The quantitative relationships between “single value” properties and mechanical analysis of the soil are of some considerable importance in the textural classification of soils, and have received much attention since the original work on moisture equivalent by Briggs and McLane (1907). The empirical nature of the moisture equivalent, with the consequent trend towards standardisation of technique, has led to frequent re-examination of the relationship between the mechanical analysis and the “single value.”

Four plant materials of widely different origin and age were used as green manures mixed with soil for decomposition studies under laboratory conditions.

Provided the conditions of temperature, moisture, aeration, and micro-flora, are optimal, the decomposition depends upon the chemical constituents of the plant materials. It is shown that the soluble carbohydrates, hemicelluloses and cellulose are the compounds mainly responsible for the loss of total organic matter during decomposition.

In order to ascertain whether subsoil salts moved upwards under the influence of irrigation an elaborate investigation was carried out at the Gezira Kesearch Farm, Medani. It wasfound that the small apparent changes which occur under normal irrigation and cultivation are largely due to swelling and shrinking of the surface soil occasioned by changes in moisture content and to mechanical disturbance and settling which depend on cultivation. Apart from these apparent changes there may be a small downward movement of salt through the soil material; there is no upward movement.

1. This article describes the comparative results of the determination of shrinkage constants (Haines’ method) and of certain soil moisture constants for a series of clay soils representative of three important classes, namely, tropical red soils derived from igneous rocks and from limestone, kaolinitic soils and materials, and grey and yellow soils, mainly derived from aqueous sedimentary rocks.

2. An attempt is made to interpret the data in terms of Wilsdon's micro-reticular hypothesis of soil colloidal structure, and to explain the physical significance of some of the constants measured, particularly sticky point moisture (S), loss on ignition (I), water uptake from aqueous vapour (H, R), and Haines’ “residual shrinkage” moisture content (d).

3. The results indicate that tropical red soils closely resemble kaolinitic materials in their shrinkage behaviour and moisture relations, but that they are intermediate between this type and grey and yellow soils, which exhibit characteristic high total shrinkage, marked residual shrinkage and high adsorptive capacity for moisture and for cations.

4. A brief review of recent literature concerning the mineralogy of clay minerals (based on X-ray analysis and optical examination) is offered in support of these findings.

5. The need of detailed mineralogical investigations of the products of weathering of rocks under humid tropical conditions is urged. Such study might reveal the causes of the characteristic and peculiar field properties of tropical red soils which appear to have been neglected by soil physical-chemists.

1. The formation of alkali soils is primarily a question of soluble salt accumulation. Those processes which bring about the accumulation of soluble salts in soils also tend to cause the accumulation of CaCO3. Under certain conditions simple calcium silicates may also be precipitated in alkali soils. Hilgard's researches were concerned chiefly with the soluble salts. On the other hand, more recent investigators have emphasised the base-exchange aspects of the subject. Sodium salts tend to react with the clay and humus constituents of the soil, converting them into Na-absorption compounds. These components produce extremely adverse conditions in the soil.

2. Under certain conditions alkali soils tend to pass through four evolutionary stages, namely, salinisation, alkalinisation, desalinisation, and degradation. As to whether or not an alkali soil will pass beyond the salinisation stage, depends on the composition of the soluble salts that accumulate in it. Where sodium salts predominate, more or less alkalinisation of the exchange complex has taken place. However, this is not true where soluble calcium is relatively abundant.

3. Desalinisation (by leaching, whether natural or artificial) of alkalinised soil is usually accompanied by the formation of Na2CO3 and by pronounced deflocculation. If CaCO3 be present, the formation of Na2CO3 is accompanied by the replacement of absorbed sodium by calcium. Under these conditions the degradation stage will not be attained. If CaCO3 be absent, base-unsaturated constituents arise under leaching conditions, and more or less of the inorganic-exchange complex becomes decomposed into simple oxides.

In this communication are brought forward the results of digestion trials designed to discover the degree to which pigs are able to digest and utilise young grass. Three digestion trials have been carried out. In the first trial, the digestibility of a basal ration composed of equal parts of maize meal and coarse middlings was determined. In the following two periods, the amount of basal food was cut down to an appropriate level and definite weights of the grass to be tested were added. In period 2, very short, leafy grass, containing, on the basis of dry matter, 26·04 per cent, of crude protein and 16·73 per cent. of crude fibre, was used, whilst somewhat older grass, containing 16·76 and 19·42 per cent. crude protein and fibre respectively, was fed in the third period.

It was found that the Large White hogs, which averaged about 195 lb. live-weight during the carrying out of the grass periods of feeding, were unable, with the exception of the fibrous component, to digest the constituents of even young grass with anything like the same degree of efficiency as they displayed in the digestion of the basal ration of middlings and maize meal. The constituents of the older grass, with the exception of the crude protein, were not markedly less digestible than those of the very young grass. The relative values of the pasturage and mixed meal are best brought out by the data for the digestion coefficients of the total organic matter; the pigs were able to digest about 85 per cent. of the organic matter of the meal, and only 60–62 per cent. of that contained in the grass.

1. Partial regression equations representing the average drainage observed in any month in terms of the temperature and rainfall of that month, and including terms representing the mean secular rate of change of the drainage discharge and of its regression coefficients on rainfall and temperature, have been fitted to the thirty-six series of observations provided by the three Rothamsted drain gauges in the twelve months of the year.

2. An account is given of adequate and direct numerical methods of handling equations involving observed quantities, and chosen functions of them, as independent variates, and of calculating standard errors appropriate to the several sorts of comparison which are to be made.

3. In the absence of direct knowledge of the amount of water contained from time to time in the soil mass of the gauge it has been customary to assume that the lower average drainage of the summer months is directly due to a greater amount of evaporation taking place in these months. The results of the present enquiry direct attention to a second possibility, namely that the water content of the gauges differs considerably at different times of the year, and that the high drainage in winter is in part to be ascribed to the accumulation of water during the rainy months of autumn, while the lower drainage in summer is due to the partial depletion of the gauges during the lower rainfall of the spring months.

The heat of wetting measurement has been introduced into soil science by E. A. Mitscherlich(1), who constructed for his investigations a rather complicated apparatus, consisting of an ice calorimeter which had been adapted for the special requirements of soil tests. Mitscherlich used the heat of wetting as a measurement of the heaviness of different soils, but soon found the technique too difficult, and later preferred the wellknown hygroscopicity determination which he had worked out in collaboration with H. Rodewald(2).

The economic importance of the common heather or ling (Calluna vulgaris) is little appreciated by those not intimately concerned with the preservation of game, or the management of hill sheep, and investigators have given scant attention to its composition and feeding value. Yet it is the staple food of the grouse and, in many districts, contributes largely to the diet of the Blackface sheep. The young and tender shoots are eaten at all seasons of the year, but are of special value in winter, for heather is evergreen and withstands the action of frost in normal years. Further, its habit of growth is such that sheep may obtain access to it during snowy weather.

1. Humic acids and ammonium humates prepared by a patented process of gentle oxidation of coal were examined as fertilisers by laboratory nitrification experiments and pot-culture tests on four soils and by a number of field experiments on a range of soils and crops during a single season.

2. In all tests the effects of ammonium humate could not be distinguished from those of ammonium sulphate of equal ammonium content. The nitrification tests and the pot cultures afforded some evidence of a slow production of nitrate or available nitrogen from the humic acid.

3. In the field experiments as in the pots there was no clear evidence of any fertiliser value apart from that due to the ammonium present.