FALL-SOWN OATS IN THE SOUTH 3 
CLIMATIC FACTORS 
It is not possible tc place definitely the northern limits of successful 
fall-sown oat culture. Winter temperature undoubtedly is the 
limiting factor in the production of the crop. Studies by Salmon (6)? 
on the relation of winter temperature to the distribution of winter 
- and spring grains in the United States indicate that winter oats are 
adapted to the region lying south of the isotherm of 30° F. In 
Figure 1 are shown the locations of the isotherms of 10°, 20°, and 
30° and the distribution of oats in the United States in 1919. Between 
the isotherms of 30° and 20° both fall-sown and spring-sown oats 
are grown. North of the isotherm of 20° fall-sown oats usually do 
not survive the winter, and spring-sown oats produce better average 
yields. The northern limits of successful fall-sown oat culture are 
roughly marked by the States of Maryland, Virginia, Kentucky, 
Fic. 1.—Distribution of the oat acreage in 1919 and the location of the three isotherms of 10°, 20°, 
and 30° F. (Isotherms adapted from Salmon) 
Tennessee, Arkansas, and Oklahoma. South of these States in the 
Cotton Belt, oats when fall sown are grown more successfully than 
when spring sown. Fall-sown oats occasionally suffer severe winter 
injury even in this latter area, but the yields are so much superior 
on the average to the spring-sown crop that there is no question 
of relative values. 
The distribution of fall-sown oats in the South is illustrated by the 
distribution in 1919 of the three leading varieties. This distribution, 
determined by a varietal survey, is shown in Figures 2, 3, and 4. 
The Red Rustproof and Fulghum varieties are confined almost entirely 
to the area south of isotherm 20° F. The Winter Turf variety is 
erown in the area between the isotherms of 20° and 30° F. This 
distribution of varieties shows a rather definite relationship between 
varietal type and climate. In the northern part of the winter-oat 
2 Italic numbers in parentheses refer to “‘ Literature cited. ’’ p. 32. 
