CHAPTER IX 

 FERTILIZERS AND MANURES FOR THE ORCHARD 



The supplying of artificial plant-food materials to fruit- 

 trees introduces a problem on which there is some differ- 

 ence of opinion among authorities. However, much exper- 

 imental evidence is available and in many sections the 

 results of proper fertilization can be predicted with consider- 

 able certainty. The original conceptions of this problem 

 were based largely on the findings of the chemists, for it 

 seemed logical to conclude that the elements found in the 

 plant and its products in greatest amounts were the ones to 

 return to the soil in like proportions. This doctrine led the 

 horticulturists somewhat astray for a time, for valuable as 

 it is, such a theory does not take into consideration the 

 mechanical or physical condition of the soil or the impor- 

 tant role of micro-organisms to soil fertility and the asso- 

 ciated factors of heat, moisture, and soil sanitation. Obvi- 

 ouslj^, the amount of artificial "feeding" that trees will 

 require depends basicly on the original or native fertility 

 of the soil together with its physical condition and mois- 

 ture-content. Hence a wide variation in the practical re- 

 sults of fertilizing orchards is to be anticipated, especially 

 in the relative length of time that will be necessary to pro- 

 duce like results. The problem should be studied from the 

 standpoint of several generations of trees on the same land, 

 yet the longest experiments have been in p-rogress scarcely 

 a quarter of a century. 



148. Criticisms of orchard experiments. — The field 

 tests of orchard fertilizing have been seriously criticised 

 179 



