1. Measurements on the loss of ignition of four soils of different physical type are not affected by changes in the temperature of furnace, provided that the temperature is above 600°. Errors in the determination of the loss on ignition are of the order of 1 per cent. of the true value.

2. The loss in weight of the soils can be ascribed in the main to loss of free and interstitial water up to about 100°; to destruction of organic colloids between 100° and 250°; and to destruction of inorganic colloids at higher temperatures.

Thanks are due to Miss T. Alper, M.A. (Cape Town) for assistance in making some of the preliminary measurements.

The main conclusions from the present investigation, which was undertaken in order to obtain an insight into the consequences of the adoption of a 5-weekly rotational close-grazing system, may be summarized as follows:

The lengthening of the interval between successive cuts from a month to 5 weeks leads to a definite, though not very serious, reduction in the digestibility of the herbage. This reduction is most noticeable during the flush period of growth, and the constituent most affected is the crude protein. During the fore-flush and post-flush periods, it appears to be immaterial, from the standpoint of digestibility, whether a system of monthly or 5-weekly cutting is adopted. The falling off in digestibility is not connected with the onset of lignification in the herbage, since the digestion coefficient of the fibrous constituent remains high throughout the season, and it may be concluded that, during a season of favourable rainfall, it is possible by cutting (or close-grazing) at intervals of 5 weeks, to prevent the herbage from becoming lignified and of greatly reduced digestibility. The possibility, however, during seasons of a droughty character, of a premature onset of lignification under a system of cutting (or close-grazing) at 5-weekly intervals is discussed.

1. From the results of calcium and phosphorus balances on laying pullets, it is shown that the pullets displayed a diminution of the calcium and phosphorus in their droppings over a period of about 2–3 weeks before laying, and a correspondingly increasing retention of these elements.

2. Egg laying was correlated with a relatively heavy voiding of phosphorus in the droppings, involving a temporary negative phosphorus balance. This confirms and amplifies the results of other workers on this subject. The nature and meaning of the phenomenon are discussed.

1. A uniformity trial with potatoes was used for investigating the effect of size and shape of plots on the precision of field experiments. Up to a certain limit the S.D. in per cent. of the mean decreases when the size of plots is increased; further increase of plot size increases the errors as a lesser part of the soil variation can be removed.

2. Two-row plots show less variation than either 1 or 3-row plots. This may be explained by row competition.

3. When the area to be used is fixed, smaller plots are more efficient than larger, owing to the greater number of replications in the former case. One exception occurs in the case where border rows are not harvested; here 4-row plots are more efficient than 3-row plots, owing to the fact that a larger part of the soil is included in the calculations when 4-row plots are used.

4. Long and narrow plots are more efficient than shorter and wider of the same size. The only exception is again explained by row competition.

5. In field experiments with potatoes fairly large plots should be used; at least 2 rows wide and preferably long and narrow strips.

1. The action of the following sulphur compounds on the conidial stage of the hop powdery mildew (Sphaerotheca Humuli) has been examined:

Sodium sulphite, prepared by direct solution or by the neutralisation of solutions of sodium metabisulphite and applied with either 0·5 per cent, gelatine or 0·5 per cent. Agral I as the spreader, proved fungicidal at a content of 0·25 per cent, sulphur, and non-fungicidal at a content of 0·16 per cent, sulphur. The solutions, at these concentrations, caused injury to the leaves, which is not prevented by the neutralisation of solutions of sodium metabisulphite by calcium hydroxide instead of sodium hydroxide.

Retarded growth and poor bone development resulted from feeding both a ration containing only 0·26 per cent. calcium and with a Ca:P ratio of 0·44:1 and from a ration in which 5 per cent, of maize meal had been replaced by 5 per cent, of ground limestone to give a calcium content of 3 per cent. and a Ca:P ratio of 4:1. The basal or No Limestone group confirms previous results indicating that ground limestone may have a depressing effect on growth.

The authors wish to acknowledge the assistance of Mr G. H. Botham, B.Sc, A.L.S., who did the chemical analysis of the food and bones, Mr J. Lavelle, who made and interpreted the skiagrams, and Mr F. J. Dudley, who statistically analysed the results.

The moisture equivalent has been measured (by a technique requiring only small quantities of soil) for a number of samples comprising Natal and Sind soils. It is concluded that while with the latter (alkaline and saline) soils the moisture equivalent gives valuable information, it adds little to the data obtained by other methods for the Natal soils. The xylene equivalent of the Natal soils has also been measured; from the moisture equivalent and the xylene equivalent, the imbibitional water can be calculated if the specific gravity of the soil is known.

Equations expressing the moisture equivalent and the xylene equivalent of the Natal soils in terms of their loss on ignition and mechanical composition are obtained, and the significance of the relative values of the numerical coefficients in these equations is discussed.

The present investigation consists of the statistical analysis of a uniformity trial with potatoes conducted by Dr Kirk. In this study the standard error in per cent. of the mean decreased slightly with the increase in the widths up to plots 5 rows wide, but any further increase in the width of the plot resulted in the higher standard error. The fertility contour map of the field is given in Fig. 1 to show graphically the effect of soil heterogeneity on the yield. The increased size of the plot resulted in the decreased efficiency in the use of the land when the entire plot was harvested; in other words, given a piece of land of certain size, it is advantageous to have a greater replication of smaller plots than a smaller number of larger plots. Four-row plots proved to be the most efficient when the border rows are discarded. The superiority of long and narrow plots over shorter and wider ones is demonstrated.

With the greatest pleasure I acknowledge my indebtedness to Dr Kirk, who supplied me with the data, to Dr Fisher for his valuable suggestions and to Dr J. Wishart for useful advice and criticism.

1. Samples of tea leaf from different portions of the same field were analysed for ash, nitrogen, potash and phosphate on thirty-five consecutive plucking rounds extending over a period of seventeen months for which yields were also recorded.

2. The significant variations obtained are shown to be partly due to seasonal differences which affect all the constituents and to persistent differences between portions of the field in the case of yield, ash and potash. No significant differences were detected between the nitrogen and phosphate status of different portions of the field, although the sampling errors were not larger than those of the former category.

3. These results indicate that the sampling technique is satisfactory, a point of some importance in view of laboratory investigations on tea manufacture, and confirm the finding from other considerations that the standard of plucking can be maintained at a reasonably high level.

Several factors affecting the electrical conductivity of soil suspensions have been studied leading to the development of a simple and rapid technique for its measurement, and suitable for both moist and air-dry soils.

The possible use of the method in soil fertility studies necessitated examination of the effects of cultivations, manures, crop, meteorological variations, etc., on the conductivity measurements. This involved periodical determinations of initial conductivity (i.e. the specific conductivity of a 1 to 5 aqueous soil suspension determined at 25° C.) and the 7 days’ increase (i.e. the rise in specific conductivity of the same aqueous suspension after standing for 7 days in a thermostat at 25° C.). Soil samples were examined from several Rothamsted classical and nonclassical plots (over twenty plots were investigated for 15–20 months), and samples from experiments were also utilised during two growing seasons.

1. The paper deals with the yields of seed cotton grown under irrigation in the Sudan in the seasons 1929–30, 1930–1.

2. Interactions of four factors were studied in all possible combinations. The factors were: four sowing dates, three spacings, three water duties, and nitrogen application.

1. Pyrethrum powders and dusts, prepared by grinding or by the incorporation of extracts of pyrethrum flowers upon absorbent earths, such as talc and kieselguhr, lose their insecticidal activity on exposure to light and air. The loss is more rapid in the case of artificially prepared dusts than with ground flower-heads.

2. Both light and air play an important part in the process of inactivation, as samples of kieselguhr-pyrethrum and talc-pyrethrum dusts stored in closed vessels in the dark or exposed to air in the dark are relatively stable; also samples exposed to light in an atmosphere of carbon dioxide, nitrogen or in vacuo lose little of their toxicity under the same conditions of illumination; samples exposed in oxygen, however, rapidly lose their activity.

3. Both wet and dry oxygen were effective in destroying the activity of the dusts, but apparently at different rates, and there is some suggestion that the type of reaction may be different in the two cases.

Vol. XX, Part 4, Oct. 1930

p. 539, line 6 for “1N sulphuric acid”

read “10N sulphuric acid”

Vol. XXI, Part 4, Oct. 1931

p. 764, line 14 for “mallee”

read “mallet”

p. 777. The last three lines belong to the legend to Fig. 3 on p. 770.

1. It is shown that the plasticity of a soil, as measured by the flow-plasticity test, is correlated with soil temperature and moisture. Although the measurement is made on a paste of the soil made smooth by working the mass of soil with water, and then forcing it through a fine sieve, the flow plasticity of the paste still depends on the climatic history of the soil from which it is prepared.

2. The soil has, in general, a higher plasticity in cold and dry weather and a lower plasticity in warm and wet weather. These results seem to confirm the conclusions of Vinokurof about seasonal fluctuations in the quantity of highly dispersed particles.

This enquiry has emphatically shown the high protein character of young grass, and this fact undoubtedly constitutes the outstanding feature of the scheme. Herbage of from one to three weeks’ growth is a rich protein forage; its dry matter has a range of from 20 to 30 per cent. protein.

The unsatisfactory nature of empirical formulae for the determination of surface area in metabolism work, especially with reference to pigs, is discussed, and the conclusion reached that the actual estimation of the area is the only satisfactory method where an accuracy greater than ± 10 per cent. is desired.

It is pointed out that surface area is to some extent variable in animals and that direct determinations are from this point of view less satisfactory than might have been thought.

A new method is proposed for estimating the surface area of a pig in a definite standing position depending on mathematical and photographic conditions only, and therefore applicable to the living animal, and to the same animal at different times during its life. Full sets of computations are given and one case is noted where the method affords a correct estimate as between two pigs where the formulae are all clearly wrong.

Oats have never been used widely in this country for feeding to pigs. Their relative unpopularity for this purpose is attributable to their content of fibre, which, on account of the fibrous husk surrounding the kernel, is high compared with that of the other cereals. This prejudice is, in the main, perfectly logical, since the pig's digestive system is not designed to deal with foods of a fibrous nature. The most successful rations for growing and fattening pigs contain no more than 4–5 per cent. of fibre, this amount being necessary to facilitate the passage of the food residues along the intestinal tract. Higher amounts than this, however, are known to lead to a reduction of the efficiency of the ration. In a study of the influence of fibre on the utilisation of pig rations, Robison(1) noted a continuous decline in growth rate as the percentage of fibre in the ration was increased up to 9 per cent., the amount of food required for 1 lb. of live-weight gain displaying meanwhile a corresponding increase.