108 LUTHER BURBANK 



ern orchardists that care should be taken to avoid 

 too much nitrogen. The roots of the tree reach 

 down to rich subterranean sources that are likely 

 to be well supplied with nitrogen, because the 

 nitrates are very soluble and are pretty rapidly 

 leached or filtered into the subsoil. 



After preliminary treatment it has been found 

 in many States best to sow a crop of clover, often 

 with other perennial grasses, as a permanent 

 crop, which should be cut and all material left 

 on the ground for the protection and support 

 of the orchard. This has been found to be 

 an extremely profitable method both in the 

 old neglected and in the new; orchards of 

 New England and in the orchards of the north- 

 western Pacific coast. A small space about 

 the trunk of the tree should be kept free from 

 grass. 



The experts of the Indiana Experiment 

 Station recommend as a fertilizer, for soil of 

 fair natural fertility and where a leguminous 

 nitrogen-gathering cover crop such as suggested 

 may be grown, the additional use of a fertilizer 

 having the following formula: "A thousand to 

 fifteen hundred pounds per acre of a mixture 

 containing one part (100 pounds) each of 

 ground bone, acid phosphate, and muriate of 

 potash. On soils that are somewhat exhausted 



