66 



Journal of Agricultural Research voi. xvin, No. 



place. For this purpose we present the data on the periodic water 

 extractions (i part of soil to 5 parts of water by weight) of the soil of 

 the 1 91 7 experiment. 



Table V. — Water extractions of fine sandy loam soil (15) 

 [Expressed as parts per million of soil] 



4 NITRATE (NO3) 



SCALE ^S ' 



Fig. 9. — Absorption of nitrogen by barley, expressed as the nitrate (NO3) equivalent and computed to parts 



per million of soil. 



In order to bring out more clearly certain apparent relations between 

 the water extracts and the amounts of soil solutes taken up by the plant, 

 we have computed the plant constituents in terms of the corresponding 

 ions of the soil and expressed these in terms of parts per million of the 

 mass of soil upon which the plants were grown and in which the various 

 constituents must have originated. The data from the soils are expressed 

 in similar terms (fig. 9-13). It should be pointed out at once that 

 the soil data are not to be too literally interpreted. For instance, it is 

 clear that we can not expect that the gains and losses of a given con- 



