
208 Report OF THE DiREcTOR OF THE 
The explanation may perhaps be found in the fact, that, while 
grain crops derive their nourishment largely from the surface 
soil, owing to their comparatively shallow distribution of roots, 
nursery stock, on the other hand draws largely upon the subsoil, 
where comparatively a more limited amount of such available 
food exists, and that the growth of such a crop results, therefore, 
in a comparative, and as the testimony of many of the nurserymen 
indicates, a temporary exhaustion of the subsoil, while the super- 
ficial surface soil, through the thorough cultivation which attends 
the growing of nursery stock, actually becomes richer through 
the constantly increasing amount of availaole food, both mincral 
and organic, which accumulates during the three or four years — 
‘dvring which the crop of nursery stock is reaching a marketabie 
size. | 
It will be seen that generally the’ testimony of the nurseryinen 
indicates that while a crop of stone fruits could successfully 
follow a crop of seed fruits, the reverse is not found to be the 
case, and this may be due to the fact that as generally the size 
attained by the latter trees is larger, the demand upon the soil 
is greater in proportion, and this change is equivalent vo follow- 
ing with a crop requiring less plant food for its development. 
In the case of the stock furnished for this experiment there were 
fifteen seed fruits and sixteen stone fruits, and the average 
amount of ash found in the trees of seed fruits was thirty-five 
per cent. greater than the ash. found in stone fruits. 3 
There is another question which may be of importance in con- 
nection with this matter which deserves more than a passing 
consideration, especially since it may have a very wide influence 
in connection with the successful production of many of our crops. 
In our discussion of the importance of sufficient supplies of plant 
food, we may omit to give any weight to what we may term the 
excreta which are produced in the development of the plant and 
which may, and perhaps do, in many cases so change the char- 
acter of the soil in which such plants grow as to render it unfit 
for the further cultivation, at least in immediate suecession of 
such plants, as well also of other plants to which the soil has 
been rendered, in some way as yet not understood, unwholesome - 

