Phosphatic Manures for Root-Crops. 
55 
to the land is invariably beneficial and never hurtful. The pre- 
ceding experiments place this beyond doubt ; for they prove 
that soils of most varied characters — clay or sand, chalk or loam 
— render soluble phosphate insoluble. Although some soils 
possess this power in a higher degree, and some effect this 
change more rapidly than others, it may be safely asserted that 
there is no arable soil which does not possess it to a considerable 
extent. If there were any such soil, the application to it of acid 
soluble phosphate would, we may rest assured, do harm to the 
crop ; for in water containing ever so little free acid no plant 
can exist in a healthy condition for any length of time. 
The proportion of soluble phosphate to that of the soil in my 
experiments was taken purposely very much larger than it ever 
will be found in practice ; and as in every instance c^uite a 
limited quantity of soil rendered a large proportion of the soluble 
phosphate insoluble, it cannot be doubted that the whole amount 
of soluble phosphate in 4 or 6 cwts. of concentrated superphos- 
phate will be retained in a neutral and insoluble condition in 
the large bulk of soil to which it is applied. The assumption 
that this fertiliser does not sustain the after-growth of turnips, 
because the soluble phosphate which it contains is less readily 
■washed into the subsoil, is thus founded in error. Equally fal- 
lacious is the dictum of some agricultural chemists who maintain 
that a good turnip-manure should contain one-half of its phos- 
phates in a soluble, and the other half in an insoluble condition, 
in order that the soluble phosphates mav push on the young 
plant, and the insoluble phosphates vigorously maintain its after- 
growth. In reality soluble phosphate, soon after its application, 
is converted in the large mass of soil into insoluble phosphate ; 
and the first as well as the sustained invigorated growth of our 
root-crops is alike promoted by insoluble phosphatic combina- 
tions. If, therefore, it is at all desirable to submit phosphatic 
materials to the action of sulphuric acid, which renders the 
phosphates soluble, we should aim at perfection, and not be led 
asti-ay bv fallacious speculations and perform this work by halves. 
Practical proofs are not wanting which clearly demonstrate the 
efficiency of superphosphate, containing, practically speaking, no 
insoluble phosphate of lime. It will suffice to mention only one 
that will be found in my Paper on Experiments upon Swedes, 
in vol. xxii. part 1, of this Journal. 
One of the experimental turnip-plots was manured with 
3 CAvts. of dissolved bone-ash, prepared by treating 100 lbs. of 
good commercial bone-ash with 70 pints of brown sulphuric 
acid, and drying up this mixture with 50 lbs. of gypsum. In 
this way an excellent superphosphate was obtained, which on 
analysis furnished the following results : — 
