CHAPTER XIII 

 FERTILIZERS, OTHER THAN NITROGENOUS, IN THE ORCHARD 



The conclusion should not be drawn from the statements in pre- 

 ceding chapters that in practice only nitrogenous fertilizers are of value 

 in the deciduous fruit plantation. A single instance in which a favorable 

 response attended the use of some other fertilizer would indicate that 

 the problem should be considered from other points of view; there are 

 many such instances. 



The Indirect Effects of Fertilizers. — Repeated reference has been 

 made to the direct and possibly indirect effects of fertilizers on the solu- 

 biUty or availabihty of other soil ingredients, on soil reaction, or on the 

 plants that constitute the mulch or the cover crop. Without doubt 

 this last mentioned influence is one of the most important, especially 

 in orchards not under clean cultivation. In either a sod- or grass-mulch 

 or a cover-crop method of culture the vegetation produced between the 

 trees is returned to the soil. Only those mineral constituents are 

 returned that are obtained from the soil, but in every case there is added 

 a considerable amount of organic matter which, through its effect on soil 

 texture and water-holding capacity as well as through the chemical effects 

 of its decomposition products, plays a very important part in the general 

 aspect of productivity; with leguminous crops the nitrogen supply is 

 actually augmented. Furthermore the mineral constituents may be so 

 changed in form by these intercrops as to be much more available to the 

 crop plants. It is generally considered that the value of these inter- 

 cultures is more or less directly proportional to the amounts of vegetation 

 produced. If this is the case any soil treatment or fertilizer which results 

 in an increased growth of the interculture may be of indirect benefit to 

 the tree. As a rule these crop plants grown between the trees are greatly 

 helped by apphcations of nitrogen-carrying fertilizers made primarily 

 for the trees' direct and immediate use. Under such circumstances the 

 trees consequently receive a double benefit from their application, an 

 immediate benefit from such portions as they are able to absorb before 

 it leaches away or is used by the other plants and a deferred benefit 

 realized only when these plants decay. 



Phosphoric Acid. — Phosphoric acid is frequently of much indirect 

 benefit to orchard trees. Some measure of this influence may be obtained 

 from data presented in Table 74, for an orchard under the sod-mulch 

 method of management in southern Ohio. Acid phosphate alone in- 

 creased the yield of mulching material more than threefold and a so- 



218 



