On Rape-dust. 
183 
Glh. That it is necessary to apply saline and earthy matters to 
soils, after a course of rape-dust, is on the principle that we can- 
not maintain fertility without returning to the earth all that we 
have taken from it. And, in a course of crops, we take away 
many earthy and saline substances, while we return little of the 
former, and scarcely any of the latter, when we apply rape-dust. 
When we use bones, they return earthy phosphates, &c. ; but it 
is still necessary that the saline matters should be restored. 
Practical experience has fully proved to the writer the advantasre 
of such a course during the present year. Four separate appli- 
cations upon land in this condition have all more than equalled 
my anticipations.* The sample will in some cases be as much 
improved by the application as the gross produce is increased. 
the ears were badly fed, and the weather discoloured them, so that when 
ihraslied it was found to be deficient both in quality and quantity. 
The common explanation ofiered by most, that "there was more straw 
than the land could bear," liad some truth in it, though not sufBcient to 
justify the conclusion which is often drawn in such cases, " that, manure 
as you will, you can only get a certain, quantity of corn and that " there 
is no use in manuring so hard ; for if you plough and sow your land 
properly, in good seasons, and give it a fair quantity of manure, so as to 
keep it always in the same heart, you will grow as much as it is possible 
for the soil to produce." 
It is true that in the above case there was more straw than the 
land could bear; had that soil, however, been as rich in the other ele- 
ments of nutrition as in those supplied by rape-dust, it would have pro- 
perly matured the crop. It is also true that there are certain limits to 
the crops we can produce, but the whereabouts of those limits, in my 
opinion, are uncertain. It is also true, that if we cultivate a soil in the 
manner spoken of, we may ensure its producing a fair amount of pro- 
duce ; and by giving it a larger share of one sort of manure, or by chang- 
ing one part of our system, we may produce no increase of crop ; yet, 
from this we are not to conclude that it will produce no more. We have 
perhaps only supplied one condition essential to further fertility, and 
we must endeavour to supply all. It is useless to apply steam to a car- 
riage, unless we give it wheels; but it is also necessary that many other 
pieces of mechanism should be employed before we can travel at all ; be- 
fore, however, we can say that we can travel as fast as it is possible for us 
or any others, we must be certain that every piece of the machinery is 
perfect in relative size, nature, and make, and that everything is beyond 
future improvement. So, before we say that we can grow no more, let 
us ask ourselves if every element or circumstance which the plant requires 
is in the soil, or ensured by our management. 
* A top-dressing of 4 cwts. of salt per acre, at a cost of 8?., gave an 
increase of barley of 229 sheaves per acre, in my experiments last year. 
The soil had been subject to a long course of rape-dust tilling for the 
barley and wheat crops. Upon soil of a similar nature, the same appli- 
cation gave an increase of 128 sheaves of oats per acre. The grain was 
