EFFECT OF SOIL FACTORS ON WATER REQUIREMENT. 29 
From a single pot experiment in which 3 beet plants produced 479 
grams of diy matter in a pot containing 420 pounds of soil, Sleskin 
found the water requirement of sugar beets, exclusive of evaporation, 
to be 337. The beets were grown in an open pot, but by alternately 
covering the soil surface and leaving it exposed the evaporation was 
computed. This in turn was used as a basis for computing the 
evaporation loss from the cultivated plat. If the computed evapora- 
tion loss is accepted, it follows that the water requirement of the beets, 
exclusive of evaporation, was less under the cement-covered than in 
the cultivated plat. 
Table XVIII. — Water consumption of sugar beets in cement-covered and in cultivated 
pints, according to Sleskin (1908). 1 
Cement- 
covered 
plat. 
Culti- 
vated 
plat. 
Number of beets harvested 
Weight of beets in kilograms 
Water added to soil by rainfall millimeters. 
Computed loss by evaporation do. . . 
Loss in excess of rainfall , . . . do . . . 
Water content of the soil at the end of experiment per cent . 
59 
26.9 
3.4 
78 
16.1 
226 
247 
21 
2.7 
1 The writers are indebted to Raphael Zon, Chief of the Office of Silvics of the Forest Service, for assist- 
ance in translating Sleskin's and Schroeder's articles. 
widtsoe's experiments. 
Widtsoe (1909) has investigated the effect of shallow cultivation 
on the water requirement of corn (Zea mays). The pots, 24 inches in 
diameter by 30 inches high, were cultivated 48 hours after surface 
irrigation, and then weekly until irrigated again. The cultivation 
was done with a gardener's comb to a depth of 1 inch. Four pots 
were used for each soil type investigated, two being cultivated. 
Corn was grown in one cultivated and one uncultivated pot. The 
other two pots were without crops. The difference in the amount of 
water lost from the cropped and barren pot in each treatment was 
taken to represent the transpiration loss of the crop. The experi- 
ment was conducted for three years. The results are given in 
Table XIX, and show in most instances a marked reduction in the 
water requirement, due apparently to the cultivation. 
This is a subject regarding which it is extremely difficult to obtain 
reliable and concordant results. The uncertainty arises in the 
assumption that the evaporation loss from the cropped pots is the 
same as from the barren pots. The pots must be left open and freely 
exposed, and this means a high evaporation loss. In fact, the average 
transpiration of all the cropped pots in Widtsoe's experiments was 
but 55 per cent of the total loss, the extreme values being 14 and 
82 per cent. 
It seems remarkable that the cultivation of the surface inch of 
soil should have had an appreciable influence on the actual water 
285 
