148 FERTILIZING SUBSTANCES. 
we get ‘30 of phosphoric acid and ‘27 of potash. 
Such soil would grow anything; but what could be 
expected from another soil shewing only -02 of phos- 
phoric acid and ‘04 of potash? ‘This was a dark 
patana soil, an¢, although it looked well, did not, of 
course, grow coffee well. Even the richest manure 
would probably be thrown away in this case, unless 
the ground were first well stirred up and left for a 
couple of years to be aeratel. ‘The great desiderata 
seem to be simple tests for phosphoric acid and potash, 
which any superintendent could apply. So long as 
a soil is found to contain appreciable quantities of 
each, it will grow coffee well and require but a mo- 
derate expenditure for manuring. If phosphoric acid 
is so low as ‘10, and potash down to ‘15 per cent, 
then only heavy manuring with potash, bones, su- 
perphosphate, and ammonia, with or without poonac, 
pulp, &c., will enable the soil to yield good crops 
of coffee. 
THE NECESSITY FOR TRIALS OF DIFFERENT MANURES 
AS THEY MAY SUIT SOILS is thus indicated by one 
who has devoted his life to scientific agriculture :— 
‘* Whenever,” says Mr. Mechi, ‘‘I use an artificial 
manure, I leave a portion of the field unmanured with 
it, and am thus enabled to judge by the crop if I 
am remunerated for the outlay. So various are the 
soils and conditions of each field that such a com- 
parative test becomes absolutely necessary, for where 
the whole field is manured and no portion left un- 
dressed, no just conclusion can be arrived at. On 
this farm I have frequently applied bone dust, super- 
phospi ate, blood manure, and other artificial manures, 
without the least increase of crop, while Peruvian 
guano, and especially our shed monure are always 
profitable. As I know that on many farms such man- 
ures have been found very effective, there must be 
causes that render them inoperative on this soil. No 
doubt shed manure, resulting from animals fed with 
corn, cake, roots, and hay, malt-combs, and bran, 
eontain all the elements for every crop. Possibly it 
may be that, having thus enough phosphates, the 
addition of more is not required or availed of by the 
plant. At all events my case proves the necessity 
for comparative trials.” 
THE COST OF ARTIFICIAL MANURES. 
The following analyses and calculations of cost of 
several descriptions of manure may be worth insert- 
ing for the information of coffee planters. They have 
been lying among our papers for some time, haying 
