the Progress of English Agriculture. 813 = 547 
ipplieil bv the sulphate of potash, passed into the solution, 
hilst potash took its place and was retained in the soil. 
The sterile sand used in this experiment hardly contained any 
me, whilst the marly soil, it need hardly be said, contained it 
I a large proportion. Lime not merely acts beneficially on 
ndy soils in a direct manner, by supplying a deficient element 
nutrition, but also because it preserves in the soil the more 
iluable fertilising matters, which, like salts of potash or am- 
onia, rapidly filter through sandy soils, unless a sufficient 
lantity of marl or lime has been previously applied to the 
nd. By these means the bases of the more valuable saline 
nstituents of rotten dung or of guano are retained in the land, 
ailst the acids filter through it in combination with lime — a 
nstituent which is, comparatively speaking, inexpensive. 
The presence of much or little lime in a soil has also a Influence of 
iiwerful influence on the changes which soluble phosphates, or "^P""* 
.inures containing soluble phosphates, undergo in contact with taini^'<^^sol*uble 
e soil. It is a curious, and apparently anomalous, circum- phosphates. 
:mce, that on sandy soils, and on all soils deficient in lime, 
tncentrated superphosphates, rich in soluble phosphate, do not 
voduce nearly so beneficial an effect upon root-crops as upon 
ilcareous soils, or upon soils containing even a moderate pro- 
jrtion of lime. 
.When applied to root-crops upon sandy soils greatly deficient 
i lime, a concentrated superphosphate produces a smaller crop 
iin a manure containing only one-fourth the percentage of 
! uble phosphate. When this fact was first brought under my 
itice I ascribed it to prejudice, or accidental and unobserved 
« cumstances, but direct experiments and an extended personal 
(perience have shown me that there is no mistake about this 
litter. The true explanation no doubt is, that the excess of 
I d soluble phosphate in a concentrated superphosphate is not 
];cipitated as efficiently in a soil deficient in lime, as it is 
i land containins: a good deal of lime. 
... . • 
A.cid compounds are extremely injurious to vegetation, even in Beneficial i"- 
( ute solutions ; and hence concentrated superphosphates used ^^^ll^^^^^^' 
i large quantities, say at the rate of 5 to 6 cwts. per acre, do j^ops on light 
jsitive injury to root-crops, and more moderate applications of laud. 
3 cwts. per acre produce a less favourable result on sandy 
sis, and on all land poor in lime, than the same amount of super- 
fjsphate poor in soluble phosphate. Indeed, the experience 
0 light-land farmers in districts in England where the land 
1 deficient in lime, goes to prove that on land of that descrip- 
t n it is better to apply bone-dust or precipitated phosphate, or 
pjsphatic manures containing no soluble phosphate, to root- 
< ps than to use superphosphate, or similar artificial manures 
