io8 
Journal of Agricultural Research 
Vol. II, No. a 
Tabi^L III .—Effect of certain salts and combinations of salts on grapefruit seedlings 
growing in California soil at Washington , D. C. —Continued. 
Lab¬ 
oratory 
No. 
Soil treatment. 
' 
Condition of trees 
after 22 days. 
Condition of 
trees after 48 
days. 
Condition of trees 
after 88 days. 
922 
N as JCNO3 (0.04 per cent) + Cl asKCl 
Normal. 
Subnormal.... 
Subnormal. 
(0.05 per cent).* - 
92s 
.do.*. 
Dead; replanted,. 
Dead. 
Dead. 
926 
Cl as XCl (0.02 per cent) + CaC 03 (3 
Normal. 
Normal. 
Normal; growing. 
per cent). 
927 
.do. 
.do. 
.do. 
Subnormal. 
916 
Cl as KC 1 (0.05 per cent) + CaCOs (3 
.do. 
Dead. 
Dead, 
per cent). 
917 
.do. 
..... do... 
.do. 
Do. 
918 
Cl as KC 1 (0.05 per cent) + CaCOa (10 
.do. 
Normal. 
Do. 
per cent). 
919 
.do. 
.do. 
Do. 
Percentage of nitrates present after 88 days: r 0.0042 per cent. * 0.0275 per cent. 
It should be noted also that the virgin California soil used in these 
experiments would naturally endure greater additions of nitrate salts 
before the toxic limit of 
orange plants would be 
reached than would the soils 
of the older groves. In the 
latter soils there has been an 
appreciable accumulation 
of soluble salts, and, as will 
be shown later, this would 
intensify the effect of high 
nitrates. 
As will be seen by an ex¬ 
amination of the analyses of 
nitrate nitrogen made at the 
close of several experiments, 
a considerable though rather 
erratic decrease of this salt 
took place, and it is prob¬ 
able that this denitrifica¬ 
tion occurred during the early periods. The toxic limits of the pot ex¬ 
periments therefore are actually between 0.05 and 0.0100 per cent, as 
against 0.005 to 0.015 per cent in the field, exclusive of crusts. It is 
evident, therefore, that nitrates are more fatal than chlorids, that nitrates 
and chlorids together intensify the symptoms of injury, and that mod¬ 
erate quantities of lime—less than 10 per cent of calcium carbonate 
0-07 
0.06 
0.65 
0 . 0 + 
0.03 
002 
00 / 
GREEAt 
VETCH 
Fig. 5.—Diagram showing effect upon nitrate nitrogen in 
samples of California soil of additions of 2 per cent of green 
vetch, green barley, and mature barley straw. 
