2 BULLETIN" 1320, IT. S. DEPARTMENT OF AGEICULTURE 



interval of 10 days between plantings was used in South Carolina 

 and Florida and 7 days in Texas. 



As these experiments were conducted under boll-weevil conditions, 

 measures were taken to protect the early plantings from infestation 

 by overwintered weevils. Uncontrolled infestation in the early 

 plantings would have caused excessive infestation in the adjacent 

 later plantings and would have prevented comparable data being 

 obtained from the different plantings. The method of weevil con- 

 trol was by removal of squares and the application of poison after 

 most of the weevils had emerged from hibernation. 



At San Antonio, Tex., it was only necessary to apply pois n to 

 the two later plantings, those of May 5 and May 12, as these plant- 

 ings had not reached the fruiting stage at the time squares were 

 removed from the early plantings. 



A separate late planting was made at San Antonio on May 12 in 

 order to compare the development and fruiting habits of cotton in 

 rows that were left unthinned with rows that were thinned to two 

 plants in a hill with hills 12 inches apart. This comparison showed 

 that plants left in hills had a larger individual fruiting capacity than 

 the unthinned plants, due to the production of more nodes on the 

 fruiting branches. But this difference in the fruiting capacity of 

 individual plants was counterbalanced by the greater number of 

 plants in the unthinned rows. More flowers were recorded from the 

 unthinned cotton, and a marked difference in the rate of flowering 

 occurred during the first half of the flowering period, the unthinned 

 rows producing flowers at almost twice the rate of the rows that 

 were thinned. 



No trace of weevil infestation was found in this separate late- 

 planted field until July 8, after the beginning of the flowering period. 

 Thus, it appeared that the planting of May 12 had been late enough 

 to avoid any infestation from overwintered weevils in the season of 

 1923 at San Antonio. 



SOIL, CLIMATIC, AND WEEVIL CONDITIONS AT SAN ANTONIO, TEX. 



The United States San Antonio Field Station is located about 5 

 miles south of the city. The soil on the farm is typical of a large 

 part of the cultivated land in that region and is technically described 

 as Houston clay loam. It is of high natural fertility and is fairly 

 retentive of moisture. The subsoil is a coarse gravel, which affords 

 good drainage but limits the water-storage capacity of the soil. 



The annual precipitation is variable, ranging from 13 to nearly 40 

 inches. The average annual rainfall over a period of 15 years is 

 about 26 inches. Although the precipitation is usually sufficient for 

 cotton production, the distribution is very irregular. Periods of 

 excessive rainfall are frequently followed by protracted periods of 

 hot dry weather which deplete the soil moisture and cause serious 

 injury to crops. 



The precipitation during the season of 1923, from January 1 to 

 October 1, was 23.47 inches, which was about 4 inches in excess of 

 the 15-year average for the same period. The heaviest monthly 

 rainfall, 6 inches, was recorded in February. Rains occurring during 

 the winter months are often an important factor in this section, as 

 stored moisture in the soil may enable the plants to continue growth 



