258 



Bulletin 275. 



in the form of ammonium compounds, which as we shall attempt to 

 show later must be largely used by plants on sterilized soils. The 

 total matter in solution is large, and especially the organic portion. 



The transpirations and weights of the plants given in these extracts 

 for four weeks are given in Table VI. 



Table V. — Extracts of Sterilized and Unsterilized Soils and Same Diluted 



Preparation of solution from 

 Soil I. 



1. Extract of sterilized soil, i part 



water, i part soil 



2. Extract of unsterilized soil, i part 



water, i part soil 



3. Extract i diluted, i part extract 



3 parts water 



4. Extract 2 diluted, i part extract 



3 parts water 



Substances in solution p. p. m. 



NO3 



16.2 



65.0 



4.0 



16.2 



PO4 



150 

 2 .0 



3-7 

 0.5 



9.0 



4-3 

 2 . 2 



I . I 



Solids. 



I 700 

 158 

 425 



39-5 



Inor- 



254 

 61 



64 



15 



Or- 

 ganic. 



1446 



97 



362 



24 



Table VI. — Crops of Wheat Seedlings Grown in Extracts from Sterilized 

 and Unsterilized Soils, and in these Extracts Diluted 



Transpi- 

 ration 

 grams. 



1. Extract of sterilized soil, i part water, i 



part soil 



2. Extract of unsterilized soil, i part water, i 



part soil 



3. Extract i diluted, i part extract, 3 parts 



water 



4. Extract 2 diluted, i jiart extract, 3 parts 



water 



61,3 



152.9 



89.6 



1 1 1 . 5 



Dry Wt. 

 of crop 

 grams. 



,1918 



2599 



1492 



, 1076 



Green Wt. 

 of crop 

 grams. 



•75 

 1 . 21 



•63 

 ■52 



It is quite apparent that the extract of the sterilized soil was not 

 a favorable medium for the growth of the seedlings. The transpiration, 

 dry weight of crop and green weight of crop were all less than in the 

 plants grown in the extract of the unsterilized soil. The difficulty 

 may have been due to the density of the solutions, but an ordinary, 

 well-balanced, nutrient solution of that strength will produce a better 

 growth than a less concentrated one. The large quantity of organic 



