ruanui, Manawa and white clover respectively. It is suggested that the micro-organisms digesting Manawa synthesized protein more efficiently.

Of a group of 24 pregnant Scottish Blackface sheep 12 were killed at the outset and the remainder offered, ad libitum, a poor quality hay. At the end of pregnancy seven more were killed and the remainder offered, during lactation, 3 kg/head/day of a semipurified diet of 64% dry-matter (D.M.) digestibility, and containing 18% crude protein (CP), 1·17% Ca and 0·82% P in the D.M. Milk production was determined at weekly intervals and milk samples obtained at these times for estimation of Ca and P concentrations. These sheep were killed 42 days post-partum. The shorn empty bodies were analysed for fat, protein, Ca and P contents.

The feeding of the poor quality hay caused losses of 76, 37, 15 and 15% of the body contents of fat, protein, Ca and P, respectively, during pregnancy. Despite maintaining a moderate milk yield (1·5 kg/day) the ewes were in positive Ca and P balance during early lactation and had restored the skeleton to its initial mineral content by 42 days post-partum. The rate of absorption of Ca was calculated to have been at least 115 mg/ kg body weight (BW) which is double other estimates in the literature for sheep at this stage of lactation.

These differences are discussed in relation to mechanisms for adaptation of Ca metabolism which have been proposed for other species.

In one experiment, variety Kutsaga 51 was grown at inter- and intra-row spacings of 60, 80 and 100 cm. Both yield and quality of leaf were improved as plant density per unit area increased. The greatest yield and highest quality were obtained from the 60 x 60 and 80 x 60 cm spacings while the lowest yield and quality were obtained from the 100 x 100 and 100 x 80 cm spacings.

In a second experiment the same variety was subjected to three levels of N and four levels of K. Higher doses of N or K were not necessarily effective in increasing the yield or improving the quality of leaf; on the contrary rates higher than 42/ha reduced both yield and quality of the leaf. Progressively higher doses of K did not offset the ill effects of excessive N.

Yield of leaf was primarily a function of leaves per unit area in the plant density experiment and number of leaves per plant in the fertilizer experiment.

Residual effects of N, P and K applied to cotton on the following crops of dura (Sorghum vulgare), lubia (Dolichos lablab) and wheat (Triticum vulgare) were investigated using data obtained over a 30-year period from a factorial field experiment including various levels of the three nutrients. The three crops differed in their response to residual N, P and K. Dura and wheat, being nitrogen depleters highly responsive to fertilizer nitrogen, were consistently affected by residual N. The residual effects of N on grain and straw yields of both dura and wheat were significant in all seasons and the effects were proportional to the amount of N applied to the preceding cotton. There were indications, however, that a much greater part of the N applied in the preceding year was not available to the succeeding crop. Residual P did not have a significant effect on dura but it varied in its effect on the different components of wheat in different seasons. Residual K did not have any effect on dura or wheat. Data on nutrient uptake and composition of wheat tended to support the yield responses. Contrary to the response of the two cereal crops lubia, being a nitrogen fixing legume, did not respond to the effect of residual N and was consistently affected by residual P. Residual K had a slight effect on lubia in only a few seasons.

Two obstacles to achieving diets which maximize farm profits are discussed: (1) the continuing inability to predict reliably the response of animals to a diet with any given composition, and (2) batch-to-batch variation in the true nutrient content of a diet with a fixed nominalcontent. With the aid of simple practical examples it is demonstrated that diet recommendations can be more sensitive than might be expected to the type of function used to predict response, and that variation in dietary nutrient content may reduce farm profits (though the size of the reduction is not clear because of (1) above).

To test the hypothesis that the ingestion of Mo-rich soils by ruminants might adversely affect Cu metabolism, four groups of initially hypocupraemic ewes were repleted with a Cu-supplemented diet either soil-free or containing 10% of one of three soils of low, medium and high Mo content. The three soils were equally effective in inhibiting the response in plasma Cu and probably reduced the availability of Cu by more than 50%. The ingestion of certain soils produced increases in urinary Mo and Zn concentrations, indicating that the Mo and Zn ingested in soil can be biologically available: however, these Cu antagonists were probably released in insufficient quantities to have contributed greatly to the observed interference with Cu metabolism. Soil ingestion may be involved in the aetiology of hypocuprosis in cattle and swayback in sheep, since it commonly constitutes 10% of the D.M. intake of animals grazing winter pasture.

64Cu and an indigestible 103Ru-labelled marker were administered into the alimentary tract of six artificially reared lambs on four occasions, 28 and 14 days before weaning and 15 and 42 days after weaning. The ratio of 64Cu: 103Ru excreted in the faeces was used to measure the apparent availability of Cu.

Mean Cu availability decreased from 71·0 ± 3·7 to 47·2 ± 7·8% immediately before weaning and to 10·8 ± 1·4% 15 days after weaning.

The relationship between availability (y, %) and age (x, days) prior to weaning was described by the equation

When half of the lambs were given abomasal doses of 64Cu + 103Ru 42 days after weaning, the mean Cu availability was 21·4±4·0% compared with 3·7±2·1% for those dosed via the rumen.

64Cu present in the whole plasma volume 20 h after dosing (y, % dose) was highly correlated with availability (x, %), the equation being

Four out of a group of eight milk-fed lambs were given access to a proprietary concentrate from birth and milk intake was progressively restricted so that by 15–21 days they were wholly dependent on the concentrate. Mean Cu availability at 23 days was 8·3±3·4% compared with 75·0±5·4% for lambs continuing to receive milk substitute alone. The corresponding values for 64Cu in plasma were 0·34±0·03 and 1·41±0·14% dose.

Less than 1·1% of the 103Ru and 64Cu doses were excreted in the urine after 48 h and no 103Ru was detected in the plasma.

The nutritional significance of and mechanisms for the reductions in Cu availability with age and weaning are discussed and methods for measuring Cu availability compared.

The annual patterns of infestation of sugar-beet root and seed crops by green aphids (Myzus persicae) and by black aphids (Aphis fabae) were similar, paralleling population changes shown by catches on sticky traps in southern England, but the incidence of yellows in root crops was not correlated with incidence in seed crops in the same year. Few green aphids overwintered on beet-seed plants and the incidence of yellows was consistently low in the main seed-growing areas where all the stecklings are raised under cereal cover crops. Elsewhere, yellows sometimes spread in the autumn and many green aphids occasionally overwintered. Black aphids were seldom prevalent; the severity of attack correlated with the number of eggs laid on spindle (Euonymus europaeus) during the previous autumn.

Twenty-two per cent of mangold clamps checked in mid-April contained aphids, but only about 5 % contained M. persicae. Seventeen per cent of the infested clamps contained aphids infective with BMYV and 10% contained aphids infective with BYV. However, the acreage of mangolds grown in England has decreased.

Myzus ascalonicus overwintered on weeds more often than M. persicae or other species likely to act as vectors of viruses affecting sugar beet. Forty per cent of samples of some common weeds collected from sheltered sites during mid-April from 1963 to 1973 were infested with aphids, and those on chickweed (Stellaria media), groundsel (Senecio vulgaris) and shepherd's purse (Capsella bursa-pastoris) were commonly infective with yellowing viruses. Weeds are probably a major source of yellowing viruses in southern England.

The aim of the present investigation was to determine the effect of adding urea to a diet based on ground maize and dried sugar-beet pulp (2/1) on the composition of duodenal content and diet digestibility in calves.

Two bull calves (140 kg) were provided with duodenal fistulae and pair fed the ration alone or with 1·2% urea in a cross-over design. Lucerne hay was also given. The difference in intake of nitrogen between the two diets was 18·4 g/day.

The results obtained showed negligible differences between the diets in the amounts of dry matter, organic matter and energy disappearing both before and after the duodenum. Digestibility of nitrogen was greater with the urea-containing diet.

Although some of the added urea (25%) was apparently lost from the forestomach, the duodenal digesta contained 13·7 g N/day more with the diet containing urea. Of this a minimum of 6·5 g was in the form of amino acid-N and only 0·4 g as ammonia-N. All the amino acids determined were present in increased amounts but lysine and isoleucine showed smaller relative increases than the other amino acids.

From these results and calculations based on measurements of 2,6-diaminopimelic acid it is suggested that the extra protein in the duodenal content derives from both more efficient bacterial protein synthesis in relation to energy expended and decreased degradation of plant protein in the rumen.

Experiments in England from 1970 to 1973 investigated the possibility of extending the growing season and increasing yields of bolting resistant sugar beet by sowing in autumn rather than in spring. September-sown plants grew rapidly in spring and achieved a complete leaf cover by mid-June by which time they had intercepted 40 % of radiation incident since mid-April compared with 28 and 9% for crops sown on 13 October and 13 April respectively. By early June autumn-sown plants were 20 fold heavier than spring sown but this advantage was progressively lost with the onset of bolting. Root growth slowed as assimilates were diverted to stem and inflorescence growth. Delaying autumn sowing from late September until mid-October delayed and reduced the frequency of bolting, probably because of a shortening of the period when plants were sufficiently large to respond to cold. Cutting down bolting inflorescences at frequent intervals improved root growth of both bolters and non-bolters. However, yields from autumn sowing never exceeded those from spring sowing, the best yield from an autumn-sown crop was 6·1 t/ha of sugar which was similar to that of the spring-sown crop. To try to prevent bolting of overwintered plants the growth regulator ethephon was applied at 10000 mg a.i./l water sufficient to wet the foliage in mid-April. Growth was severely checked and 55 % of plants died. Of the remainder 25–30% fewer than in the untreated crop bolted but yields were 26–42 % less. Less concentrated doses of ethephon did not affect bolting.

Observations were made over a period of 3 years on a total of 331 Nungua Black Head and 104 West African Dwarf sheep. It was shown that ewes of these breeds responded strongly to stimulation occasioned by the sudden introduction of rams which had been separated from them for 10 months. Sudden ram presence apparently altered the normal oestrous cycle of a substantial number of ewes which unlike temperate breeds showed behavioural oestrus soon after being run with the rams resulting in about a quarter of the flock being bred on the first day of association with the ram. This behavioural oestrus must have been accompanied by ovulation as shown by the lambing records 5 months later. The observations also suggested the existence of breed differences in the degree of ewe response to sudden ram presence.

Wool growth rates were estimated in Merino ewes differing in their red blood cell concentrations of reduced glutathione ([GSHRBC]). Over a 42-day wool growth period, sheep with low [GSHRBC] maintained significantly higher rates of wool growth. Red blood cell concentrations of K+, ([K+RBC]), [GSHRBC] and estimated gene frequencies for the low [GSHRBC] and high [K+RBC] genes were determined in flocks of Merino ewes bred for high or low clean fleece weight. The high fleece weight flock had a significantly lower [GSHRBC] and higher gene frequency for the low [GSHRBC] allele than the low fleece weight flock. The high fleece weight flock also had a significantly higher [K+RBC] and a higher gene frequency for the high [K+RBC] allele than did the low fleece weight flock.

A substantial loss in yield usually occurs when oilseed rape is sown later than mid-September. Field experiments in 1972–3 tested whether this is because all plants, irrespective of size, initiate inflorescences during the winter, thus restricting the eventual size of the leaf canopy and the yield potential of late-sown plants, which are still very small when the change to the reproductive phase occurs.

Sowing a standard winter variety, Victor, from mid-August to mid-October resulted in initiation occurring from late October to February. When sown after mid-September yields were proportional to plant size at initiation. The winter was mild, and in colder conditions earlier sowing may be required to enable plants to reach a critical size before initiation takes place. When sown in August plants were very large but yield was not improved. A study of the development of the pod canopy showed that the extra yield potential was not realized because heavy losses of pods and seeds occurred, particularly in the more shaded positions.

When a range of winter varieties, chosen to contrast the timing of phasic development, was sown on two dates yield was proportional to the interval between sowing and initiation, particularly when late sown, presumably because late initiators were able to lay the foundation of a more substantial root and shoot system. This has implications for plant breeding programmes because the low erucic acid varieties currently being grown initiate inflorescences early. When spring types were sown in mid-October they formed floral initials very early, and gave particularly small and weak plants, with a low yield. Winter types sown in March did initiate flowers and produce large plants, but yields were no better than spring types as flowering and ripening were irregular and late, the cold requirement for initiation being only marginally fulfilled.

An appraisal of the value of S. 59 red fescue (Festuca rubra L.) for grazing was made using ewes and lambs (Clun Forest in 1969, Welsh Mountain in 1970) at a site 305 m O.D. in mid-Wales. S. 23 perennial ryegrass (Lolium perenne L.) was used as a control, and the value of S. 184 white clover (Trifolium repens L.) in conjunction with both grasses was examined.

In the first year, under a rotational grazing regime at a fixed stocking rate of 22 ewes and single lambs/ha, lamb live-weight gains were significantly poorer on S. 59/S. 184 and significantly better on S. 23/S. 184 than on either of the pure grass swards. For the 130 days grazing season, mean daily lamb live-weight gains were 157, 126, 78 and 120 g on S. 23/S. 184, S. 23, S. 59/S. 184 and S. 59 treatments respectively.

During the second year lamb growth rates on S. 59/S. 184 improved by 59%, whereas those on the other treatments were marginally lower than in 1969. Stocking rates were increased on the grass swards and decreased on the grass/clover swards for most of the grazing period in the second year in accordance with herbage availability. No significant difference was detected between the four treatments in total lamb liveweight production as a result of better individual growth rates on the grass/clover swards.

In both years wide variations were recorded between treatments at different periods within the grazing season. Red fescue swards maintained superior lamb production in early spring and late autumn, but were inferior to ryegrass in mid-summer.

Seven determinations of energy and nitrogen retention using four adult wether sheep were made when they were fed a complete cobbed diet. The diet contained 30% of barley straw and had a metabolizable energy value of 10·9 kJ/g organic matter and the net availabilities of its metabolizable energy were 52·8% for fattening and 72·8% for maintenance. The starch equivalent on a dry basis was 53.

Tubers of Dioscorea rotundata yam obtained from the same harvest were stored at room temperature (25–30 °C). After storage for various durations, tuber samples were taken and used as planting material. The number of days to sprouting, for head pieces and non-head pieces alike, decreased with increasing storage time up to 159 days. Heads sprouted earlier than non-heads. The number of days to formation of new tubers also decreased with increasing storage age of the parent tuber up to 226 days. The interval from sprouting to tubering was constant up to 106 days of storage, decreased rapidly between 106 and 226 days, and thereafter remained constant. The implications of these results for off-season yam production are discussed.