An analysis of the data from the continuous manurial experiment in Woodlands Field, Craibstone Experimental Farm, Aberdeen, has demonstrated the effects of fertilizers and of rainfall on the yields of various crops grown on a six-course rotation plan with a basal application of dung to the roots. The soil is a dark brown medium loam of which the parent material is ‘drift’ from the grinding down of granite and metamorphic rocks and is typical of a large class of glacial soils in the north-east of Scotland.

Of the three major nutrients nitrogen gave the largest mean response on every crop except hay. The hay yield was benefited least by nitrogen and most by potash. The effect of nitrogen was to depress slightly, but not significantly, the total production of the ley for the 3 years. Potash, on the other hand, significantly improved the yield of hay as well as of the aftermath and the following ‘pastures’. The phosphate and potash responses were approximately equal in respect of barley, oats and potatoes. Turnips, swedes and potatoes responded similarly to potash, but in terms of dry matter the response was markedly higher for potatoes.

Superphosphate proved more effective than ground mineral phosphate on every crop except turnips. Further study of the data revealed interesting differences between the crops in respect of their capacity for utilizing ground mineral phosphate. Oats gave negligible responses to mineral phosphate throughout the experiment.

Evidence is presented, based on feeding tests, that at Hanns Hall Farm it has been impossible to control bacillary white diarrhoea of chicks (pullorum disease) by blood testing when foods of c. 20% protein content have been fed as the sole diet of chicks.

Evidence is presented, based on feeding tests, that at Hanns Hall Farm epidemic bacillary white diarrhoea (pullorum disease) has occurred in brother chicks when fed foods of c. 20% protein content and that epidemic bacillary white, diarrhoea has not occurred in sister chicks which have been fed crushed oats for the first 72 hr. and thereafter have been fed a diet of c. 14% protein intake.

Evidence is presented, based on feeding tests, that at Hanns Hall Farm epidemic bacillary white diarrhoea (pullorum disease) not only did not occur in sister chicks in which B. pullorum had been demonstrated to be present in one of their number, but also epidemic bacillary white diarrhoea failed to develop despite the lack of hygienic precautions when these chicks had been placed in an uncleansed brooder from which the survivors of a severe epidemic of this disease had just been removed, and when they were brooded adjacent to chicks which suffered severe mortality from the disease, thereby undergoing all the chances of infection by wide dissemination of B. pullorum within a small area.

The bacterial syndrome encountered in epidemic bacillary white diarrhoea of chicks (pullorum disease) is initially one of invasion by faecal type organisms, this is followed by invasion by anaerogenic B. pullorum.

Evidence is presented to show that ostensibly pure cultures of anaerogenic B. pullorum, consist of two organisms, a true aerogenic B. pullorum in symbiosis with an anaerobe, morphologically of the welchii type.

Evidence is presented to show that variation in fermentation reactions of ostensibly pure cultures of anaerogenic B. pullorum depend upon the degree of symbiosis exerted between the anaerobe and the aerobe and this degree of symbiosis is greatly affected by methods of cultivation on solid media.

It is proposed that the ovarian blight peculiar to adult hens which are carriers of bacillary white diarrhoea infection is caused by putrefaction of ovarian material in vivo by the activities of a morphologically welchii type organism.

It is proposed that B. pullorum exists in one form only, namely, the aerogehic form, and that this organism is a potential pathogen only.

A feeding test performed on Hanns Hall Farm chicks demonstrates that a diet conducive to intestinal putrefaction fed to chicks after 14 days from birth initiates an epidemic of bacillary white diarrhoea (pullorum disease).

If is proposed that measures for the control of epidemic bacillary white diarrhoea of chicks (pullorum disease), which consist of the detection and removal of reacting hens from the flock by means of a diagnostic and sensitive antigen, cannot be effective unless accompanied by an alteration in nutrition for the purpose of reducing intestinal putrefaction.

Experiments at this laboratory show that the agglutination test for bacillary white diarrhoea cannot differentiate between fowls which produce diseased chicks and fowls which produce chicks resistant to disease.

Experiments at this laboratory show that B. pullorum as a potential pathogen does not remain viable to an extent that it is able to produce bacillary white diarrhoea in chicks from an incubator or brooder which has held diseased hatches or broods, respectively.

A method is presented for the preparation of a sensitive and diagnostic stained antigen for the detection of fowls suspected of infection by the organisms found in epidemic bacillary white diarrhoea (pullorum disease).

Evidence is presented that an antigen prepared from organisms grown in a medium which provides for the peculiar growth requirements of the anaerobic organism associated with anaerogenic pullorum, is more sensitive than antigens prepared from organisms grown on media which lack these peculiar growth factors.

A stained antigen has been prepared which is agglutinated by pullorum antisera in 15 sec. at 4°C. and in 6 sec. a t 15°C. and which is not agglutinated by normal sera in 5 min.

The author wishes to thank the Directors of Messrs J. Bibby and Sons, Ltd., for permission to publish these papers.

In particular he would thank Mr J. Pye Bibby for his keen interest in the investigations and for his loyal support throughout.

In addition he wishes to thank Miss Margaret Davies for her assistance in the bacteriological investigations, and Miss Margaret Shafto for laboratory work and the compilation of relevant data.

A comparison of four methods for the determination of the exchangeable hydrogen content of soils was carried out on 157 soils, from twenty-one profiles and representative of four soil types.

The methods employed were those of: (1) Hardy & Lewis, (2) Mehlich, (3) Bradfield & Allison, (4) Schofield.

The best agreement was obtained between methods (2) and (3) which are also the simplest to apply.

A positive correlation was found between low values given by method (1) and the organic matter content of the soil.

1. Substantial control of covered smut of wheat, Tilletia caries, was obtained when seed was treated with an approved organo-mercury seed disinfectant using both rotational and gravitational machines for mixing.

2. Good control of leaf spot of oats, Helminthosporium Avenae, was also obtained, using an approved organo-mercury seed disinfectant and mixing grain and powder together in a model rotational-type machine.

3. The model rotational machine gave an even mixing of grain and seed disinfectant with as few as forty-eight turns. Twenty-four turns was almost as effective but the mixing was much less even.

4. The gravitational machine was not so efficient in producing an even mixing as the rotational machine as assessed by the control of covered smut of wheat.

5. There was an indication that the rotational machine gave a better disease control.

6. Improvement was effected in the efficiency of mixing with the gravitational machine by the addition of a felt lining to the feed hopper.

Many estimates have been made of sperm production in various species, but in most cases examinations have been made infrequently or with irregular intervals between successive collections. Since during a period of sexual rest spermatozoa may accumulate in the epididymis, or with longer periods may undergo disintegration and absorption in the vas and ampulla (Simeone & Young, 1931), the number ejaculated at an particular collection will not necessarily reflect the level of sperm production in the testis. Moreover, there is the possibility that copulation may actually stimulate spermatogenesis. In horses, Chang (1943) found that more sperms were ejaculated if collections were made frequently and at regular intervals. In the present experiments an attempt has been made to determine the effect of frequency of collection upon the sperm production of rams, the collections being taken at regular intervals and for a definite period, in this case ten days.

1. A method is described whereby absolute changes in the organic and mineral constituents of cacao leaves during decomposition may be followed.

2. On a basis of their behaviour during decomposition, the components measured fall naturally into three groups. The first group comprises lignin, total protein, resistant protein, dilute-acid protein, concentrated-acid protein and nitrate-nitrogen; these exhibit an absolute increase during decompositión. The second group, represented by hemicelluloses, cellulose and pentosans, all show a downward trend, the decrease being most rapid at the outset. Alcohol- and ether-soluble substances constitute the third group and are characterized by a very rapid decrease during the first few weeks of decomposition.

3. A large amount of material soluble in dilute acid which is neither protein nor reducing sugar is not accounted for; this on a carbon basis constitutes over 50% of the dilute acid hydrolysable fraction. The trend of this fraction is somewhat similar to the carbohydrate fractions. It is pointed out that this fraction should not be neglected in a proximate analysis of decomposing organic matter.

4. Potassium exhibits a very rapid decrease at the onset of decomposition, and the trend is closely parallel to the alcohol- and ether-soluble substances. At times of heavy leaf fall there is consequently a marked manurial effect which may amount to the equivalent of 1 cwt. of sulphate of potash per acre.

While numerous studies have demonstrated the essential role of magnesium in the normal development of plants, the information as to the soil conditions governing the availability of this nutrient is relatively limited. In general it is considered that a true lack of magnesium in the soil, such as might result from leaching or overcropping, is the main cause of magnesium deficiency in plants. This aspect of the problem has received considerable attention (Imp. Bureau, 1940). It has become evident in recent years, however, that the absorption of magnesium by plants may be depressed under the influence of an excess of other nutrients, notably potassium and calcium, in the soil. In some instances this has been noted to result in the onset of magnesium deficiency in plants, despite an apparently adequate concentration of this element in an easily available form in the soil as shown by chemical methods.

The literature having a bearing on the inducement of magnesium deficiency in this manner has been reviewed by Walsh & Clarke (1944). These workers, from a study of magnesium deficiency chlorosis in tomatoes, showed that it was induced by heavy dressings of potassium causing a depression in magnesium uptake. While the effect of potassium alone in this respect was sufficient to induce the deficiency, it was also found that the sulphate radical played a prominent part. Where potassium was added other than in the form of the sulphate salt, the onset of the chlorosis was retarded and the symptoms were reduced in severity.

A laboratory study has been made of nitrification rates of the soil's own nitrogen, ammonium sulphate and certain organic nitrogen compounds. It is shown that nitrification in this soil is substantially normal, with no striking differences from that in soils of other arid regions.

I am indebted to H. Greene and E. M. Crowther for access to their earlier unpublished work on nitrification in Gezira soil, and to O. W. Snow of this Service for advice during the course of this work.