Experiments using intact seedlings and detached leaves failed to confirm previous reports that ammonia gas is evolved from barley leaves during the establishment of infection by the powdery mildew fungus Erysiphe graminis f.sp. hordei.

In the experiments using intact seedlings infection did, however, lead to greater concentrations of ammonium nitrogen in the senescing leaves and, in one experiment, the subsequent evolution of ammonia gas from these seedlings. Losses of nitrogen as ammonia gas from crops are probably small, but it is possible that under some circumstances they may represent a significant proportion of the otherwise unexplained nitrogen losses and hence be important in experiments which aim to study the nitrogen balance of crop-soil systems.

Hermetic cold storage without previous drying (wet–cold storage) was experimented for the preservation of yam pollen grains. Pollens collected from white yam D. rotundata and a wild relative, D. praehensilis, were stored at −80, −20, 5, and 15 °C in sealed packs for 2 years. Pollen samples were drawn for in vitro germination tests after 100 and 700 days, and hand pollination was conducted after 365 and 730 days in storage. Pollen germination responses were not significantly different among the two species. Though pollen maintained germination capacity at all the storage temperature regimes, there was a significant loss in the viability of pollen stored at 5 and 15 °C after 100 days of storage. After 700 days in storage, pollens stored at 5 and 15 °C had lost germination capacity while there were no significant differences in the germination of fresh pollen and pollen frozen at −80 and −20 °C. Hand pollination with pollen of D. rotundata frozen at −80 °C for 365 days gave 69·5% fruit set and 50% fruit set after 730 days in storage. From these results, the wet–freeze procedure appears promising to execute the establishment of pollen gene banks for yam breeding and for conservation of haploid gene pool of yams in base collections. A pollen storage protocol based on the procedure is recommended.

The interactions between nitrogen fertilizer and crop rotations in their effects on the yield of cotton in the Sudan were studied by superimposing fertilizer treatments on a rotation experiment which was already more than 30 years old. This experiment compared ten rotations comprising various combinations of cotton with fallow and an alternating crop of dura (a sorghum millet) and lubia (Dolichos lablab. L.). The results support the concept that low basic yields in the absence of a nitrogen dressing are primarily due to nitrogen deficiency. In general the response to nitrogen was greater on rotations which led to low yields of cotton so that rotational effects were greatly reduced or eliminated when a nitrogen dressing was given. Although in some cases cotton following fallow out-yielded cotton following dura, in general rotations containing dura and lubia gave higher yields of cotton than rotations with the same intensity of cotton cropping combined with fallows only. These beneficial effects of other crops instead of fallows in the rotation, although not in agreement with the long-term averages wereto be expected from the long-term trends in yields with time. Combined with the finding that even the most adverse effects of dura could be largely compensated for by a fertilizer dressing, this indicates that cropping in the Gezira could be considerably intensified without loss of cotton yield per acre per year. The difficulties of such intensification would centre around weed, disease and pest control rather than soil fertility. Further experiments are required to determine the fertilizer nitrogen requirements of cotton following different crops.

The feed conversion efficiency of four intensively fed, partially castrated male cattle, measured over an 11-week period from approximately 9-months of age, was found to be significantly higher (P <0·05) than that of four steers.

The effect of adding 5% beef tallow to the diet during this period was also studied. Although no statistically significant result of this on feed conversion was obtained, there was an indication that fat in the diet improved the bulls' efficiency, but not that of the steers. Added dietary fat had an effect on carcass composition, increasing signifioantly (P < 0·05) the deposition of carcass fat by steers but having no such effect in bulls. It appears, therefore, that the two sex types metabolized the added dietary fat differently, the steers converting much of it to depot fat; the bulls using it (with some evidenoe of greater efficiency) for growth of non-adipose carcass components.

An attempt was made to re-assess the results of irrigation experiments carried out in the UK during the last 30–40 years in order to develop functional relationships between crop yield and actual wateruse. It was first necessary to develop a model, based on relatively simple functions, which could be used to predict actual water-use (evaporation and transpiration). The derivation of this model, known as WATYIELD, is reported here, whilst its application and validation for sugarbeet and for potatoes are described in subsequent papers. Simple functions relate components of evaporation to the proportion of the incoming solar radiation intercepted by the crop canopy, reference crop evapotranspiration, the precipitation and irrigation amounts and the soil water deficit. Transpiration is also related to soil hydraulic characteristics, rooting density and potential evaporation rate.

Sorghum grain was included in a basal diet of molasses (molasses 505, urea 21, sunflower meal 191, pangola grass hay 250, minerals 31 g/kg as fed) at rates of 0, 202, 391 and 707 g/kg, generating diets in which grain replaced 0 (diet A), 33 (diet B), 66 (diet C) and 100% (diet D) of the molasses and hay. The four diets were fed to groups of four Hereford steers (293–334 kg liveweight) over a 96-day period. One half of each treatment group was implanted with a growth promotant (zeranol), and all were slaughtered at a commercial abattoir at the end of the trial. The inclusion of 33% grain increased voluntary feed consumption, digestible dry matter (DM) intake (from 57·6 to 82·0 g digestible DM/kg0·75 per day and significantly increased liveweight gain from 592 to 900 g/day. Zeranol implantation also increased liveweight gain but not feed intake. Steers given only grain (diet D) had the highest liveweight gains (1127 g/day). The addition of grain to molasses diets decreased urinary N excretion and increased ammonia and volatile fatty acid (VFA) concentrations in rumen fluid. Molar proportions of propionic acid in total VFA increased from 0·15 to 0·20, and butyric acid decreased from 0·36 to 0·29 when 33% of the molasses was replaced by sorghum grain. The fat content (depth at sacral position) of the carcasses of steers given grain only (diet D) was significantly greater (14 mm) than that of steers given the basal diet of molasses (4 mm), and carcass fat contents were intermediate (10 and 11 mm) for steers given diets B and C respectively. It was concluded that the inclusion of small amounts of grain in molasses-based diets increased cattle growth principally by increasing digestible energy intake without decreasing molasses intake, thus improving the efficiency of utilization of molasses in molasses-based diets.

The availability of more resistance genes to Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko) may provide additional protection from new virulent strains or biotypes of the insect. This genetic study was conducted to determine the allelic relationships of resistance genes in two Iranian wheat (Triticum aestivum L.) lines, SHZ.W.102 and SHZ.W.104 and lines PI 137739, PI 262660, PI 372129, PI 294994 and PI 243781, carrying resistance genes Dn1, Dn2, Dn4, Dn5 and Dn6 respectively. The two Iranian lines were crossed to each of the other resistant lines, and F1 and F2 seedlings were screened for RWA reaction. The resistance gene in 102 was allelic to Dn1, however, the resistance gene in 104 was different from other known genes. The resistant line 104 is an effective source of genetic resistance to RWA and the gene symbol Dn7 is proposed for its resistance gene.

In an empirical manner cod liver oil has been used for many years as an occasional food for farm animals. Generally speaking, its use has been chiefly confined to the rearing of calves and to improving the condition of horses. It is difficult to glean from the literature of animal husbandry information about the use of this oil, but it would appear that whilst the majority of authorities favour its employment in small amounts in special cases others are inclined to regard the oil with suspicion. Thus, Campbell (1900) (i) recommends cod liver oil as an efficient substitute for cream in the rearing of calves; a conclusion that was confirmed in a later publication from the Leeds Station (Seton, 1901) (2). These reports warn users against the inferior grades of oil and show that if good preparations are used there is no detrimental effect on the flesh when animals are afterwards slaughtered as bullocks.

Weaned cross-bred lambs either grazed mature pasture or were confined to yards where they were offered material cut from ungrazed areas of the same pasture. A 1:2 mixture (on an air-dry basis) of sunflower meal and oat grain was offered for 81 days at 0, 200, 400 or 600 g/head or ad libitum. Individual estimates of intake of pasture and supplement by grazing sheep at four levels of supplementation were made on four adjacent plots.

Weight gain increased from –30 to 178 g/day in the grazing animals as supplement intake increased up to 1030 g D.M./day and from –25 to 142 g/day in the yarded animals as supplement intake increased to 1076 g D.M./day. Growth of greasy wool increased from 4·5 to 11·7 g/day for grazing animals and from 4·5 to 10·2 g/day for those kept in yards.

At levels of supplement intake below 400 g D.M./day, the intake of grazed pasture increased by up to 58% compared with unsupplemented animals. However, when the intake of supplement was increased to about 650 g D.M./day, pasture intake fell, with an estimated substitution rate of 1·1 g D.M. pasture per g D.M. supplement. At all levels of supplementation, the intake of hay by the yarded lambs was less than half the intake of herbage in the field. However, at levels of supplement intake between 300 and 500 g D.M./day, the substitution rate was similar to that measured in the grazing animals, suggesting that this is an attribute of roughage quality, rather than differential eating behaviour between grazing and yarded animals.

The wastage, w (g D.M./day), of supplement was linearly related to the amount offered, s (g D.M./day), by the equation

w = 0·263s − 38·8; R2 = 0·89

Variability in supplement intake between individual grazing lambs was not affected by the level of supplementation but the coefficient of variation of supplement intake was considerably greater than that of the intake of unsupplemented pasture. Variability in the intake of pasture increased with the level of supplementation but variability in the total intake of food was similar at each level of supplement, indicating some degree of individual compensation in the intake of the two components.

Responses in live weight, milk production and calf growth to cobalt supplementation of groups of three and four pregnant heifers were measured to assess the value of serum vitamin B12 concentrations and the urinary concentrations of methylmalonic acid (MMA) and formiminoglutamic acid (FIGLU) for the detection of cobalt deficiency in cattle.

The administration of cobalt bullets to pregnant heifers, grazing pastures containing between 0·03 and 0·05 mg/kg cobalt, had no effect on either their live-weight change or milk production, or on the birth weight of their calves. MMA and FIGLU concentrations in the urine of unsupplemented heifers were low for the majority of the experimental period, although the concentrations of vitamin B12 in their serum (< 100 pg/ml) were in the range usually considered indicative of cobalt deficiency.

Calves from unsupplemented heifers had lower growth rates during the first 3 months of life and this was associated with intakes of 0·24–0·46 μg/day of vitamin B12 from milk, only 1–3% of those received by calves from supplemented heifers. Poor growth was associated with high urinary FIGLU concentrations, which increased from 500 to 2000 μmol/l between 1 and 3 months of age but decreased to less than 100 μmol/l between 3 and 4·5 months of age. Urinary FIGLU was a more reliable indicator of vitamin B12 deficiency in suckled calves than was urinary MMA, elevated levels of which were observed only at 3 months of age. The concentration of vitamin B12 in the serum of calves from unsupplemented heifers was consistently less than 100 pg/ml, but was not a reliable indicator of their functional vitamin B12 status, as judged by urinary concentrations of FIGLU and/or MMA.

Thirty-one laporotomies, in addition to a number of confirmatory operations, were performed to determine the time of ovulation in the ewe. It was found that (1) ovulation did not occur during oestrus, (2) in ewes with oestrous periods lasting 30 hr. or more ovulation occurred a short time after the end of oestrus and that the time of its occurrence is related to the end and not to the beginning of oestrus, and (3) there is a minimum period of approximately 23–25 hr. before which ovulation does not occur, irrespective of the duration of oestrus.

Individual analyses of forty Light Sussex cockerels of twenty-two weeks of age yielded the following results:

1. There is a highly negative correlation between the fat percentage of the carcass and the moisture percentage.

2. Owing to the large variability in the fat content of individuals, live-weight increases are unreliable as a measure of energy storage.

3. Comparison of the fat content of the bones with that of the flesh and offal leads to the conclusion that the bones as well as the flesh and offal play a significant role in the general fat metabolism of the body.

4. There exists a strongly positive correlation between the ash content of the bones and that of the flesh and offal.

5. The protein ash ratio of both the Light Sussex breed and the White Leghorn breed is practically constant for all individuals after the age of seven weeks, indicating that the growth of the skeletal and the muscular tissues are closely correlated and controlled by the same growth impulse.

6. The individual variation in energy content is shown to be ± 11.42% of the total energy content.

The growth, development, chemical composition and nutritive value of sunflower (cv. Fransol), was examined from the flower-bud (12 July) to milky-ripe seed (late September) stages. Dry-matter yield increased from 2·1 to 14·1 t/ha over the period. Drymatter content was low (100–110 g/kg) up to flowering, early in August, and then increased to 193 g/kg. Crude protein content declined after flowering and ether extract values were low throughout the period. Organic-matter digestibility in vitro and derived metabolizable energy values declined rapidly with the onset of flowering. Gross energy values, calculated from the proximate constituents, increased to 17·6 MJ/kg D.M. at the end of the period. Calcium to phosphorus ratios varied from 5·6 to 7·4:1.

Sunflower was cut and fed to eight Friesian heifers over 3 weeks from the onset of flowering. Average daily D.M. intake was 63·5 g/kg W0·76 and the organic-matter digestibility was 0·684. Average live-weight gain was 0·79 kg/day.

Fresh sunflower was successfully ensiled without an additive 2 weeks after flowering and the silage (pH 4·0) was fed to three cross-bred wethers in a feeding trial. The organic-matter digestibility was 0·649, the metabolizable energy 8·0 MJ/kg D.M. and the average D.M. intake 6·73 g/kg W0·75. In a metabolism trial, with four fistulated sheep, the organic-matter digestibility was 0·718, the metabolizable energy 9·4 MJ/kg D.M. and the D.M. intake 43·1 g/kg W0·75. Rumen pH decreased and total volatile fatty acid concentration increased markedly within 2 h of feeding the silage. Molar proportions of acetic and propionic acid (0·539 and 0·381), 1 h after feeding, were typical of cereal-based diets. Ammonia-nitrogen concentration increased to a maximum of 216 mg/1 within 2 h of feeding.

The good yield and animal performance from fresh sunflower make it a possible annual crop for zero-grazing in late summer in northern Britain. Satisfactory results from feeding sunflower silage suggest that the crop has potential for ensilage if the problem of effluent can be overcome.

In a former paper, one of us has discussed the Palaeozoic soils of North Wales. In that paper, the Carboniferous soils were omitted as being rather apart from the other Palæozoic soils, which formed a convenient group for study by themselves. In the present paper, the authors discuss Carboniferous soils and the soils derived from the Northern Drift, together with the associated deposits of more recent origin.

Swarm preparations are leas frequent (at least during July and August in southern England) among colonies with queens reared in the current year than among those with queens of the previous year (Simpson, 1957). Queens which had survived one and two winters are now considered; they are described as 1- and 2-year-old, respectively.

Maiden 18-month-old Cashmere does (JV=254) were inseminated laparoscopically with frozenthawed semen after treatment with Controlled Internal Drug Release devices and pregnant mare's serum gonadotrophin (PMSG) in the breeding season of 1989 in Tasmania. Kidding rates(does kidded/inseminated) were not statistically different after the insemination of 1, 5 or 25 × 106 motile spermatozoa (50·0, 55·8 and 56·4%), andfor semen frozen by the pellet or straw methods (56·8 and 50·8%). The fertility results suggest that the critical threshold may not have been reached at 1 × 106 frozen-thawed motile spermatozoa.

Dairy cows grazing a tropical grass pasture fertilized with 300 kg N/ha and with a 7-year history of phosphorus fertilizer at either 0 or 45 kg P/ha were given a P supplement in a 2 × 2 factorial experiment at Kairi Research Station, Queensland, Australia. Milk yield, fat-corrected milk yield, yields of milk fat, protein and lactose, and protein content of milk were increased (P<0·05) with P fertilizer. There was no response in milk yield or any component of milk to the provision of a P supplement. It is concluded that the milk response recorded in this experiment was due to P fertilizer leading to additional pasture on offer and increased pasture intake. The lack of response to additional P in the form of a supplement indicates that these pastures can supply adequate P for cows producing 20 kg/day even after 8 years without P fertilizer.

Field experiments with Italian ryegrass cut four times a year compared aqueous ammonia with ammonium sulphate and with a mixture of ammonium nitrate and urea (equal parts by weight). In 1963 four rates of nitrogen, 224, 448, 672 and 896 lb/acre, were applied as single and split dressings of injected aqueous ammonia, as solid ammonium sulphate and as injected solution of ammonium sulphate. There was little difference in total dry-matter yield between a single injection of aqueous ammonia and the split dressing of solid. Injecting ammonium sulphate solution eliminated scorch caused by single applications of solid supplying 448 lb N/acre or more and gave significantly greater dry-matter yields. A single application of 448 lb N/acre provided enough nitrogen to sustain the response of the grass to the end of the season.

In 1964 a single injection of aqueous ammonia was compared with ammonium nitrate/urea applied as solid or solution at 280, 560 and 840 lb N/acre. There was no difference in total dry-matter yield between aqueous ammonia and ammonium nitrate/urea at rates of 560 and 840 lb/acre. At 280 lb/acre a split dressing of solid produced most dry matter. More than 280 lb N/acre was required, therefore, as a single application in spring to last the whole season, but this rate of nitrogen applied as a split dressing was almost sufficient to give maximum yield.

In both experiments the seasonal distribution of dry matter was similar for single and split applications except in 1963 when large single injections of ammonium sulphate produced greater yields at the third cut than the split applications. The percentage of nitrogen recovered in the harvested grass decreased as nitrogen rate was increased and was greater from single than split applications. Recovery of nitrogen from aqueous ammonia was less efficient from four injections than one, and was greater in 1964 than 1963 due to better penetration of the sward by injector tines. Least nitrogen was recovered from surface-applied solutions of ammonium nitrate/urea. Regressions of dry-matter yield on nitrogen yield showed that single injections of aqueous ammonia were as efficient as other fertilizers tested.

Seven commercial barley varieties were inoculated with mycelial suspensions of different isolates of Gescosporella herpotrichoides. There were significant varietal differences in eyespot susceptibility. There were significant differences between isolates which originated from both wheat and barley. The yield of the varieties was reduced between 30 and 50% depending upon the isolate used. Significant interactions between isolates and varieties were found for the incidence of disease, its effect on tiller number and upon total yield.

Chicory (Cichorium intybus L.) crops can increase milk production on New Zealand dairy farms through providing high-quality feed in late lactation. Non-linear optimization models of three Waikato dairy farms, differing in the degree to which imported supplement is used, were employed to evaluate chicory crops in this environment. At a baseline milk price of $NZ 7/kg milk solids, it was only profitable for chicory to be used on a farm where no imported supplement was fed. However, even then, only 0·04 of the farm area was planted and profit only increased by $NZ 30/ha (0·006 of baseline profit), relative to where it was not used. It was not optimal to plant any chicory on farms where imported feed was available, at the baseline milk price and cost of establishment considered here. This was evident because imported feed is more flexible than chicory for filling temporary feed gaps; also its use does not displace pasture production. Sensitivity analysis indicated that the unprofitability of chicory is robust to broad variation in calving date and the relative growth of chicory and pasture. Overall, results indicate that farmers are unlikely to receive adequate reward for the additional complexity arising from the utilization of chicory crops, especially when imported supplement provides more flexibility.