116 
IOWA ACADEMY OF SCIENCE 
residue, and these portions applied to two different pots to find which one con- 
tained the plant food. 
The series w^as planted October 19th, and harvested January 18, 1907, when 
ninety-one days old. The following table gives the treatment of each pot In 
the series, the green weight of the crop when harvested, and the relative 
weight of the crop on each pot. 
OCTOBER PLANT FOOD SERIES. 
o 
ft 
6 
Iz; 
Treatment 
Green wt. 
No. 
plants 
Relative 
weight 
Average 
200 
Check - - 
4.1 
101 
90 
2oa 
Check 
4.4 
10 
103 
100 
202 
Manure leachings 
7.9 
10 
186 
208 
Manure leachings __ 
0.5 
10 
223 
20'5 
204 
Distillate from teachings- 
4. 
10 
94 
205 
Distillate from leachings 
4.6 
10 
108 
101 
206' 
Residue from distillate- _ __ _ ___ — _ 
10.1 
10 
237 
207 
Residue from distillate 
8.5 
10 
200 
218 
208 
N. P. K 
7.65 
10 
180 
200' 
N. P. K 
6.85 
10 
161 
170 
210 
Sodium nitrate -- 
4.15 
10 
97 
211 
Sodium nitrate _ _ _ _ 
5.75 
10 
135 
116 
212 
Dried blood _ 
5.5 
101 
129 
213 
Dried blood _ 
5.05 
10 
140 
135 
214 
Peptone _ _ _ _ _ 
5. 
10 
118 
215 
Peptone _ - 
5.45 
10 
128 
123 
218 
Potassium sulfate _ _ __ 
3.65 
10 
86 
210 
Potassium sulfate 
5.7 
10 
134 
no 
220 
Sodium phosphate __ __ __ 
6.75 
10 
160 
221 
Sodium phosphate - _ 
5.65 
10 
133 
147 
The above table shows that the manure leachings have a relative standing 
of 205, while the distillate from this made no gain whatever. The residue 
resulting from the distillation gave as good gains as the fresh leachings. The 
point is thus proved from two directions that the fertilizing value of the 
manure leachings were not volatile but remained in the fiask during distilla- 
tion. 
The next point is the effect of the mineral fertilizers. This is 170 which 
is considerably below that found for the manure. 
What part did the different elements play? Taking the data as it stands, 
the evidence is that the nitrogen gave an increase of 16 per cent, potassium 
10 per cent, and phosphorus 46 per cent, a total of 72 per cent which is very 
close to the gain resulting from the three together, 70 per cent. However, as 
the duplication was not very good in any of these cases, it is not wise to 
adhere too closely to these figures, hut this probably is true; the phosphorus 
helps the most, the nitrogen next and the potassium the least of three ele- 
ments. Concerning the different forms of nitrogen, the dried blood and the 
peptone seem to be as good as the nitrate, but as one of the nitrate pots had 
a standing of 135, it is not certain that these forms are better than the nitrate. 
Several other series were run, for it was necessary to thoroughly establish 
the point that the manure had a beneficial action other than that attributable 
to the soluble mineral plant food found in it. Summing up these experiments 
where different samples of soil from this field, and both solid and liquid manure 
were used, the results show that if the clover on the manured pots is ranked 
as 100, the mineral fertilizers gave a growth equal to 75 in the first series, 93 in 
the second, 80 in the third, 80 in the fourth, 72 in the fifth and 61 in the last 
