HUMUS IN NURSERY LANDS. . 14! 



at a rate of about eight dollars per acre per year, for the 

 ordinary type of farm lands. 



The reason for this condition of treed lands is that the 

 soil is injured in its physical texture by the methods of cul- 

 tivation and treatment. The best nursery lands are those 

 which contain a basis of clay, and these are the ones which 

 soonest suffer under unwise treatment. The land is kept 

 under high culture, and it is therefore deeply pulverized. 

 There is practically no herbage on the soil to protect it dur- 

 ing the winter. When the crop is removed, even the roots 

 are taken out of the soil. For four or five years, the land 

 receives practically no herbage 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 

 summer ; 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 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. It would seem, therefore, that some of this 

 mechanical injury to nursery lands might be prevented by 

 the growing of some cover crop between the rows late in 

 the season, to be plowed under the following spring. It is 

 well known that the plo wing-in of very coarse manure 

 between the trees in fall or spring, for two or three years, 

 will sometimes so greatly improve the land that a second 

 good crop of trees can be grown upon the land with ease. 

 This is particularly true for plum trees, as already noted, but 

 the results do not seem to be so well marked for pears and 

 some other trees. It is probable that one reason for the 

 very general refusal of pear trees to follow pear trees is 

 the fact that they demand heavy clay, and this is just the 

 land which is most injured by nursery practices. Some 

 lands are naturally so loose and open in structure that two 

 or three crops of trees can .be grown in succession, but 



