Oct. 15, 1919 



Relation of Nutrient Medivtni to Plant Absorption 107 



remained in each jar after changing solutions. There were three to five 

 plants in each jar. 



Lyon and Bizzell (25) found that wheat seedlings gave increased 

 growth with increasing concentrations from 83 to 4,525 parts per million 

 total salts. They used 1 20-cc. bottles in the water-culture series. 



Bouyoucos (2) also states that increased yields occur with increasing 

 concentrations up to 4,500 parts per million. In his experiments 1 20-cc. 

 bottles were used with four plants in each bottle. The period of growth 

 was three or four weeks. Solutions were changed once each week. 



Other experiments similar to these have been carried out, but these 

 citations will suffice for the present purpose. The point which it is 

 desired to emphasize now has been clearly stated previously by Stiles (44) 

 in his criticisms of Brenchley's conclusions, but these criticisms have 

 apparently been neglected in later work. In all of the above-mentioned 

 experiments no sufficient distinction has been made between supply of 

 nutrients and concentration of nutrients. If we compare the quantities 

 of nutrients per plant available between changes of solutions with quan- 

 tities of nutrients actually absorbed, as shown by data given in this 

 article, we must conclude that in many cases the total supply may have 

 fallen far short of the requirements, so that the solutions were constantly 

 undergoing a great change, due to absorption. Moreover the relative 

 changes may be very different in different solutions. For example, in 

 those solutions in which only one-tenth of the total concentration was 

 due to Ca(N03)2 the NO3 supply conceivably may have been entirely 

 insufficient, whereas in solutions with a higher ratio of Ca(N03)2 the 

 supply of NO3 may not have- been exhausted. If all the ions were not 

 absorbed in the same proportion, the result woHild be a continuously va- 

 rying solution, with regard to both total concentration and ionic ratios. 

 Without knowing precisely the nature of these changes it would seem diffi- 

 cult to interpret the results in terms of ionic ratios. Perhaps it is sig- 

 nificant that in many cases the areas of low yields in the triangular dia- 

 grams have been found near the line of least Ca(N03)2. NO3 is the 

 element of greatest importance quantitatively. In the following table 

 some estimates are made of the total volume of solution per plant nec- 

 essary to furnish total quantities of nutrients equal to those absorbed by 

 the plant, under conditions permitting good yields of crop. 



As another basis of calculation we may use the data for the sand cul- 

 tures of series i. It can hardly be denied in this case that a lack of 

 total NO3, K, PO4 were limiting factors, and that the total yield per 

 plant was greatly reduced by reason of these deficiencies. Yet even 

 under these conditions the total quantities of nutrients found in each 

 plant were 0.15 gm. K, 0.15 gm. PO4, and 0.30 gm. N calculated to NO3. 

 To supply these quantities of NO3 would require i liter per plant of a 

 nutrient solution containing 300 parts per million of NO3 or 20 changes 



