EFFECT OF DRYING SOILS ON WATER-SOLUBLE CONSTITUENTS 179 



Stone and associates (97) report greatly increased bacterial develoi)ment in extracts from 

 soils rich in organic matter, which had been heated previously, while it was retarded in 

 extracts from [)oor soils. They consider the chemical factor most important in accounting 

 for the elTect of heating. 



Leather (59) in studying the nitrate content of soils, at Tusa states that drying in the 

 sun effected an increase as great as 400 per cent. 



Seaver and Clark (93) found an increase in total soluble solids, organic matter, inorganic 

 matter and total nitrogen, in soil when heated at 90°C. and still greater increases at 120, 

 150 and 170°C. Plant growth was accelerated by heating at 90 and 120°C. but retarded 

 at the higher temperatures, which, however, increased the growth of fungi. They noted that 

 heating increased acidity and suggest that this may account for the better growth of plants 

 such as blueberry on " burned over" soils. 



Lyon and Bizzell (63) have shown that when a soil has been heated to complete sterility 

 by steaming and subsequently maintained at a moisture content of 25 per cent of its dry 

 weight, the total solids decrease rapidly, as shown in table B. 



TABLE B 

 Effect of standing on the water-soluble constituents of heated soils 



Soil 1 , Dunkirk clay loam 



Freshly heated 



5 weeks after heating 



14 weeks after heating 



Soil 2, Volusia silt loam 



Freshly heated 



5 weeks after heating 



14 weeks after heating 



Soil 3, Dunkirk clay loam with extra organic matter 



Freshly heated 



5 weeks after heating 



10 weeks after heating 



19 week safter heating 



PARTS PER MILLION OF DRY SOIL 



Total solids 



3334 

 2161 

 1740 



3020 

 2098 

 1801 



7194 

 3288 

 2719 

 2173 



Nitrates 



64.9 

 61.9 

 69.0 



175.1 

 178.2 

 191.5 



234.0 

 306.0 

 282.5 

 160.0 



Ammonia 

 nitrogen 



33.0 

 41.5 

 51.0 



33.5 

 36.5 

 45.0 



84.1 



79.5 



96.0 



111.0 



The nitrates have been affected but slightly, except in Dunkirk clay loam with extra 

 organic matter, where there was an increase during first 5 weeks, but a rapid decline later, 

 and, in general, an increase in ammonia nitrogen. 



In another experiment, freshly heated soil had 1010 parts per million of total soluble solids 

 and 246 parts per million of inorganic, while after 3 months the corresponding amounts are 

 590 parts per million of total soluble solids, and 126 parts per million of inorganic. When 

 aerated during the 3-month period, there is a further decrease to 434 and 120 parts per million, 

 respectively. 



Russell and Petherbridge (87) state that plants grown on soils heated at 100°C., in com- 

 parison with unheated soils, have larger leaves of deeper green color and stouter stems, they 

 flower earlier and more abundantly, the fruiting is more prolific, and they contain a higher 

 percentage of nitrogen and sometimes phosphoric acid in their dry matter. 



Konig, Hasenbaumer and Glenk (56) heated soil at 95°C. in a vacuum, which, in most 

 cases contained markedly more water-soluble organic matter as well as total soluble solids 



