Oct. IS, I9I9 Rate of Absorption of Soil Constituents 65 



both barley and wheat. The losses noted by them were, however, in 

 every instance final and not succeeded by a further period of absorption 

 as in our experiments. 



The behavior of maize as reported by Hornberger (4) presents some 

 very interesting analogies to the facts brought out in the present work. 

 It is true that the author quoted shows no absolute losses of constituents 

 derived from the soil prior to the ripening stage. He does show, however, 

 that immediately after the period of maximum absorption and when the 

 heads are beginning to form there is an abrupt slowing down of the rate 

 of absorption of • practically all elements. This again is followed by a 

 period of rapid absorption, which in turn is succeeded by the ripening 

 period in which there are absolute losses of all constituents except 

 phosphorus. 



Jones and Huston (5), also working with maize, showed a period of 

 very rapid absorption of potassium at the eighth week from germination, 

 just prior to the beginning of head formation, followed by a long period 

 of slow absorption, succeeded in turn by a rapid absorption during the 

 sixteenth week, and finally by an absolute loss in the seventeenth. The 

 peak absorptions for nitrogen in the same plants were during the eighth 

 and sixteenth weeks, with an intermediate period of decreased absorption. 



On the contrary, the field experiments of Wilfarth, Romer, and 

 Wimmer (9) show no losses of potassium and nitrogen at any stage in the 

 growth of potatoes nor very striking changes in the rate of absorption 

 of these elements. 



The behavior of maize and barley as contrasted with that of potatoes 

 would seem to indicate that the tendency toward a materially delayed 

 rate of absorption, or absolute loss of constituents at an early stage of 

 development, is probably a characteristic of types of plants whose growth 

 cycle includes a period of extreme differentiation in constructive metab- 

 olism. We may, for instance, expect to find such a tendency in other 

 cereal crops and in fruit trees at the period of fruit formation. On the 

 other hand, the discrepancies in the behavior of barley, as shown by im- 

 portant differences of our results from those of Wilfarth, Romer, and 

 Wimmer, indicate that other factors also have an important influence. 



SOIL RELATIONS 



The abrupt change in the water content and the loss of certain soil 

 constituents from the barley plant at the height of the growing season 

 have no very obvious relation to concurrent changes in external condi- 

 tions. We can hardly conceive, how^ever, that changes of this kind and 

 magnitude are conditioned entirely by the specific peculiarities of the 

 plants in which they are observed, even though they are ^ot to be found 

 in other types. It is pertinent to inquire more particularly, therefore, 

 into the condition of the soil at the time these important changes take 



