A recent paper by W. B. Haines on soil shrinkage is discussed and his explanation of residual shrinkage criticised in the light of earlier work by the writer on evaporation of water from soil. A modification of Haines' tentative explanation is suggested.

The experimental results of Haines nave rendered it possible to define more clearly than previous work allowed the significance of the critical moisture content and the divergence between the first sloping portions of the rate of evaporation curves and the corresponding portions of the vapour pressure curves.

The object of this note is to call into question the soundness of the generally accepted method by which the so-called apparent protein digestion coefficients of foodstuffs are corrected.

The digestion coefficient for the protein of a foodstuff as ordinarily determined by animal experiment does not afford a strictly accurate idea of the actual digestibility of that constituent. The figure represents a minimum value, and this arises from the well-known fact that the faeces do not consist solely of undigested food residues, but are to an appreciable extent contaminated by nitrogenous products which have been secreted into the alimentary tract and have escaped reabsorption. The nature of this so-termed metabolic material is twofold, being partly protein (mucus, epithelium, etc.) and partly non-protein (residues of digestive secretions, etc.). Before proceeding to a critical survey of the correction method, which is designed ostensibly to enable allowance to be made for the presence of such products in the faeces, it is of essential interest to consider briefly the true significance of the term “protein digestibility.”

Two objectives were in view in undertaking this research.; to ascertain the cost in energy of muscular work in the goat and to investigate the adaptability of the Douglas-Haldane method of indirect calorimetry to work experiments on this animal. It is to the results of human experiments chiefly, that the present position of the physiology of muscular exercise is due which owes comparatively little to experiments on other animals. Zuntz and his school (1) have, however, compared the effect of a fixed amount of work on men, horses and dogs, and Lusk (2) has carried out some investigations into the influence of work on the dog. The principal obstacle hitherto in the way of employing animals other than man for work investigations has been the want of a sufficiently adaptable technique. Zuntz's experiments on the horse were conducted by means of a tracheal cannula, a device that, though fairly adaptable for work experiments, is not always desirable. Lusk's experiments were carried out in his respiration calorimeter where the applicability was very limited. Boothby and Sandiford(3) and Kunde(4) have carried out metabolic investigations on dogs by means of the Benedict apparatus, but here again the device is only of limited value for work experiments, which none of these workers have apparently yet undertaken. It was believed therefore that, if the proposed experiments were a success, in addition to possessing a certain physiological value, they would open up a wide field of research of great practical significance.

It has been shown in earlier papers that the water present in soils is held in two ways: as capillary or interstitial water present as water wedges between the soil grains and as imbibitional or “gel” water which is associated in some way other than interstitially with the clay particles and with the colloidal coating of the soil grains. Imbibitional water is the cause of the swelling in water of soil and other colloidal (gel) systems such as cotton, wool, gelatin.

The nature of the imbibitional process is discussed and it is suggested that with clay, wool and soil imbibition may be due to the attainment of a Donnan equilibrium as is the case with gelatin. Experiments are quoted and discussed in support of this suggestion; and in particular it is pointed out that such swollen colloids appear to behave as perfectly elastic solids when under compression. This is not the case with sand and water nor with soil, wool or cotton in xylol, i.e. when no swelling occurs.

Imbibition may be a factor in the movement of soil water, in addition to capillarity, and it is shown that such a factor is quite consistent with the general mathematical treatment of the movement of soil water as developed by Gardner and others.

[It is realised that the point of view outlined above rests, as far as soil is concerned, on a very slender experimental basis, but it appears to be of sufficient interest to merit further investigation. The writer, however, has neither facilities nor opportunity for developing the matter further and this paper is published in its present form in the hope that it may prove of some interest to other workers more directly connected with soil research.]

(1) It is shown that the presence of chloric acid in the perchloric acid used for the estimation of potassium in soils, fertilisers, and plant material, by Davis's method (l) gives rise to very erratic and erroneous results. Every sample of perchloric acid should, therefore, be tested for freedom from chloric acid before being used for the estimation of potassium.

(2) Results are quoted which indicate that in the application of Neubauer's method of treatment of the soil extract to a soil deficient in carbonates, it is sufficient to add only 0·1 gm. of calcium carbonate to the extract instead of the 0·5 gm. generally used. A considerable economy of perchloric acid is thereby effected.

An electrical method is suggested for reducing the friction between a metal surface and soil, or other moist substances; and its possible application to soil cultivation is considered.

Large reductions in friction were obtained in laboratory tests with a metallic slider moving over moist soil.

Preliminary tests in the field demonstrated that the draught of a plough was reduced by applying a current between the coulter and the mouldboard. The magnitude of the reduction obtained with this arrangement was too small to have immediate practical value, but the possibility of increasing the effect is discussed.

(1) Further experiments are described, the results of which support the relationship between the presence of vitamin A in the diet of the cow and its presence in milk fat.

(2) The typical winter ration of concentrates, roots and hay may be adequate to maintain the vitamin A value of the milk fat for considerable periods provided that at least one of the components supplies adequate amounts of that dietary principle. Well cured green meadow hays are in this respect greatly superior to dry brown seeds hays.

(3) The addition of cod liver oil to a winter ration deficient in vitamin A will induce a sharp rise in the vitamin A value of the milk fat of cows. No such effect is seen when oils deficient in this dietary factor (coconut oil, arachis oil) are given.

(4) The administration of cod liver oil in doses from 1 to 8 ozs. daily to milking cows caused no “fishy” taint in the milk or butter-fat.

(5) The administration of cod liver oil caused no appreciable change in the yield of milk but the higher doses appeared to cause a noticeable drop in the percentage of fat. Further experiments are required to throw more light on this observation.

1. Of the three sources of supply of nitrogen, rape cake gave the highest mean yields in the absence of superphosphate; while nitrate of soda gave results significantly better than those obtained from ammonium salts.

2. Superphosphate is of importance to the barley crop, giving greatly increased yield when applied.

3. Sulphate of potash seems to have an adverse influence upon the barley yield.

4. The deterioration of the barley plots is much heavier than on the wheat plots. The convention of ascribing the whole linear term to deterioration may not be as true for some plots as for others. Part of the diminution in mean yield may be due to slow changes other than deterioration.

5. The mean annual percentage diminution is least on those plots in receipt of superphosphate and emphasises the importance of phosphoric acid not only in increasing the mean yield, but in maintaining the fertility of the soil.

6. Barley is more variable than wheat and is more subject to the influence of meteorological conditions.

7. The slow changes other than deterioration are relatively unimportant and seem closely connected with the manurial treatment. The cause of the slow changes is obscure, but there were probably special influences operating on certain of the plots.

In June, 1921, the writer undertook a series of soil analyses in connection with the field trials organised by Dr J. A. Hanley for the Department of Agriculture at the University of Leeds. The soils were of diverse kinds and included samples of most formations from the Carboniferous upwards, most of which were from poor unmanured grass land. They were of obviously low potash content.

It has been shown that maize silage of good quality can be produced with losses of dry matter which are not necessarily much greater than those which characterise the production of oat and tare silage.

Excessive drainage of juice consequent on immaturity of crop contributes materially to the total loss of dry matter.

The main reason for the comparative failure of attempts in this country to produce maize silage successfully from the points of view of quality and economy lies probably in the general use of the late maturing variety, American Horse Tooth. Success will probably depend on growing a variety of maize which is able to reach a desirable stage of maturity under English conditions before being cut for the silo. Preliminary trials have indicated that the necessary qualities may be found in certain varieties like Saltzer's North Dakota, Longfellow, Compton's Early and White Cap, all of which mature at least a month before American Horse Tooth.

A method for the determination of ammoniacal nitrogen in soils is described. It is an extension of the Hissink method for exchangeable bases to ammonium present in the soil. The working details are similar to the Hissink method, except that the leaching process is entirely carried out in the cold. The ammonia is distilled off with magnesium oxide.

Using normal sodium chloride as a leaching solution and collecting half a litre of leachings for distillation with magnesia, results were obtained which showed excellent agreement with those by the aeration method. Similar results were obtained using 250 c.c. of 15 per cent, sodium chloride solution, but the results are on an average about 1·6 per cent, lower. With high proportions of ammoniacal nitrogen a second half litre of normal sodium chloride leachings should be taken, or half a litre of 15 per cent, solution used.

The leaching method is economical of apparatus and water supply. It is therefore suitable for small laboratories with limited resources. It is fairly rapid: six estimations can be completed in a day.

The close agreement of the new method with the aeration method suggests that the amount of ammoniacal nitrogen in the soil at any given time is not an arbitrary quantity depending on conditions of estimation, but a definite amount. It is improbable that any ammonium compounds exist in the soil apart from those which take part in base exchange.

The measurement of the hydrogen-ion concentration of soils often presents great difficulties. When ordinary hydrogen electrodes are used, constant potentials are, in many cases, only obtained after hydrogen has been passed for several hours, while in many instances hydrogen electrodes cannot be used at all. The other important method of determining “pH,” the colorimetric method, can only be used in testing clear and almost colourless soil extracts, but not in testing soil mixtures.

Odén has shown that colour intensity comparisons between alkali extracts of peat soils of varying origin can be made since, despite the possible difference in the nature of their humic matter, the absorption spectra are almost identical within the visible range. These absorption spectra are also comparable with that of Merck's Acidum Huminicum, which is a standard preparation. Odén developed his colorimetric method as a means of measuring the degree of humification of the organic matter of peat soils, that is to say, the proportion of the total organic matter which could be classed as humic matter. In this way the disadvantages of Grandeau's method, in which there is no discrimination between the coloured and the colourless parts of the soil organic matter, are obviated.

Four years' additional experimental work on the application of a high tension discharge to the growth of field crops is described. Ten experiments with spring-sown oats and barley, two with winter-sown wheat, one with spring-sown wheat, and four with clover-hay have now been described.

The discharge was usually given at the rate of 0·5 to 1·0 milliamp. per acre from thin insulated wires stretched above the crop at a height of about 7 ft. and charged to a voltage of 40,000 to 80,000 (crest value). The discharge was usually given for 6 hours a day in two periods, 3 hours in the morning and 3 hours in the afternoon.

If the two experiments with spring-sown oats described in previous papers are included and the experiment of 1919 with spring-sown wheat (which yielded only 8 bushels to the acre) is excluded a series of 18 results is available spread over a period of 6 years. Of these 18 field experiments with various crops, 14 gave positive results in favour of the electrified plots, while 4 showed negative results, i.e. decreased yields compared with the controls. Of the 14 positive results only 3 show increases of less than 10 per cent, while 9 show increases of 30 per cent, and over, some reaching 50 per cent, and over. Of the 4 negative none shows a decrease of as much as 10 per cent.

Of the 12 experiments with spring-sown cereals 10 were positive and 2 negative. Of the positive results only 2 show increases of less than 10 per cent, while 6 show increases of 30 per cent, to 57 per cent.; on the other hand both the negative results are quite small, being 6 per cent. and 9 per cent. respectively.

The effect of electrification in increasing the yield of spring-grown oats and barley has thus been demonstrated. The mean increase in yield for such crops was 22 per cent.

A beneficial effect of the discharge on clover-hay is probable while the effect on winter-sown wheat is still uncertain.

Our knowledge of the proper conditions under which the discharge should be given is still so meagre that there is no reason to believe that the increased yields here described are the maximum obtainable as a result of electrification.

The mode of action of the current in producing increased growth and yield is still obscure. In several cases the electrified field crops showed a deeper green tint than that of the controls, and work already published has shown that in the case of the coleoptile (plumule sheath) of barley minute electric currents are able to bring about an increase in the rate of growth.

The effect of the discharge is of the nature of a stimulus. The additional energy available from the current is too small to have any direct effect since it is only about 1/1000th, or less, of the energy which the plant obtains from sunlight.

There is no evidence that gaseous products of the discharge play any part in the stimulation of growth. The additional supply of nitrogen brought to the soil from oxides of nitrogen produced as a result of electrification must be exceedingly small.

Various investigations on the decomposition of organic matter in the soil have brought out the fact that there exists a more or less constant ratio between the carbon and nitrogen content of the soil, whatever the ratio between these elements in the organic matter originally added to the soil. This ratio varies from 8: 1 to 12: 1, i.e. for every 8 to 12 parts of carbon, there exists in the soil one part of nitrogen; the average ratio is about 10 to 1. Brown and O'Neal (1923), for example, found that the ratio of the carbon to the nitrogen in a Carrington loam is 12: 1 to 13: 1, while, in the case of a Tama silt loam, the ratio may go down to 10: 1. According to Sievers (1923), the ratio of carbon to nitrogen in the soil is about 11·6: 1. Russell (1923) stated that, although there is about 40 times as much carbon as nitrogen in the original plant residues, the ratio will drop down to 10 to 1, before these residues have been very long in the soil. This ratio seemed to be in a stable position, for which no explanation could be suggested. Fraps (1922) found the ratio of carbon to nitrogen in the surface soil to be 9·2: 1 and in the subsoil 8·3: 1; he suggested, therefore, to judge the percentage of organic carbon in the soil from the percentage of nitrogen present.

Pot-culture experiments carried out during a period of four years with Wheat, Barley and Maize show that these plants exhibit increase of dry weight when subjected to minute electric currents (of an intensity as low as 0·1 × 10–10 amp. per plant) from wire networks charged to a high voltage suspended above them. Of 28 sets in which the cultural conditions were satisfactory 23 showed an increased yield.

A percentage increase in dry weight of 27 ± 5·8 was shown by Maize plants grown under glass and little more than a month old. With Barley the largest percentage increase was 18 ± 2·4.

Direct currents were mostly studied, but increased growth was obtained with both direct and alternating current, the alternating current being apparently as effective or even more effective than the direct; the plants themselves, however, are able to bring about a slight rectification of the current.

Electrification of Barley for the first month of the growing season appears to be as effective as electrification during the whole growing season.

The discharging networks were usually charged positively, but a similar stimulating effect on dry weight production was obtained with a negative charge on the network.

Currents of the order of 1 × 10–8 amp. per plant and higher are injurious, causing a reduction of dry weight.

In one experiment plants screened from the normal atmospheric current by a series of parallel “earthed” wires (0·35 mm. diameter) showed, by comparison with the controls, a percentage decrease of 4·7 ± 2·3, which is hardly significant. It indicates however that though a favourable effect may be exerted by the normal atmospheric (air-earth) current, yet the effect can be but slight.

In one experiment with Barley indications of a differential effect of the discharge were obtained, for the increase in grain yield brought about by the discharge was greater than the increase in total dry weight.

The effect is to be.classed as of the nature of a stimulation since the energy-value of the additional plant material produced is out of all proportion to the energy supplied by the electric discharge.

These experiments with pot-cultures fall into line with those from the field (1) and from the laboratory(2); they leave no uncertainty as to the favourable action of the electric discharge.

The connection which has been shown to exist between the strength of wheat flour and the chemical individuality of the glutenine fraction of the wheat protein (Woodman, 1922) (1) led the writers to institute an enquiry into the manner in which the individual wheat proteins are developed and stored during the progress of the grain from the early stages after flowering to ripeness. The immediate object of the investigation was to secure information in regard to the stages at which the different proteins made their appearance in the grain and to determine at what point the character of the grain contents was such as to enable a tenacious gluten to be obtained by grinding up the kernels with successive quantities of dilute NaCl solution. It was also intended to follow the rate of alteration of the amounts of the several proteins during the growth of the grain and to attempt to elucidate as far as possible the relationships which exist between the simple and complex forms of nitrogen at the various stages.

Wheat owes its enormous importance to certain physical properties which are absent in the flours of other cereals, chief among which is the capacity of making a coherent dough on the addition of water.

Different wheats make loaves of different size and texture, a strong wheat being denned by Humphries and Biffen(1) as one which yields flour capable of making large well-piled loaves. From this definition it is seen that the conditions required of a strong flour are two, the first being that there must be a sufficiency of sugar or other materials available for fermentation and consequent production of gas in the dough, the second, that there must be some substance present in the flour which is capable of retaining a sufficiency of the gas so generated. The constituent of wheat flour in virtue of which its dough possesses this quantity of gas retaining power is the gluten. Many workers have attempted to explain strength in terms of the relative amounts of gliadin and glutenin in the gluten, or on the percentage of gliadin in the flour.