3G6 
Field Experiments on Root-Crops. 
gained by such experiments that cannot be obtained far more 
economically and rapidly in nine cases out of ten by the careful 
analysis of the different artificial manures ? The time, fortunately, 
has now passed when the action of manures and the functions 
of the soil and the atmosphere in relation to plant-life were 
shrouded in impenetrable mystery. We now know very well 
that a manure must contain certain specific fertilizing constituents 
in order to produce a good crop of wheat, grass, or roots. Nobody 
at all acquainted with the chemical names of the chief fertilizing 
constituents of artificial manures need be told that guano which 
on analysis yields 15 per cent, of ammonia is likely to produce 
a better crop of wheat than another sample containing only 10 
per cent., or that a superphosphate or turnip manure Avhich con- 
tains 20 per cent, of soluble and 10 per cent, of insoluble phos- 
phates in the shape of bones is a better manure than that of a 
maker who sells badly dissolved coprolites containing, it may be, 
only 15 per cent, of soluble phosphate. 
Moreover, such field experiments are often very deceptive in 
their results, for, generally speaking, farmers who go to work in 
a practical fashion in testing, as they think, the money A'alue of 
various prepared manures, take little or no notice of the previous 
agricultural conditions of the land upon which the different 
manures are tried, nor of the effects which certain fertilizing 
matters produce under specially favourable or adverse circum- 
stances. It thus happens that on land in a high agricultural 
condition a really poor and cheap manure often gives as good 
a crop of turnips as a good and intrinsically valuable turnip 
manure. 
In a bad and very dry season it is well known that concentrated 
artificial manures often do harm to crops, whereas no injury to 
them results from the application of indifferent and all but 
valueless compounds sold as artificial manures. 
To mention only another instance, I would say that I know 
it to be a fact, that on sandy soils, altogether deficient in lime, 
a superphosphate comparatively poor in soluble phosphate has a 
better practical effect on turnips than a superphosphate, Avhich 
is very rich in soluble phosphate, and more expensive in con- 
sequence. The results of field trials upon turnips with the 
two kinds of superphosphate on such a sandy soil would lead 
the purely practical experimenter, as he is fond to style himself, 
to the erroneous conclusion that the better and dearer super- 
phosphate is not nearly so good as the really less valuable and 
cheaper sample ; whereas the same experience teaches the think- 
ing farmer, to apply to such land a good superphosphate sparingly 
and mixed with ashes, avoiding thereby a great excess of acid 
soluble phosphate, which if not neutralized by the soil is injurious 
L 
