CJ 
BULLETIN OF THE 
No. 151 
Contribution from the Bureau of Plant Industry, Wm. A. Taylor, Chief. 
September 19, 1914. 
EXPERIMENTS IN CROP PRODUCTION ON FALLOW 
LAND AT SAN ANTONIO. 1 
By C. R. Letteer, Assistant, Office of Western Irrigation Agriculture. 
INTRODUCTION. 
The practice of fallowing land varies widely in different regions. 
In the experiments ^conducted at San Antonio, Tex., and reported 
hi this paper the word "fallow" is used to mean thorough cultiva- 
tion of the land from the time it is plowed after the removal of a 
crop throughout the next season and until the crop is planted at 
the beginning of the second season. The fallow period at San 
Antonio varies from 16 to 19 months, depending on the crops grown. 
The chief ostensible purpose of fallowing in this region is to store 
in the soil for the benefit of the next crop the moisture which falls 
during the fallow period. 
In order to determine whether or not this practice is to be recom- 
mended in the San Antonio region, the experiments reported herein 
were started in 1910. 
CLIMATIC CONDITIONS. 
The climatic conditions at San Antonio are much different from 
those in the dry-farming regions farther north. 
The conditions fluctuate irregularly from semiarid to humid. 
Droughts of many weeks' duration are common and may come at 
almost any season of the year, but they are more frequent and more 
serious during the summer months. The mean annual rainfall at 
San Antonio for a period of 33 years, as reported by the United 
States Weather Bureau, is 26.83 inches. The mean annual rainfall 
for the 7-year period from 1907 to 1913, inclusive, as measured at 
the San Antonio Experiment Farm, 5 miles south of the city, is 
24.66 inches. While the normal precipitation would appear to be 
sufficiently large to make crop production fairly certain, yet on 
account of the unequal distribution of the rainfall and the high 
1 From January, 1010, to October, 1011, the experiments here reported vcre under the direct supervision 
of Mr. S. II. Hastings, superintendent of the San Antonio Experiment Farm. Mr. C. R. Letteer has had 
direct charge of the work since October, 1011. 
:.:770°— 14 
