262 Bulletin 275. 



The data show a loss of all of the determined constituents in the un- 

 steamed soils on which a crop was grown, indicating that the plants 

 used plant food more rapidly than it became available, as there was a 

 good supply in a soluble form at time of planting. The increase in the 

 percentage of inorganic matter in both unsteamed soils shows that the 

 organic matter disappeared more rapidly than the inorganic. 



In both of the steamed soils there was more total soluble matter in 

 the cropped soils than in the uncropped ones. The effect of plant 

 growth was unmistakably to retard the absorption of the soluble matter 

 by the soil. The absorption of organic matter was retarded to a greater 

 extent than was that of the inorganic matter. The absorption of in- 

 organic salts by the plant would account for this in part at least. 



The other determined constituents of the soluble matter are all less 

 in the soils growing plants, with the exception of the nitrates in Soil 2, 

 in which the amount is slightly greater in the cropped soil. 



As nitrification is practically non-existent in these soils for at least 

 three months after they are steamed, as shown by all of our analyses, 

 it is evident that the plants grown for that period on the steamed soils 

 have secured almost no nitrogen from nitrates. There is present a 

 nitrogen supply in the form of ammonia, part of which is in a water- 

 soluble condition. This, doubtless, has been used by the plant in de- 

 fault of the nitrates, as indicated by the entire exhaustion of the water- 

 soluble ammonia in steamed Soil No. 2.* 



It may be stated that the only way in which any of the data collected 

 by these experiments could be interpreted as indicating the relative 

 productiveness of the soils used is in the time required to recover from 

 the effects of steaming. In this respect they show partial but not entire 

 agreement. Soils i, 2 and 5 recovered in the order of their produc- 

 tiveness. Soil 6 was the first to recover and is for many crops, as for 

 example maize, the most productive soil, but for wheat (the crop used 

 in these experiments) it is not equal to Soil i . While it is likely that the 

 time required to recover from steaming, as shown by the growth of 

 plants on the steamed soil, is associated with some properties possessed 

 by soil under natural conditions, there are so many factors affecting 

 soil productiveness that it is hardly probable that soils of widely dif- 

 ferent texture or composition could be compared in this way. Never- 

 theless it does seem to throw some light on certain fundamental dif- 

 ferences in closely related soils. 



*NoTE. — This has already been noted by the writers in a paper read before the 

 Seventh International Congress of Applied Chemistry in London, Eng., June 2, 

 1909, and by Russell & Hutchinson in the Jour, of Agr. Sci., October, 1909. 



