Oct. 15, 1919 



Rate of Absorption of Soil Constituents 



61 



(optimum) water content. This loss of water points to abrupt changes 

 in the character of the internal activities of the plant, in complete 

 accord with the vegetative changes to which attention has been called. 

 Absorption by the pIvANT. — (Fig. 3-8.) The expedient we have 

 adopted of plotting the various elements on an enlarged scale brings 

 out important differences in their behavior. Potassium and nitrogen, 

 both in magnitude and in rate of absorption by the plant at all stages, 

 are more nearly proportional to the total growth and water content of 

 the plant than to that of the dry matter, while the reverse is true of 

 calcium, magnesium, and phosphorus. 



Vkeki 



Ji^G. 4. — Relation of growth of barley to absorption of potassium, nitrogen, phosphate, calcium, and 

 magnesium, for entire plant except roots. To emphasize the comparative differences in absorption 

 of these elements, the quantities actually found have been multiplied by 250. Experiment of 191 7. 



During the first period of growth, ending eight and nine weeks from 

 planting, the increase of potassium and nitrogen appears to conform 

 very closely to the gain in total weight and water content of the plant. 

 At the inception of the second growth period the interesting fact is 

 developed that both of these elements diminish, apparently indicating 

 a movement from the plant to the soil. 



The increase of calcium, magnesium, and phosphorus closely parallels 

 the formation of dry matter in both experiments up to eight and nine 

 weeks, respectively, after which these elements lag behind. In the 

 1 91 7 experiment a slight loss of calcium appears to take place between 

 the ninth and eleventh weeks. The variation of the calcium in the 



