THE USES OF LIME IN AGRICULTURE AND HORTICULTURE. 243 
of a certain amount of ammonia ; for a similar reason it is best to use 
the carbonate on light sandy soils, as the caustic is apt to cause a too 
rapid decay of the organic reserves in the soil. When growing crops 
are on the land, especially young plants with delicate roots, the caustic 
form is apt to cause damage. 
On heavy clays where the chemical activity of the lime is required 
to set free the dormant food materials, where the coagulation above 
referred to and the consequent improvement of the texture are of 
paramount importance, the more active caustic lime should be used. 
Whatever kind of lime is decided on, it is imperative that it should 
be in a fine state of subdivision, as in order to get effective action it 
must be as evenly distributed as possible throughout the soil. Users 
should therefore see that their ground limestone is in a very fine 
powder. If the lump caustic or burnt lime is used it should be put 
in heaps over the land to be treated, covered with soil, and allowed to 
slake gradually, and then spread as evenly as possible. Care should 
be taken not to allow lime so treated to become wet — otherwise 
spreading is impracticable. It is because of this necessity that lime 
should be in fine particles that the ground caustic form has been put 
on the market. Although rather more expensive than the lump, it 
can be sown through a drill, and even distribution is readily secured. 
It will be obvious that it is always preferable to apply lime when there 
is no crop on the land ; and the autumn or winter, especially in the case 
of caustic lime, is naturally the more convenient time.* It can be 
applied either before or after digging or ploughing : the former is 
naturally the more convenient, as it is easier at that time to get on to 
the soil, but it must be remembered that the tendency of lime is always 
to sink in the soil, and there is therefore a constant loss in the drainage 
water. This movement of lime is due to the fact that it is soluble in 
water containing carbonic acid (C0 2 ), under the influence of which 
it becomes bicarbonate of lime — a compound which is responsible 
for the temporary hardness of water and is the chief ingredient of our 
natural mineral waters. The idea, therefore, that lime is brought back 
to the surface by ploughing is only partially true. 
The quantity of lime to be applied on an acre will naturally largely 
depend upon the extent of the deficiency, and it must always be 
remembered that carbonate contains less lime than caustic. From 
half to twice as much again of the former must be used to supply the 
same amount of actual lime to the soil.f To obtain the best results, 
from 30 cwt. to 2 tons an acre of the carbonate may be safely used ; of 
caustic lime 1 ton to the acre is a good dressing, and of ground caustic 
10 to 15 cwt. will be sufficient. All these quantities refer, of course 
to open land. Market growers' — especially of tomatos under glass — 
are accustomed to use much heavier dressings, even up to 15 to 20 
tons to the acre — but knowledge and experience are necessary with such 
* On ordinary arable agricultural soil it s best to apply it to the stubble 
in the autumn before ploughing preparatory to a root crop, 
t Chemically 100 of quick-lime =a 178 6 of carbonate of lime. 
