Partial regression analyses have been used to calculate mean values for the cation exchange capacities of the clay and organic matter from five groups of soils.

It has been found that figures obtained for exchange capacities of the clays were in accord with what was known of their mineralogical composition. The corresponding figures for humus differed widely, the differences approaching significance, and were related to the mean pH of the soil group concerned.

The data on which this paper is based were obtained when the authors were at the Agricultural Chemistry laboratories of the University of Sydney, to the Research Grants Committee of which they are greatly indebted for generous financial assistance. They are particularly indebted to Dr G. Wilkinson, C.S.I.R.O., Division of Statistics, Adelaide, for helpful discussions, to Miss H. V. Rayner and Miss J. Walker for certain of the analyses.

Eight Merino and eight Dormer ewes, none of which had been on heat for 2–3 months prior to treatment, were given six intra-muscular injections of 30 mg. progesterone at 3-day intervals. The ewes were divided into four groups, each consisting of two Merinos and two Dormers. On the second day after the last progesterone injection, 1000 i.u. P.M.S. were administered to each of the ewes in group I. The remaining ewes each received an injection of 500 i.u. P.M.S. on either the first and second days (group II), the second and third days (group III), or the first and third days after the end of the progesterone treatment (group IV).

Five of the Dormer ewes, but not one of the Merino ewes, were served after the treatment. Mean ovulation rates for the four groups were 2·50, 2·75, 2·00 and 2·50, respectively, and the mean numbers of large follicles (i.e. those which were observed at laparotomy, approximately a week after treatment, to have a diameter of not less than 4 mm.) were 3·00, 2·75, 1·00 and 2·00, respectively. Contrary to expectation, it was observed that only one of the ewes (a Merino) showed evidence of a silent ovulation shortly before treatment.

It is suggested that (i) the amount of oestrogen produced by the ovarian follicles of the Merinos may have been exceptionally low, thus accounting for the non-occurrence of oestrus in these ewes, (ii) ovulation rates might be increased by greater reductions in the time between the last progesterone injection and P.M.S. treatment, and (iii) if silent heat in the Merino is rare, it may be simpler to induce coincident heat and superovulation in ewes of this breed by two injections of P.M.S. at 16-day intervals.

A method has been described of assessing the average degree of medullation in fleece samples. This method combines information about the various fibre types and the proportion of each present in the sample, by assigning 100 fibres to classes with scores 1–5 according to the degree of medullation. A weighted mean score was determined, ten times this mean being defined as the ‘medullation index’. The index has been used for 2 years on samples taken from 2-month-old lambs and 14-month-old hoggs of the Blackface breed. Drawings of fibre types showed that the internal and external diameters and their ratio all increase with the score.

The mean medullation index for the 2-month-old lambs in the 2 years was 25·6 and 24·8. The effects of sex and type of birth of lamb and age of dam were assessed by fitting constants, but their contribution to the total variance was very small. The regression of medullation on age of lamb when sampled was −0·11 units per day in both years, and was highly significant. Possible explanations for this decline of medullation are discussed.

The mean medullation index for 14-month-old hoggs was 16·1 in both years. Estimate of correlation between lamb and hogg for the 2 years were + 0·45 and + 0·33. It is probable that variation in medullation within the fleece and in fibre shedding account for these low values.

1. The age changes in carcass composition of female kids killed at birth, 9, 16, 25 and 30 lb. are described.

2. The organs and tissues of the kids were weighed both wet and oven-dried, allowing the dry-matter percentages at different stages of growth to be calculated. The total dry-matter percentage for day-old kids averaged 26·5%, rising to a maximum of 40·5% at the 25 lb. stage. The greatest increase in dry-matter percentage was between birth and the 9 lb. stage, which was reached at approximately 1 month. This increase in dry matter is chiefly due to a steady rise in the dry-matter content of the muscular and skeletal tissues; from 20·2 to 25·4%, and from 34·3 to 59·6%, respectively, between birth and maturity.

3. The various joints of the kid were weighed and recorded separately, and the changes in the proportions of the joints illustrated centripetal growth. At birth, the joints were present in the following proportions: thorax 30%; legs 40%; head 20%; pelvis 10%. As the kid developed, there was a marked increase in the proportion of thorax and pelvis, accompanied by a corresponding decrease in the proportion of the head and foreleg.

1. An experiment involving fifty Romney ewes of known history is described. These ewes were randomized to ten treatment groups of five ewes so that group mean live weights were approximately equal. The average live weight of the ewes was 147 lb. at selection and 135.5 lb. at the beginning of the 28-day experimental period. Three levels of L-thyroxine implants, viz. 150, 210 and 270 mg. were used on six groups of ewes, three of which (LT: NP, MT: NP, HT: NP) were on a normal plane of nutrition and three (LT: LP, MT: LP, HT: LP) on a low plane of nutrition. One group of ewes (DT: LP) was daily injected with 5 mg. L-thyroxine; one group of ewes (CB) was slaughtered at the commencement of the 2 8-day experimental period; one group of ewes (C:NP) was maintained for 28 days on a normal plane of nutrition and did not receive thyroxine therapy, and another group of ewes (C:LP) was on a low plane of nutrition for 28 days and was not treated with thyroxine.

2. Live-weight losses of up to 24.4 lb. for the low thyroxine (150 mg.) low-plane group of ewes (LT:LP) and 30.0 lb. for the three surviving ewes of the DT: LP group were recorded at the end of the 28-day experimental period. The daily injection of 5 mg. L-thyroxine treatment had to be modified because of two deaths.

In a small plot experiment in which the crop was protected from rain, the application of large amounts of water to keep the soil water stress to a minimum gave very large crop yields. One-fifth of this amount of water gave 80% of the maximum yield. Small, frequent applications of water appeared to give higher yields than the same amount of water in one large application. Yield differences were due to differences in leaf areas rather than to differences in net assimilation rates.

1. Methods of investigating denitrification in soil are critically discussed with special reference to methods based on total-N analysis.

2. A modified Kjeldahl method of determining nitrogen which includes nitrate and nitrite and is applicable to waterlogged soil is described and the use of this method in studies on denitrification in soil is illustrated and discussed.

3. It is shown that rapid denitrification of nitrate in soil can be induced by incubating the soil under waterlogged conditions with organic materials such as glucose and that denitrification can be followed by total-N analyses if the organic material used to induce denitrification is not added in such excess that it also promotes significant fixation of atmospheric nitrogen.

4. The percentage of added nitrate-N lost by denitrification on incubation of waterlogged soils with different amounts of nitrate and sufficient glucose for denitrification was found to be the same whatever the level of application of nitrate.

5. Denitrification of nitrate in waterlogged soil containing glucose was found to be accompanied by a rapid but temporary accumulation of large quantities of nitrite and by the formation of smaller amounts of ammonia. Hydroxylamine could not be detected during denitrification, but it was found that this compound was rapidly decomposed in the soils examined by a process which appeared to be purely chemical.

6. It is shown that denitrification of nitrate in soil is a microbiological process and that the viability of the micro-organisms responsible for denitrification is not affected by air-drying and storage of the soil.

The growth and carcass composition of two strains of mice (N- and C-strain), which had both been selected for large and small body size by Falconer, have been studied.

Differences in body weight between mice of the N-strain and their controls were apparent at birth and were fully maintained up to 30 weeks of age. The patterns of growth were similar in all three lines, although the large line grew at a faster rate than the small line, the controls being intermediate. Differences in absolute and relative rates of growth between the three lines reach a maximum from 21 to 35 days of age and declined thereafter.

Growth in the large line of the N-strain from 14 to 40 days of age was largely due to an increase in body protein and water; after this age, increase in weight was caused mainly by fat deposition. In the small line of this strain, protein, water and fat were deposited at a more constant rate during the whole growing period. Differences in rates of growth may account for the differences in the percentage composition found between mice of the large and small lines of the N-strain at the same age.

1. The effects of l-thyroxine therapy and a low plane of nutrition on some of the non-carcass components of live weight in New Zealand Romney ewes were investigated.

2. Thyroxine treatment significantly lowered the weight of the gastrointestinal tract contents. A low plane of nutrition and a longer total starvation immediately pre-slaughter had little effect in lowering the weight of the gastrointestinal contents. Alimentary tract ‘fill’ accounted for a group mean loss of live weight of up to 5 lb.

3. Thyroxine treatment lowered the weight of the empty gastric tract, while a low plane of nutrition reduced the weight of both the empty gastric and intestinal tracts. The combined treatment effects accounted for a loss of up to 3 lb. in the weight of the empty gastrointestinal tract.

4. Neither treatment significantly reduced the weight of the omental and mesenteric fat depots.

5. The weight of the thyroid gland was unaffected by either treatment.

6. A low plane of nutrition significantly reduced the weight of the liver, kidneys and the heart but had no effect on the weight of the spleen. Thyroxine therapy significantly reduced the weight of the liver and tended to increase the weight of the kidneys and the heart.

1. Ten successive trials with two Rahmany adult ewes were carried out with the aim of comparing the nutritive values of the nitrogenous constituents of some concentrates used in Egypt as supplements in summer rations (decorticated cottonseed cake, linseed-oil meal and beans (Vicia faba)) and of animal proteins (meat meal, fish meal and casein) and of barseem (Trifolium alexandrinum). Wheat straw was employed as the main roughage in the ration. Nitrogen intake for all supplements was 10·16 g./day.

2. Apparent digestion coefficients for crude protein were estimated. Casein had the highest digestibility coefficient while meat meal was the least digestible.

3. Nitrogen retention and ruminal ammonia curves are given for each period. Only three proteins, namely, barseem, cottonseed cake and linseed meal gave positive nitrogen balance at the critical level of nitrogen intake used throughout the trials. Fish meal improved nitrogen retention significantly. Meat meal and beans did not improve nitrogen retention. The addition of 70 g. starch to beans improved nitrogen retention significantly.

1. The factors affecting denitrification in soil have been studied by determining loss of nitrogen from soil under various conditions by total-N analysis.

2. It was found that the rate of denitrification of nitrate in soil was dependent upon various factors such as the pH, temperature and water content of the soil and that, under conditions conducive to denitrification, 80–86% of nitrate-N added to Rothamsted soils was lost by denitrification in 5 days.

3. The rate of denitrification was greatly affected by the pH of the soil. It was very slow at low pH (below 4·8), increased with rise in soil pH and was very rapid at pH 8·0–8·6.

4. The rate of denitrification increased rapidly with rise in temperature from 2° to 25° C. The optimum temperature for denitrification was about 60° C.

5. The degree of water saturation of the soil had a profound influence on the rate of denitrification. Below a certain moisture level practically no denitrification occurred; above this level denitrification increased rapidly with increase in moisture content. The critical moisture level was about 60% of the water-holding capacity of the soil.

The apparent digestibility of crude protein by the non-ruminants, pigs, horses, rats, man and the rabbit, is shown to be related to the crude protein content of the feed, and the form of the relationship is similar to that for ruminants. With non-ruminants the apparent digestibility of crude protein is markedly depressed by the crude fibre content of the feed, whereas with ruminants the depression is only slight. The relevant equations show that pigs are much more sensitive to crude fibre than horses and rabbits, and both the latter react more markedly to crude fibre than do the ruminants.

Despite the apparently significant differences between the equations for the ruminant and nonruminant herbivores, it is shown that over the normal range of crude protein and crude fibre content in feedingstuffs suitable for herbivores, the apparent digestibility coefficient of crude protein is similar for all. In other words, despite different abilities to cope with crude fibre, the herbivores as a class digest crude protein in normal feeds to much the same extent. On the other hand, the pig, an omnivore, is shown to be very markedly affected by the crude fibre content of such feeds.

1. Most of the bees which drift do so during their orientation flights and before they become regular foragers.

2. Bees emerging in August and September drift less than those emerging earlier in the year.

3. Drifting varies considerably in different circumstances, and may be extensive.

4. Drones drift two to three times as frequently as workers.

5. An individual bee is more likely to drift from a small to a large colony than vice versa, but the greater number of bees flying from the large colonies may result in a net gain in bees by the smaller ones.

6. When hives are arranged in repetitive patterns, bees drift to hives occupying similar positions in the pattern to their own. When hives are arranged in rows, bees from the centre colonies drift more than those at the end, resulting in the latter colonies gaining numerically. In some circumstances, more bees drift to hives in one direction than in the opposite direction.

7. Facing hives in different directions and painting them different colours considerably reduces drifting, the facing of hives in different directions being of the greater significance.

1. In a series of digestibility trials using two Rahmany ewes (see previous publication, el-Shazly, 1958), protein supplements in the form of concentrates, pure proteins or green roughage, supplying 10.16 g. N per day, did not affect significantly the digestibility of cellulose in wheat straw.

2. Decorticated cottonseed cake given at three different levels, i.e. 10.16, 20.32 and 30.48 g. N, did not produce a significant change in wheat-straw cellulose digestibility.

3. The digestibility of dry matter was significantly improved by all supplements used except fish meal and decorticated cottonseed cake at a level of 10.16 g. N per day.

4. Total volatile fatty acids were estimated just before feeding and at different intervals after feeding.

5. The implication of these results for microbial activity are discussed.

1. In eight experiments on main-crop potatoes in 1953–4 placing 0·5 cwt. N/acre in a band beside the seed tended to give higher yields than broadcasting the dressing; when 1·0 cwt. N/acre was applied, broadcasting tended to be superior to placement. There were no consistent gains from placing 1·5 cwt. K2O/acre.

2. Four other potato experiments in 1954–6 tested all combinations of placing and broadcasting two levels of nitrogen and potassium. There was no clear relationship between the effects of broadcasting or placing one nutrient and the way in which the other nutrient was applied. When 0·5 cwt. N was applied, placing gave higher yields in seven out of ten possible comparisons (one effect was significant). With 1·0 cwt. N/acre there were also seven of ten comparisons in favour of placement (three significant effects), but in two other comparisons broadcasting gave significantly higher yields. Placing potassium gave higher yields than broadcasting in sixteen out of twenty comparisons (six significant effects), in one of the remaining comparisons broadcasting potassium was significantly superior. Placing of the potassium and, to a lesser extent, the nitrogen components of a complete potato fertilizer is likely to be beneficial.

3. In two experiments each on green peas and broad beans placing of phosphorus and potassium separately and together gave consistently higher yields than broadcasting these nutrients. When nitrogen was used in addition to phosphorus and potassium there were small gains in yield of broad beans provided the mixture was placed. There were no gains in yields of green peas from nitrogen however the mixture was applied.

1. In a series of tests chicks were fed up to 4 weeks of age on a ‘purified’ diet supplemented with 10% of protein from either herring meal or condensed herring solubles.

2. The solubles alone appeared of negligible value as a protein source, but certain mixtures of solubles and meal protein proved superior to meal alone, although the levels of the essential amino acids plus cystine and tyrosine were lower in the mixture than in meal alone. The supplementary effect may possibly be due to changes in the aminoacid ratio or balance.

3. Only tryptophan improved growth and viability when free amino acids were added singly to the solubles. Simultaneous supply of all 10 essential amino acids elevated growth to about 80% of that on meal alone. A combination of tryptophan, isoleucine, histidine and phenylalanine appeared nearly as effective as the 10. Depressant effects of free amino acids at the low levels used were also met with. The chick results followed closely the predictions made from the results of microbiological assays of the amino-acid composition of the solubles, and these were in conformity with the composition of the ‘ideal’ amino-acid mixture for chicks proposed by Fisher & Johnson (1957).

4. The small weight gains of the chicks on solubles alone consisted largely of water rather than true tissue. Appetite appeared to be governed by the balance of amino acids, this appearing to be more important than the absolute levels fed. This applied to diets with heated meal as well as the solubles.

1. An experiment was carried out in which twelve Romney Marsh ewes were separated into two groups, one kept on a high plane of food intake and one on a low plane during pregnancy and lactation. Skin and wool samples were taken from the progeny at birth and weaning; the ratio Sf/Pf was determined for these ages as well as the proportion of follicles of various kinds and in different phases of activity. The results are compared with those of Ryder from an earlier experiment with Cheviots.

2. Differences in food intake of ewes of the order described affected live weight at weaning, but did not significantly affect the differentiation and development of secondary follicles in the foetus nor their number at weaning.

3. Lambs in the low-plane group shed secondary fibres at 12 months old much more than those which had been in the high-plane group.

4. A partial association of variation in birth Sf/Pf with variation in birth weight was demonstrated, but more than half the variation in this ratio is not accounted for in this way, and the same applies to the variation in birth S/P of the Cheviots in Ryder's earlier experiment. It is suggested that variations in foetal environment and in the early post-natal period affect the rate at which the secondary follicle population in a lamb develops towards its mature genetic maximum.

1. An experiment with dairy cows is described in which the production per animal and per acre obtained in three methods of grazing management were compared during 2 years.

(A) An intensive method. Strip-grazing daily on heavily fertilized grass sward.

(B) A modified intensive method. Continuous, free-range grazing on a heavily fertilized grass sward.

(C) An extensive method. Continuous, free-range grazing on a grass and clover sward receiving a basic application of phosphate and potash only.

The intensively fertilized swards received a total of 212 lb. fertilizer nitrogen per acre, together with adequate amounts of phosphate and potash throughout the grazing season. No supplementary foods of concentrate type were fed to the cows during the experiment.

2. For the comparison of production per animal 3 × 3 Latin-square experimental design, with twelve Ayrshire cows and periods of 3 weeks' duration, was used. Two separate trials were conducted during the grazing season of 1955 and a third trial during 1956.

3. The different methods of grazing management and intensive use of fertilizer had little influence on the milk yield and butterfat percentage of the milk of the cows.

1. Attention is drawn to the enormous variations in yield experienced in commercial cotton growing under rain-fed conditions. Yields at Namulonge have ranged from 161 to 1163 lb./acre.

2. In seeking an explanation of this enormous variation past and present fertilizer trials in Uganda have failed to show that much of this variation is due to nutrient status.

3. From Manning's previous analysis of yields in relation to seasonal rainfall, over many district trials, it is evident that 20–25 in. of rainfall per season is optimum.

4. The purpose of more recent studies has been to examine the effect of distribution of rainfall within the season. Clearly the pattern of crop water requirement, also within the season, must supersede a simple seasonal concept of crop water use.

5. Experimental evidence, based on several seasons' data, led to the conclusion that evapotranspiration rates exceeding the commonly accepted figure of 0·8E must in fact occur in order to provide a satisfactory explanation of results recorded.

6. The within-season pattern of water requirement of an annual arable crop is shown to be more dependent on its state of development than on the pattern of a physical model based on calculations of energy availability.

1. Fifty buffalo-cows were used for studying the pH of the vaginal secretion at different stages of the sex cycle.

2. Highly significant differences were found in the pH value of the vaginal secretions during the different stages of the sex cycle. The average was 7·3 during oestrus, 8·1 during dioestrus and 8·3 during pregnancy.