HORTICULTURAL EXPERIMENTS AT SAN ANTONIO. 3 



records kept by the Weather Bureau at San Antonio for a much 

 longer period will show that the mean rainfall for the last seven years 

 is slightly below what is to be ordinarily expected. The year 1909, 

 which was the driest that has been known during the observed period 

 (more than 40 years), was followed by two years when the rainfall 

 was considerably below normal. In spite of the adverse conditions 

 during this period, the orchards came through with no loss of trees 

 which could be traced directly to a lack of moisture. 



Table II.— Annual precipitation at the San Antonio Experiment Farm, 1907 to 1913, 



inclusive. 



Year. ' 



Precipi- 

 tation. 



Year. 



Precipi- 

 tation. 



Year. 



Precipi- 

 tation. 



1907 



Inches. 

 26.68 

 26.27 

 13.14 



1910 



1911 



1912 



Inches. 

 20.02 

 23.93 

 26.37 



1913 



Inches. 

 36.71 



1908 



1909.. 





24.66 









THE SOIL CONDITIONS. 



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 



t &0 



/.o 



I 



I 



1 



mmm 





Fig. 1.— The mean monthly rainfall at San Antonio, Tex., from 1891 to 

 1913. (Compiled from the records of the United States Weather 

 Bureau.) 



area known geograph- 

 ically as the Rio 

 Grande Plain. The 

 soil is mostly the re- 

 sult of the weathering 

 of limestone rocks of 

 the Upper Cretaceous 

 period. Recent allu- 

 vial deposits have been washed down from the higher lands north- 

 west of the city, resulting in modifications through the addition of 

 coarser material. The typical soil is a heavy black or brownish loam. 



The lime content of the soil is unusually high, the proportion of 

 carbonate of lime in the upper 12 inches ranging from 7 to 23 per 

 cent. This lime occurs in the soil both as a finely divided material 

 and as gravelly concretions. In the former condition i,t is generally 

 dark colored through staining by decomposed organic matter, while 

 in the latter condition it is usually white 



This excess of lime is believed to be the cause of one of the most 

 serious disorders of fruit trees that have been encountered in the experi- 

 mental work reported in this paper. The chief symptom is a yellowing 

 of the leaves, and in the later stages the leaves drop and the tree 

 gradually dies. Often in less severe cases the tree may continue to 

 five and make a poor growth and bear some fruit for several years 



