488 Journal of Agricultural Research voi. xv. No. 9 



In the control solutions, a rough idea of the growth that can be made 

 on the reserve potassium stored in the seeds is shown in the first line, in 

 which sand and a nutrient solution containing no potassium were present. 

 In the second line the development made in the complete Shive culture 

 solution gives what should be a maximum result. It is but fair to point 

 out that in working out this formula Shive used wheat, for which it 

 was the most favorable combination he obtained. It is quite possible 

 that red clover might prosper better in a somewhat different combination. 

 Since, however, no carefully worked out data, such as Shive has given 

 for wheat, were known for clover, it was decided to use the same solution 

 for both plants in the belief that this same solution would be favorable, 

 though perhaps not the most favorable that might be found. 



As a general outstanding feature of this series it will be noted that 

 growth decreases as concentration increases. This seems to indicate that 

 the concentrations lie between the maximum and the toxic, contrasting 

 sharply, as will be seen, with the slowly soluble marls and greensands. 

 A number of cases seem to call for comment. 



For both the potassium-nitrate and potassium-phosphate series it 

 seems likely that the minimum concentration of 88.6 pounds of potassium 

 per acre is the most favorable one offered for wheat, the increase in 

 quantity of salt being accompanied by a decreasing growth. In the case 

 of the clover 433.2 pounds of potassium, offered as potassium phosphate, 

 is a little more favorable than 88.6 pounds, indicating that neither of 

 these quantities is injuriously high. 



It may be noted that in all nitrate cultures except the most concen- 

 trated the growth of the Shive control is equaled or exceeded, whereas in 

 no clover culture was the control quite equaled. 



In the case of potassium chlorid and potassium sulphate a somewhat 

 different result appears. In no culture with either wheat or clover con- 

 taining either salt was the growth made in the Shive control equaled. 

 A further point of interest lies in the fact that the maximum growth of 

 wheat was found in higher concentrations, 866.4 pounds of potassium 

 in potassium chlorid and 433.2 pounds in potassium sulphate, indicating 

 that the most favorable concentration lies somewhere in the range here 

 covered and that reduced growth in the less concentrated members of 

 the series is not due to harmful concentration of salts. In the case of 

 the clover the best result with potassium chlorid is seen in the greatest 

 dilution, and a more favorable result still might have been gained had a 

 still smaller quantity of this salt been used. In the case of potassium sul- 

 phate the best result is seen in higher concentration, 866.4 pounds per 

 acre. 



Since the two latter salts have a greater commercial significance in 

 coimection with the commercial potassium supply, it is of especial im- 

 portance to note the results following their use. 



