EXPERIMENTS IN SUBSOILING AT SAN ANTONIO. 1 



P.y S. II. Hastings, Farm Superintendent, and C. u. Letteer, Assistant, Office 



of Western Irrigation Agriculture. 



INTRODUCTION. 



San Antonio, Tex., is in what is classified as a semiarid region, 

 the normal annual rainfall, as shown by the records of the United 

 States Weather Bureau for the years 1891 to 1910, inclusive, being 

 24.77 inches. Because of the irregularity of the rainfall, the com- 

 pact character of the soil, which during torrential rainstorms causes 

 a large loss in surface run-off, and the high evaporation as compared 

 with more northern sections, soil moisture is one of the most im- 

 portant limiting factors in crop production. Any farm practice, 

 therefore, which will result in increased moisture content of the soil 

 will be of much importance to the agriculture of the region. It is 

 popularly thought that subsoiling will effect this and by so doing will 

 increase crop production. 



Subsoiling consists in loosening the soil to a depth greater than it 

 can be loosened with an ordinary plow. This is accomplished by a 

 subsoil plow, which operates in the bottom of the furrow left by a 

 breaking plow, loosening the soil to the additional depth of about 

 12 inches. It requires a 2-horse or 3-horse team and a man to per- 

 form the operation, in addition to the man and team that do the 

 plowing, so that the cost of plowing and subsoiling is practically 

 double what is required for ordinary breaking. It is readily seen 

 that the practice is an expensive one, and adds so much to the cost 

 of preparation for a crop that unless it results in materially increased 

 yields it can not be profitably followed as a regular farm practice. 

 The cost of subsoiling at San Antonio has been found to be practi- 

 cally the same as plowing, or about $2 per acre. 



SOIL CONDITIONS OF THE REGION. 2 



San Antonio lies in the southern extension of what is known as 

 the Black Prairie region, or the Black Lands of Texas, and near the 

 northern edge of an area known geologically as the Rio Grande 



i Issued Feb. 22, 1913. 



"See Circular 34, Bureau of riant Industry, U. S. Department of Agriculture, entitled 

 " The work of the San Antonio Experiment Farm in 1908." 



78241°— Cir. 114—13 2 9 



