_ type of soil to which this result is applicable. 
OcTOBER 30, 1913| 
the new thing produces a greater return per acre, but 
that the increased return is worth more than it costs 
to produce, and we must also define the area or the 
This 
implies in practice that each field trial should confine 
itself to the investigation of only one, or, at most, 
two, definite points, since five pairs of plots will be 
required to settle each point; that the experimental 
results should be reviewed in the light of a thorough 
knowledge of farm book-keeping, and that accurate 
notes should be taken of the type of the soil, and the 
area to which it extends, and of the various meteoro- 
logical factors which make up the local climate. At 
present we are not in possession of a sufficient know- 
ledge of farm accountancy, but there is hope that this 
deficiency will be removed by the work of the Insti- 
tute for Researchin Agricultural Economics, which has 
recently. been founded at Oxford by the Board of 
Agriculture and the Development Commission. The 
excellent example set by Hall and Russell in their 
“Survey of the Soils and Agriculture of the South- 
Eastern Counties,’ an example which is being fol- 
lowed in Cambridge and elsewhere, seems likely to 
result in the near future in a complete survey of the 
soils of England which will make a sound scientific 
basis for delimiting the areas over which the results 
of manurial or variety trials are applicable. 
Reviewing this branch of agricultural science, the 
outlook is distinctly hopeful. New fertilisers are 
coming into the market, as, for instance, the various 
products made from atmospheric nitrogen. New 
varieties of farm crops are being produced by the 
Plant-breeding Institute at Cambridge, and elsewhere. 
It is to be hoped that the work of the Agricultural 
Economics Institute at Oxford will throw new light 
on the interpretation of experimental results from the 
accountancy standpoint. Finally, the soil surveys on 
which the colleges have seriously embarked will assist 
in defining the areas over which such results are 
applicable. It only remains for those of us who are 
responsible for the conduct of field trials to increase 
the accuracy of our results, and the steady accumula- 
tion of a mass of systematic and scientific knowledge 
is assured. It will be the business of the advisory 
staffs with which the colleges have recently been 
equipped by the Board of Agriculture and the De- 
velopment Commission to disseminate this knowledge 
in practicable form to the farmers of this country. 
One more point, and I have finished this section of 
my address. I have perhaps inveighed rather strongly 
against the publication of the results of single-plot 
trials. I quite recognise that the publication of such 
results was to a great extent forced upon those ex- 
perimenters who were financed by annually renewed 
grants of public money. Nowadays, however, agri- 
cultural science is in a stronger position, and I venture 
to hope that most public authorities which subsidise 
such work are sufficiently alive to the evils attendant 
on the publication of inconclusive results to agree to 
continue their grants for such periods as may suffice 
for the complete working out of the problem under 
investigation, and to allow the final conclusions to be 
published in some properly accredited agricultural 
journal, where they would be readily and permanently 
available to all concerned. This would in no wise 
prevent their subsequent incorporation in bulletins 
specially written for the use of the practical farmer. 
So far I have confined my remarks to subjects of 
which I presume that every member of the section has 
practical experience, subjects which depend on the 
measurement of the yield per unit area. These sub- 
jects, however, although they have received far more 
general attention than anything else, by no means 
comprise the whole of agricultural science. Certain 
NO. 2296, VOL. 92] 
NATURE 
281 
scientific workers have confined their efforts to the 
thorough solution of specific and circumscribed pro- 
blems. I propose now to ask the section to direct its 
attention to some typical results which have been thus 
achieved during the last twenty years. 
The first of these is the development of what I may 
call soil science. Twenty years ago the bacteriology of 
nitrification had just been worked out by Warington 
and by Winogradski. The phenomena of ammoniacal 
fermentation of organic matter in the soil were also 
fairly well established. The fixation of atmospheric 
nitrogen by organisms symbiotic on the leguminosz 
had been definitely demonstrated. Fixation of 
nitrogen by free-living organisms had been sug- 
gested, but was still strenuously denied by most soil 
investigators. No suggestion had yet been made of 
the presence in normal soils of any factor which in- 
hibited crop production. The last twenty years have 
seen a wonderful advance in soil science. Our know- 
ledge of nitrification and ammoniacal fermentation 
has been much extended. The part played by the 
nodule organisms of the leguminosz has been well 
worked out, has seen a newspaper boom, and a sub- 
sequent collapse, from which it has not yet recovered. 
But the greatest advance has been the discovery of 
the part played by protozoa in the inhibition of fer- 
tility. 
The suggestion that ordinary soils contained a 
factor which limited their fertility emanated in the 
first instance from the American Bureau of Soils. The 
factor was at first thought to be chemical, and its 
presence was tentatively attributed to root excretion. 
Certain organic substances, presumably having this 
origin, have been isolated from sterile soils, and found 
to retard plant growth in water-culture. It is claimed, 
too, that the retardation they cause is prevented by 
the presence of many ordinary manurial salts with 
which they are supposed to form some kind of com- 
bination. 
Contributions to the subject have come from several 
quarters, but whilst the suggested presence of an 
inhibitory factor has been generally confirmed, its 
origin as a root-excretion and its prevention by 
manurial salts has not received general confirmation 
outside American official circles. The matter has been 
strikingly cleared up by the work of Russell and 
Hutchinson at Rothamsted, who observed that the 
fertility of certain soils which had become sterile was 
at once restored by partial sterilisation, either by 
heating to a temperature below 100° C., or by the 
use of volatile antiseptics such as toluene. This ob- 
servation suggested that the factor causing sterility 
in these cases was biological in nature, that it con- 
sisted, in fact, of some kind of organism inimical to 
the useful fermentation bacteria, and more easily 
killed than they by heat or antiseptics. After a long 
series of admirable scientific investigations these 
workers and their colleagues have shown that soils 
contain many species of protozoa, which prey upon 
the soil bacteria, whose numbers they keep within 
definite limits. In certain circumstances, such, 
for instance, as those existing in the soil of sewage 
farms, and in the artificial soils used for the cultiva- 
tion of cucumbers, tomatoes, &c., under glass, the 
protozoa increase so that the bacteria are reduced 
below the numbers requisite to decompose the organic 
matter in the soil into substances suitable for absorp- 
tion by the roots of the crop. Practical trials of 
heating such soils, or subjecting them to the action 
of toluene, or other volatile antiseptics, have shown 
that their lost efficiency can thus be easily restored, 
and the method is now rapidly spreading among the 
market gardeners of the Lea Valley. 
I have attempted to sketch the chief points of this 
