Oestrous activity of three flocks of Ossimi, subtropical fat-tailed ewes was detected by teaser rams over a calendar year. The flocks were raised at north Delta, mid-Delta and middle Egypt.

The two Delta flocks showed irregularity in percentage of ewes coming into oestrus monthly, with a marked decrease in March, April and May, April being the lowest. On the other hand, the mid-Egypt flock showed consistent oestrous activity throughout the year, with small fluctuations.

The three flocks showed month-to-month variation in incidence of oestrus per ewe, with lower activity in the spring months. Neither of the two Delta flocks showed real regular oestrous activity in any month throughout the year, with high ewe variation. Some ewes showed regular activity throughout the year (16–20 cycles), whereas some others showed only 4–7 cycles per year.

There were two periods of the year with high frequency of anoestrus. The more intense was March–May while fewer ewes had an anoestrous period in July–August. This was the case in the three flocks but with varying intensity.

A period of more than 1 year of detecting oestrus affected oestrous performance of the ewes and should be avoided.

Field experiments to study the effect of pre-sprouting, cutting seed and seed soaking in plant regulators on the number and size of seed tubers and yield of potatoes were conducted during the autumn crop seasons of 1978–9 to 1980–1. At the same seed rate, cut seed produced significantly more sprouts and stems, seed-size tubers and seed yield than the whole seed without affecting the aggregate yield. Similar effects were recorded with soaking whole non-dormant tubers in 10 mg GA 3/1 solution for 15 min before planting. Soaking whole non-dormant seed in 0·5% thiourea solution for 1 h increased the number of sprouts and seed-size tubers, giving increases in seed yield of 2·26, 2·73 and 2·65 t/ha over soaking seed in water in the three consecutive years. The corresponding increases in aggregate yield were 1·79, 1·48 and 1·60 t/ha. Soaking cut seed in solutions of 10 mg GA 3/1 and 0·5% thiourea singly or in combination had an adverse effect on the yield of potatoes.

In four consecutive experiments, plasma uric acid (PUA), hepatic xanthine dehydrogenase (XDH) and body-weight gains (WG) of broiler chickens were measured under varying dietary methionine, protein and energy. In Expt 1, increases in WG with increasing dietary methionine peaked at 0·60%, a level where the initial decreases in either PUA or XDH reached a minimum. PUA and XDH in broiler finishers (Expt 2) decreased between 0·26 and 0·50% dietary methionine while WG improved between 0·26 and 0·50% methionine. XDH in the 18% protein and 0·68% methionine + cystine (MC) diet combination for Expt 3 was 66·4 μtmol/10 min/total liver weight, a value higher than either the 43·5 or 46·5 μtmol/10 min/total liver weight, respectively obtained in the 21% protein + 0·68% MC and 24% protein + 0·68% MC diet combinations. Both PUA and XDH, however, increased with increasing dietary protein when MC was either 0·76 or 0·84% diet. XDH in Expt 4 decreased between 11·7 and 13·4 MJ ME/kg diet that contained either 0·76 or 0·84% MC, tending not to vary between 13·4 and 15·1 MJ ME/kg diet. This enzyme activity remained essentially similar between 11·7 and 15·1 MJ ME/kg diet that contained 0·68% MC.

Three trials were conducted over two cropping seasons, on portions of the production fields of the Nigerian Sugar Company sugar-cane estate, Bacita, to evaluate the efficacy of several herbicide mixtures for weed control in sugar cane using the varieties Co. 957 and Co. 1001. With a broad spectrum of weeds, early post-emergence applications of diuron + hexazinone (2·0 + 0·7 kg a.i./ha) followed by hexazinone + paraquat (0·5 + 0·3 kg a.i./ha) about 8 weeks after the first application gave satisfactory weed control that resulted in high cane yields. Addition of glyphosate to the mixture for the first application or its substitution for paraquat in the second application, or both, resulted in increased suppression of nutsedge. This was, however, more phytotoxic to the sugar-cane plants. Addition of pendimethalin to either diuron or hexazinone improved the control of grass weeds. Hexazinone-based mixtures were found to give longer-lasting weed control than the diuron-based mixtures. Both diuron and hexazinone were generally more selective on Co. 957 than on Co. 1001. The degree of weed infestation between 6 and 12 weeks after planting was inversely related to cane yield.

Heterosis and combining abilities for yield, bollworm resistance, fruiting efficiency and photosynthesis were studied in a five-parent diallel involving cotton (Gossypium hirsutum) strains differing in their resistance to the bollworm complex (Heliothis zea and H. virescens).Substantial magnitudes of useful heterosis (over the commercial cultivar ‘Coker 304’) were observed for yield and other agronomic characters. Useful heterosis for yield ranged from 1 to 32·7%. The highest yielding hybrid was Coker 304 × PD 695. The strain PD 695 is moderately resistant to bollworms.

All the hybrids having at least one resistant strain as their parent suffered less damage from bollworms than Coker 304. The resistant strains (BW 76–31, PD 695 andred leaf cotton) had desirable general combining ability (GCA) effects for bollworm damage. Relative yield (yield without protection expressed as percentage of yield with protection) was used as a measure of bollworm resistance. The high gossypol strain BW 76–31 had desirable GCA effects for relative yield, bollworm damage to buds, number of live worms and for bolls per plant. The fruiting efficiencies and photosynthetic rates of some bollworm-resistant strains were similar to those of a high-yielding, moderately susceptible cultivar.

Combining-ability analysis indicated BW 76–31 to be a desirable parent for use in hybridization programmes for improving agronomic performance, fruiting efficiency, photosynthetic rate and bollworm resistance. It was also observed that bollworm-resistant cottons do not always have lower fruiting efficiencies and photosynthetic rates and it might be possible to combine this resistance with high yields.

Plants of the Cucurbita pepo L. cultivars Cinderella, Cobham Bush Green and Gold-rush were inoculated with six strains of cucumber mosaic virus (CMV) from different geographical areas and known to differ in pathogenicity and virulence. The cv. Cinderella showed high resistance to all strains, cv. Cobham Bush Green was moderately resistant and cv. Goldrush was highly susceptible particularly to the CMV–SEV strain which caused necrotic symptoms.

To ascertain the inheritance of seed shape and resistance to Ascochyta blight and to incorporate resistance in commercial cultivars, crosses were made between cv. Kinnauri, a round-seeded resistant source and commercially important cvs Bonneville, Lincoln, GC 141, and Selection 18, highly susceptible to disease but wrinkled-seeded. The F1, F2 and F3 data indicated that seed shape and resistance to Ascochyta blight is determined by two independently inherited genes. Round seed and disease resistance are dominant over wrinkled seed and susceptibility. Commercially desirable lines have been selected which combine the resistance gene of Kinnauri with wrinkled seed from susceptible commercial cultivars, and which also possess high pod yields and other desirable characters.

In six experiments the effects of various factors on plant-weight variation (sum of squares of deviation from the mean shoot weight) at harvest were examined. These factors were seed size, sowing depth, time of seedling emergence, size at different stages of development, within-row spacing, density and row position within a bed.

In a drilled experiment, up to 25% of the variation in mature leek size could be attributed to variation in time of seedling emergence. Similarly, in the experiments which used transplants, 15% of the variation in the mature crop could be associated with variation in size shortly after seedling emergence from peat blocks.

Variation in row position within a 4-row bed never accounted for more than 11% of the weight variation at harvest, and variation in within-row spacing never accounted for more than 4% of weight variation. However, the coefficient of variation (c.v.) of leeks growing at 22 plants/m2 was 44% whereas the c.v. of those growing at 50 plants/m2 was 61%.

Using large seeds or sowing deeply gave a quicker emergence and a higher percentage emergence than using small seeds or sowing shallowly. However, these factors each never accounted for more than 7% of the weight variation in mature leeks.

Most of the plant-weight variation could not be attributed to any of the measured factors in any of the experiments. The c.v. of leeks which had emerged on a specific day and had been grown in a uniform environment, was between 50 and 66%, which was similar to the c.v.s observed in the transplant and drilled experiments. However, selecting for large transplants reduced the c.v. to 28% in one experiment; this effect was only partly attributable to the greater mean plant size resulting from this treatment.

A field experiment was made on rice during the rainy seasons of 1982 and 1983 to study the relative efficiency of prilled urea and urea super granules (USG) applied broadcast or deep placed at different times. USG gave more, longer and heavier panicles with a higher percentage of filled grains than prilled urea. Deep placement of 60 kg N/ha as USG in two applications (half 10 days after transplanting and half at panicle initiation) gave the same grain yield as 120 kg N/ha of prilled urea applied half at final puddling and half at panicle initiation. Urea super granules, therefore, hold considerable promise as a nitrogen fertilizer for rice.

The data obtained from 360 progeny families produced by crossing 40 F2 plants from each of three wheat crosses HD 2009 × HD 1949, Raj 821 × WH 147 and NP 876 × HD 1949, to three testers (the testers being the two parents of each original cross and their F1 in each case) were subjected to triple test cross analysis for detecting and estimating additive, dominance and epistatic components of genetic variation and interaction of these components with environment for plant height, spike length, number of tillers per plant, number of spikelets per spike, number of grains per spike, 1000-grain weight, number of days from sowing to heading and to maturity, grain yield per plant and grain yield/above ground dry matter ratio (harvest index). Epistasis was an important element for plant height, number of tillers per plant, number of grains per spike and grain yield per plant in all three crosses. Both the i type and j and l type epistasis were equally important. In general, the magnitude of additive component was larger than that of dominance component. The additive gene effects were more sensitive to environmental change than the dominance gene effects. Similarly, j and l type epistasis was relatively more sensitive to environment than the i type epistasis.

A surgical procedure is described for placing a catheter in the mesenteric vein of sheep, such that blood draining the reticulo-rumen is not sampled. This catheter, together withothers in the mesenteric vein and carotid artery, was used to determine mesenteric blood flow and the net absorption of glucose in five sheep fed both dried grass and ground maize-based diets. The mean (± S.E.) mesenteric blood flow rates were 33 ±0·9 and 37 ± 5·7ml/min/kg live weight when fed the dried grass and maize-based diets respectively. These flow rates, together with the small venousarterial differences in plasma volatile fattyacid concentrations observed, indicated that the mesenteric catheter did not sample blood draining the reticulo-rumen in the conscious, fed animal. Further confirmation was provided by subsequent post-mortem examinations of the catheters. When fed the dried-grass diet, a significant net absorption of glucose could not be detected. However, when fed the maize-based diet a net glucose absorption of 19·3 ± 0·75 mmol/h was observed.

Experiments testing the effects of variety, sowing date, seed rate, amount and time of application of nitrogenous fertilizer in the spring, application of nitrogenous fertilizerin the autumn and disease control at four sites in the north of England in 1980, 1981 and 1982 are described and the results are discussed.

The siting of the experiments and the seasons had important effects on grain yield and influenced the response to the total amount of nitrogen used and to disease control. The other husbandry factors produced more consistent effects. The choice of variety and drilling date had thegreatest influence on yield. The responses to the different seed rates, to the method of applying nitrogenous fertilizer and to autumn-applied nitrogen were smaller. The effects were additive.

It is argued that differences in the efficiency of light interception by the foliage affects grain yield; that light interception may be influenced by the state of the foliage at the start of the period of rapid growth from April onwards; and that site, season and husbandry all affect the development of the crop up to that point.

Although a given foreign breed may offer worthwhile genetic improvement, the cost of importing purebred stock makes its evaluation difficult. An experiment was performed in which the breeds compared were represented instead by semen from boars standing at national artificial insemination stations in their native countries. Contemporary groups of Large White × Norwegian Landrace females were inseminated, some with British Large White (LW) semen, and some with semen from Canadian Yorkshire (CY), Danish Landrace (DL), Norwegian Landrace (NL), or United States (American) Duroc (AD) or Yorkshire (AY). One pair (male castrate and gilt) from each litter was performance tested from 27 to 82 kg live weight fed ad libitum (AL), another pairwas tested over the same weight range but fed to a time-based scale (TS). The number of LW, CY, DL, AD, AY and NL sires used was 51, 12, 21, 7, 6 and 23 respectively; a total of 401 litterswas evaluated. The differences between the progeny of LW sires and those of CY, DL, AD, AY and NL were, respectively: in daily live-weight gain (g), AL, –30, 40, –80, –50, –40 (maximum s.E. 16) with no significant differences for TS; in food conversion ratio, AL,0·02, – 0·13, 0·03, –0·05, 0·00 and TS, 000, – 0·14, 0·05, –0·03, –0·06 (maximum S.E. 0·049 for both feeding regimens); in percentage of lean by weight in the rumpback joint, AL, –2·1, –1·9, –1·8, 2·3, –0·7 and TS, – 0·1, –0·9, –1·9, 3·0, – 1·4 (maximum s.E. 1·28 for both); in overall economic worth (pence per pig sired), AL, – 150, 50, – 170, 110, – 40 and TS, – 10, 100, – 200, 190, 30 (maximum s.E. 83 for both). The U.S. Yorkshire and Danish Landrace seem unlikely to be of use commercially in the U.K., while the most promising breeds, U.S. Duroc and Canadian Yorkshire, have not yet been evaluated with sufficient precision to reduce the risk involved in their use to an acceptable level.

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.

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.

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.

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.

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.

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.