280 
kinds of farm crops. In testing a new variety it is 
necessary to measure two properties—its quality and 
its yielding capacity—for money-return per acre is 
obviously determined by the product of yielding capa- 
city and quality as expressed by market price. I 
propose here to deal only with the determination of 
yielding capacity. The determination of quality is not 
allied to manurial trials. 
In attempting to determine yielding capacity there 
has always been a strong temptation to rely on the 
measurement of obvious structural characters. For 
instance, in the case of cereals many farmers like 
large ears, no doubt with the idea that they are an 
indication of high-yielding capacity. Many very 
elaborate series of selections have been carried out, on 
the assumption that large grains, or large ears, or 
many ears per plant implied high yield. 
We may take it as definitely settled that none of 
these characters is trustworthy, and that the deter- 
mination of yielding capacity resolves itself into the 
measurement of the yield given by a definite area. 
The actual measurement, therefore, is the same as 
that made in manurial trials, and is, of course, sub- 
ject to the same probable error of about 5 per cent. 
It follows, therefore, that it is subject to the same 
limitations. Variety trials on single plots, and that 
is the method commonly used, will serve to measure 
variations in yielding capacity of 30 per cent., or 
more, but are totally inadequate to distinguish be- 
tween varieties the yielding capacities of which are 
within 10 per cent. of each other. 
Numbers of such single-plot trials have been carried 
out, with the result that many varieties with yielding 
capacities much below normal have almost disappeared 
from cultivation, and those commonly grown do not 
differ greatly from one another—probably not more 
than ro per cent. 
Ten per cent. in yielding capacity, however, in 
cereals means a return of something like 15s. to 20s. 
per acre—a sum which may make the difference be- 
tween profit and loss; and if progress is to be made 
in manuring and variety testing, some method must 
be adopted which is capable of measuring accurately 
differences in yield per unit area of the order of 10 per 
cent. 
The only way of decreasing the probable error is to 
increase the number of plots, and to arrange them 
so that plots between which direct comparison is 
necessary are placed side by side, so as to reduce as 
much as possible variations due to differences in soil. 
Thus it has been shown that with ten plots in five 
pairs the probable error on the average can be reduced 
to about 1 per cent., in which case a difference of 
from 5 to Io per cent. can be measured with consider- 
able certainty. 
Such a method involves, of course, a great deal of 
trouble; but agricultural science has now reached 
that stage of development at which the obvious facts 
which can be demonstrated without considerable effort 
have been demonstrated, and further knowledge can 
only be acquired by the expenditure of continually in- 
creasing effort. In fact, the law of diminishing return 
holds here, as elsewhere. 
It appears, then, that for questions involving 
measurements of yield per unit area, such, for 
instance, as manurial or variety trials, further ad- 
vance is not likely to be made without the expendi- 
ture of much more care than has been given to such 
work in the past. The question naturally arises: Is 
it worth while? I think the following instance shows 
that it is :— 
Some years ago an extensive series of variety trials 
was carried out in Norfolk, in which several of the 
more popular varieties of barley were grown side by 
NO. 2296, VOL. 92] 
NATURE 
[OcToBER 30, 1913. 
side at several stations for several seasons. In all, 
the trial was repeated eleven times. As a final result 
it was found that Archer’s stiff-straw barley gave 
Io per cent. greater yield than any other variety in- 
cluded in the trials, and by repetition of the experiment 
the probable error was reduced to 14 per cent. The 
greater yield of 10 per cent., being over six times the 
probable error of the experiment, indicates practical 
certainty that Archer barley may be relied on to give 
a larger crop than any of the other varieties with 
which it was compared. One difficulty still remained. 
It was almost impossible to obtain anything like a 
pure strain of Archer barley. Samples of Archer sold 
for seed commonly contained 25 per cent. of other 
varieties. This difficulty was removed by Mr. Beaven, 
who selected, again with enormous trouble, a pure 
high-yielding strain of Archer barley. Since this 
strain was introduced into the Eastern Counties the 
demand for it has always exceeded the supply which 
could be grown at Cambridge and at the Norfolk 
Agricultural Station, and it is regarded by farmers 
generally as a very great success. 
The conclusion, therefore, is that a ro per cent. 
difference is well worth measuring, that it cannot be 
measured with certainty by the single-plot method, 
and that it behoves those of us who are concerned 
with field trials to look to our methods, and to avoid 
printing figures for single-plot experiments which may 
very well be misleading. Almost everyone thinks him- 
self competent to criticise the farmer, who is com- 
monly described as too self-satisfied to acquaint him- 
self with new discoveries, and too conservative to try 
them when they are brought to his notice. Let us 
examine the real facts of the case. Does the farmer 
ignore new discoveries? The largely increasing prac- 
tice of consulting the staffs of the agricultural colleges, 
which has arisen among farmers during the last few 
years, conclusively shows that he does not; that he 
is, in fact, perfectly ready to avail himself of sound 
advice whenever he can. Is he too conservative to 
try new discoveries when brought to his notice? The 
extraordinary demand for seed of the new Archer 
barley quoted above, and for seed of new varieties 
generally, the continuous advance in the prices of 
phosphatic manures, as the result of increased demand 
by farmers, the trade in Scotch and Irish seed pota- 
toes, all show how ready the farmer is to try new 
things. The chief danger seems to be that he tries 
new things simply because they are new, and he may 
be disappointed if those who are responsible for the 
new things in question have not taken pains to ascer- 
tain with certainty that they are not only new but 
good. Farmers are nowadays in what may be called 
a very receptive condition. Witness the avidity with 
which they paid extravagant prices for single tubers of 
so-called new, but inadequately tested, varieties of 
potatoes some years ago, and in a less degree the 
extraordinary demand for seed of the much-boomed 
French wheats, and the excitement about nitragin for 
soil or seed inoculation. Witness, too, the almost 
universal failure of the new potatoes and French 
wheats introduced during the boom, and the few cases 
in which nitragin gave any appreciable result. The 
farmer who was disappointed with his ten-guinea 
tuber, his expensive French wheat, or his culture of 
nitragin cannot but be disillusioned. Once bitten, 
twice shy. He does not readily take advice again. 
Let us, therefore, recognise that the farmers of the 
country are ready to listen to us, and to try our 
recommendations, and let that very fact bring home 
to us a sense of our responsibility. All that is new is 
not, therefore, necessarily good. Before we recom- 
mend a new thing let us take pains to assure ourselves 
of its goodness. To do so we must find not only that 
