88 FERTILITY AND FERTILIZER HINTS 



How to Make Superphosphate at Home. — Sometimes farmers 

 live far away from places where fertilizers may be purchased 

 and should such farmers save the bones that accumulate on the 

 farm, superphosphate may be made at home. The process may 

 be conducted as follows : Break up the bones in as small pieces 

 as possible and add one-third their weight of water to them in a 

 long wooden trough lined with sheet lead or with a thick coat- 

 ing of pitch ; the lead is better. To the bones and water, add 

 very slowly sulphuric acid (oil of vitriol). This acid must be 

 added very slowly as great heat is evolved on the addition of sul- 

 phuric acid to water. The amount of acid to add depends upon 

 its strength or concentration. About one-third the weight of 

 the bones of strong white sulphuric acid or one-half of the brown 

 sulphuric acid should suffice. The whole mass should be thor- 

 oughly mixed with a wooden shovel, allowed to stand for an hour 

 and removed to some dry place and stored for two months when 

 it will be ready for the land. If sulphuric acid gets on your 

 clothes it will ruin them and it will burn the skin wherever it 

 touches it.* 



Amount of Phosphoric Acid in Soils. — The phosphoric acid in 

 soils is generally found in largest amounts in the surface soil and 

 is usually derived from the disintegration of rocks. It is often 

 deficient and many soils show only traces of phosphoric acid. 

 Even fertile soils only contain small amounts of this constituent. 

 Soils average from traces to 0.25 per cent, of phosphoric acid. 

 We may figure than an average soil contains about 3,500 to 4,000 

 pounds phosphoric acid per acre. Only a small amount of this 

 is available. Some soils may contain larger quantities of phos- 

 phoric acid but the poor condition of the soil keeps this locked up 

 so that plants cannot utilize it. Organic matter, lime and good 

 tillage help to increase the available supply of phosphoric acid. 



Fixation of Phosphoric Acid. — When soluble phosphoric acid 

 is added to soil it becomes fixed and does not wash out readily. 

 It is generally supposed that soluble phosphoric acid from fer- 

 tilizers becomes readily distributed and unites with the minerals 

 forming compounds insoluble in water ; the phosphoric acid in 

 «;oluble phosphoric acid is in a very finely divided state and the 



