124 



BULLETIN 1233, U. S. DEPARTMENT OF AGRICULTURE. 



In considering soil-moisture quantities that approach the wilting 

 coefficient and that present conditions under which capillary move- 

 ment may almost wholly cease, it is preferable to assume that an 

 osmotic equilibrium is being approached by vapor transfers between 

 the well soil- and native soil. In this event. OE, the osmotic equiva- 

 lent, might be substituted for 2IE above. Unfortunately, there are 

 neither sufficient osmotic equivalents for well soils and native soils, 

 nor sufficient wilting coefficients for well soils, to make this desirable 

 method of computation possible in the present study. 



Comparative moisture of native soils, local stations. — In Table 39 

 are shown the results of sampling the native soils at three points near 

 the Fremont station, under the conditions already described. These 

 are essentially the data published in the preliminary report on this 

 project (8) j referring to the three stations which were operated 

 comparatively from March, 1910, to February. 1912. 



Table 39. — Comparative moisture data from samples of native soil, July, 1910, to 



October, 1911. 





Station No. 



Percentages of dry-soil weight. 



Mean 

 an- 

 nual. 1 



Mean 

 grow- 



Depth. 



April. 



May. 



June. 



July. 



Au- 

 gust. 



Sep- 

 temoer 



Octo- 

 Der. 



ing 

 sea- 

 son.= 



1 fooc 



[F-l, control 



^F-2,pine 



a 75 

 7.72 



6.87 



4.96 

 16.35 

 5.31 

 4.19 

 8.46 

 6.09 

 4.58 

 12.40 



5.09 

 4.30 

 9.92 

 2.15 

 3.60 

 4.99 

 3.62 

 3.95 

 7.46 



4. 98 

 5.16 

 12.31 

 4.28 

 4.10 

 4.86 

 4.63 

 4.63 

 8.58 



5.64 

 5.78 

 9.98 

 5.32 

 4.34 

 9.04 

 5.48 

 5.06 

 9.51 



4.65 

 4.46 

 10.07 

 5.56 

 4.08 

 6.68 

 5.10 

 4.27 

 8.38 



1.40 

 3.34 

 7.55 

 4.15 

 3.68 

 2.83 

 4.28 

 3.51 

 5.19 



5. 77 

 5.10 

 11.02 

 4.68 

 4.09 

 6.14 

 5.23 

 4.60 

 8.58 



5. IS 

 5.02 







10.67 



2 feet 



F-l, control 



^F-2,pine 



6.01 

 4.66 



4. OS 

 4.02 







6.34 



Average of 



f F-l. control 



<F-2, pine. 



7. 38 

 6.19 



4.63 

 4.52 



depths... 



[F-3, spruce 



8,50 















1 Arithmetic means of the months. 



1 Growing-season means obtained by giving September quantities one-third the value of June, July, and 

 August quantities. 



It is to be noted that the south-slope pine site (P— 2) shows scarcely 

 less moisture than the control station, the latter being subject to no 

 depletion of moisture through use by trees. The spruce site (F-3) 

 at the foot of a north slope shows considerably more moisture than 

 the other stations, except at a depth of 2 feet at the end of the sea- 

 son. This exception would be very significant if the result were 

 based on more data: but, as the measurements covered only October, 

 1910, they can not be given much weight. 



Periodic moisture at the control station. — As the data for native soils 

 are meager and can be compared only on their face value, in the 

 absence of physical data on the soils themselves, an examination may 

 be made of the more extensive data secured by taking samples from 

 the "wells." 



In Table 40 are given the monthly mean moisture figures for the 

 control station for the greater part of five seasons. Each mean figure 

 is based on four or live determinations, at intervals of a week, except 

 where otherwise indicated by a number in parentheses, which denotes 

 the number of determinations. Only the data for 1914, 1915, and 

 lit 17 are used in computing the averages, as this is the basis at other 

 local stations. 



