158 
Journal of Agricultural Research 
Vol. XXI, No. 3 
Table l—Effect of iron-sulphate spraying on mortality of western yellow pine seedlings 
Age of 
stock 
during 
treat¬ 
ment 
period. 
Treatments. 
Dead seedlings. 
Series and plot. 
ber of 
seed¬ 
lings 
per 
square 
foot. 
Dates. 
Strength 
of 
solution 
(grams 
per 
100 cc.). 
Amount 
FeSOi 
per 
square 
foot of 
bed. 
Sept. 3 to 
Oct. 22, 
1917. 
Oct. 22, 
19x7, to 
Apr. 23, 
19x8. 
(winter- 
killed). 
Sept. 3, 
1917, to 
Apr. 23, 
1918. 
T t treated. 
Months. 
14 to 18 
108 
1917. 
(Aug. 2, 
j 24,Sept. 
2 
Grn. 
a 0. 95 
Per cent. 
4 
Per cent. 
0 
Per cent. 
4 
II, treated. 
75 
115 
and 
Oct. 2. 
1 
0.47 
5 
0 
5 
.do_ 
3 
8 
11 
^do.... 
80 
4 
15 
19 
Ill, treated. 
2 to 5 . 
52 
Sept. 3 
2 
0 -95 
13 
0 
13 
'Do. 
58 
and 
1 
0.47 
14 
0 
14 
Do. 
63 
•5 
0 .24 
14 
XI 
24 
76 
14 
9 
22 
a o.i pint of solution per square foot, equivalent to 0.02 inch of rain, applied to each treatment. 
The prevalence of chlorosis in the Pocatello Nursery during Septem¬ 
ber, 1917, was determined by examining several thousand plants of the 
different age classes of western yellow pine and Douglas fir. Of the first- 
and second-year western yellow pine seedlings 82 and 62 per cent, re¬ 
spectively, were chlorotic; while 74 P er cen t of the transplants grown 
two years in the seed bed and one year in the transplant bed were 
chlorotic. First-, second-, and third-year seedlings of Douglas fir were 
chlorotic to the extent of 6, 65, and 26 per cent, respectively; while 15 
and 62 per cent of the transplants grown three years in the seed bed 
and one and two years, respectively, in the transplant bed were chlo¬ 
rotic. 
EFFECT OF WATERING 
It was at first thought that too heavy watering might have been 
responsible for the chlorosis at the Pocatello Nursery. While an exam¬ 
ination of the condition of the soil did not indicate water-logging, varia¬ 
tions in the amount of artificial watering were tested. Four plots of 
Douglas fir seedlings approximately 2 months old were given varying 
amounts of water throughout a period of slightly over two months. 
The results appear in Table II. The artificial watering was at first 
given approximately once a week and amounted to the equivalent of 
0.55 inch of rain on plot D, the most heavily watered plot. Plot C 
received two-thirds of this amount, plot B one-third, and plot A none. 
After the first month the amount of water added at each watering was 
decreased because of the difficulty of avoiding run-off, and the frequency 
of application was increased. The plots in this experiment were free 
from chlorosis at the beginning of the period, and all of them later 
exhibited more or less yellowing. The amount of water applied arti¬ 
ficially, combined with the natural precipitation, did not total an ex- 
