200 
NATURE 
[| NOVEMBER 30, 1916 
tion if the farmer has sufficient capital, or if his hold- | 
ing is so small that his capital can be more intensively 
used. It is possible to grow nothing but crops bring- 
ing in a large gross return; in districts round Sandy, 
Biggleswade, etc., the market-garden crops have been 
exclusively grown for very many years with great 
success; this method also proves very successful on the 
Bagshot sands. It is not clear, however, that this 
type of farming could be indefinitely extended. 
The best hope for improvement of these light soils 
lies in increasing the number of money-finding crops, 
improving the methods of growing them—e.g, the 
introduction of the boxing and spraying of potatoes— 
and their relation to the other crops or the live stock, 
and improving the organisation for disposing of them, 
so that farmers will feel justified in spending the rather 
considerable sums of money without which light soils 
cannot be successfully managed. 
We can now leave these light soils and pass to the 
opposite extreme—the heavy clay soils. These suffer 
from the fundamental defect that the clay easily de- 
flocculates and assumes a sticky, pasty condition when 
wet, and a hard, lumpy condition when dry. In spite 
-of a good deal of laboratory work, deflocculation is not 
well understood; it is known, however, to be a special 
-case of a very general phenomenon—flcculation of 
suspended colloids—and it will presumably succumb 
to treatment when the general problem is solved. Im- 
portant advances have been made in the last few years 
by Perrin, and it would be interesting to apply his 
methods to clay. 
For the time being the only feasible method of floc- 
culating clay is to add lime or chalk, but experience 
shows that liming and chalking must be accompanied 
by drainage to be a complete success. Any attempt to 
improve crop production on heavy lands involves these 
as the first steps. 
Where clay soils are drained and limed it is possible 
to begin to do something with them. Wheat, beans, 
mangolds, cabbages, and grass can all be produced. 
But, when all is said and done, clays still suffer from 
two disadvantages: they are only suited to a limited 
number of crops, and they are difficult to cultivate. 
The land may be too hard in autumn to be ploughed 
for winter corn; too wet in winter to be ploughed for 
spring corn; and too dry in spring to be prepared for 
mangolds. There are times in between when some- 
thing can be done, but only the man who is skilful 
enough to take full advantage of these intervals has 
any hope of success. Most men, therefore, prefer not 
to run the risk of cultivation, and lay the land down 
to permanent grass. 
There are two directions in which the risk can be 
reduced, though it will still remain a serious factor. 
The great difficulty of cultivation arises largely from 
the circumstance that only on a relatively small number 
of days are both soil and weather suitable for plough- 
ing. The result is that much of the work is left until 
late, and late work tends to be bad work. This can 
only be overcome by speeding up the process of plough- 
ing during the favourable opportunities, and so far as 
I can see this is only possible by the use of motors. 
I believe, therefore, that motor-ploughs and cultivating 
implements will play a considerable part in the im- 
provement of heavy land. 
A second direction in which the risk can be reduced 
is by keeping up the supply of organic matter in the 
soil. Probably the cheapest and most satisfactory way 
of doing this is by ploughing in crop residues, such 
as, for example, are left by a seeds mixture, a clover 
ley, or ploughed-up grass-land. 
Once these great fundamental things have received 
attention, all these soils—loams, sands, and clays—can 
be further improved by proper treatment with fer- 
tilisers. A great deal of good work has been done on 
NO. 2457, VOL. 98] 
this subject, and the results are steadily being diffused 
among farmers, ; 
In most field experiments there is no indication of 
any end-point, and apparently the more the crop is 
fed the larger would be the yield. But the process 
does come to an end. The final limit is ceanhea by 
the inability of the plant to stand up any longer or to 
grow any bigger. \When the corn-crop gets beyond a 
certain size it is almost invariably beaten down by the 
wind and rain, so that the difficulty of getting it in 
becomes considerable. Heavy dressings ot nitrogenous 
manures also predispose the crop to fungoid disease, 
attacks apparently being facilitated by the thinning of 
the cell-walls and the change in composition of the 
cell-sap. 
The way for further progress is then to seek new 
varieties that can stand up and resist disease. And 
here a good deal has been done. Biffen has shown 
how desirable properties may be transferred from one 
wheat to another, and his investigations are revealing 
the limits within which it is possible to construct a 
variety of wheat according to the grower’s specifica- 
tion. Similar work is badly wanted for other crops. 
Fortunately our great seedsmen are fully alive to the 
possibilities in this direction, and have already done 
much useful work. It is not only in the case of 
cereals and potatoes that new varieties can be sought; 
there is great scope also for new varieties of all other 
crops. 
But there is another way in which science can further 
the problems of crop-production. Instead of aiming 
solely at increased yields per acre, attempts may be 
made to reduce the cost and increase the certainty of 
production per acre. 
One of the most hopeful ways of attacking this ~ 
problem is to increase the efficiency of the manurial 
treatment. No manurial scheme is perfect; no farmer 
ever recovers in his crop the whole of the fertilising 
constituents applied to the soil; there is always a 
loss. In our Broadbalk experiments, where wheat is 
grown year after year on the same land and large © 
dressings of artificials are used, we do not recover in 
the crop more than about 30 to 4o per cent. of the 
added nitrogen. f 
Now, whilst we can never hope for perfect efficiency, 
i.e. for 100 per cent. recovery, we can hope to do better 
than this. On our own fields we improve considerably 
on it every year by the adoption of a proper rotation. 
Further experiments on the relationship between the 
efficiency of fertiliser action and the rotation are very 
desirable. 
Another great direction in which economy is possible 
is in.the management of farmyard manure. It has 
been a common complaint against agricultural inves- 
tigators that they have concerned themselves exclu- 
sively with artificials, and left untouched the greater 
problem of the manure-heap. For farmyard manure 
is the staple manure of the countryside, about 37 mil- 
lion tons being made per annum in this country The 
value at 5s. per ton is 9,250,000l.; all the artificial 
manures consumed in Great Britain probably do not 
much exceed 6,§00,0001. in value each year. 
Through the generosity of the Hon. Rupert Guinness 
we have been able at Rothamsted to attack this impor- 
tant subject, and Mr. Richards has obtained some 
striking results, showing what losses may take place 
and indicating methods of avoiding them. 
Another direction in which saving is possible is in 
the soil itself. It is now forty-six years since Lawes 
and Gilbert built those remarkable drain gauges at 
Rothamsted which for the first time enabled chemists 
to determine precisely the quantity of fertilising mate- 
rial washed out from the soil by rain. When there 
was no crop on the ground the soil lost by drainage 
about 4o Ib. of nitrogen in the form of valuable 
