174 - *••' , '*.• : :A- t;./-GUST.vFSON 



Warington (k)2)'(v<)rtc&igwitli i^oUs l^>at Jiatl been dried at SS'C. for 8 hours found that 

 the first 150 cc. of extract from 7 pounds of dry powdered soil, contained all the chlorides and 

 98.8 per cent of the nitrates. He states that, if the soil were wet, a much greater volume of 

 water would be required to leach out all the chlorides and nitrates as it would be necessary 

 to displace all the water present in the soil. He noted that oven-drjang caused a reduc- 

 tion in quantity of nitrates, that the decrease was not so great when the soil was dried slowly 

 and that, when air-dried at 10°C., there was an increase in nitrates. 



Frank (24) extracted 30 gm. of soil with 2 liters of distilled water, comparing unheated, 

 air-dry soil with the same heated in an autoclave at 100°C. Heating increased the total 

 soluble matter in sand 50 per cent and in the swamp soil over 150 per cent. The soluble 

 organic matter was almost trebled in each case. Larger crops of oats and yellow lupines 

 were produced on the heated soils. 



Liebscher (60) found that heating soil with steam increased the solubility of phosphorus 

 and nitrogen compounds. 



Schmoeger (88) heated moor soil at 150 to 160°C. for 10 hours, with the result that the 

 phosphorus soluble in hydrochloric acid was doubled. 



Deherain and Demoussy (18) heated two soils in an autoclave at 120°C. for 1 hour. When 

 these heated soils were inoculated with fresh soil, they produced more nitrate nitrogen and 

 ammonia than did the original soils. 



Pfeifler and Franke (73) heated soil under a pressure of 1 atmosphere for 3 hours. The 

 soil so treated produced a larger crop of mustard than the unheated soil and it contained a 

 higher percentage of nitrogen. 



On heating a garden soil in an oven at 100°C., on 3 successive days, Richter (82) found 

 that the amount of water-soluble organic matter trebled, and the total soluble matter almost 

 doubled. 



Tacke (100) showed that a fresh swamp soil contained very little water-soluble phos- 

 phorus, and drying at 70 to 80°C. rendered more than half of the total phosphorus soluble 

 in water. 



Tacke and Immendorf (101) found the solubility of phosphorus and potassium in some 

 swamp soils was increased by drying at 80°C. In another experiment they found heating at 

 100 and 180°C. doubled and trebled, respectively, the amount of water-soluble phosphorus. 



Stone and Smith (99) report that heating soil improves the color and causes an accelera- 

 tion of growth of lettuce, cucumbers and tomatoes and that saprophitic fungi not found in 

 unheated soil grew profusely on heated soil, indicating a change in the organic matter. 



Kriiger and Schneidewind (58) showed definitely that soluble nitrogen and phosphorus was 

 greatly increased by heating. On both unmanured soil and that supplied with sodium 

 nitrate, the growth of mustard was nearly doubled by heating the soil before planting, 



Deitrich( 19) heated garden soil and secured increased crops; but, curiously enough, 

 pasture soils did not respond in the same way. 



Whitney and Cameron (103) found that air-dried soils, in general, had more soluble 

 phosphoric acid, nitric acid, calcium and potassium than fresh soils, and that with few excep- 

 tions oven-dried soils had still greater quantities of these materials in soluble form. Nitric 

 acid was most variable. 



Card and Blake (9) report in each of two trials, a decrease in yield of lettuce due to sofl 

 sterilization, while in one trial radishes gave an increase where nitrate of soda was added to 

 sterilized soil. 



Hassenbaiimer, Coppenratli, and Konig (29) report that the solubility of inorganic con- 

 stituents was increased when 250 gm. of soil and 3 liters of water were heated together under 

 a pressure of 3 atmospheres for 3 hours. 



King (45) reviewed fully the recorded experimental work on water extracts of soils and 

 extraction with dilute acids. These reports date back to the work of Grouven in 1858 and 

 include that of Wunder and Eichhorn, 1860, Peters, 1860, Jarriges, 1861-1862, Hoffman, 

 1863, Schulze, 1864, and Ilayden, 1865. Nearly all of these investigators report potash, 



