86 Journal of Agricultural Research Voi. xvni. No. 2 



condition. Other pot experiments with soils uphold this view. When a 

 mixed fertilizer was added to the soil so as to produce, by the freezing- 

 point method, an osmotic pressure similar to that just mentioned, equally- 

 striking inhibitive effects were noted. 



The data for the total quantities and the percentages in the composi- 

 tion are very definite and confirm the conclusions drawn from series 2. 

 Again we find K and N stored in the tops, while the principal accumula- 

 tion of Ca and P is in the roots. The heads are only slightly affected in 

 their percentages. Evidently not only concentration but the period 

 during which the concentration is maintained markedly influence the 

 percentage of inorganic elements and the total quantity absorbed per 

 plant. These factors of concentration and period of maintenance of con- 

 centration in the soil solution doubtless govern the variations of the 

 plant in its content of inorganic elements under any particular climatic 

 conditions. 



WATER CULTURES, SERIES i 



Although the method of sand culture devised by McCall offers very 

 great advantages in control, it is not easily possible to determine the 

 exact composition of the solution at any given time. In order to make 

 an intensive study of the influence of the solution on the plant, and of 

 the plant on the solution, it became necessary to employ the method of 

 solution culture. The technic adopted differed from that in general 

 use in that fewer plants and larger volumes of solution were employed. 

 Observations were made at all stages of growth to maturity. The first 

 experiments were carried out in the greenhouse during the winter months, 

 and the later series were placed out of doors in good light during the spring 

 and summer months. 



The first series of experiments was planned to furnish preliminary 

 information with regard to the optimum concentration and the relation 

 of concentration to absorption and transpiration. One-liter bottles were 

 used, with 3 plants in each bottle. Solutions were changed every 

 3 days after the plants had started to make appreciable growth. 

 After 54 days the plants were cut and the dry weight determined. 

 Four concentrations of solution were tested, and for each concentration 

 there were 8 jars, or 24 plants. The composition of the solution was 

 similar to that given by Shive (jp) for his best cultures. Table V 

 summarizes the most important results obtained from this experiment. 



The data indicate that for these conditions a concentration of o.io 

 atmosphere is sub-optimum and one of 2 atmospheres super-optimum. 

 Concentrations of 0.32 and 0.85 atmospheres were equally efficient if 

 we consider the mean deviation in the yields of individual plants. The 

 greatest total transpiration occurred in solution 2. Transpiration per 

 unit of dry weight was decidedly greater in lower concentrations. 



