92 BULLETIN 1059, U. S. DEPARTMENT OE AGRICULTURE. 



Table 3. — Wilting coefficients of four species in five types of soil. 



Sample No. and description. 



590. Sifted granite gravel with loam. 

 604. Composite limestone 



602. Composite sandstone 



601. Prairie soil from shale 



603. Composite lava 



Averages. 



Capillary 

 moisture. 



Per cent. 

 26.58 

 31.85 

 35.34 

 37.77 

 43. 16 



Moisture 



equiva- j 



lent i ^ ln 

 100-G. Yellow 

 pine. 



Mean wilting coefficient. 



Per cent. 

 10.55 

 22.00 

 21.77 



28.79 

 27.80 



Lodge- , Douglas ; English 

 pole. fir. I spruce. 



Per cent. 

 2.50 

 3.82 

 5.01 

 8.65 

 5.56 



5.11 



Per cent. 



Per cent. 



2.79 



2.60 



4.74 



4.06 



6.30 



5.08 



9.65 



8.52 



7.48 



5.44 



6.19 



5.14 



Per cent. 

 2.72 

 4.03 

 4.87 

 8.76 

 5.31 



5.14 



Ratio wilting coefficient to capillary moisture, j Fine material. 



Sample No. and description. 



Yellow 

 pine. 



Lodge- 

 pole. 



Douglas 

 fir. 



Spruce. 



All. 



Silt. 



Clay. 



590. Sifted granite gravel with 



loam 



604. Composite limestone 



602. Composite sandstone 



601. Prairie soil from shale 



603. Composite lava 



0.094 

 .120 

 .142 

 .229 

 .129 



0.105 

 .149 

 .178 

 .256 



.174 



0.098 

 .128 

 .144 

 .226 

 .126 



0.102 

 .127 

 .138 

 .232 

 .123 



0.100 

 .131 

 .150 

 .236 

 .138 



Per cent. 

 13.5 

 45.8 

 41.8 

 53.3 

 51.9 



Per cent. 

 5.4 

 11.4 

 11.0 

 17.2 

 11.1 





.1428 

 .0346 

 24.2 



.1724 

 .0364 

 21.1 



.1444 

 .0324 

 22.4 



.1444 

 .0348 

 24.1 



.151 

 .0389 



25.8 







Mean variations of single 

 determinations . .. 







Percentage of mean varia- 

 tions 













Sample No. and description. 



Ratio of wilting coefficient to 

 equivalent. 



moisture 



Yellow 

 pine. 



Lodge- 

 pole. 



Douglas 

 fir. 



Spruce. 



590. Sifted granite gravel with loam. . . 



0.237 

 .174 

 .230 

 .301 

 .200 



0.265 

 .215 

 .290 

 .335 

 .269 



0.247 

 .185 

 .233 

 .296 

 .196 



0.258 



604. Compositelimestone 



.183 



602. Composite sandstone 



.224 



601. Prairie soil from shale 



.305 



603. Composite lava 



.191 











Averages 



.2304 

 .0328 

 14.2 



.2748 

 .0302 

 11.0 



.2314 

 .0328 

 14.2 



.2322 



Mean variation of single determinations. . 



.0394 



Percentage of mean variations 



17.0 







The wilting coefficient tests given in Table 3 bring out the follow- 

 ing facts: 



1. The line showing the percentage of the mean variations indicates 

 that the four species taken together and comprising 20 cases have a 

 larger variation from an established mean ratio than any of the 

 individual species. Lodgepole pine shows the highest relative wilt- 

 ing coefficient, and, since the other three species gave almost identical 

 results, it follows that a ratio established by the promiscuous use of 

 species would be most largely in error when applied to calculations 

 for lodgepole. 



2. The relatively high wilting coefficient for lodgepole pine has 

 been thoroughly established by numbers of other tests, which, how- 



