216 



will tletermine the growth and the production but that i» 

 not so. You must remember that the growing process is a 

 gradual process, that there are certain checks to this grad- 

 ual process, that there may be relatively rapid growth 

 through a period of ten days or two weeks, depending on 

 the moisture and temperature relations. You will also re- 

 member that the soil machinery on which you depend for 

 making plant food available is influenced directly by mois- 

 ture and temperature conditions. If you could sterilize 

 your soil by means of heat or chemicals, the production of 

 available nitrogen comi)ounds would cease, and no matte^ 

 how great an amount of nitrogen the soil might contain, it 

 v.'ould be of no use to crops unless there were bacteria and 

 other invisible plants active in decomposing the vegetable 

 and other compounds in the soil, so that out of these com- 

 ])ounds simple nitrogenous materials may be formed that 

 could be used l)y the trees or other crops, and in so far as 

 The activities of the bacteria in the soil are cheeked, the 

 growth of the trees themselves is checked. In order to have, 

 then, growth that would be adequate for profitable produc- 

 tion, plant food must be produced, not in amounts merely 

 sufficient for a certain amount of growth but a greater 

 Hmount of plant food must lie furnished if there is to be 

 profitable growth. 



We often wonder, those of us who study plant food re- 

 lations, why it is that the fertilizer formulas of the most 

 jtopular fertilizers do not correspond at all with the propor- 

 tions of jilant food that the crop takes out of the land. T 

 r-^aid a fcAv rjioments ago that your apple orchard of bearing 

 t\ge may be taking out 60 pounds of nitrogen and 15 pounds 

 of phosphoric acid and, we will say, 60 pounds of potash 

 })er acre, per annum. That means -i times as much nitrogen 

 a« phosphoric acid ; f(mr times as much potash as phosphoric 

 acid. But do we, Avhen we buy fertilizer, a fruit fertilizer, 

 do we ask for, let us say, a four-one-four formula. You 

 know that we use more phosphoric acid in proportion in our 

 fertilize)' mixture than we use nitrogen or potash. Did you 



