Plant-food Consumed by Apples. 205 
“These investigations, when considered in all their 
bearings, lead one to wonder not why old orchards 
are failing, but why they have not ceased to pro- 
duce merchantable fruit long since.” 
Another ealeulation by the same _ investigator 
shows the amount of plant-food which may be ex- 
pected to be carried away in the fruit, and blown 
off in: the leaves (not computing the amount in the 
wood), for the period between the ages of 13 and 
33 years of apple trees: 
Apples. Leaves. Value. 
WNUGPOP CT ae saya serecreeicis as 498.60 Ibs. 456.75 lbs. $143.30 
Phosphoric acid ........ 38.25 ¢ 126; gy 11.50 
Potash « tere dean te ows 728.55 ** 441, oe 52.63 
Total value.sccs ois. $207.45 
“While the above results are reached by assum- 
ing a given amount of apples and leaves per year 
in a bearing orchard, and while the facts in any 
given case at any given time may vary widely, yet 
it is believed that they are valuable, as they fur- 
nish a means of measuring in any given case, with 
a great degree of accuracy, the amount of soil ex- 
haustion.” 
He also “shows that an average crop of apples 
removes in round numbers eleven pounds of nitro- 
gen, nearly one pound of phosphoric acid and six- 
teen pounds of potash, and that the leaves of a 
tree large enough to produce the apples would con- 
tain ten pounds of nitrogen, nearly three pounds of 
phosphoric acid and ten pounds of potash, or a total 
