EFFECT OF SOIL FACTORS OX WATER REQUIREMENT. 
39 
Table XXIX. — Effect of different fertilizers on the water requirement of potatoes } accord- 
ing to Wilms (1899, pp. 288-289). 
Water content, in terms of moisture-holding capacity. 
Fertilizer. 
33 percent. 
58 pei 
cent. 
SO per cent. 
Mean 
Water 
Tubers, require- 
ment. 
Tubers. 
Water 
require- 
ment. 
Tubers. 
Water 
require- 
ment. 
water 
require- 
ment. 
Check 
KCL. . 
Grams. 
123.5 
38.7 
144.7 
215.8 
137.2 
137.4 
138.5 
178.4 
134.6 
124.5 
131.2 
40 ±0 
5.5 ±3 
36 ±2 
37 ±1 
35 ±2 
36 ±0 
3fi ±2 
40 ±0 
39 ±0 
39 ±0 
39 J-l 
Grams. 
178.4 
47.9 
190.2 
30.4 
204.1 
192.7 
179.7 
279.2 
183.3 
168.8 
1.85.4 
192.8 
48+2 
88±6 
47±2 
51±1 
44±1 
43±1 
44±0 
49±2 
46±0 
48±0 
47±1 
46±0 
Grams. 
196.5 
41.8 
246.4 
380.5 
240.9 
192.8 
181.4 
311.0 
203.7 
205.0 
206.2 
-193. 3 
57±1 
138±5 
52±1 
53±0 
49±0 
57±0 
62±1 
54±1 
53±1 
55±1 
57±2 
61±2 
48 
94 
K 2 S0 4 
45 
KXO3 
47 
KsCOa 
XaCl 
43 
45 
Xa 2 SG 4 
XaXOs 
47 
48 
NajCOj- 
46 
MgCl 2 
MgSO< 
47 
48 
MgC0 3 
130.0 39 ±1 
49 
Mean 
39 
50 
02 

1 The water requirement, based on the green weight of the tubers only, is recalculated from the data. 
Two open pots containing about 17 kilograms of soil were used for each determination. The amounts of 
the various salts were equivalent to 3 grams of K 2 0, 3 grams of Na 2 0, and 3 grams of MgO. The variety 
used was Paulsen's July. 
2 Wilms gives 197.3, which appears to be an error. 
DASZEWSKl's EXPERIMENTS. 
» 
Daszewski (1900) determined the dry weight of some of the potatoes 
grown by Wilms and expressed the water requirement in terms of 
the dry weight of the tubers. The results are given in Table V. 
From these results it would appear that the use of potassium nitrate 
and potassium sulphate reduced the water requirement slightly. 
WILFARTH AND WIMMER'S EXPERIMENTS. 
Wilfarth and Wimmer (1902), using the results obtained in con- 
nection with an extensive series of fertilizer experiments, have 
determined the effect of varying amounts of potash and other salts 
upon the water requirement of various crops. The experiments 
were for the most part made in small, open pots, containing only 
a few kilograms of soil. Each experiment was duplicated, but in 
calculating the water requirement the results were combined as if 
only a single pot of double the capacity had been used. This method 
does not show to what extent the duplicate determinations agree. 
Accordingly, the water requirement for each individual pot has been 
recalculated by the writers and the probable error of the mean com- 
puted. One determination only was made where no probable error 
is given. In cases where more than two determinations were made 
the treatment was not exactly the same for all pots of the series. 
The pots received the amounts of fertilizer indicated in Table 
XXX and XXXI, but for a full report of the treatment the reader 
is referred to the original publication. These results include meas- 
285 
