POT EXPERIMENTS WITH FERTILIZERS. TS9 
ascertain if more uniform results may be obtained where the 
conditions of soil, moisture and fertilizer are more nearly 
under control. 
Pots used.—In these experiments the plants are grown in 
galvanized iron pots 18.5 inches deep and 10 inches in diam- 
eter. These pots hold from 60 to 80 pounds of the soil, sand 
and gravel used. Each pot is fitted outside with a half-inch 
pipe, entering about an inch from the bottom, for use in water- 
ing the plants. 
Soil used.—The soil used in these experiments was taken 
from plots on the field used for special nitrogen experiments. 
The mineral plots were selected, for the reason that nothing 
but mineral fertilizers—phosphoric acid and potash—had been 
applied to them since 1890. ‘There seemed to be but a small 
amount of organic matter in the soil, and judging from the 
crops that had been grown on it, there was but little nitrogen 
available for plant food. In order to make the soil more or 
less uniform in character it was hauled into a pile and thor- 
oughly mixed. 
Filling the pots and adding the fertilizers.—In filling the pots 
medium coarse gravel was put in at the bottom to the depth of 
about two inches, and this was covered with a layer of sand. 
About an inch of soil was put on this and lightly pressed with 
a tamper about the diameter of the pots, then a little more soil 
was added and tamped, and so on till the pot was full. The 
soil was then allowed to settle. In all the experiments up to 
1900, 10 pounds of gravel and sand and 50 pounds of soil per 
pot were used in each of the series of experiments when the 
pots were first prepared for use. In the soy bean experiments 
for 1900, 10 pounds of gravel and sand and 56 pounds of soil 
were used in each pot. As the moisture in the soil doubtless 
differed the second year from what it was the first year, in 
cases where the same soil was used the second time, the actual 
weights of dry soil may have differed for the two years. But 
as the conditions under which the soil was stored for the — 
winter were uniform the quantity of moisture in the soil of 
‘each of the pots of a series would have been essentially the 
same when the second year’s experiments were started, as it 
was in the first year. 
