146 



SCIENCE. 



[N. S. Vol. XXII. No. 553. 



SPECIAL ARTICLES. 



EFFECT OF THE COINTCENTRATION OF THE NU- 

 TRIENT SOLUTION UPON WHEAT CULTURES. 



The work here reported was undertaken to 

 determine the concentration of a nutrient so- 

 lution which is best adapted to the growth of 

 wheat, and further to find out whether or not 

 an increase in concentration alone may ac- 

 celerate growth aside from changes in the 

 nutrient value of the solution. The nutrient 

 solution used contained calcium sulphate, 

 magnesium phosphate, potassium carbonate, 

 sodium nitrate and ammonium chloride in 

 chemically equivalent amounts. It was made 

 up to concentrations of 10, 70, 150, 745 and 

 1,545 parts per million, respectively. To each 

 solution 5 parts per million of ferric chloride 

 were added, thus making the concentrations 

 of total salts 15, 75, 155, 750 and 1,550 parts 

 per million. In the two higher concentra- 

 tions some phosphates and carbonates of cal- 

 cium and magnesium were precipitated out, 

 but the error thus produced is too small to 

 affect the general results under consideration. 



A series of cultures of wheat seedlings was 

 grown for 28 days in these solutions, the latter 

 being changed every day. At the end of the 

 period the plants in the solution of 15 parts 

 per million were the poorest of the lot, being 

 remarkably stunted, as though suffering for 

 want of water. Those in the solution of 75 

 parts per million were consideraWy better, 

 while those in the solution of 155 parts per 

 million were unmistakably the best. Those 

 in the solution of 750 parts per million were 

 similar to those in the one of 75 parts, while 

 those in the solution of 1,550 parts per million 

 were again very poor and showed the same 

 stunting of growth as do plants growing in 

 alkali soils. 



This experiment was performed six times 

 with different growing conditions, and each 

 time the results were in the same order. The 

 general development was always in the same 

 relative order as the transpiration.* 



^ For evidence in regard to the use of transpira- 

 tion as a criterion here, see a paper about to ap- 

 pear in the Botanical Gazette, Livingston, B. E., 

 ' Relation of Transpiration to Growth in Wheat.' 



In Table I. are given the number of plants 

 used in each experiment and the relative 

 transpirations for the different cultures of the 

 six experiments, all calculated to a uniform 

 basis of 15 days each. In calculating the 

 relative transpirations, the total transpiration 

 of the culture in the weakest solution is con- 

 sidered as 100. 



Table I. 

 Data for Experiments I. to VI. 



It will be seen from the table that curves 

 of these transpirations would have maximum 

 points somewhere between 155 and 750 parts 

 per million of total solids in solution. No 

 attempt was made to determine the maximum 

 point more accurately, but by interpolation it 

 is estimated to lie in the vicinity of 300 parts 

 per million of total solids. This may be taken 

 as approximately the concentration best suited 

 to growth under the conditions of these ex- 

 periments. 



Whether the depression noticed in the lower 

 concentrations of the above series is due to a 

 scarcity of one or more of the nutritive ele- 

 ments or to the low concentration of the solu- 

 tion as a whole is considered in the following 

 experiments. In experiment VII. to each of 

 four portions of the solution above described, 

 containing 15 parts per million of total salts, 

 were added 140 parts per million of one of 

 the salts occurring in the original solution, a 

 different salt being used in each case. To a 

 fifth portion was added 140 parts per million 

 of a mixture of all four of these salts in 

 chemically equivalent amounts. Twenty-four 

 plants were grown in each of the five solutions 

 for thirteen days, and their growth was com- 

 pared with that of a similar culture in the 



