The general principles regulating soil temperature are well known.

Measurements in deep mines and wells indicate the existence of a temperature gradient in the earth's crust from the interior outwards, which causes a flow of heat to the surface at a sensibly constant rate. Extensive measurements were carried out by Forbes1 and by William Thomson (afterwards Lord Kelvin) who worked up the former's experimental values, and later by a Committee of the British Association, which concluded that an average of “41·4 gramme-degrees of heat escape annually through a sq. cm. of a horizontal section of the earth's substance.” For our present purpose this source of heat is negligible.

In Part I is given a survey of the results of a statistical examination of the yield of the plots of Broadbalk “Wheat field during 67 years. The main features of the comparison of mean yields are well known; the comparative rates of decrement, shown in Section 5, supply a class of facts well worthy of further study. Particularly striking are the relatively slow rates of decrement of plots 2b and 8, compared with plot 7, which would seem to show a permanent advantage in very high nitrogenous dressings, and to emphasise the need for caution in the application of the principle of diminishing returns. The evidence of the influence of potassium sulphate and its substitutes, sodium sulphate and magnesium sulphate, shown in Table V, is also very striking. An unsuspected feature of the changes of mean yields, which precludes the possibility of obtaining from these data true curves of exhaustion has appeared in the slow changes which have taken place in all the plots in a similar manner. In Part II the mathematical methods by which the variation has been analysed has been discussed, partly as a justification of novel procedure, partly, to make clear that the three types of variations found have been genuinely distinguished. In Part III such evidence as is available has been presented, in order to throw light upon the possibility that the changes in mean yield have been caused by variations in the prevalence of weeds at different periods.

One point of importance which should be emphasised is that average wheat yields, even over long periods, from different fields or for different seasons cannot approach in accuracy the comparison of plots of the same field in the same seasons. The advantage of the method adopted by Lawes in the permanent experiments which he instituted is very evident. The effects of weather clearly require that the seasons should be identical, unless the series be very long, but the slow changes in mean yield show that even comparatively long series of different years from the same field cannot be accurately compared. Within the same field, however, the slow changes have almost proportional effects, and comparison between the mean yields of neighbouring plots may be made with great accuracy. The only case in which changes in mean yield sensibly affect the comparison of averages is that of plots 17 and 18. In comparing these with plots 3 and 4, 5, 7, and 10, it would be more accurate to confine attention to high yielding periods, at which the disturbing causes are at their minimum.

It is believed that the deviations from the smooth curves, which have been freed, for the most part, from the effects of exhaustion and weeds, form statistically homogeneous material for the study of meteorological effects.

1. A sample of marine silt taken from the foreshore of the N.W. coastal belt of the Wash was found as the result of a mineralogical examination to contain dolomite in its mineral assemblage.

2. It was surmised from this discovery that should dolomite be a normal constituent of soils derived from marine silts, its presence might modify in them certain processes such as nitrification in which the neutralising effect of a quick acting base is an essential factor.

3. This supposition was strengthened by certain culture experiments on nitrification, and was to some extent established as a fact by a detailed chemical investigation into the nature of the carbonate content of several soils of known geological and agricultural history.

In a previous paper (1) some of the factors which control fertility in domestic animals were discussed. These for purposes of clearness in investigation were divided into two groups: (1) The factors which control the number of eggs shed; and (2) The factors which control the number of eggs which develop to reach birth size. By this means the way in which the various factors which affect fertility could be determined, for example, it was shown that the effect of age on fertility, the literature of which has been reviewed by Harris (2), is due to the number of eggs shed at each oestrus period. Young sows examined had on the average 14 corpora lutea in the ovaries while old sows had 20 corpora lutea.

1. Two colorimetric methods of estimation of phenol and the cresols in soil have been developed,—one for small quantities down to 0·01 mgm. in 50 c.c. of the soil distillate, and the other for larger amounts of the substances.

2. It is found that, even by starting the distillation of the soil within 20 minutes of the application of phenol, a 100 per cent. recovery of the added phenol cannot be effected, except in the case of autoclaved or steamed soil. This instantaneous disappearance is followed by a further loss, slower and different in character.

Phenol and the three cresols disappear, with more or less ease, in all soils examined.

3. The slow disappearance is apparently largely brought about by micro-organisms which are capable of decomposing phenol. There appears, however, to be some non-biological action also, since the disappearance in unmanured soil poor in micro-organisms, besides being much slower than in manured soil, is altogether different in character.

4. Autoclaving the soil at 130° C. for 20 minutes destroys the cause or causes of disappearance altogether, but the action proceeds, although much more slowly than in untreated soil, in the presence of a considerable amount of toluene and mercuric chloride. Further support is thus given to the view that a non-biological action accompanies the biological decomposition.

5. Partial sterilisation by treatment with toluene which was evaporated before the addition of phenol increases the rate of loss, but steaming does not.

6. The disappearance takes place even in soil air-dried to 2·4 per cent. moisture, but it is extremely slow compared with the rate in normal soil.

7. By applying a number of successive doses of phenol to the same soil it has been found that each dose disappears at a higher rate than the preceding one. This is entirely in accordance with an action mainly biological in character. The same effect has been observed in the case of m-cresol.

8. Two types of bacteria have been isolated from soil which are able to decompose phenol in culture solutions containing mineral salts and phenol. A third type capable of decomposing m-cresol has also been isolated from soil. A detailed study of the isolated organisms is being made in the bacteriological laboratory.

9. The instantaneous disappearance of phenol occurred in all soils examined. Its cause appears to be non-biological, but its exact nature has not yet been elucidated. There is reason to believe that the loss varies with the clay content of the soil. The loss does not appear to be materially affected by the period of contact of phenol with the soil prior to distillation, and is presumably complete only when the soil (air-dry) has been uniformly moistened with steam. Up to a certain point the loss is proportional to the concentration of the phenol solution.

10. The factor causing the loss is destroyed by autoclaving the soil at 130° C. for half an hour or by steaming it at 100° C. for one hour.

The treatment of the soil with sulphuric acid (50 per cent. by volume) either before or after addition of phenol greatly augments the loss, which may amount to 90 per cent, in case of phenol and 96 per cent. in case of m-cresol. This loss is not affected by autoclaving the soil.

11. Thus there appear to be at least three processes whereby phenol disappears from soil: one biological, one instantaneous chemical or physical and a third slow, chemical or physical. The mechanism of these changes, however, has not been elucidated.

This work was carried out during my tenure of the Earl Grey Memorial Fellowship awarded me by the Council of Armstrong College to whom and also to the Lawes Agricultural Trust I wish to express my thanks for facilities for carrying out this work.

My best thanks are due to Dr E. J. Russell at whose suggestion the investigation was undertaken and under whose direction the work has been carried out: and to Mr. H. G. Thornton for assistance on the bacteriological side.

Records of the live and carcase weights of sheep exhibited at the Smithfield Show from 1893 to 1913 have been treated statistically. The results show the average weights, rates of growth, and proportions of the carcase in the different breeds of sheep at 9 months and at 21 months of age (see Tables II and V).

On the average of all breeds the rate of growth declines from 4·7 lbs. per week from birth to 9 months of age to 1·7 lbs. per week from 9 to 21 months of age.

The carcase percentage increases with age on the average from 61 per cent, at 9 months to 65 per cent, at 21 months and with it the percentage of fat from 5·7 per cent, at 9 months to 64 per cent, at 21 months. On the other hand the proportions of pluck, skin and alimentary canal (“Unaccounted for”) decrease with age.

Ratios of early maturity are given for the various breeds and the factors which affect it are discussed.

The average weights, rates of growth and proportions of the carcase are given for the different crosses of sheep (see Tables IX and XIII).

From a comparison of crossbreds with pure breeds it would appear that crossing leads to increase in live weight and probably more early maturity. There is an indication that the proportions of carcase, fat and pluck are less but the proportions of skin and alimentary canal are greater in crossbreds than in the pure breeds of sheep.

There is greater variation in live weight in the Cheviot and Blackface breeds than in the Leicester, Southdown, Hampshire and Suffolk breeds; in the latter breeds variability decreases but in the former breeds it increases with age.

Variability in live weight at 9 months old has steadily increased from 1893 to 1913 but at 21 months old there has been little change.

Some parts are more variable in their proportion to live weight than are others. Fat and alimentary canal are most variable, skin and pluck slightly less variable, while the proportion of carcase is less variable even than live weight.

The variability of the proportions of carcase, pluck and alimentary canal increase while the variability of the proportions of fat and skin decrease with age.

Within a breed and among animals of the same age the heaviest sheep generally have the highest carcase and fat percentage and the lowest percentage of pluck, skin and alimentary canal.

A high proportion of carcase is correlated with a high proportion of fat and a low proportion of skin and alimentary canal at 9 months old. At 21 months old the same holds true with the exception that the sheep with the highest carcase percentage have not the most fat.

The proportion of pluck does not appear to be correlated with any other part of the body except inversely with the live weight.

During the period 1893–1913, although individual breeds show differences, the majority have increased in live weight at 9 months old but at 21 months old have remained practically constant in weight.

The sheep exhibited in 1840 were very much fatter than those shown in the Carcase Classes of to-day and are probably comparable with those of the present-day Live Classes. Since 1840 Leicesters have shown a great increase and Southdowns a small increase in weight.

The carcase percentage of sheep both at 9 and 21 months of age has steadily decreased during the period 1893–1913; this has been attended by an increase in the proportion of pluck, skin and alimentary canal.

There is an indication that the influences which affect sheep in their first year of life (store period) affect their ultimate size.

The seasonal variation in the weight attained by sheep is dependent on the rainfall; a high rainfall through increased root and fodder crops causing increased live weight.

Soil fertility is often spoken of as though it were an absolute property of the soil; in reality it is a particular relationship subsisting between soil conditions on the one hand and crop growth on the other. The conditions conducive to soil fertility are the resultant of two main groups of factors, the intrinsic properties of the soil which are dependent on its chemical, physical and biological nature, and those extrinsic properties impressed on the soil by topographical and climatic factors*. These two groups cannot be sharply distinguished from each other, nor can any hard and fast line be drawn between the various factors comprised in them, because few are at present susceptible of exact measurement. In other words, that particular group of conditions that make up the fertility of a soil is an equilibrium brought about by the interaction of numerous factors some of which however can be varied by the agriculturist by manurial and cultivation operations.

In an attempt to estimate starch in the grain of wheat grown under varying manurial conditions the writer has obtained results which it seems desirable to put on record for the information of others who may be using or propose fco use the Taka-diastase method.

Before devoting attention to wheat, experiments were made with pure potato starch under the conditions advocated by Davis and Daish. At first, owing to the use of insufficient enzyme, the results were low but immediately 0·1 gm. was taken the results were satisfactory (Table I).

The methods used for the determination of — log [] fall naturally into two groups:

(a) Electrometric, and

(b) Colorimetrie methods.

Electrometric methods were first introduced into analytical practice in 1897 by Böttger(l) who determined the neutral point in titrating acids with alkalis by using a gas chain; subsequent improvements were made by Hildebrand (16), Gumming and Gilchrist(10); Hasselbalch(15), W. M. Clark(6), Michaelis(19), Walpole(28, 29) and others. The method has been applied to the measurement of [] of biological fluids with considerable success*. It was first applied to the measurement of [] of soil suspensions by G. Fischer (12) in Germany in 1914 and subsequently in America by Sharp and Hoagland(23), and by Gillespie(13, 14) and his co-workers.

Some interesting contributions to this subject have appeared during the past three years. They contain somewhat discordant ideas and it has therefore been concluded that the present time is suitable for a brief review of the whole matter and for the publication of further experimental results. A striking susceptibility to environmental change is evinced by both the awn and the lateral floret, and it is part of the purpose of this paper to describe the nature of the fluctuations involved and to indicate the extent to which they militate against the reliable determination of genetic ratios.

The rate of growth of the animal is a matter of considerable importance in the economics of meat production, but the subject does not appear to have been studied with the close scientific attention it deserves. The literature was reviewed in a recent paper by Hammond and need not be further referred to as it is scanty and uninteresting.

In recent years the measurement of the heat output of animals has taken a prominent place in investigations on the physiology of nutrition, and especially so as regards farm animals. As it is now accepted that the conservation of energy applies to the chemical changes in the living body, the total metabolism can be measured equally well by the indirect or by the direct method. The indirect method using the Douglas bag has been shown by Benedict and others to be simple and satisfactory in the case of human beings, but it is not so easily applied to farm animals, and for these the direct method by the use of a calorimeter has advantages.

Further experiments have been done on the evaporation of water from soil, using the same apparatus and technique as described in an earlier paper. The present series of experiments was designed to investigate the effect of clay content and manurial treatment on the evaporation. Two soils have been used, one containing only 6% clay and the other 15%, and from each soil samples were taken from plots which had received (a) no manure, (b) artificial manure, (c) farmyard manure. The rate at which the soils lost water over concentrated sulphuric acid and at a constant temperature, was found to depend firstly on the amount of clay present, and secondly on the amount of organic material in the soil. The differences due to content of organic material were more obvious in the soil containing the larger amount of clay; the farmyard manure plot lost water at the slowest rate, and the unmanured plot occupied an intermediate position. In the sandy soil the differences in evaporation due to manuring were small.

There is evidence that the moisture equivalent of these soils measures the percentage of water at which the evaporation is first directly affected by the soil particles, and that at percentages of water in excess of the moisture equivalent evaporation is taking place substantially from a free water surface.

The early authorities, Mulder, de Saussure, Berzelius and others, considered the whole of the precipitate obtained by adding acid to an alkaline extract of soil to be humic acid,—a single substance to which they assigned a definite formula. Hoppe-Seyler and others found, however, that the precipitate was not homogeneous; a portion dissolved in alcohol, which he named hymatomelanic acid. It was from this that Schreiner and Shorey isolated a number of organic acids, all of which were either colourless or only faintly coloured.

The probable error on one pig calculated on the average daily live weight increase was found to be for cross-bred pigs about 7 per cent.; for pure-bred pigs from the same litter and each of similar live weight about 3 per cent.; for cross-bred pigs each of similar live weight but from different parents about 4 per cent.

The error is greatest in experiments of short duration and it decreases as the period of the experiment is lengthened. The decrease is slight if the experiment is prolonged beyond seven weeks.

The errors on 18 separate pens containing four pigs to each pen (the total initial live weight of each pen being similar) varied from 2·3 per cent, to 12·08 per cent., the average being 6·21 per cent.

The percentage probable error is relatively low when the pigs are fattening rapidly and high when the pigs are fattening slowly. The average daily increase of the quicker fattening female pigs when un-speyed appears to be depressed as a result of periodic sexual disturbances.

The stage of fattening does not appear to influence the probable error. Animals in the later stages of fattening show a greater range in their rate of fattening than animals in the early stages, see Fig. 2, p. 284.

Weekly weighing of individual pigs is recommended as it gives an indication of the health of each pig. It also enables each experimenter to discriminate between differences in the rate of fattening due to individuality and differences due to ill health, etc.

The rate of fattening of pigs is very variable, periods of rapid fattening are followed by periods of depression.

The discovery that partial sterilisation by heat is capable of greatly increasing the fertility of the soil, opens up possibilities full of interest both to agriculturist and to horticulturist. Steaming the soil has already become a common practice by growers of tomatoes under glass, where the soil in the houses when “sick,” that is, infertile no matter how heavily manured, is treated with steam, whereby its fertility is completely restored.

In the year 1904, a grass field at Saxmundham Experiment Station was taken in hand by East Suffolk County Council. At that time the herbage in the field was very poor and consisted chiefly of weeds—largely Wild Carrot.

The soil is a typical chalky boulder clay of a poor type very stiff to work, but capable of producing good crops of wheat and beans when well drained.

It was early noticed that soil on treatment with a solution of an alkali yielded a dark coloured solution which gave a black flocculent precipitate on acidification. Decomposing vegetable matter behaved in a similar way.

A simple experimental method has been described for measuring certain physical constants of soil, using small brass boxes into which soil passing a sieve of 100 meshes to the inch has been packed by hand. The quantities determined are:

(1) The weight of unit volume (100 c.c.s.) of air-dry soil, or the apparent specific gravity.

(2) Amount of water taken up by unit weight of soil.

(3) Pore space.

(4) Specific gravity of the soil.

(5) The volume expansion of unit volume (100 c.c.) of soil when saturated.

The results for one soil only are given, and discussed, to illustrate the method. With the co-operation of the Science Masters Association it is being applied to a number of soils by various schools.

The particular soil used was obtained in six depths as follows: 0–6–12″, 12–18″, 18–24″, 2–3′, 3–4′, and the above constants were determined on each depth. It was shown that (1) and (4) varied inversely with the percentage of clay in the soil, while (2), (3), and (5) varied directly with the clay percentage. The effect on the constants of the larger quantities of organic, matter present in the top two layers of soil was, weight for weight, approximately equal to that of the clay, except in the volume expansion results where the effect if any was within experimental error.

It is possible that the fraction fine silt II, whose upper limit of diameter is ·005 mm., has similar effects to the clay fraction.