no 



SOILS AND FERTILIZERS 



humus materials are precipitated and purified by wash- 

 ing, the impurities are largely removed and the mineral 

 elements which are chemically united with and form a 

 part of the humus can then be determined. Analyses 

 of eight samples of purified humus ash, from produc- 

 tive prairie soils, gave the following average : 9 



PER CENT 



Ash (precipitated humus) . 



Composition of ash : 

 Silica . 

 Potash, K 2 O . 

 Soda, Na 2 O . 

 Lime, CaO 

 Magnesia, MgO 

 Ferric oxide, Fe 2 O y . 

 Alumina, A1 2 O S 

 Phosphoric acid, P 2 O >5 

 Sulphuric acid, SO 3 

 Carbonic acid, CO 2 



12.24 



61.97 

 7.20 



8.13 

 0.09 

 0.36 

 3.12 



3-48 



12.37 



0.98 



1.64 



118. Amount of Plant Food in Humate Forms. - - In a 

 prairie soil containing 3.5 per cent of humus there are 

 present 100,000 pounds of humus per acre. Combined 

 with this humus are from 500 to 1500 pounds each of 

 phosphoric acid and potash. Similar soils which have 

 been under long cultivation without the restoration of 

 any humus, contain from 300 to 500 pounds each of 

 humic potash and phosphoric acid. 9 A decline in crop- 

 producing power has in many cases been brought 



