Oct. Ts, 1919 



Rate of Absorption of Soil ConstitiA£nts 



63 



ing of the leaves, such as those suggested by LeClerc and Breazeale (6) 

 and others, were rendered impossible by the protection of the plants 



HEADS 



TOTAL 



WATER 



DRY MATTER 



Fig. 7. — Relation of growth of barley to absorption of potassium, nitrogen, phosphate, calcium, and 

 magnesium, for stems and leaves. To emphasize the comparative differences in absorption of these 

 elements, the quantities actually found have been multiplied by 250. Experiment of 1917. 



from rain at all times. If we eliminate the rather remote possibility 

 of losses of volatile nitrogen from the leaves, which seems all the more 



improbable since potassium could 

 not be eliminated in that way, it 

 would seem that the constituents 

 lost either became localized in the 

 roots or returned to the soil. 

 Either condition would represent a 

 very important phenomenon; but 

 migration of potassium and nitrogen 

 from the plant into the soil is such 

 a complete reversal of the ordinary 

 condition that it must be in obedi- 

 ence to causative changes of con- 

 siderable magnitude, which may be 

 capable of measurement and if so 

 would presumably shed light on the 

 nutritional relations of plants and 

 soils. 



The data we have presented 

 above are conclusive only of losses 

 of nitrogen and potassium from the part of the plant growing above 

 ground, inasmuch as we did not include the roots in our study. 



Fig. 8. — Relation of growth of barley to absorption 

 of potassium, nitrogen, phosphate, calcium, aud 

 magnesium, for heads. To emphasize the com- 

 parative difTerences in absorption of these ele- 

 ments, the quantities actually found have been 

 multiplied by 250. Experiments of 1917. 



