115 



so that the only loss was by transpiration. Thus the meaning of 

 the term "water requirement" differs according to investigational 

 practices followed. 



The results of the investigations at Akron indicate that 

 pigweed, tumbleweed, Russian thistle, purslane, buffalo grass, 

 and grama grass use small amounts of water in relation to weight 

 of dry matter harvested, and that cocklebur, buffalo bur, and sxin- 

 f lower use medium amounts. Some of these results do not agree 

 entirely with those of investigations in the Sacramento -San Joaquin 

 Delta, Calif., where the water table was close to the gro\ind sur- 

 face and weeds consumed greater quantities. Table 33 shows the 

 use of water by weeds presented as weight of water absorbed to 

 weight of dry matter harvested. 



MIDDLE RIO GRANDE VAi-T.T^Y, NEW MEXICO 



Investigations were started in 1926 by the United States 

 Bureau of Reclamation in cooperation with the Middle Rio Grande 

 Conservancy District and the Weather Bureau (10, 14) to determine 

 monthly and annual use of water by saltgrass and by tules at a 

 station established at Los Griegos, near Albuquerque, N. Mex. 

 The purpose of the investigation was to study natural losses from 

 undrained bottom lands along the Middle Rio Grande Valley. Evapo- 

 ration from moist sands with water at various depths was included 

 in the investigation. 



Saltgrass . --Saltgrass was grown in galvanized iron stock 

 tanks approximately 4 feet in diameter with depths from 2 to 4 feet. 

 Soil obtained from excavations in which the tanks were set was 

 placed in thin, tamped layers in approximately the same order as 

 excavated. Samples were classified as Gila clay loam. Tules also 

 were grown in a tank set in a small swamp one -half mile from the 

 original station. Water in the tule tank was approximately 2 in- 

 ches above the surface. 



Mariotte supply tanks, similar to those described on page 19, 

 were used. The soil tanks, however, were the single-wall type, and 



