EFFECT OF SOIL FACTORS ON WATER REQUIREMENT. 
19 
Table VIII. — Effect of different soil-moisture contents on the water requirement of 
squarehead summer wheat. 1 according to Preul (1908, pp. 12-13). 
Soil moisture, in terms of moisture-holding capacity during period. 
Water requirement 
in— 
45 per cent. 
80 per cent. 
Rich soil. 
Poor soil. 
Mar. 12 2 to Julv31. 
Mar. 12 to July I... 
Mar. 12 to June 15. 
Mar. 12 to June 1.. 
Mar. 12 to May 15.. 
Mar. 12toMav 1... 
July 1 to July 31.. 
June 15 to July 31. 
June 1 to Jury 31.. 
May 15 to Julv31. 
May 1 to July 31.. 
' 158±1 
July 1 to July 31 147±6 
June 15 to July 31 ■ 228±7 
June 1 to July 31 235± 2 
May 15 to July 31 248±2 
Mav 1 to Julv 31 ! 251± 1 
Mar. 12 2 to Julv 31. 
Mar. 12 to July 1.. 
Mar. 12 to June 15. 
Mar. 12 to June 1.. 
Mar. 12 to Mav 15. 
Mar. 12 to May 1 . . 
248 ±5 
209±1 
207 ±4 
207±3 
194 ±1 
187 ±3 
224±4 
220 ±7 
274 ±3 
281±4 
268 ±4 
261 ±3 
259 ±1 
263 ±4 
259 ±2 
222 ±5 
256 ±4 
246 ±3 
Mean . 
210 
253 
1 Zinc pots were used in these experiments. They were 33 centimeters in height, 25 centimeters in diame- 
ter, and contained 20.5 kilograms of soil. Each series consisted of 3 or 4 pots, 96 pots being used in all. 
The poor soil consisted of good soil mixed with heath sand. Each pot contained 1.47 grams K 2 C0 3 and 1.65 
grams CaH<(P04)2. In addition, each pot of good soil received 9.11 grams NaN03 and each pot of poor 
soil 3.04 grams of NaN0 3 . Each pot of good soil contained 18 wheat plants and the pots of poor soil 9 
wheat plants each. Several minor errors occurring in the original data have been corrected here. 
2 The pots of good soil were planted Mar. 12 and those of poor soil Mar. 16. 
widtsoe's experiments. 
Widtsoe (1909) investigated the effect of the soil-moisture con- 
tent on the water requirement of wheat, sugar beets, corn, and peas 
(Table IX). Maximum water contents of 10 and 20 per cent of 
saturation were chosen, and when any plant needed water all pots 
were brought up to weight. The pots were of galvanized iron, 24 
inches in diameter and 30 inches high. A single open pot of each 
crop was used for each moisture content, the evaporation from a bare 
control pot being deducted. The results for the same crop fluctuate 
to such an extent from year to year as to render conclusions uncertain 
except in the case of corn, where the lower moisture content consist- 
ently gave the higher water requirement. 
Table IX. — Influence of soil-moisture content on the water requirement of certain 
crops, according to Widtsoe (1909. p. 39). 
Crop. 
Satura- 
tion. 
Per cent. 
Wheat { ™ 
Sugar beets j ™ 
Com .'...I g 
P - |{ ig 
L'85 
Water requirement. 
1902 
25S 
511 
639 
420 
490 
106 
1,658 
1903 
340 
523 
227 
696 
280 
256 
789 
1904 
too 
664 
645 
403 
424 
276 
510 
1,704 
1905 
356 
261 
570 
697 
306 
525 
Ratio of water requirement, low to 
high soil moisture. 
1902 
K).51 
^1.52 
[l.21 
^2. 05 
1903 
0.65 
.33 
1.09 
.34 
1904 
1.54 
.30 
1905 
1.36 
1.21 
2.28 
Average. 
0.91±0.16 
1.17± .20 
1.53± .19 
.90± .46 
