8 o 4 
Journal of Agricultural Research 
Vol. XXIV, No. 9 - 
eter by 4 feet 4 inches deep (PI. 3, A). The bottom of each tank tapers 
toward the center, which is 6 inches deeper than the circumference. 
The center of the bottom of each tank bears a perforated brass plate, 
beneath which is attached a 4-inch elbow that connects with 2-inch 
galvanized-iron piping leading to a trench. Each tank has its individual 
drainage outlet. Crushed quartz rock was placed in the bottom of each 
tank above which is placed sand or soil, as the case may be. 
The nutrient solution employed in the present experiments was that 
used by Hoagland (5) in the culture of barley. Filtered carbon-treated 
distilled water was used whenever water was required. The stock 
solutions were made up as follows: 
Solution A. Gm. 
KNO3. 1,200 
MgS04-i-7H20. 1,800 
NaCl. 55 
H2O to give volume of 18 liters. 
Solution B. 
Ca(N03)2-|-4H20. 2, 600 
H2O to give volume of 18 liters. 
Solution C. 
KH2PO4. 900 
H2O to give volume of 18 liters. 
Solution G. 
MnS04-t-4 H2O. o. 406 
H2O to give volume of 2 liters. 
The nutrient solution was prepared by using the following amounts 
of the stock solutions: 55 cc. of solution A, 65 cc. of solution B, 30 cc. of 
solution C, and 20 cc. of solution G, made up to 10 liters with distilled 
water. 
The nutrient solution as thus made had a Pg of 5.2 and an osmotic 
pressure of 0.728 atmospheres. The composition of the nutrient solution 
was as follows: 
Parts per million. 
NO^ S'04 K Ca PO^ Mg Cl Na Fe Mn Total 
718 216 185 159 105 54 10 7 I o. I 1455 
The iron was not added to the nutrient solutions until they were ready 
to be added to the cultures. As a rule 5 to 10 parts per million of Fe 
were used in the nutrient solution, the plan being to have sufficient Fe 
present, as indicated largely by the appearance of the tree. Small 
quantities of ferric tartrate were subsequently added whenever the 
cultures were irrigated. 
The trees were planted on May 21, 1920, and were removed September 
20, 1921. Trees i and 2 were typical of the sand cultures (1-5), and 
tree 85 was typical of the soil cultures (84-88). The tree in can 2 was 
much smaller than the others in its series at the start, although it made 
excellent growth. 
Plate 2 B, is a photograph of trees i, 2 and 3 taken August 20, 1921. 
The photograph indicates that citrus trees can be grown in pure sand to 
which no organic matter has been added, except the small amount as 
iron tartrate. Plate 4 shows the leaves of tree No. 3 which were typical 
of the series, being dark green in color and giving no indications of mal¬ 
nutrition. 
This is of interest in connection with the results (i) of field studies in 
which it was found that low humus content of the soil was associated 
with the mottling of orange trees and also that applications of organic 
