BULLETIN OF THE 



USIPMIIOFAffldM 



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 

 in 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 



i From January, 1910, to October, 1911, the experiments here reported were under the direct supervision 

 of Mr. S. H. Hastings, superintendent of the San Antonio Experiment Farm. Mr. C R. Letteer has had 

 direct charge of the work since October, 1911. 

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