Studies of Health in Potatoes. 
17 
for all the period in the second row; 20% for 75 days for the 
third and fourth rows, and then for 5 days 30% for the third row 
and 40% for the fourth. We did not dare use 30% and 40% 
during the main growing period because we believed these high 
percentages of moisture would cripple the plants (see Figures 9, 
10 and II). 
We found that when the moisture in the 10% row fell to 7%, 
the plants wilted, and that they recovered all right and quickly 
when watered again. In practice, we ran the water from 2 or 3% 
above to 2 or 3% below the standard. 
The soil used was a mixture, about half and half, of a light, 
sandy loam from Farmers’ Spur near Greeley and'clay loam from 
an alfalfa held on the college farm at Fort Collins. The sandy 
loam was from a held where leaf-roll had been serious during 
1911, and the seed potatoes were Pearls from the same held. The 
study was made to determine what conditions would bring health 
and what conditions disease. The potatoes were planted on Febru¬ 
ary 5, 1912, and the temperatures and percentages of moisture 
were maintained from that date. 
The health of the 10% lots, whether in cold, medium or con¬ 
stantly warm soil, was in entire accord with the experience of prac¬ 
tical potato growers under irrigation. They hnd that almost no 
harm comes in early summer to dry plants, even though the sun 
be steadily hot and the soil hot. If obliged to irrigate-at such 
times, they do Jt at night, but the wisest of them often let potatoes 
get very dark and the leaves droop, hoping for cool weather and 
showers to put the plants along to where they will shade the ground 
before irrigating. Then they uniformly practice, on the more 
level fields, irrigating every other row only, until the vines have 
reached good size. Some irrigate alternate rows at the second 
watering and others irrigate the same alternate rows each time 
until cool weather or self-shade, or both, are at hand. We favor 
the latter method, because it leaves half of the surface mulched and 
half of the roots free from soakage while warm. 
In times of great scarcity of water less has been used and good 
crops have been made by irrigating the same alternate rows 
throughout the season. Dry times are hot times and reservoir 
water used then is both warm and extremely alkaline. By a prin¬ 
ciple well known to botanists strong alkalinity makes it somewhat 
more difficult for the plants to secure water enough for their needs. 
Conser\^ative irrigation to avoid root injury at such times is im¬ 
perative for health and a good crop. It is equally reckless in cost 
