July 11, 1903. 
THE GARDENING WORLD . 
597 
Something about Plant Food. 
(Continued from page 553.) 
. By J. J. Willis, Harpenden. 
Since plants feed under ground, and hence out of sight, and 
because their food is largely invisible to the unaided eye, their 
dikes and dislikes are not easily observed. But we can under¬ 
stand to a very large extent what are the food requirements of 
different plants by studying the chemical composition of the 
various parts of the plants themselves. Therefore analysis 
of plants sometimes answers questions which could not be 
reached in any other way, and usually indicate the directions 
which should be taken in manurial applications in order to 
obtain the most satisfactory results. 
Food Requirements of Fruit Trees. 
Fruit trees, like other garden products, in order to live and 
fructify, require certain elements of plant food, some of which 
are supplied by the air and some are found in the soil. The 
mineral part, of the plant, which is represented by the ashes left 
behind when a plant is completely burnt, constitute the inor¬ 
ganic or mineral constituents, which are derived from the soil 
alone, although some of this may have been supplied as manure. 
The following data shows the demands that are likely to be 
made on the soil by the growth of different fruit trees ; the 
wood onlv in this case is considered, as our last article dealt 
with the fruit requirements. 
Table showing the amount of selected chemical constituents in 
the ashes of the wood of various fruit trees. Percentage 
quantities: — 
Description of fruit tree. 
Potash. 
Lime. 
Magnesia. 
& 
"u 
© . 
-r "2 
on 
S 
Apple. 
per cent. 
192 
per cent. 
63 6 
per cent. 
7*5 
per cent. 
4-9 
Pear . 
42 
77'2 
5 1 
3-8 
Cherry. 
20'S 
28-7 
9-2 
7'7 
Blackberry . 
10-3 
35-1 
— 
7 3 
Gooseberry . 
131 
20 6 
2 6 
7-0 
Raspberry . 
14-2 
38-2 
10 8 
23-6 
Clie>tnut . 
101 
43-6 
3 2 
1-5 
Walnut . 
11 3 
35 9 
37 
4T 
Run the eye down the column of figures under the heading 
of potash, and see how widely the percentages differ. The ashes 
of the Apple and Cherry wood contain from 19 to 20 per cent, 
of the element potash, while the Pear requires not much more 
than one-fifth of that amount. It is somewhat surprising that 
Apples and Pears, whether of wood or of fruit, should differ 
so largely in their food requirements. 
Selected constituents in the ashes of Apple and Pear fruits : — 
Potash ... 
Soda 
Lime 
Phosphoric acid 
Apples. 
46 per cent. 
„ 
5 „ 
11 
Pears. 
55 per cent. 
9 „ 
8 „ 
15 
These figures show that Pear fruits require 9 per cent, more 
potash, 3 per cent, more lime, and 4 per cent, more phos¬ 
phoric acid than do Apples, while Apple fruits require 5 per 
cent, more soda than do Pears. 
Turning again to the composition of the wood, we find under 
the heading of “ Lime ” that the ashes of the Pear tree contain 
1 7 per cent, of this substance, while the wood of the Goose¬ 
berry contains little more than 20 per cent. Again, see the 
exceedingly large amount of phosphoric acid that is required 
m the production of Raspberry canes, as compared with the 
lequirements of the harder wooded trees. This is also found 
to be the case with Grape Vines, which are large consumers of 
phosphoric acid. 
As a rule, the element magnesia may be left out of considera¬ 
tion in any manurial supply for fruit trees, as most fertile 
soils afford sufficient of this substance in an available form. 
The importance of lime in the growth of fruit trees is very 
clearly shown by the foregoing figures. It is, further, a matter 
of common observation that in the production of stone fruits 
particularly lime is an essential constituent. Its function 
seems to be to strengthen the stems and woody portion of the 
tree, to shorten the period of growth, and hence to hasten the 
time of ripening, Lime is also very directly connected with 
Kalanciioe FELTH amex sis. (See p. 605.) 
increased production of fruit. Fruit trees growing on soils rich 
in lime, if they are not too chalky, show a stocky, steady, 
vigorous growth, and the fruit ripens well; whereas fruit trees 
growing on soils which contain but little lime, particularly the 
heavy clays, appear to have an extended period of growth, the 
result of which is that the wood does not mature, and the fruit 
does not ripen or colour properly. And although potash, which 
is a very prominent constituent in most clay soils, and materi¬ 
ally tends to maturation and seed formation, yet the coldness of 
many clay soils prevents a free absorption by the plant of this 
ingredient; and hence comes in the value of lime, which by 
decomposition set up in the soil by its action a warmer and 
more agreeable habitat is given to the growing plants, of what¬ 
ever their nature. Time also helps to set free the otherwise 
locked-up potash that may be in the soil. 
