Experiments on spring barley at Rothamsted over the years 1974–81 were used to study how sources of powdery mildew inoculum affected responses to fungicide sprays applied at different times. Reinfection of early-sprayed plots was generally faster where they were close to a potent source of inoculum than where they were not. Conversely, effects of sources on yield, although not always significant, occurred mainly in the later-sprayed plots. Sources thus had their most important effects before these later sprays were applied, and probably during the very early stages of the epidemic. This implies that if experiments are to approximate to fields, they should, initially, be part of a large, uniformly-susceptible area of crop.

Regression analyses showed that delaying the application of fungicide sprays after the optimum date caused smaller yield losses in plots near minimal sources of inoculum than in plots near more potent sources. There was no conclusive evidence for effects of inoculum sources on the optimum date to apply a fungicide spray but the tendency was for the optimum to become later as inoculum pressure increased.

Separating fungicide-treated plots with mildew-resistant barley resulted in larger treatment effects and smaller residual mean squares than where there was no separation. Judged by residual mean squares alone, precision was approximately doubled by separation.

On January 3rd, 1915, the Little Ouse burst its right bank not far from the Feltwell 2nd District Pumping Station, and as a result thousands of acres of fenland became flooded. The portion of the flooded land on which the following observations were made is a part of Southery fen situated near Southery, Norfolk. It lies between Peckett's Farm and Turf Fen Farm, and belongs to the Norfolk County Council. This land is some distance from the place where the burst occurred, and as a consequence there was no deposit of silt. The height of the flood here was about nine feet. The water was gradually pumped off and the land cleared by September, 1915.

Although the infertility of the subsoil in humid, semi-arid and arid regions has received much attention from investigators in Europe and America, in South Africa, as far as the writer is aware, no such work has been done.

Repeated attempts have been made, both during the recent war and the war of 1914–18, to make the store of starch and other nutrients in the horse-chestnut available for farm animals. Unfortunately, the extremely bitter taste of the horse-chestnut, due to the presence of saponins and, to a smaller extent, of tannins, has proved a severe obstacle, and horse-chestnuts have been found to be an unsuitable food for livestock both on account of their unpalatable character and their constipating action.

Four varieties of Italian ryegrass (Lolium multiflorum), which have been found to differ in voluntary intake by livestock at the same level of digestibility, were examined in the year of sowing and in the two subsequent years in a field experiment. Eight dates of first harvest during May–June in the years after the year of sowing were compared. During May–June in these years the proportion of leaf in the crop was closely related to the stage of development of the crop relative to heading date, whereas yield and digestibility were more closely related to calendar date. As a result the later-heading varieties, S. 22 and Sabalan, had a higher proportion of leaf than the earlier-heading varieties, RvP and Tetila Tetrone, at a given yield and digestibility and this may at least partly account for higher intake in the former varieties. In addition, in Sabalan, the proportion of green leaf relative to dead was particularly high and the proportion of cell wall particularly low. The surface area per unit dry weight of leaf blade was much higher than that of ‘stem’, which may contribute to shorter retention time in the reticulo-rumen. Surface area per unit weight of both leaf blade and ‘stem’ declined with delay in date of first harvest.

The yield of RvP relative to the other varieties was modest at the first harvest in the years after the year of sowing and high at subsequent harvests, in accord with National Institute of Agricultural Botany results. The high yield of RvP relative to the other varieties after the first harvest appeared to be associated with a relatively large number of tillers with their shoot apex below cutting height at the time of first harvest. It seemed that most of these tillers had emerged during the few weeks before that harvest. The proportion of tillers with their shoot apex below rather than above cutting height at the time of first harvest was higher in all four varieties than casual observation would suggest and the proportion remained rather high throughout May and June. The rapid rate of turnover of tillers in Italian ryegrass was confirmed.

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.

Experiments were designed to assess the effects of cover crops, compared with bare stubble, on the establishment and yield of a following crop of vining peas sown in March. The cover crops of winter wheat (to simulate self-sown wheat) or winter rye, and bare stubble, were ploughed in on different dates: 1 December, 1 February or 1 March. Cover crops were destroyed with or without the use of herbicide. The three experiments in 1990/91, 1991/92 and 1992/93 were sited on a free-draining, sandy loam soil at Thornhaugh, Cambridgeshire.

The cover crops, sown as soon as possible in September following a winter wheat crop, had low dry matter (DM) production and nitrogen uptake in the dry autumns of 1990 and 1991, but in the third experiment (1992/93), autumn rainfall was higher than the long-term average and DM production and N uptake were greater. Cover crops reduced the overwinter soil mineral nitrogen (SMN) content in all 3 years compared with bare stubble. However, in spring, SMN increased where cover crops had been incorporated, due to the mineralization of the cover crop residues. Rye captured more nitrogen than wheat.

Vining pea vigour and maturity at quick-freezing harvest stage were not affected by cover crop, destruction date or method in any of the three seasons.

On the light soil, satisfactory seedbeds were achieved after ploughing at all three timings for experiments in 1990/91 and 1992/93 and vining pea yields were not reduced by cover crops or by destruction date or method. However, delayed ploughing in February and March in the 1991/92 experiment resulted in lower vining pea yields compared with ploughing in December. This was due to poor seedbeds after late ploughing rather than cover crop, stubble treatment or method of destruction.

1. An accurate method of estimating the density of spermatozoa in a suspension by the haemocytometer is described.

2. A rapid method of estimating the density of a semen sample by the use of Brown's opacity tubes is given. There is a simple linear relation between opacity and density, the latter expressed in terms of millions of spermatozoa per ml. being approximately five times the opacity standard.

3. The rapid method is sufficiently accurate for use in insemination centres.

Six nitrosoguanidine-induced manganese-resistant mutants of Azospirillum brasilense were isolated and used for associative N2 fixation studies with cheena (Panicum miliaceum L.) in acid soil. Three mutants showed cross-resistance to aluminium and neomycin, but of these three only one showed cross-resistance to streptomycin. Inoculation of cheena with A. brasilense and its mutants at different rates of applied nitrogen led to a significant increase in associative N2 fixation, N content, dry-matter production and grain yield in acid soil. A saving of about 20 kg N/ha could be achieved by inoculating seeds of cheena with these mutant strains in acid soil.

Conscious selection is the prime means of keeping the useful qualities of domestic animals at the level they have attained, and of improving them. Valuable economic qualities mostly show the polygenic type of inheritance and therefore continued selection can improve them by sorting out those genes in a herd or breed which are.most desirable for the breeder At the presenttime there is probably not one breed in existence with quantitative characters brought to the homozygous condition. It is the great genetic variation present in breeds which enables selection to be effective in bringing out desirable economic characters.

Water buffaloes (Bubalus bubalis) are reared in many tropical and subtropical countries for meat and milk production and to serve as draught animals. The improvement of milk yield in water buffaloes has been handicapped by the absence of physiological data that may provide means of rapid genetic improvement. Endocrine function is known to vary with lactation intensity. Thyroid hormones seem to have a stimulatory effect on the metabolic rate and, consequently, on the productivity of dairy animals (Lenon & Mixner, 1957; Picha, Pichova & Karasek, 1970; Swanson, 1972). Anderson (1969) also reported an increase in thyroid activity in lactating cows and rats, although other investigators (Johnson & Vanjonack, 1976; Hart et al. 1978; Hart, Bines & Morant, 1979) reported that lactation induced a decline in plasma thyroid hormones. None of these studies performed measurement of plasma thyroid stimulating hormone.

At the beginning of October, 1904, many agricultural chemists in England received copies of the above publication from the Secretary of the commission, Dr M. Ullmann, of Hamburg, together with a letter asking all who were willing to agree with the recommendations printed in the report to signify their assent to him. Copies of the report were circulated to members of the Chemical Committee of the Agricultural Education Association, and the recommendations were informally discussed at a meeting of the committee on Dec. 8th. It was suggested that a note should be published in order to call the attention of agricultural chemists to the subject, and facilitate further discussion.

Two indigenous breeds of sheep in Nigeria, the Yankasa and Uda and crosses of these with exotic breeds, were evaluated for lamb weights at birth, 3 months and 6 months of age and for adult ewe weight. The cross-bred lambs were significantly (P < 0·05) heavier than the indigenous breeds at all ages. Differences among the indigenous breeds were not significant. Mature ewe weight was 40·8 kg in the cross-bred and 36·0 and 31·1 kg in the Uda and Yankasa respectively, differences between all breeds being significant (P <0·05). Lamb productivity (lamb weight per kg of ewe metabolic body weight) estimates demonstrated that the differences between breeds were small.

Least-squares estimates of effects of environmental factors on lamb performance showed that type of birth and age of dam were important for lamb weights at the three ages. Season and sex also had significant effects on birth and 6-month weights respectively. Correction factors for lamb weights were derived from least-squares estimates.

The correlation coefficient between birth and 3-month weight was significant in all breeds and ranged from 0·39 to 0·55. Three-month and 6-month weights were highly correlated with estimates of correlation coefficients ranging from 0·71 to 0·74. Repeatability estimates of birth, 3·month, 6·month and ewe weights, all as traits of the ewe in the Yankasa, were 0·25, 0·21, 0·09 and 0·48, respectively.

Two pairs of rams with different degrees of scrotal cover were subjected to hot room temperatures ranging from 26.7 to 4.5 °C to study the effect of elevated ambient temperatures on rectal temperature, respiration rate, scrotal length, flank temperature, scrotal temperature and intra-scrotal temperature.

Increase in room temperature caused increase in intra-scrotal temperature, but there was no significant difference between the two pairs.

1. The findings presented in two previous papers on the yields of volatile fatty acids, obtained by the action of rumen liquor in the artificial rumen, from fresh grass, dried grass and the water-soluble and water-insoluble separates of the latter, have been amplified by a consideration of the acids similarly obtained from specimens of chemically prepared crude fibre and cellulose, from four of the dried grass specimens.

2. The proportions of different volatile fatty acids from grass crude fibre and grass cellulose resemble those obtained from cellulose powder, propionic acid being produced in greatest relative yield.

3. A general review of these latter findings, in relation to those already presented, has been given.

An indirect method of estimating the heat value of food stuffs, such as milk, is to determine the amounts of fat, sugar, and proteid chemically, and to multiply by the average caloric value of each; but since the amounts of these substances themselves indicate the quality of the milk their calculated caloric value need not be employed as a test of its quality.

Growth and visceral organ weights of male guinea fowl (Numida meleagris) given different levels of oxytetracycline have been studied in two experiments. In the first experiment 0, 5·0, 10·0, 15·0 and 20·0 mg oxytetracycline per kg diet were given to male guinea fowl from day 1 to 12 weeks. Body weight showed significant (P < 0·05) increases with incremental levels of the antibiotic up to 10 mg/kg diet. No further increases in growth were recorded with supplementation above this level. There were no treatment effects on the gizzard, lungs and male reproductive organs. Only the heart, liver and intestine weights were significantly (P < 0·05) affected by the treatment, and then only at the highest (20 mg/kg) of the inclusion rates examined. A second experiment was conducted to find out if the growth response obtained with 10 mg/kg oxytetracycline could be produced with a smaller dose. This was achieved at 6·6 mg/kg.

An observed positive correlation between tuber sprout growth in store and yield and tuber weight was due to the association of short sprouts with small tubers (less than 75 g). Sprout growth in larger tubers appears to be unaffected by tuber weight.

Low quality roughages are a major feed resource for ruminants in Australia and many other parts of the world. Factors limiting the intake of these roughages include their high cell wall component and low crude protein content. Palatability may also be important. Low quality roughages are frequently dusty. Hence, the present experiment was initiated to determine whether water would affect the intake of paspalum hay (Paspalum dilatatum).

In a series of five irrigated cotton sowings (T2, T7, T9, T11, T14) evapotranspiration (Et) was determined for the period between October 1961 and October 1962 by observing frequently the changes in soil moisture storage, calculating through drainage, and solving for evapotranspiration in the water balance equation. Thus a water balance was obtained for each sowing extending over the entire crop.

The average evapotranspiration in wet season sowings was of the order of 6·5 mm day−1 and in dry season sowings of the order of 4·5 mm day−1. The highest evapotranspiration values ranged between 10 and 12 mm day−1 in T2, T7 and T9 and between 7 and 9·5 mm day−1 in T11 and T14.