466 

NATURE 
[APRIL 7, 1923 
Rothamsted and Agricultural Science.* 
By Sir Joun RusseEtz, F.R.S. 
HE Rothamsted Experimental Station has just 
passed its eightieth year, having been founded 
in 1843. Its study has always been the growth of 
crops, with periodical excursions into problems of 
utilisation ; the method of experiment has always 
been essentially statistical in that the field experiments 
were repeated year after year without modification, 
with the result that a unique mass of data has now 
accumulated which is proving of the greatest value 
for statistical investigation. 
The work at Rothamsted falls into two great periods : 
the first, when Lawes and Gilbert were actively explor- 
ing the possibilities opened up by the knowledge of 
plant nutrition gained by the early nineteenth-century 
workers; and the more recent period, when- close 
study of the soil has revealed certain factors of high 
scientific interest, and, one is constrained to believe, 
ultimately of great practical importance. 
The great problem which Lawes and Gilbert set out 
to solve was to account for the fertilising value of 
farmyard manure. The fact was well known, but 
there was no satisfactory explanation. Lawes and 
Gilbert proceeded by a method that still—after eighty 
years—remains our best. It was known that farm- 
yard manure contained three groups of components : 
organic matter ; nitrogen compounds ; and ash con- 
stituents—potassium, calcium and magnesium salts, 
phosphates, silicates, etc. They therefore arranged 
vegetation tests with these various groups. The old 
idea was that the fertilising value lay in the organic 
maiter, but Liebig, in 1840, had argued brilliantly 
against this view, and suggested instead that the ash 
constituents, especially the potassium, calcium and 
magnesium salts, were the effective agents. Lawes 
and Gilbert were prepared to recognise the neceSsity 
for these mineral salts, but insisted that the nitrogen 
compounds were equally required. To put the matter 
to a test, they laid out four plots of ground, receiving 
respectively no manure, farmyard manure, ashes of 
an equal amount of farmyard manure, and these 
ashes plus a nitrogen compound (ammonium sulphate). 
The results were as follows : 
PRODUCE OF WHEAT PER ACRE, BROADBALK 
FIELD, ROTHAMSTED, 1844. 
Grain. Straw. 
(bush.) (cwts.) 
No manure . : ; 2= 56 I120 
Farmyard manure (14 tons per 
ACTE) ss \ : . ee 1476 
Ashes of 14 tons of farmyard 
manure ; - = ao II04 
Ash constituents + nitrogen 
compounds and ammonium 
sulphate, up to . 264 1772 
They concluded that farmyard manure owes its value, 
not to the organic matter as was for long supposed, 
nor to the ash constituents as Liebig had suggested, | 
but to the ash constituents plus nitrogen compounds. 
Now this discovery was of the greatest importance 
in plant physiology, but Lawes and Gilbert did not 
follow it up in that direction. Instead they applied 
1 Discourse delivered at the Royal Institution on Friday, February 9. 
No. 2788, VoL. 111] 


it at once to an important agricultural problem then 
ripe for solution. There was then (as nearly always 
now) a shortage of farmyard manure on farms, and 
agriculturists had for generations sought for sub- 
stitutes, but with little success. Lawes and Gilbert 
saw that the mixture of ash constituents and nitrogen 
compounds would form an effective substitute, and 
further, that it could be obtained in very large quanti- 
ties, and of course independently of farmyard manure. 
Geologists had discovered vast deposits of calcium 
phosphate, which chemists had shown how to render 
soluble. Engineers were developing the manufacture 
of coal gas and producing large quantities of ammonium 
sulphate, while potassium compounds could be ob- 
tained without difficulty from wood ashes. Lawes and 
Gilbert therefore proceeded to make mixtures of these 
substances which they advised farmers to use. 
Few experiments have proved so fruitful in stimulat- 
ing scientific inquiry—it is still opening up new fields 
at Rothamsted—and in ministering to human needs, 
as this simple field trial carried out eighty years ago 
on the Broadbalk field at Rothamsted. At first 
farmers looked with some misgiving upon this new 
kind of manure (which was called “ artificial manure ” 
to distinguish it from farmyard manure, then 
known as “natural manure’’); it seemed incredible 
that a harmless-looking powder without smell or 
taste could act as potently as the old-time richly 
odorous farmyard manure. But they soon came to 
recognise its value, and before long they were using 
many thousands of tons a year. It is safe to say 
that the remarkable development of British agriculture 
which took place between 1843, when Rothamsted 
began, and 1870, would have been impossible with- 
out artificial fertilisers. During that period British 
farmers kept pace with the growing needs of the popu- 
lation; indeed they did more, for they helped to 
change the “ hungry ’forties ’”’ into the more plentiful 
‘seventies. The use of artificial fertilisers is now 
developed throughout the civilised world and the 
industry has attained enormous dimensions. 
This was the greatest achievement of Lawes and 
Gilbert. They did many other things for the farmers 
of their day, but this alone leaves us owing them a 
great debt of gratitude. 
As the use of artificial fertilisers spread there arose, 
as one might expect, many problems of great scientific 
interest or technical importance. Thus it soon 
appeared that weather conditions profoundly affected 
the response of crops to artificial fertilisers. The same 
fertiliser mixture which in one season gave results 
fully equal to, or even surpassing those of farmyard 
manure, would, on the same farm and even in the 
same field, prove a failure in another season. This 
is well shown in the fluctuations in yield on the Broad- 
balk wheat field at Rothamsted. 

The effect of soil is also sharply marked. On our 
heavy soil at Rothamsted the best results are usually 
obtained by a fairly liberal use of phosphates, but 
there is less necessity for large dressings of potash. 
But on the much lighter soil of Woburn potash 
is considerably more important, while phosphates 

