632 
Journal of Agricultural Research vot xxiii, no. 8 
land is typical eastern Kansas prairie. Using Clements’ 4 classification, 
the vegetation belongs in the “True Prairie” (Stipa-Koeleria) association. 
TOPOGRAPHY AND SOIL 
The topography is rolling and the land is too hilly for cultivation. 
The soil ranges from a dark brown to black loam with an underlying 
subsoil composed of clays and shales. There are many outcroppings 
of limestone, and many of the slopes and ridges are covered with loose 
chert rock. The elevation varies from 1,200 to 1,400 feet above sea 
level. 
CLIMATIC CONDITIONS 
The average, annual precipitation based on a 59-year period preceding 
1918 is 31.50 inches. Table I shows the monthly precipitation at Man¬ 
hattan for the duration of these experiments—namely, from 1918 to 
1921 inclusive. It will be noticed that the rainfall during each of these 
years was less than the 59-year average, indicating that conditions, so 
far as rainfall was concerned, were subnormal but probably insufficient 
to influence the experiments to any marked degree. 
The average date of the last killing frost in the spring at Manhattan 
is April 25 and that of the first killing frost in the fall is Oc¬ 
tober 8, both based on the 59-year period. The average frost-free period 
is, therefore, 166 days. The growing season for the principal native 
grasses is much longer, however. 
Table I .—Precipitation by months at Manhattan , Kans. t from igi8 to 1921 and the 
59-year average 
Month. 
Precipitation. 
19x8. 
1919. 
1920 . 
1931. 
1859 to 1917 
(average). 
Inches. 
Inches. 
Inches. 
Inches. 
Inches. 
Jan . 
0.65 
O. 26 
a 13 
I.08 
O. 81 
Feb. 
•52 
I. 24 
•55 
• 3 & 
I. 26 
Mar.. 
.76 
5-03 
. 20 
. 16 
I. 46 
Apr. 
4. 60 
3*40 
4.09 
2. 95 
2. 56 
May. 
5. 28 
3 - 15 
i- 75 
3 - 32 
4.63 
June. 
I. 56 
4.66 
2. 24 
6. 26 
4 - 57 
July. 
I. 98 
1* 45 
4-83 
4. 21 
4. 67 
Aug. 
3 - 34 
i *43 
6.76 
4.65 
3. 66 
Sept. 
2.35 
2.65 
4-39 
3 - 
3 - 34 
Oct. 
4.87 
.68 
.90 
1.38 
2. 26 
Nov. 
*• 55 
2. 62 
2. 20 
0.00 
i -37 
Dec . 
2.30 
.08 
i -35 
O. OO 
.91 
Total . 
29. 76 
27. 65 
28.39 
27 - 54 
31- 5° 
The principal growth takes place from March 15 to July 1. If rainfall 
is deficient in March, April, and May a “backward” season results, but 
this may be made up by heavy rains in July and August, which will 
start vigorous growth, resulting in abundant late summer pasture. 
4 Clements, Frederic E. plant indicators, xvi, 388 p., as fig., 92 pL Washington, D. C. 1930. 
Bibliography, p. 364-373. (Carnegie Inst. Wash. Pub. 390). 
