EFFECT OF SOIL FACTORS ON WATER REQUIREMENT. 
45 
Table XXXIII. — Effect of different fertilizers on the water requirement of squarehead 
wheat, 1 according to Ohlmer (1900, p. 157). 
Water content, in terms of moisture-holding 
capacity. 
Fertilizer. 
45 per cent. 
70 percent. 
Dry 
matter. 
Water re- 
quirement. 
Dry 
matter. 
Water re- 
quirement. 
K. 
Grams. 
18.8 
57.5 
19.2 
69.5 
74.4 
19.4 
72.2 
20.5 
64.8 
17.8 
68.5 
1 Grams. 
277 22. 2 
219 105. 2 
282 23. 1 
209 121. 9 
208 130. 8 
304 
N 
248 
P 
294 
KNP 
251 
KXoP 
242 
Check 
274 
22.8 
281 
KX 
204 
248 
216 
282 
242 
120.0 
21.7 
111.3 
21.5 
120.4 
246 
KP 
328 
PN 
265 
Ca 
320 
CaKXP 
256 
242 
276 
1 Four pots for each determination; probably 20 kilograms of loam per pot. The fertilizer was added 
per pot as follows: K=l gram K2O as K2CO3; N= 1.5 grams N as NaN03j N2= 1.5 grams N as (NHOjSCm; 
P=l gram P 2 5 as CaH 4 (P0 4 ) 2 ; Ca=5 grams CaC0 3 . 
PREULS EXPERIMENTS. 
Preul (1908) used a good and a poor soil in connection with an 
investigation of the effect of the soil-moisture content on the water 
requirement. The poor soil was simply a mixture of the good soil 
with heath sand. The results of his experiments (Table VIII, p. 19) 
show a consistently lower water requirement for the wheat grown in 
the good soil, in which the average water requirement was approxi- 
mately 80 per cent of that of the wheat grown in the poor soil. 
SUMMARY OF EXPERIMENTS AT GOTTINGEN, GERMANY. 
Several of the experiments heretofore cited were carried on at 
Gottingen under comparable conditions. The results of the experi- 
ments are summarized and combined in Table XXXIV and show that, 
with the exception of the potash series, the unfertilized check gave 
the highest value. Nitrogen reduced the water requirement decidedly, 
whether alone or in combination with phosphorus or potash. The 
lowest results have been obtained by a combination of potash, nitro- 
gen, and phosphorus. In these results the evaporation from the soil 
has apparently been included with the transpiration, and the water 
requirement calculated on the basis of the air-dry weight of the crop. 
285 
