88 



BULLETIN 1059, U. S. DEPARTMENT OF AGRICULTURE. 



light than now seems desirable, although not enough to develop ex- 

 cessive temperatures. In contrast, there are also presented the re- 

 sults of nine tests on coarse granitic gravels, from depths of 1 to 3 

 feet, containing minimum amounts of humus and clay. The wilting 

 coefficients were determined in the same manner as the other group, 

 and at almost the same time. 



Table 2. — Capillary moisture, moisture equivalent, and wilting coefficient of 19 soils. 



(Wilting coefficients determined synchronously.) 



Capil- 

 lary 

 Sample No. meas- 

 ure 

 (G). 



539. 

 555. 

 534. 

 547. 

 545. 

 549. 

 544. 

 526. 

 546. 

 538. 



Per 



cent. 

 17.07 

 20.29 

 24.06 

 29.34 

 33.77 

 36.16 

 41.56 

 49.92 

 60.00 

 89.05 



Clay. 



Per 



cent. 

 11.68 

 11.72 

 14. 45 

 20.32 

 22.02 

 19.95 

 26.30 

 29.84 

 42.72 

 73.50 



Per 



cent. 

 3.17 

 3.00 

 3.90 

 6.01 

 6.02 

 7.04 

 8.68 



S.til) 



20.46 

 21.71 



Per 



cent. 



3.29 



3.52 



3.00 



6.56 



7.09 



6.04 



11.64 



9.75 



21.10 



27.00 



Per 



cent. 

 4.5 

 0.4 

 2.2 

 6.7 

 3.6 

 4.2 

 3.4 

 3.2 

 2. 6 

 2.7 



Water 2 

 soluble 

 matter. 



Ratio mean 

 wilting coeffi- 

 cient . 



To 

 capil- 

 larity. 



Parts 

 per 

 million. 

 305 

 275 

 165 

 270 

 845 



1,030 

 .530 

 200 



1,250 



a w. 

 .us 



. 162 

 .205 

 .17s 

 . 196 

 .209 

 .172 

 .341 

 .244 



To 

 mois- 

 ture 

 equiva- 

 lent. 



Ratio final 

 willing coeffi- 

 cient. 



Final 3 

 wilting 

 coeffi- 

 cient . 



To 

 capil- 

 larity. 



0.271 

 .256 

 .270 

 . 296 

 .273 

 .353 

 .330 



.479 

 .295 



Per 



cent. 



2.56 



2.52 



3. 30 



5.26 



5.18 



6.10 



7. 83 



6.95 



11.17 



13. 89 



Group averages, granitic loams. 



204 



,311 



0.150 

 . L24 

 .137 

 .179 

 .1.53 

 .169 

 . L88 

 .139 

 . L86 

 .156 



To 

 mois- 

 ture 

 equiva- 

 lent. 



. 158 



o. 219 

 .215 

 .228 

 .259 

 .235 

 .306 

 .298 

 .233 

 . 282 

 . 189 



.214 



292. 

 37.. 

 235. 

 36.. 

 293. 

 82.. 

 83.. 

 85.. 

 84.. 



Group averages, granitic gravels 200 



Grand averages .415 



Mean variation of single values 13 .1157 



Percentage of mean variation 16. 5 



Probable error in average . U230 



1 In these tests spruce and fir gave almost the same figures, on the average. 



2 200 grams soil leached on filter, with 1 liter water, through 24-hour period. For the gravel group re- 

 sults are approximations, on account of lack of sensitive scale. 



3 Average of the moistures existing for last tree of each species. 



To avoid duplication of tables later there are also inserted here 

 the moisture equivalents of the same soils. 



The comparison of capillary moisture and wilting coefficients 

 given in Table 2 brings out the following facts: 



1. An examination of the column headed u Ratio of mean wilting 

 coefficient to capillarity " shows that there is considerable variation 

 in the individual results. In the first group the two results which 

 are appreciably higher than the average are those for samples of the 

 highest capillarity, resulting from unusual quantities of humus. 



