r 
Studies of Health in Potatoes. 25 
very high surfaice temperatures have been observed. At Briggsdale, 
on July 16, 1912, in a patch of potatoes in a garden we found a sur¬ 
face temperature of 133° (It has reached 142° in the writer’s 
garden at Ames, Iowa), while at four inches the temperature was 
81°. The surface temperature in the shade of a potato plant was 
93°, on the center of a hill 80°, and four inches deep, 74°. Sandy 
road dust was 130°, and the side of an ant hill was 135°, and level 
coal dust was 134°. 
Because the Greeley district slopes to the sun, slightly more 
heat per square foot is absorbed than would otherwise be the case. 
y\t Ault, on July 13, 1912, at noon, road dust piled on a newspaper 
in the full sun was 130° on the side facing the sun and 123° on 
the side sloping away from the sun. That afternoon at i 130 in a 
crusted potato field near the pea huller, the temperature was 110°, 
at three-fourths of an inch below the surface, and at five inches, 
84°, which are dangerous temperatures for potatoes. At the same 
time, in a well cultivated beet field, the top soil was 115° and at five 
inches the instrument read 78°. 
At 3 p. m. on June 22, 1912, on the Rasmussen Brothers’ farm 
five miles east of Greeley, in a crusted potato field, the temperature 
at the seed pieces was 89°. In a portion of the field cultivated the 
night before the temperature at the seed pieces was 75° and in rows 
cultivated that morning, 72°. Driving out the next morning tO' the 
same place at sunrise, the temperatures at seed pieces were found 
to run about 67°, at eight inches deep 70°, and at fifteen inches 70°. 
The air at 5 o’clock, five feet from the ground, registered 54°. As 
the sun came up, shallow temperature changed almost instantly. 
In the sun at 5 130 surface soil temperatures were 70°, in the shade 
of a row 62°, in a horse track 57°. Mr. Charles Rasmussen sug*- 
gested the use of a beet cultivator to break the crust without destroy¬ 
ing the planter ridge. 
The above temperatures are typical of hundreds taken. The 
eight to ten inch cultivation, which is the universal practice of potato 
growers in the Greeley district, is needed to hold the soil open for 
protection against the effect of heavy rains, and to make a good 
ditch possible, but we are fully persuaded that it is necessary, also, 
to influence deeper rooting early in the season and to provide a very 
deep, porous blanket against the entrance of heat. 
In 1914, Mr. E. E. Isaac, a graduate student, working under 
the author’s advice, found that at Ames, Iowa, in less intense sun¬ 
shine and with less thorough cultivation than is practiced at Greeley, 
deep cultivation (6 to 7 inches) as compared tO' shallow cultivation 
(3 inches) made the soil at a depth of the seed piece, on the average, 
