1 May, 1898. ] QUEENSLAND AGRICULTURAL JOURNAL. 401 
Chemistry. 
POTASH AND ITS FUNCTIONS IN AGRICULTURE. 
Tux following is a brief summary of an exhaustive paper on the above subject 
by the Chief of the Division of Chemistry in the United States Department of 
Agriculture :— ; 
1. The potash used in fertilisers and found in the soil has been derived 
from the decay of minerals containing it as an ingredient, and chiefly from 
feldspars. 
2. During the progress of weathering, a portion of the potash in original 
rocks becomes soluble and is lost by lixiviation. Asa rule, about 25 per cent. 
of the potash finds its way by this means into the streams and seas. 
3. There is usually a less percentage of potash in the finer particles of 
soil than in the coarser particles, and this is due to the fact that the solvent 
action of water is more strongly exerted upon the finer particles. 
4. The potash is quite evenly distributed both in the soil and subsoil, 
there being only a slightly greater proportion in the deeper layers, doubtless 
owing to the fact that they have not been so thoroughly leached. 
5. The solubility of potash in the soil is very different for different 
solvents, the least for the weak organic acids and greatest for the strong 
mineral acids. Hot hydrochloric acid extracts from the soil about 20 per cent. 
of its total potash content, which is about thirty-two times as much as is 
removed by a 1 per cent. citric acid solution. 
6. A fertile virgin soil contains about 2 per cent. of total potash, or about 
70,000 lb. per acre taken to the depth of 1 foot. A crop removing 50 lb. of 
potash a year could be grown consecutively for about 1,400 years on such a 
soil before exhausting all the potash which it contains. 
7. The soil retains a certain quantity of fertilising material with such 
tenacity as to render it practically impossible for plants to withdraw the whole 
of it, thus protecting the future against the rapacity of the present. 
8. The quantity of potash removed by various crops per annum varies 
greatly. The largest quantities are removed by beets, and the smallest 
quantities by cereals and cotton. Beets may remove as much as 100 1b. per 
acre, cereals about 80 ]b., and cotton about 23 lb. for the average crops as 
produced in this country. In Germany, beets grown for forage remove often 
over 200 1b. of potash per acre from the soil, clover hay about 74 1b., and 
tobacco the same quantity. 
9. Tobacco contains a larger proportion of potash than any other common 
crop—viz., about 40 parts per 1,000 of the dry leaves. Jorage beets contain 
35, potatoes 20, sugar beets 18, clover hay 19, beans 18, and cereals 5 parts 
per 1,000. ~ 
10. There is about four times as much potash in the straw of cereals as 
in the grains, while in peas and beans the proportion is about as two to one. 
11. A soil which yields about 0°01 per cent. of potash to a 1 per cent. 
citric acid solution, and contains about 030 per cent. soluble in hydrochloric 
acid does not usually need a potash fertiliser. “ 
12. The potash salts which supply the commercial potash fertilisers of 
the world have been deposited as the result of the evaporation of saline lakes ~ 
charged with potassic materials. 
13. The commercial potash of the world is derived almost exclusively 
from the neighbourhood of Stassfurt, in Germany. The quantity of crude 
salts annually mined is about 750,000 tons, worth nearly 3,000,000 dollars. 
