104 FERTILIZERS 



that it requires the application of lioth nitrogen and potash at one 

 time, and this may not always be desirable. 



We ought to add to the forms of nitrogen " cyanamid, " the 

 newly developed combination of lime with atmospheric nitrogen. 

 It has not yet been in use long enough for its (lualities to be 

 tested, but it has this to recommend it, that it is relatively cheap. 



Among- phosplioric add fertilizers are bone meal, rock phos- 

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

 tilizer 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 w^th sulfuric acid. This takes 

 up a part of the lime, rendering the phosphoric acid more avail- 

 able. The superphosphates are especially 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 dis- 

 solving 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 o-ne 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. 



