112 



until late in the season. Readings of all apparatus were made 

 two to three times a week. Daily temperature, wind movement, 

 precipitation, evaporation, and evapo-transpiration records were 

 kept . 



Tanks Nos. 1, 2, and 3 were 3 feet in diameter and 3 feet 

 deep, sunk in the ground nearly flush with the rim and filled with 

 sandy loam soil. The soil was placed in these tanks in the spring 

 of 1927; therefore, both soil and vegetation were well stabilized. 

 Tanks Nos. 1, 2, and 3 had a growth of saltgrass with water levels 

 maintained at approximate depths of 4, 12, and 2k inches, respec- 

 tively. The water table was maintained below the surface by means 

 of Mariotte apparatus. Tank No. 4-A was similarly installed in 

 1930 except that it was 4 feet deep with the water level kept at 

 about 38 inches below the surface. 



The results of these experiments are siimmarized in Table 32. 

 The investigation was divided into two periods, separated by the 

 year 1929, during which no records were obtained. Although the 

 Mariotte apparatus was designed to hold the water table in the 

 soil tanks at constant levels, fluctuations of 2 to 3 inches 

 occurred. Total consumptive use during the growing season is 

 influenced by the depth to water, plants located where water is 

 near the surface showing the greater consumptive use because of 

 more luxuriant growth and increased soil evaporation. Fluctuation 

 of 2 or 3 inches is, however, too small noticeably to influence 

 the quantity of water used. 



Averaging the total use of water during the 4-year period, 

 from June to October, inclusive, shows that saltgrass in tank No.l 

 used 20.19 inches with an average depth of 4-2 inches to the water 

 table. Tank No. 2 consumed 19.47 inches with an average depth of 

 12.8 inches to water -- practically the same as the tank with a 

 higher water level. Tank No. 3 used 16.05 inches with the water 

 table 24.2 inches below the surface. Tank No. 4-A used 16.92 in- 

 ches of water with an average depth to water table of 38 inches 

 in 1931 1 the only year in which observations were taken. The 



