24 



FERTILIZERS 



tilizer but not necessarily the agricultural value. 

 (67). 



Most authorities claim as great a value for the 

 insoluble form, in finely ground materials, provided 

 there is a normal or plentiful supply of humus in the 

 soil. (40). 



REVERSION. 



35. It must be remembered that in using acidu- 

 lated goods (bone or rocks) if an abundance of lime 

 be present in the soil, the soluble form of phosphoric 

 acid unites chemically with the lime and is made 

 again insoluble as if it had never been treated. Iron 

 and alumina, and other bases, produce the same 

 effect on acidulated phosphates. The reversion, how- 

 ever, depends on the amount of acid used by the 

 manufacturer and the quantity of lime, iron, etc., in 

 the soil. (77). 



"FIXING" POWER OF SOILS. 



36. The following table will show the "fixing" 

 power of a lime soil : 



PHOSPHORIC ACID "FIXED" BY SOIL. 



Kind of Soil. 



Grains. 



Grains of Soluble 

 Phosphoric Acid 

 Uted. 



Phosphoric Acid 

 retained by the 

 Soil. 



Deep Red\ 

 Loam j 



Grains. 



5250 



After 



24 hours 

 8 days 



26 days 



24 hours 

 8 days 



26 days 



Even a rich peat soil, high in either lime or iron, 

 will "fix" or hold phosphoric acid in an insoluble 

 condition, as shown in 49. 



Lime soil 10500 



40.67 



81.17 



24.29 

 31.49 

 38.23 

 72.81 

 80.31 

 81.17 



