Measurements have been made of the electrical conductivity of aqueous suspensions of stored soil samples taken at intervals of several years from four of the Rothamsted classical plots bearing the same crop every year. The results show that under continuous cropping:

1. The initial conductivity (and therefore the soluble salt content) of an unmanured soil decreases steadily to a minimum value, which then remains fairly constant over a long period of years. There is reason to believe that, under the same conditions, the normal initial conductivity of a continuously manured plot (excluding the temporary increased measurements due to application of manure) decreases similarly to a fairly constant minimum value, which is slightly greater than that of an adjacent unmanured soil depending on the kind and probably on the quantity of manure applied.

2. The 7 days’ increase of both unmanured and manured soil decreases progressively. In the case of an unmanured soil for which earlier samples were available, the 7 days’ increase is found to decrease comparatively rapidly during the first few years of continuous cropping.

In the course of the last 20 or 25 years it has been established clearly that agricultural experiments carried out under field conditions are subject to an appreciable error, due chiefly to soil heterogeneity. In order to avoid the effect of this disturbing factor, which greatly affects the reliability of data given by field trials, two questions had to be carefully considered: (1) how to secure greater uniformity in soil conditions; and (2) what is the best method of getting a criterion of the accuracy of the experiment and an adequate interpretation of the results obtained?

Decomposition experiments were carried out in the laboratory with different kinds of farmyard manure in various soils (sand and clay, acid and neutral). In neutral or slightly acid soil there was a very strong multiplication of bacteria and, to a smaller extent, of actinomycetes immediately after the addition of manure. This increase, which was especially marked when fresh straw was present in the manure, was sooner or later followed by a rather sudden decrease, which caused the numbers of bacteria gradually to approach those in the control soils. The actinomycetes were generally more abundant in the later stages of the process. This suggests that they may be especially active in the decomposition of the more resistant residues. The “numbers” of fungi were not affected by the addition of manure alone (except to a slight degree in strongly acid soil, where the bacteria seemed inactive), but the presence of fresh straw caused them to become active, especially in strongly acid soil, where their “numbers” remained at a very high level for a long time, this abundance of fungi consisting of both mycelium and spores.

1. Addition of farmyard manure to soil gives rise, in laboratory experiments, to an abundant development of cellulose-decomposing bacteria of the genus Vibrio in approximately neutral soils (pH 6.5–7.0). In faintly acid soils (pH 5.7–6.2) these organisms develop less abundantly, and are partly replaced by Spirochaeta cytophaga. At lower pH values only the fungi are active in the decomposition of cellulose. Similar results were obtained by adding filter-paper or straw to soils of different reactions. Of the fungi, Trichoderma and Penicillium appear more active in acid soil, whereas other forms, among others Mycogone nigra, Stachybotrys sp., Coccospora agricola (?), and Botryosporium sp. seemed prominent in neutral soil.

2. The vibrios, of which four strains were studied in pure culture, are very sensitive to acidity. They fail to develop in the pH interval 6.0–6.4, and have an optimum at p 7.1–7.6. Spirochaeta cytophaga appears to be slightly more resistant to acidity, being able to grow at pH 5.6–6.0.

3. The bacteria as well as the fungi are capable of decomposing the lignified cellulose of straw.

1. The addition of a pyrethrum extract to a petroleum solvent, semirefined white spirit, considerably lowers its interfacial tension against water. The tension also depends upon the reaction of the aqueous phase, decreasing as the alkalinity increases.

2. The addition of agral W.B. to a solution of pyrethrum extract further lowers the interfacial tension more especially against acid solutions, thereby decreasing the sensitivity of the tension value to the pH of the aqueous phase.

3. The presence of calcium salts in the aqueous phase raises the interfacial tension of solutions of pyrethrum extract.

4. Alkaline salts counteract the effect of calcium salts, and the resulting tension values can be correlated with the ratio of calcium to hydroxyl ion concentration.

1. The analytical methods of Tattersfield, Hobson and Gimingham(6) and Gnadinger and Corl(1) for the determination of the pyrethrins in pyrethrum flowers are compared, and certain modifications in technique suggested.

2. Good concordances have been obtained between analytical data and insecticidal tests employing Aphis rumicis.

3. A new method for the rapid and approximate evaluation of unadulterated samples, employing small quantities of material, is described.

4. Observations on the pyrethrin content of individual flowers in the various stages of development are recorded, making use of a modification of the method indicated under (3).

From the herd book records of six leading breeds of cattle in Great Britain (Shorthorn, Aberdeen-Angus, Hereford, Ayrshire, Jersey and British Friesian) the ages of the parents of 2618 pedigree calves born in 1925 were tabulated.

The average age of cows at calving is found to be 5·722 years ± 0·04, with a standard deviation of 2·816. In four dairy breeds the average age is 5·485 years ± 0·05, while for the three beef breeds it is 6·022 ± 0·05.

The “annual replacement percentage” is the number of heifers drafted annually into a herd or breed as first calvers expressed as a percentage of the total number of actively producing cows in the herd or breed. It is in effect the number required annually to make good the losses, and can be calculated from the average age of the cows at calving. This is found to be at least 27 per cent. and agrees substantially with the work of other investigators.

1. An alizarin-adsorption method discovered by Schmelev has been successfully applied, with suitable modification, to the identification and approximate estimation of the free sesquioxide components of clays and soils.

2. Details of the tested procedure are presented, together with some preliminary results obtained.

3. The free alumina component of clays and soils appears to adsorb alizarin only after ignition, whereas the free iron oxide component adsorbs it only in the fresh, unignited state. Hence, by applying the procedure to the fresh, as well as to the ignited material, an approximate estimate of both components may be accomplished in a relatively short time.

There is still much difference of opinion as to the effect of temperature on milk production from the point of view of its effect on both quantity and quality at successive milkings or on successive days.

This paper describes a uniformity trial with irrigated broadcast rice and shows the large inter- and intra-field variation which exists.

The standard deviations decrease with the increased size of plots and vary from 20–1 per cent, with 1/436 acre plots to 7–8 per cent, with 1/22 acre plots.

The decrease of the standard deviation is small with plots larger than 1/87 acre. This size of plot is considered to be the most practicable for field trials.

The influence of proximity to bunds, irrigation channels and drains on increasing yields is discussed and methods of reducing errors due to this cause are suggested.

It is shown that the use of a Latin square extending over more than one field has not produced a more accurate experiment than the use of randomised blocks. The latter method would therefore appear to be the more suitable for manurial and other trials, under the particular conditions of rice growing.

Hart(1) has recently emphasised the importance of obtaining soil colour data. The following method, which is an elaboration of one proposed by Monie(2), has proved satisfactory in practice.