RELATION OF YIELD TO RAINFALL IN SOUTHERN TEXAS. 31 



years, in which the rainfall was about normal. The rain which fell 

 each year during the growing season of each crop is given in the col- 

 umn headed " Seasonal rainfall. ;; 



The seasonal rainfall for corn is taken from March 1 to July 1; 

 for cotton,, from March 1 to October 1; for sorghum, from April 1 

 to October 1. The cotton yields include weight of both seed and 

 fiber. The sorghum (Sumac) was grown in drills for forage, and two 

 cuttings were made, the total yield being given in the table. The 

 figures in all cases represent the average of a number of plats, varying 

 from 8 to 46 in number each year in the case of the corn and cotton 

 crops and from 3 to 4 in the case of the sorghum. 



It will be noted that the yields increase with the seasonal rainfall 

 in every instance except that of the cotton crop of 1907. The low 

 yield in this case is due to an extremely dry August and September, 

 only about 1 inch of rain falling during this time, which is a critical 

 period in the growth of cotton in this region. The effect of the rain- 

 fall on the growth of sorghum is especially marked, the yield varying 

 from 1.9 tons with a seasonal rainfall of 8 inches in 1909 to 13 tons 

 per acre with a seasonal rainfall of 16 inches in 1908. This latter 

 yield, which is^extremely high, was the average of four plats, of which 

 the lowest gave a yield of over 12 tons per acre. All of these four 

 plats were cropped to either sorghum or cotton the previous year, 

 and were plowed the preceding fall in time to take advantage of heavy 

 fall and winter rains. The water which was stored in the soil as the 

 result of the fall plowing, amounting probably to 6 or 8 inches of rain- 

 fall, was thus available to the crop in addition to the seasonal rain- 

 fall of 16 inches. But even granting that the sorghum had 24 inches 

 of water during its growing period and assuming that the forage con- 

 tained 20 per cent of water when weighed, this crop still shows the 

 remarkable efficiency of 1 pound of dry material produced for every 

 260 pounds of water used. 



SUMMER TILLAGE AT SAN ANTONIO. 



The increased yield obtained on summer-tilled land during a dry 

 season is strikingly illustrated in the results given in Table V, which 

 were obtained at the San Antonio Experiment Farm in 1909. 



Table V. — Comparison of yields from crops grown on summer-tilled land and on land 

 cropped the preceding year at San Antonio, Tex., 1909. 



Crop. 



On land cropped 

 in 1908. 



On land summer 

 tilled in 1908. 



Cotton 



596 pounds 



783 pounds. 

 22.6 bushels. 

 5 tons. 

 1.25 tons. 



Corn 



3.3 bushels 



Sorghum 



1.9 tons 



Oats 



0.0 ton 







188 



