1. Quantitative determinations have been made of the effect on soil protozoa and bacteria of various antiseptic substances, including benzene and its homologues and derivatives, carbon disulphide, ammonia, formaldehyde and chlorpicrin. Ammonia and nitrates were determined at the same time in many cases. The effect on fungi, eelworm, etc., was also determined roughly.

2. It was found that nearly all the substances disappeared from the soil fairly quickly and at the same time the numbers of bacteria fluctuated. The usual march of events was that the bacteria were reduced in number for the first few days, then rose to a maximum and finally fell slowly towards normal. The whole fall was sometimes very slow and the whole process was much slower in field soil than in the richer, lighter and better aerated greenhouse soils.

3. Aeration was found to have great influence on the rapidity of the changes.

4. The increase of the bacteria during the early days of an experiment varied in the same direction as the molecular weights and heats of combustion of the antiseptics and is attributed to the latter property. Naphthalene, for instance, which has a large heat of combustion, caused enormous rises, while benzene with its lower heat caused smaller rises.

5. This rise was independent of the effect of the substance on the protozoa. Both naphthalene and toluene in large doses cause high rises; the first has no effect on the protozoa, while the latter kills all amoebae and ciliates.

6. Similar results were obtained when the experiments were made on soils already free from protozoa, such as a field soil which had been in bottle for 76 years, soil in which they had been killed by steaming, and soil in which they had been killed by antiseptics. If the protozoa were killed by the use of a strong dose of a suitable antiseptic and the soil were then set aside for a long period, a second dose caused an even greater rise than the first.

7. It is therefore concluded that the rise in the number of the bacteria is largely due to the feeding effect of the antiseptic on the bacteria and not only to the destruction of the protozoa, and that the increased fertility observed by Russell and Hutchinson is to be attributed in large measure to the activity of the greater bacterial population in breaking down the organic matter of the soil. Bacterial rises following treatment with lime or steam are similarly caused in part by the preparation of the plant residues.

8. Aliphatic compounds cause quicker but smaller rises than those of aromatic series.

9. The introduction of a CH3 group into the benzene ring lessens toxicity to soil organisms, while a single Cl or nitro-group increases both toxicity and stability in the soil.

This investigation was undertaken in response to an enquiry respecting the value of lead nitrate as a source of nitrogen for manurial purposes. The ordinary commercial outlets for lead nitrate at the present time are in the manufacture of paper, printing ink and paint, also, in calico printing, where it is employed as a mordant. In the early stages of the War it was used as a shell-filling compound. Scrap lead is generally employed for its manufacture; a process which is protected by several patents. The trade in this commodity is relatively small.

Considerations which are dealt with at length in Appendix III governed the form of the investigation upon tillering. In essence, the intention was to compare the pure lines P and A and to explore the possibilities of making accurate determinations of tillering. For reasons discussed in the Appendix, special steps were taken to secure for observation a population of plants which had had as great a uniformity of conditions as was attainable. The selection and sowing of the seed have been described in § I above. To promote further uniformity, plants of the following categories were excluded from observation: (i) all the plants of end rows; (ii) the end plants of all rows; (iii) plants which did not germinate on 26. iii. or 27. iii. (these days constituted the “modal” 2-day period of germination for the whole population); (iv) plants damaged to a noticeable degree by wire-worm or any other such agency; (v) plants whose immediate neighbour(s) in the row had died.

In recent communications accounts have been given of investigations which were designed to throw light on the nature and extent of the changes which occur when a green crop is converted into silage and to furnish information regarding the factors which influence the course of the fermentation and determine in a large measure the quality of the silage.

Most of our information on the subject of vitamins has been derived from experiments on small animals fed on synthetic diets. The direct application of the results of such experiments to the feeding of farm animals under practical conditions is not warranted. Animals differ in the degree of their susceptibility to disease caused by lack of vitamins, and laboratory diets, composed of foodstuffs subject to abnormal physical or chemical processes, such as heating under pressure, or prolonged extraction with fat solvents, have no parallel in animal husbandry.

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.

(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.

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.