pared fertilizers as we buy them, give us three times as much 

 phosphoric acid as potash, just reversing the ratio. 



Let us see what the effect of this is : suppose for example, 

 that for a crop of corn we wish to furnish the soil with forty 

 pounds of potash(K20) it will require one thousand pounds of 

 a prepared fertilizer lo give this amount ; now ordinary crops 

 would have thirteen pounds of phosphoric acid (PjOg) to go 

 with forty of potash, but in our one thousand pounds of fertilizer 

 which we must apply to get forty pounds of potash, there will 

 be one hundred and twenty pounds of phosphoric acid, over 

 nine times as much as is necessary, or suppose we apply enough 

 fertilizer to provide the necessary phosphoric acid it would re- 

 quire but one hundred pounds, but in this amount we would 

 only have four pounds of potash, or i-io of the required amount. 



The average ratio of these two forms of plant food in well 

 preserved measure is i of PgOg to 2.5 of KoO, and ashes 

 which represent the ash part of trees, we find one of phosphoric 

 acid to three of potash. Chemically then we find no support 

 for the rule so widely adopted for compounding the so-called 

 commercial fertilizers. 



I am well aware that another factor comes in here, namely, 

 the capacity of the soil for providing plant food. 



It might be true, and doubtless is in some, perhaps many, 

 localities that the soils yearly liberate more potash than phos- 

 phoric acid, and thfere are cases where phosphoric acid alone will 

 give bountiful crops, thus showing that in such soils there is 

 enough available potash, but in many cases it has been assum- 

 ed that phosphoric acid is the regulating substance, when exper- 

 iments carefully conducted have proven that it is potash. This 

 leads us to inquire whether there is any method by which we 

 may satisfy ourselves of the requirements of our particular soils. 



The answer must be, field experiments ! and the method 

 must be based upon the use of fertilizing materials which con- 

 tain the three forms of deficient plant food'vcs. seperate substances, 

 so that we may test them singly and in a variety of combina- 

 tions, having nitrogen, phosphoric acid and potash in varying 

 proportions. These tests when well conducted and when pro- 

 perly duplicated and made by the side of plots having no fer- 

 tilizer, are capable of giving a great deal of practical infor- 

 mation. 



II 



