14 RANGE INVESTIGATIONS IN ARIZONA. 



The following paragraphs relating to the work upon the small tract 

 are based upon data obtained from reports furnished this office by 

 Professor Thornbur. 



Since the winter of 1900-1901 considerable work has been performed 

 on this area in an attempt to conserve storm waters tw the erection of 

 embankments and by the introduction of forage plants which will 

 thrive under the advantages afforded by the dams. It is believed that 

 the perennial plants which have been sown thus far can not be success- 

 fully established upon these mesas without careful attention to the soil 

 and conservation of the waters, both of which entail considerable 

 expense. 



The dams built were thrown up across the w^ater courses as in the 

 winter of 1901, but their forms have been slightly changed because it 

 was found that the diversion of the water did not suffice to spread it 

 out very much nor to check its flow sufficiently to allow it to penetrate 

 the ground as much as necessary. This is especially true with refer- 

 ence to the summer rains. The precipitation during the winter months, 

 although causing considerable run-off, is much more gentle and pene- 

 trates the ground more readily. 



The work done thus far seems to indicate that the most efficient dam 

 for a gently sloping mesa is one which is so constructed that it will spill 

 around the ends when the water has reached a height of not more than 12 

 inches. This requirement demands that the dam be constructed nearly 

 on contour lines,'^' except at the ends, which are turned so as to retain 

 water up to the desired depth and spread it over as much ground as 

 possible. Besides the two dams mentioned in Bulletin No. 4, seven 

 additional ones were built in January, 1902. These vary in length 

 from 270 to 600 feet and in height from 12 to 24 inches, and are built 

 at an average cost of a little more than S13. 



In January, 1902, some seeding was done, but only in favored places, 

 mostly above the embankments. Fewer species were planted than the 

 previous year, and only two made any growth at all. Egyptian clover 

 {TrifoTnnii ah.eandrhium) and Panicum te.ranum were sown in the 

 same dam, the first in the lower situation. The Egyptian clover ger- 

 minated beautifully early in August, but all died in a very short time. 

 Panlcinii texanvm produced only a few plants, which made no seed. 



Besides the above, seeds of the following species were planted: 

 Hilaria nmtica, Bouteloua rothrockii, Atrlplex coronata^ A. elegans, 

 A. nuttallii^ A. caiuscens, A. hracteosa^ A. poli/carpa, A. ?iu/n?nularia, 

 A. halhnoides^ A. leptocarpa, A. seiirihaccata^ A. ereuiicola, Rhagodia 

 inerm/'s, and B. IhiifoUa. No seedlings of any of these species were 

 observed. 



During the last week in June, 1903, a third seeding was done. As 

 in the second operation, the seed was sown in the vicinity of the dams 



«This form of dam wa? firft suggested by Prof. S. M. Woodward. 



