244 



Bulletin 89 



No. 6948. Very limy material beneath 6947. 



No. 6949. Blown sand from beneath creosote bushes ; found on 

 the surface on all parts of the Mesa and appears less tarnished than 

 the bedded sands. 



The moisture equivalent and wilting percentage as determined 

 by C. A. Jensen of the Bureau of Plant Industry and given in the 

 engineer's report on the Yuma Mesa Project are repeated in Table 

 XL The following quotation is from Mr. Jensen's report to the 

 project manager: 



"The moisture equivalent represents approximately the amount 

 of moisture the soil will hold 24 hours after irrigation, and is prob- 

 ably about the optimum. Some of these soils have the lowest 

 wilting percentage of any that I have ever seen. The difiference 

 between the moisture equivalent and wilting percentage repre- 

 sents approximately the amount of available moisture, that is, 

 about the percentage that a plant can get after an irrigation less 

 the amount lost by evaporation." 



TABLE XI — MOISTURE EQUIVALENT AND WILTING POINT YUMA MESA 

 SOILS — BY C. A. JENSEN 



No. 1. 2, 5, 4 are from the old Blaisdell Orchard in N. E. >4» 

 N. W. M S. 33, T. 8 S., R. 2Z W. 



No. 11, 12, 13, 14 and 15 are from 300 feet S. W. of N. E. cor- 

 ner N. W. Ya N. E. Va S. 4, T. 9 S.. R. 23 W. Of 6 samples taken 

 at different points of the Mesa, this sample was found to be, by 

 mechanical analysis, the coarsest ; i. e. it contained the lowest 

 amount of fine material. 



Table XII gives the moisture holding capacity of the same 

 series of soil as was used for the mechanical analysis reported in 

 Table X. Only the soil passing a 2.0 m. m. sieve was used, and 

 the determinations were made with the soil packed in brass tubes 

 on the iron compactor in the usual way. From 2 or 3 to 24 hours 

 were required for water to rise thru the soil when the tubes were 

 placed under a water head equal to their height, about 10 inches. 



