Oct. 15, 1919 Relation of Nutrient Medium to Plant Absorption 



79 



In this first series of sand-culture experiments 3-gallon jars were used, 

 with seven plants in each jar. Nutrient solutions were added at the 

 beginning to make a moisture content of about 14 to 15 per cent. Later, 

 as transpiration occurred, more solution was added to each jar to make 

 up for water lost. The total quantity of nutrient solution applied to 

 each jar was approximately 5,000 cc. The composition of the nutrient 

 solution was based on a general formula given in texts on plant physi- 

 ology and was as follows : 



NO3 

 K. .. 

 Ca.. 

 PO4. 



p. p.m. 

 • ■ ■ 163 

 ... 85 



••• 43 

 • • ■ 163 



Mg. 

 Na. 

 CI. 

 VSO4 



P. p. m. 

 •■• 34 

 ... 68 



105 

 140 



Concentrations were in the proportions of 200, 400, 800, and 1,600 

 parts per million of total salts. For each concentration 7 jars were 

 used, with a total of 49 plants. The plants were cut when the grain 

 was in the "hard dough" stage, and separation of heads and straw was 

 made. The roots were recovered from the dried sand and freed as far 

 as possible from adhering sand. Analyses were made on composite 

 samples of the dried material, separating the plant into heads, straw, and 

 roots. The determinations on the roots were calculated to a silica-free 

 basis. In the following table are presented the data for yields in terms 

 of dry weights, with percentages and total quantities of various elements. 



TabIvE I. — Weight and composition of barley 



SAND CULTURES, SERIES I 



a Barley grown in adjacent soil tanks at the same time gave from two to five times the yield from best 

 ind culture. 



sand culture. 

 b Calculations made on silica-free basis 



After the first few weeks very marked differences were noted in the 

 appearance of the cultures, and with each successively higher concentra- 

 tion the growth was apparently nearly doubled. These general obser- 

 vations were corroborated by the final yields. 



