A Scanning Electron Microscope was used to measure wool fibre diameter, the number of cuticular scale edges, crimp wavelength, the number of shed fibres, and the number of fibre loops in normal and cotted fleeces. The main difference observed was the greater number of loops in the cotted wools. There was no evidence of an increased number of shed fibres in the cotted fleeces.

An analysis of data from the complete dissection of one side from 285 animals from a breed comparison experiment was conducted to determine whether there were important biases in the prediction of percentage lean in the side based on dissection of the rumpback joint and, if so, whether the dissection of any of five other sample joints would have been better.

For estimating lean content of the side, it was found that the lean content of any sample joint except the hand was a more precise predictor than standard carcass measurements alone, while including the latter in a prediction equation based on a single sample joint dissection improved precision further. For prediction based on lean in the sample joint alone, any one of the ribback, ham and rumpback was best. If other carcass measurements were included (in particular, C fat depth, eye-muscle area and trimming percentage were found to be useful), there was little to choose between the joints. For all joints there were differences between sire breeds (Large White, Canadian Yorkshire, U.S. Duroc, U.S. Yorkshire, Danish Landrace or Norwegian Landrace), sexes (hog or gilt) and feeding regimens (ad libitum or scale) in lean content of the side at constant lean content of the sample joint, but the regression slopes differed only when the rumpback or streak was used as a predictor, and then only between ad libitum and scale-fed pigs. It will therefore be important in any future such experiment fully to dissect a sample of each class (breed, feeding regimen and sex) to provide unbiased estimates of the differences in lean content. A sample of 30 from each class should allow the differences to be estimated adequately.

Calves from three breeds, Brahman, Hereford × Shorthorn (HS) and Brahman × HS (BX), were divided equally into two groups, one of which was treated every 3 weeks from birth onwards to control ticks and gastrointestinal helminths, and one of which was untreated. Mortalities, growth rates and levels of resistance to environmental stresses that affected both mortality and growth under grazing conditions were recorded for all animals up to weaning (6 months) and for all males up to 15 months of age. The Brahmans were the most and the HS were the least resistant to environmental stresses, each of which was shown to depress growth in proportion to its magnitude and to contribute to the high mortalities of the HS. All breeds responded positively to parasite control with the greatest response in both survival and growth in the HS breed and the least response in the Brahman breed.

Samples of males from the various breed-treatment groups were taken into pens where they were protected from environmental stresses and fed both low-quality pasture hay and high-quality lucerne hay ad libitum. Measurements were made of fasting metabolism, maintenance requirement, voluntary food intake and gain, variables related to the growth potential of each animal. The HS animals had the highest whilst the Brahmans had the lowest values for each variable.

However, despite their low growth potential, the Brahmans had the highest growtli rate, and the HS, despite their high growth potential, had the lowest growth rate, when growth was measured in the presence of all environmental stresses. When parasites were controlled, growth rates were highest for the BX, the breed with intermediate growtli potential, and did not differ between the HS and Brahmans. These interactions arose because of the different contributions of resistance to environmental stresses and growth potential to growth rate measured at the different levels of environmental stresses. The relevance of these interactions to breed evaluation and cross-breeding is considered.

Growth potential and resistance to environmental stresses were negatively correlated both between and within breeds, though the latter was biased by the effects of compensation. The influence of these relationships on the likely outcome of selection for increased growth rate, both between and within breeds, is discussed.

Field experiments were made during the rainy seasons of 1979 and 1980 at Hissar, India, to study the effect of time of weed removal on the yield of groundnut. Removing weeds from 2 to 8 weeks after sowing led to significantly larger yields than that of plots which were not weeded. Maximum pod yield in both years was obtained when weeds were removed 4 weeks after crop sowing.

In experiments with maincrop potatoes at Rothamsted in 1976, 1977 and 1978 ‘Nitro-Chalk’ was broadcast, either as a single dressing on the seed bed, or half on the seed bed and half at tuber initiation. Isobutylidene di-urea was broadcast on the seed bed and aqueous ammonia was injected into the seed bed, without a nitrification inhibitor or with either ‘N-Serve’ (nitrapyrin) or sodium trithiocarbonate; all were compared with ‘Nitro-Chalk’ at rates of 200 or 300 kg N/ha. Additionally, single dressings of ‘Nitro-Chalk’ supplied 150, 250, 350 and 400 kg N/ha. In similar experiments at Woburn in 1979 and 1980 aqueous urea replaced aqueous ammonia and the additional amounts of ‘Nitro-Chalk’ (100 and 400 kg N/ha) were tested as both single and divided dressings. Winter wheat was grown in each of the following years to measure residual effects.

Retaining half of the total N dressing of 200 or 300 kg N/ha as ‘Nitro-Chalk’ until tuber initiation improved yields at Rothamsted in 1976 and 1978 when irrigation was applied but not in 1977 when it was not. Dividing the N at Woburn improved yields at 100 and 400 kg N/ha but not at 200 or 300 kg N/ha. At Rothamsted injected aqueous ammonia was on average similar in effect to the undivided ‘Nitro-Chalk’ dressing at 300 kg N/ha, but less effective at 200 kg N/ha. In 1977, the wettest summer, it was, however, the most effective of the N-sources, provided that an inhibitor had been applied with it. At Woburn, injected aqueous urea did not differ consistently in effectiveness from ‘Nitro-Chalk’ and inhibitors did not improve its performance. Isobutylidene di-urea (IBDU) gave the smallest yields at both farms, apparently because it was too slowly available. Tuber size distributions were affected little by the amount or the form of N.

IBDU residues increased wheat yields the most following the potatoes at Rothamsted. This apart, the N-sources had similar residual values.

A 4–year experiment was conducted at two sites in each year to evaluate some of the effects of five harvesting treatments on the forage and grain production and quality of four spring barleys sown in November and grown under rainfed conditions. A single harvest during the growing season at the milk stage of grain produced the highest herbage drymatter and digestible yields.One harvest at tillering reduced significantly the plant height, grain production and dry-matter yields of straw and hay, while the digestibility of the organic matter in the dry matter (D-value) and the crude-protein content of straw, crudeprotein content of grain and the number of tillers were not affected. The weighted mean of D-value and crude-protein content of herbage was increased when a ‘grazing’ cut was taken prior to harvest. In addition lodging was eliminated. Three or four harvests during the growing season resulted in very low forage yields of otherwise excellent quality.

The seasonal and post-partum oestrus occurrence and ovarian activity, assessed by the plasma progesterone concentrations, were studied in Finn-cross ewes following autumn and winter lambings.

The last seasonal oestrous cycle was followed by a silent ovulation in C0% of the Finn × Awassi ewes. Silent ovulations during midanoestrus occurred in 50% of the ewes, and in 90% of the animals a silent ovulation preceded the normal resumption of the seasonal sexual activity.

The first post-partum oestrus occurred within C0 days after October lambings in about 90% of the ewes. Silent ovulations before the first post-partum oestrus were evident in 70% of the recycling ewes.

It is suggested that breeding ewes with ovarian activity after oestrus induction during anoestrous periods might increase the reproductive performance of the flock in a frequent lambing system.

Topsoils from eight different soil series were substituted for the local soil in three arrangements involving two depths of topsoil and either local or sand subsoils. A rotation of crops was grown with uniform annual N, P and K treatments for 24 years. A peaty soil produced the highest yields of grain, straw and grass, presumably because it released more N than the mineral soils, but an average yield of swedes. No mineral soil consistently produced higher yields of all crops and, although there were some significant differences, the variations in yield were generally relatively small. The deep topsoil consistently produced the highest yields. Topsoil with sand subsoil gave the lowest yields of grain, straw and swedes but not of grass.

All the crops on the peaty soil had higher concentrations of P in the dry matter than those from the seven mineral soils. Crops and herbage on the Laurencekirk and Foud-land soils had consistently slightly higher P concentrations than those on the other five mineral soils. Compared with the amounts applied, the crops removed considerably more K but only 45–68% of the P. There were large differences in the proportion of the P residues extractable by acetic acid from the different soil series.

The depth of topsoil was at least as important as soil type in determining yield, and the results support the use of soil depth as one of the main factors used in the Land Capability Classification for Agriculture.

From 1980 to 1982 fungicide and aphioide sprays were tested in factorial combination with four amounts of nitrogen fertilizer, applied in one or two dressings to winter wheat, on three contrasting clay soils. These experiments were at Hexton (Burwell series) in Hertfordshire, at Billington (Evesham series) and at Maulden (Hanslope series) in Bedfordshire, following a 2–year break, an all-cereal rotation, and continuous wheat respectively. The nitrogen dressings were calculated after taking into account mineral N in the soil. In 1981 and 1982 soil density was measured by penetrometer. This showed compaction in soil at Maulden 28 cm deep which caused waterlogging in spring; this delayed growth which was not made good later.

At Hexton a small seed rate was used; plant losses during winter were proportionally larger than elsewhere. At Billington, the maximum number of stems occurred in March and elsewhere in April. Despite these differences in seed rate and number of plants, number of ears varied little, and each year the wheat at Hexton accumulated dry matter most rapidly. The growth rate there ranged from 20·0 to 21·8 g/m2/day during the linear growth phase as compared with 14·4 to 16·6 g/m2/day at the other two sites. Giving N in two dressings rather than in one increased dry-matter yield at all sites in May, but later this benefit remained static and so became a smaller proportion of the total. Fungicides increased post-anthesis dry-matter yield by 0·75 t/ha, most of which was incorporated in the grain.

Mean grain yields from 1980 to 1982 where nitrogen fertilizer was given were 9·86 t/ha at Hexton, 7·88 t/ha at Billington and 6–91 t/ha at Maulden. Additional nitrogen fertilizer always increased grain yield when fungicides and aphicides were given, but not where they were not. Grain yields in excess of 10 t/ha were achieved with numbers of ears ranging between 360 and 435/m2. The components of yield showed that grain yield was related to the number of grains per ear and 1000·grain weight, but not number of ears. Grain weight was increased by 3·1 mg by the fungicides.

The fungicides controlled the diseases eyespot (Pseudocercosporella herpolrichoides), Septoria spp. and yellow and brown rust (Pucdnia striiformis and P. recondita) where they occurred, but even where these diseases were absent or at very low levels the fungicides significantly increased grain yield. At Billington and Maulden take-all (Qaeumannomyces graminis) infected between 44 and 90% of the plants and sharp eyespot (Rhizoctonia cerealis) infected from < 1 to 20% of the stems because the wheat followed cereals. Yields of straw behind the combine-harvester were from 50 to 70% of those obtained from sheaves cut at ground level.

Two experiments were conducted with milking cows on continuously stocked perennial ryegrass pastures. In each a control group, T0, received 1 kg/day of a concentrate supplement and treatment groups T1 and T2 received 4 kg (Expt 1) or 5 kg/day (Expt 2) of a low quality T1 or a high quality T2 concentrate. In Expt 1 treatments were applied continuously for 14 weeks to a total of 30 cows. In Expt 2 a Latin square design for 9 weeks was conducted with 18 cows. The stocking rate of the pasture declined from 9·6 to 5·1 cows per ha (mean 6·7 cows/ha) from May to August (Expt 1) and was maintained at 3 cows/ha in August-October (Expt 2).

Supplements increased total intakes by 0·92 and 0·77 kg organic matter (OM)/kg OM supplied in the concentrates respectively for Expts 1 and 2. Milk yields increased by 0·6 and 0·5 kg/kg concentrate supplied and supplemented cows showed small increases in live weight. Differences in lactation milk yield just approached significance. Grazing times were only slightly reduced by supplements and bite sizes were lower than normal. There was no important difference in animal performance between the two concentrates. The total output from the pasture was 19·6t milk and 115 GJ of utilized metabolizable energy per hectare.

Reasons for the high supplementary effect of the concentrates and its implications for stocking rates are discussed.

A method of assessing colour of grass leaves was developed to distinguish between cultivars. Leaves from a representative population of 60 plants of each cultivar were measured. To eliminate subjective judgment a colour difference meter was used, giving tristimulus values X, Y and Z (approximating to red, green and blue respectively), from which the colour co-ordinates L, a and b of the Commission Internationale de L'Eclairage system were calculated.

In a pilot study two visually distinguishable perennial ryegrass cultivars were easily separated (P <0·01) using the colour measurements. In a further examination comparing 23 cultivars, 68% of all possible cultivar pairs were separated (P <0·01).

One hundred and ninety-four lactating British Friesian cows were used over a 2-year period to determine the effects of mixing diet ingredients on dry-matter (D.M.) intake, animal performance, digestibility coefficients, rumen fermentation and efficiency of food utilization. Four treatments were imposed in both years and were complete diet and separate ingredients at ad libitum and restricted levels of feeding.

In Expt 1 a complete diet at ad libitum and restricted levels of feeding was compared with separate ingredients. The diet consisted of 60% concentrates and 40% forage and contained 20, 20, 10 and 50% on a D.M. basis of maize silage, lucerne silage, dried sugar-beet pulp and dairy compound, respectively. Method and level of feeding were the same in Expt 2; however, the diet in the 2nd year consisted of 50% concentrates (40% dairy compound, 10% dried sugar-beet pulp) and 50% grass silage.

In Expt 1 cows fed the complete diet ad libitum consumed 16·5 kg D.M./day which was significantly more than the 14·3 kg/day consumed by those offered the separate ingredients ad libitum. Intakes in Expt 2 were not significantly affected by method of feeding. Much of the difference in Expt 1 was attributed to the fact that many cows rejected lucerne silage when fed in an unmixed form and therefore to keep the concentrate to forage ratio constant other diet ingredients were reduced proportionately.

Mixing diet ingredients did not significantly affect milk yields, which were for the complete diet ad libitum and restricted and the separate ingredients ad libitum and restricted 22·2, 22·2; 22·1 and 20·7 kg/day in Expt 1 and 23·6, 20·8; 24·2 and 21·5 kg/ day in Expt 2, respectively. In Expt 1 when the concentrate to forage ratio was 60:40, cows fed the complete diet ad libitum produced milk with a significantly higher milk fat concentration (39·2 g/kg) than those fed the separate ingredients (31·6 g/kg). Similar effects were not recorded in Expt 2 when the concentrate to forage ratio had been reduced to 50:50. Changes in milk protein concentration were more closely related to changes in intake rather than method of feeding. Mixing diet ingredients tended to decrease live-weight loss in early lactation and accelerate live-weight gain in midlactation.

In vivo digestibility coefficients determined in lactating dairy cows showed that in Expt 1 the D.M. and organic-matter digestibility coefficients for the complete diets fed ad libitum (0·689 and 0·713) were lower than those recorded (0·712 and 0·732) for the unmixed diet ad libitum. Although the digestibility coefficient of the acid-detergent fibre of the complete diet was markedly higher at 0·519 compared with 0·478 for the separate ingredients, the difference was not significant. In Expt 2 the only difference in digestibility coefficients was that for nitrogen, which for the complete diet was significantly higher than that of the separate ingredients at both levels of feeding.

At an ad libitum level of feoding in Expt 1, the molar proportions of acetate and butyrate were 620 and 116 mM/l for the complete diet which were slightly higher than 602 and 95 mM/1 for the separate ingredients ad libitum. This diet also had a slightly higher molar proportion of propionate, 249 compared with the 221 mM/l for the complete diet ad libitum. In Expt 2 there wore no significant differences between treatments for either molar proportions of rumen volatile fatty acids or the ratio of lipogenic to non-lipogenic acids.

Field experiments with rape ovs Primor, Jet Neuf and Norli during 1979–83 tested the effects of benomyl, prochloraz, imazalil, thiabendazole, metalaxyl or triadimefon sprays applied at different times on disease, crop growth and yield. The principal disease in all experiments was light leaf spot (Pyrenopeziza brassicae).

A single spray in autumn of benomyl or prochloraz at 0·5 kg a.i./ha consistently decreased incidence and severity of light leaf spot and sometimes decreased stem canker (Leptosphaeria macvlans). Under severe disease conditions in cv. Primor an autumn spray of fungicide contributed more to disease control than a spray in spring; a decrease in light leaf spot incidence was detectable up to 8 months after application. The autumn spray maintained plant population density, increased leaf area index, dry matter, crop growth rate, earliness of flowering, and yield by up to 0·69 t/ha; an autumn + spring spray increased yield by up to 0–83 t/ha. Effects on crop growth and yield were due to disease control not direct chemical stimulation of growth. Measurements of crop growth and population per unit area revealed the effects of fungicides more clearly than traditional disease assessments based solely on randomly selected plants.

Triadimefon sprayed on rape stubble at high dose rate (1 kg a.i./ha) decreased incidence and severity of light leaf spot throughout the growing season of a subsequent rape crop, with beneficial effects on plant population density, growth, flowering and yield.

Electrostatically charged rotary atomizer and conventional hydraulic spray applications of fungicide were equally effective in disease control. A reduction to one quarter in dose rate of prochloraz and 100–fold reduction in amount of water carrier (125 g a.i. in 4·3 1/ha) when applied electrostatically in autumn or autumn + spring had similar effects on disease, crop growth and yield to those obtained with a conventional sprayer delivering 500 g a.i. prochloraz in 410 1/ha.

Fungicides, spray timing and methods of application are discussed in relation to the epidemiology of light leaf spot and canker and the economics of disease control.

Effects of three levels of N application and four intervals between harvests on field swards of perennial ryegrass (Lolium perenne L.) were studied during 6-week periods in summer and spring. Ryegrass was compared with tall fescue (Festuca arundinacea Schreb.) in spring and autumn.

The application of N increased the rate of production of leaf primordia, the number of leaf primordia per tiller, the length of the shoot apex, the rate of development of primordia into unemerged leaves, the number of leaves emerging, the number of live, emerged leaves per tiller, the leaf extension rate and weight of blade emerging and the net gain, per tiller per day, in blade length and weight. The application of N tended to reduce the number of unemerged leaves per tiller and the length of apex per primordium. Applied N retarded leaf death (whether measured as numbers, length or weight) during the first 2–3 weeks after application and accelerated death subsequently. During the 1st week of the summer periods, the net gain in green blade length and weight per tiller was doubled by 22 kg N/ha and trebled by 66 kg N (compared with nil). During the final fortnight of the summer periods, the net gain in green blade length and weight was less with the 6-than with the 3- or 2-week interval, and, in the case of the 6-week interval, the positive effect of applied N on the rate of development of primordia into unemerged leaves and on the number of leaves emerging had been lost.

The ryegrass had more leaf primordia and unemerged leaves per tiller than the fescue, and a faster rate of development of primordia into unemerged leaves and of unemerged into emerged leaves.

A ryegrass leaf spent a broadly similar length of time in each of the three stages, primordium, unemerged leaf and fully expanded live leaf, and about half as long as one of those stages as an emerging leaf. At nil N a leaf developed to about 6000 times its starting length (as a newly-formed primordium) in 67 days in summer; at high N a leaf developed to about 10500 times its starting length in 53 days. The percentage increase in length per day was greatest during the unemerged leaf stage.

An experiment to compare the effect of diverse ratios of 0–6 h old Microplitis rufiventris Kok. progeny within Spodoptera littoralis (Boisd.) larvae is described and the results discusssed. Five to 21% of parasite progeny was eliminated during the egg stage. Surplus parasite larvae were eliminated mainly by physical attack, physiological suppression and perhaps by encapsulation. Parasite larvae which escaped competition during their first instar were subjected to physiological suppression. Some of the super-numerary parasite larvae other than the winners survived competition mechanisms and developed in the host haemocoele. Nevertheless, most of these parasites suffered from moulting failure and emergence problems at the end of their endoparasitic development. The development of the winning parasite was retarded by 1–2 days during its egg-larval stage while the duration of its pupal stage was about the same as parasites from singly parasitized hosts.

An experiment has been made to study the effect of level of feeding in early lactation on the feed intake, yields of milk, fat and protein and on live-weight change over one lactation cycle. Adult British Friesian cows of high potential yield were randomly allocated to high (HP) or moderate (MP) levels of feeding for 20 weeks. They were then randomly allocated within treatments to controlled or ad libitum levels of feeding for the rest of the lactation.

There were significant effects of feeding in the early part of lactation on the yields of milk, protein and lactose but not on milk fat or live-weight change. Cows on the MP treatment produced about 450 kg milk from body energy reserves but were unable to supplement fully the dietary energy deficiency. There was no significant response to feeding ad libitum in the second part of lactation and the differences in yields established in the first part were maintained in the second. There was no relationship between feed intake and milk yield for cows fed ad libitum nor did the level of feeding in early lactation influence the level of intake in the later part.

There was little agreement between calculated energy balance and the live-weight changes but there was more between live-weight change and condition score.

Commercial Celery Cultivars Varied in their response to inoculation by celery mosaic virus. The most severe symptoms occurred in self-blanching cultivars, but a high level of resistance was found in some non self-blanching cultivars such as Solid White and Fordhook. The resistance in these cultivars was confirmed in glasshouse tests.

The soils of fields where winter wheat yields were measured for the I.C.I. Ten Tonne Club Survey in 1979 and 1980 were identified according to the soil series recognized by the Soil Survey of England and Wales. The yield distributions were almost normal, with means 1·49 and 1·60 t/ha greater than the national average. Soil series accounted for 18–19% of the yield variance in both years, which was much more than any other single factor measured. If introduced in best order, soil series, crop variety, previous crop and sowing date accounted for 31% of the variance in both years. However, classes based on soil particle size and drainage, as derived from series identifications, accounted for very little of the variance. Only thick brickearth (loess) soils gave greater mean yields in both years than the overall means of all sites where series were identified. The same soil types provided 35% of the sites where > 10 t/ha was achieved in either year, though a wide range of soil types gave such large yields.

Yields were greater in 1980 than in 1979 in almost all parts of the country. Although rainfall was only slightly less in the spring and early summer of 1980 than in the same period in 1979, many parts of the country suffered large potential soil moisture deficits in 1980, but these decreased yields slightly on a few series only. Factors other than rainfall used to calculate soil moisture deficits (radiation or wind) probably affected yields much more than rainfall itself.

Conformation of carcasses from 107 Romney ewe lambs was determined using two visual scoring systems and the scores related to chemical and dissected carcass composition. The conformation system which evaluated the lateral profile of the hind leg failed to improve the prediction of carcass composition. The Meat and Livestock Commission system used in Great Britain separated carcasses on weight and fatness, the higher classes having the heaviest and fattest carcasses. After adjustment for carcass weight and fatness the higher conformation classes had the lightest bones and the heaviest weight of muscle, and some of the muscles weighed were shorter and deeper than those of the lower conformation classes.

In each of the years from September 1977 to July 1982 winter wheat was grown on one or more of three clay soil sites (clay content 35–55%) in Oxfordshire where the climate is close to the average for the area of England growing winter cereals.

The effects on crop water use of different soil management practices, including ploughing, direct drilling and subsoil drainage, are compared. Cultivation treatment had little effect on the maximum depth of water extraction, which on average in these clay soils was 1·54 m below the soil surface. Maximum soil water deficit was also little affected by cultivation; the maximum recorded value was 186±7·6 mm. Subsoil drainage increased the maximum depth of water extraction by approximately 15 cm and the maximum soil water deficit by about 17 mm.

Generally soil management had little effect on either total water use by the crop which was found to be close to the potential evaporation estimated by the method of Penman, or water use efficiency which for these crops was about 52 kg/ha par mm water used.

Results are discussed in relation to limitations to potential yield.