In England, the corn-growing situation, after a span of precarious years, has now become critical. Even if prices rise substantially and fairly soon, what may be described as essentially the “English cereal yield problem” will remain.

The question attacked is whether soil variations are sufficiently constant from year to year to give useful corrections to the yields of experimental plots from their yields under previous uniformity trials, and the data investigated were the published results of uniformity trials carried out on two fields at Aarslev (Denmark) between 1906 and 1911. In one case the plots did tend to keep constant in their relative yields, and the precision of an experiment would be increased by nearly 150 per cent. if the regression on the mean yield in the three previous years were used: with the other field, however, the plots showed no constancy in yield (when the variation due to strips was taken out as in modern experimental methods), and consequently previous uniformity trials could give no assistance.

The work described here was done whilst I was enjoying the hospitality of the Rothamsted Laboratory: it gives me much pleasure to acknowledge my great indebtedness to Dr R. A. Fisher, F.R.S., who suggested the problem, and guided my unsteady steps throughout.

The decomposition of urea has been investigated in 59 soil samples of extremely varied character. Urea was decomposed readily in all and very rapidly in most of the samples.

In mountain and heath soils the decomposition was generally active, especially in soil tests. Strongly acid peat samples (pH. 3·1 to 3·3) decomposed from 0·44 to 0·86 per cent, of their own dry weights of urea in 24 hours at 22° to 23° C.

In solution and soil tests samples from permanent pastures produced a more rapid decomposition than those from cultivated land. In soil tests with pasture samples quantities of urea as large as 1 per cent, of the dry weight of soil were converted to ammonia in 24 hours at 22° to 23° C. Fertile arable soils produced a relatively slow decomposition in soil tests.

Keratin, prepared from horn meal, was added to moist field and garden soil and allowed to decompose in the laboratory. The keratin was found to undergo a decomposition resulting in a slow, but steady accumulation of ammonia and nitrate. 35–40 per cent, of its nitrogen was transformed into nitrate after 120 days. The addition of keratin produced little or no increase in the number of bacterial colonies on agar platings, but markedly increased the number of actinomycete colonies, especially in garden soil. Two strains of actinomycetes were isolated and found capable of thriving on keratin in pure culture, decomposing the keratin with the formation of ammonia. One of the strains could be recognised as Actinomyces citreus Krainsky, as described by Waksman. The other strain could not be named, but corresponded closely to the description of Waksman's Actinomyces 145.

(1) Thiosulphuric acid has been shown to exist in a free state.

(2) It is relatively stable in dilute solution; an M/200 solution is only half decomposed at the end of 1 day and an M/400 solution at the end of 10 days only.

(3) This degree of stability is sufficient to account for the fungicidal action of acidified thiosulphate solutions in terms of the liberated thiosulphuric acid.

(4) It can be calculated that it is only necessary to assume 6 per cent. of the minimum quantity of sulphur found effective against Wart Disease in the field to be in the form of thiosulphuric acid over a period of 10 days in order to account for its toxicity.

In cases of field experiments when one plot is missing, a method has been developed for furnishing an estimate of the yield of the missing plot, based on all the other values. The calculation is given for (a) a Randomised Block experiment, and (b) a Latin Square arrangement. In both cases the actual arithmetic is very simple.

The steps in the procedure are:

(1) Determine the desired value by an application of the equation (A) or (B) according as the experiment was arranged in Randomised Blocks or in a Latin Square.

(2) Proceed as usual with the analysis of variance, using the estimated figure for the missing yield, and remembering to deduct one from the number of degrees of freedom ascribable to error.

The growth of barley and the phosphate concentration of the soil solution, of the soil cropped and uncropped, were examined simultaneously in pot cultures, after treatment of an acid soil deficient in phosphate, with lime with and without slag or superphosphate.

Liming at the rate of half the lime requirement increased the concentration from about 0·7 p.p.m. P2O5 to about 1 p.p.m. and at the rate of twice the lime requirement to over 2 p.p.m. P205. Phosphates depressed the concentration on the lightly limed soils, and on the heavily limed had variable effects. The superphosphate-treated soils showed rather lower concentrations than the slag-treated. Cropping raised the concentration on the lightly limed treatments, but on the heavily limed reduced it on the control and had a variable effect on the phosphate treatments.

1. Herbage from pastures managed under the Intensive System of Grassland Management, and representing three to five weeks’ growth, from three centres in three seasons, was closely comparable with that obtained by other workers from “pasture cuts” at one- to three-weekly intervals from unmanured pastures, in respect of the chemical composition of its dry matter, which is, in fact, a concentrated feeding stuff of narrow nutritive ratio and low in fibre content.

2. The nutritive ratio is somewhat wider in a dry than in a wet season, but the average fibre content is not markedly different.

3. During the grazing season, drought or the early summer flush period produce some reduction in protein content and an increase in fibre content, with a recovery following the cessation of the drought or after the flush period respectively.

A modified technique for the Keen-Raczkowski box experiment is described; it is believed that this new method is as accurate as, and is more convenient than, the one employed earlier.

The results obtained for pore space by the new method are very nearly the same as those obtained by the old method. The old and new results obtained for water retention and swelling are not the same, but are related to one another by simple linear expressions, and correlations with other soil properties deduced from the old data are applicable also to the new.

A recapitulation of the main features of the moisture distribution in an ideal soil is given in order to emphasise a point previously neglected, namely, that the changes are not in the main strictly reversible, but fall into two series corresponding to the two directions of moisture change. The cellular nature of the soil pore space imposes a quantum character on the moisture changes over a great part of the higher moisture range. The individual cell does not fill or empty by smooth reversible changes but shows two unstable stages at which filling or emptying is completed at a bound. For falling moisture the suction level is that at which a meniscus can invade a cell through one of its narrow entries, which gives a value in the neighbourhood of 12 T/r for close packing. For rising moisture the suction level is that for which water returns to the cell by the collapse of a bubble in it, giving a lower value in the neighbourhood of 6·9 T/r. A still lower value of 4·5 T/r can be reached for a particular type of distribution confined to the lower moisture range.

All the above suction values are closely verified by measurements made with bronze balls and paraffin oil. A detailed exploration of the case for glistening dew and water has been made, which verifies the theory while illustrating more nearly the behaviour of an irregular soil. The two values which rule the two halves of the “hysteresis loop” for this case of natural or common packing are 6·0 T/r for falling moisture and 4·0 T/r for rising.

The new considerations resolve the differences of opinion raised by R. A. Fisher. It appears that the author has throughout supported a case which belongs correctly to the falling moisture series. Fisher considered a very limited series for the rising moisture case and a hypothetical reversible series, and has been in error in so far as his treatment was regarded as exclusive.

One of the previous papers by Coutts(1) in this series has directed attention to the value of the data obtained from what is now generally referred to as the perforated box experiment devised by the present writer and Raczkowski(3). In a further paper Coutts(2) has described an improved and simplified technique, which gives results that are either identical with the old method (pore space) or else related to them by simple linear expressions (water retention; volume expansion or “swelling”). As Coutts’ procedure is now being followed at Rothamsted, and is likely to be taken up by other workers, it appears desirable to record some hitherto unpublished data bearing on the technique of the method, obtained at Rothamsted some years ago by Prof. Ohga (S.M. Educational Institute, Mukden, Manchuria) and dealing with the effect on the results of the degree of packing to which the soil is subjected. The original method, followed by Coutts in its essential details, is to add the soil in small quantities, tapping the box on the bench after each addition, until the box is nearly full, at which stage the filling is completed in the manner described in the original communication.

(1) The skeletons of young pigs on a ration composed mainly of cereal grains but with the addition of cod-liver oil show a very distinct lack of calcification, the percentage of ash being about 12 per cent. lower than in the bones of normal animals.

(2) Calcification of the bones proceeds up to maturity. A difference of about 360 gm. tricalcic phosphate was found between the same mature bones of normal and calcium-deficient animals.

(3) The ratio of lime to phosphate is almost the same in the different bones of the same individual as well as in the normal and rachitic bones of swine. The main characteristic of the bones in low-calcium rickets is a low-ash content, but the composition of the ash is normal.

A Notable contribution to our knowledge of the factors which influence the nutritive value of grass has been made by Dr J. B. Orr in a recent publication dealing with minerals in pastures and their relation to animal nutrition (l). The treatise was primarily the outcome of the deliberations of a sub-committee appointed in 1926 by the Civil Research Committee of the Cabinet to consider and report on the relationship between the mineral content of pastures and their nutritive value. From the initial enquiries instituted by this sub-committee, it was evident that malnutrition in cattle and sheep arising from deficiency of minerals in grass was widespread in the pastoral areas of the Empire, and that the subject, which was of great economic significance, warranted close and systematic investigation. A report to this effect was duly forwarded to the Civil Research Committee, on whose further recommendation grants were made by the Empire Marketing Board in aid of a comprehensive scheme of investigations into the mineral aspects of pastures within the Empire. A two-fold scheme of work was adopted, actual investigations in selected grassland areas being supplemented by a detailed search of the literature dealing with every phase of the subject.

1. The changes in composition of the clay fraction in different horizons of some typical North Welsh profiles have been studied.

2. The changes in the molecular ratio of silica to sesquioxides (SiO2/Al2O3 + Fe2O3) throughout a soil profile afford an indication of the nature of the eluviation which has affected the mineral portion of the soil.

3. The data for North Welsh soils indicate a general tendency to enrichment of the lower layers in sesquioxides, particularly ferric oxide, at the expense of the surface layers.

4. The silica-sesquioxide ratio of the clay fraction is an important aid to series definition.

5. The soils of North Wales, particularly in the uplands, have probably been subjected to considerable erosion in the past. The profiles are therefore considered to be more or less truncated.

The conclusions of an earlier study of the yield of dressed grain from Hoos Field over the period 1852–1921 are recalled, and the method of conducting an examination of the influence of rainfall on the yield is described. The method yields a series of curves showing at any given period of the year the benefit or loss to the final yield in bushels per acre due to an additional inch of rain over the average at that period. Thirteen plots are considered, and the curves are found to fall roughly into groups corresponding to the system of manuring adopted. The main effects noted are these: (1) Excess of rain is beneficial to the barley crop for a short period in summer, and, in the case of certain plots, over the autumn and winter period. This is in contrast to the corresponding result for wheat on Broadbalk, where excess of rain was found to be beneficial only on a few plots and over a very limited period. (2) Rainfall over the six months when the barley is not in the ground is just as important as rainfall in spring and summer, and the time at which the rain falls in winter is important. Excess of rain in autumn benefits plots 1–A, 3–A and 7–2, and in winter continues to benefit 1–A and 3–A. (3) The curves for 2–O and 2–A are essentially different in character from those of the other plots, and point to the important effect of excess of winter rain in reducing the yield of the plots having phosphate but no alkali salts (i.e. no potash, soda, magnesia). (4) Excess of rain at time of sowing is harmful in all cases. (5) The curves of the “O” series (without nitrogen) are much flatter than those of the “A” series, which have a nitrogenous dressing in addition. (6) The indication of summer benefit is not inconsistent with the conclusions of Hooker that a cool summer is desirable for barley. (7) The farmyard manure plot 7–2 bears certain resemblances to the curve for the corresponding plot 2 b on Broadbalk.

From a study of the data of two season's work the following observations may be made:

Frequency of grazing with a view to the successful operation of the scheme will depend on a number of factors, chief among which is the character of the herbage and its growth. Recovery and vigour of growth are primarily dependent on rainfall and secondarily on the fertility of the soil, which may be increased by fertiliser applications. Rainfall, its amount and distribution, has in this investigation shown itself the most potent of all influences in the recovery of the plots. The results in general of 1928 indicate that the application of fertilisers, in which nitrogen predominates, greatly assisted in the maintenance of vigorous growth.

The protein content of the herbage increases with the shortening of the period between cuttings, due in the first season solely to the fact that the protein content of the grass falls off with age, but in the second and subsequent seasons, in a very large measure, to the incursion of white Dutch clover.

A consideration of protein yields per acre in relation to frequency of cutting reveals that in the first season, when the herbage is essentially grass, the shortening of the period between cuttings tends to reduce the protein yield; in the second season, when clover replaces grass, roughly in proportion to the shortening of the growing period, the higher protein content of the legume tends to counteract the depressing effect on yield of frequent cutting.

The table of results given in the last section shows that for all experiments for which the Resistance Formula has been fitted the values of the constants are consistent, bearing in mind the standard errors to which these values are subject. The constants for nitrogen may be held to have been determined with some approach to precision, but those for potash are not so well determined. We find at Rothamsted, for example, that the crop responds to a moderate dressing of potash, but higher dressings do not usually improve the yields any further. This fact limits the precision of the formula. The reader is asked to refer at this point to the full descriptions as to the meaning to be attached to the constants of the formula given by Bh. Balmukand in the earlier paper(1). The constants an and ak, called the importance factors, are interpreted as determining the capacity of the crop to recover the particular nutrient out of the soil. The chemical analysis of the tubers grown under nitrogen and potash starvation conditions should, therefore, furnish us with values which should be of the same order of magnitude as obtained by the formula. The minimum nitrogen percentage figure is 0·204, which when reduced to our units is equivalent to 4·57 lb. of nitrogen per ton of potato. The values obtained from the Resistance Formula are as close as the standard errors allow us to expect, and are also of the same order of magnitude as the chemical composition of the tubers demands.

1. A study has been made of the formation of lateritic soils in Sierra Leone and the composition is given of some of the intermediate and final products formed.

2. The detrital soils in Sierra Leone appear on the whole to contain a higher proportion of alumina to silica than the residual soils.

3. The soils described are all reddish or yellowish red soils, light in texture and generally containing a high proportion of stones. They are acid in reaction and have a definite lime requirement. The mineral constituents are low, especially the potash and the exchangeable calcium. i. Soluble phosphorus is readily removed from a solution by these soils.