280 
Journal of Agricultural Research voi. xxviii, no. 3 
T H EEFFECT OF CONCENTRATION UPON THE GROWTH AND 
COMPOSITION OF YOUNG VALENCIA ORANGE TREES IN SAND 
CULTURES 
In experiments on this question we employed 1-year-old orange trees growing 
in large galvanized iron cans containing silica sand. The cans were provided 
with means for adding nutrient solutions and collecting drainage water accord¬ 
ing to methods previously described ( 8 ). The nutrient solutions employed 
were based on that used in the water cultures described in an earlier para¬ 
graph, and were .25 C, .50 C, and 2.0 C. They had total concentrations, 
therefore, of 364, 727, and 2908 parts per million. It is not feasible to 
maintain rigidly a given concentration of nutrient solution in sand cultures, 
but by frequent renewals it was possible to maintain the approximate concen¬ 
trations. The cultures which had the .25 C solution were renewed at intervals 
of 7 to 10 days, the others were renewed at intervals of 14 to 21 days. The 
trees were planted in the sand cultures April 5, 1921, and grew for 21 months. 
The leaves of the trees receiving .25 C nutrient solution were yellow-green; 
those receiving .5 C solution were dark green but not nearly so deep a green 
as the leaves of trees receiving 2.0 C solution. The rootlets in the .25 C 
solution when in the fresh condition appeared to be finer than in the highest 
concentration. 
Table IV.— Data on the growth of young Valencia orange trees in sand cultures 
to which nutrient solutions of various concentrations were added . (.Each lot con¬ 
sisted of 6 trees , and figures represent averages.) 
Concentration of nutrient 
solution 
0.25 C 
0.50 C 
2.0 C 
Number of leaves per tree_;_ 
931 
1,162 
57 
1,351 
Nnmhflr of vaIIow leaves nar tree _ I _ -__ . _ 
48 
fLeaves 
653 
748 
ftreen weight fin mm !!k Shoots 
290 
342 
[Trunk____ 
507 
484 
[Leaves_ 
177 
227 
273 
Shoots_ 
125 
160 
187 
Dry weight (in grams) 
Trunk._ 
261 
313 
290 
Root..-___ 
243 
324 
349 
Rootlets.«,.... 
300 
376 
318 
Total.....-. 
1,106 
253 
1,400 
173 
1,417 
162 
. . .. ... v fNutrient solution 
volume oi liquids added to cultures tin liters;yn p,^ WR f- Ar 
391 
471 
462 
Volume of drainage water recovered (in liters)_ 
224 
170 
171 
Water transnired hv trees fin liters') 
420 
474 
452 
. . . . fTCntire tree 
380 
339 
319 
Katio oi transpiration to dry weigni^ T pn " OQ 
2,373 
2,090 
1,656 
Table IV gives the dry weight of the different portions of the trees, and also 
the green weights of the tops of the trees in the .5 C and the 2.0 C cultures. 
The green and dry weight of the leaves and shoots increased with increasing 
concentration of the .culture solution. The diameter and appearance of the 
trunk and root of the different trees were quite uniform at the time of planting. 
However, there must have been some initial differences in weight of the tree 
portions when planted, hence differences in the green or dry weights of the 
trunks and roots will not be emphasized. Trees receiving .5 C solution pro¬ 
duced the largest dry weight of rootlets. The total dry weights of trees receiv¬ 
ing .5 C or 2.0 C solution were practically identical, but the average dry weight 
of trees receiving .25 C solution was less than the others. The water require¬ 
ment per tree in each series showed slight reduction with increasing concentration 
