104 FERTILIZERS 



Among phosphoric acid fertilizers are bone meal, rock phos- 

 phate, and basic slag. Bone meal is an old favorite among 

 fertilizer users. Within recent years basic slag, or Thomas 

 phosphate powder, a by-product produced in the manufacture 

 of steel, has been used a great deal by orchard men. It has the 

 advantage of carrying a considerable percentage of lime, but 

 this has been reduced recently by changes in the manufacturing 

 process. Acid phosphates or superphosphates are made from 

 both bone and rock phosphates by treating them with sulfuric 

 acid. This takes up a part of the lime, rendering the phosphoric 

 acid more available. The superphosphates are specially useful 

 with young trees where the roots are extending rapidly. They 

 are the only form in which phosphoric acid should be applied 

 to orchards in sod, since in such orchards one must depend on 

 the fertilizer dissolving and being washed into the soil. 



Two forms of potash are in common use, the muriate and the 

 sulfate, the latter coming in both high and low grade. Probably 

 the muriate is more generally used than any other form at the 

 present time. It has the great advantage of being cheaper than 

 sulfate, but it also has a tendency to render the soil acid by 

 taking out the lime. This latter tendency can be overcome of 

 course by adding lime, but that means one more thing to look 

 after. The low grade sulfate carries about half the amount of 

 actual potash that the high grade does, but it also has a large 

 amount of magnesia which many consider an advantage. There 

 is the same objection to it that there is to any low grade fer- 

 tilizer, viz., that it costs more per unit of plant food to transport 

 it and to handle it in the orchard. It is perhaps best to use the 

 high grade sulfate altogether, until such time as it may be 

 shown that some other form is better. 



Fertilizer Formulas. It may perhaps be helpful to include 

 in this chapter a few fertilizer formulas which are actually in use 

 by some of our leading orchard men. 



Mr. George A. Drew, of Greenwich, Connecticut, has the fol- 

 lowing formula which is used at the rate of 400 pounds to 800 

 pounds per acre according to the condition of the soil. His 

 trees are cultivated. 



