Depletion of Nursery Lands. 179 
When the crop is removed, even the roots are 
taken out of the soil. For four or five years, the 
land receives practically no vegetation which can rot 
and pass into humus; and then, the trees are dug 
in the fall, often when the soil is in unfit condition, 
and this fall digging amounts to a fall plowing. The 
soil, deeply broken and robbed of its humus, runs 
together and cements itself before the following sum- 
mer; and it then requires three or four years of 
“rest” in clover or other herbage crop to bring it 
back into its rightful condition. This resting 
period allows nature—if man grants her the privi- 
lege—to replace the fiber in the soil, and to make it 
once more so open and warm and kindly that 
plants can find a congenial root-hold in it. 
The following synoptical sketch of the causes of 
the so-called wearing-out of nursery lands will 
serve to bring the question of productivity of lands 
into its proper relationships and perspectives :* 
a. The fertility of the soil.i—There are two analytical means 
of determining the fertility of the land. One method deter- 
mines the chemical constitution, and the other the mechani- 
eal or physical condition. 
Chemistry determines the amount and kind of plant-food 
in the soil, but it cannot tell just how useful this food may 
be to the plant. This depends upon the physical condition 
of the land, or upon the relation of the soil to warmth, 
moisture, air and mechanical constitution. The plant is not 
simply w passive agent, taking in the food which is pre- 
sented to it, but it is actively engaged in searching for and 
appropriating food. 
*.,, H. Bailey, before American Association of Nurserymen, at Chicago, as 
reported in Garden and Forest, June 24, 1896. 
