20 CIRCULAR NO. 109, BUREAU OP PLANT INDUSTRY. 



The figures for moisture equivalent in Table II show some irregu- 

 larities, doubtless attributable to errors in the method of determina- 

 tion. Such errors could be eliminated only by making a larger 

 number of determinations for each soil. The contents of water 

 available for growth in the whole series of mixtures ranged from 

 9.8 to 10.9 per cent, but these differences were hardly of sufficient 

 magnitude to affect the results of the experiment. 



Chemical analyses of extracts from each of these soil mixtures 

 showed, for most components, an increase from mixture to mixture 

 corresponding to the increase of total soluble matter. A note- 

 worthy exception was HC0 3 , of which practically the same quan- 

 tity was found in all. The mixtures having the lowest total salt 

 content had the highest content of calcium and magnesium, as would 

 be expected from the fact that larger amounts of these bases existed 

 in stock soil No. 78 than in stock soil No. 79. 



PLANTS USED AND CONDITIONS OF GROWTH. 



Kubanka wheat (Grain Investigations No. 1440) was used, the 

 stock having been the same as that employed by Messrs. Briggs 

 and Shantz in their investigations of the wilting coefficient. 



The seeds were placed in moist blotters on April 3; three days 

 later they were in proper condition for planting. While no special 

 effort was made to select seedlings of the same size, none were planted 

 winch did not have the pluinule and the rootlets extruded. All 

 seedlings planted appeared to be perfectly healthy and had no roots 

 much longer than 1 inch. The seedlings were planted in straight- 

 walled, cylindrical drinking glasses, each holding about 250 grams 

 of soil. Five seeds were planted in each glass and there were six 

 glasses of each soil mixture, making a total of 30 seedlings planted 

 in each soil mixture used in the experiment. 



In planting, most of the soil required was placed in the glass 

 and was shaken down by tapping the bottom of the glass on the 

 table. The seedlings, taken directly from the moist blotters, were 

 laid on the loose surface of the soil; the glass was then filled evenly 

 to the brim with the remaining soil, so as to completely cover the 

 seedlings, and the soil was pressed down firmly, first around the 

 edges and then in the center. 



The surface was then sealed over with- a melted mixture of 80 

 per cent of paraffin and 20 per cent of petrolatum, as described in a 

 previous publication of this bureau. 1 



In order to equalize as far as possible the temperature of the 

 soil in the glasses and to prevent condensation, which would result 

 in an unequal distribution of the water and salts in different portions 



i Bulletin 230, pp. 10-14, 

 [Cir. 109] 



