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.) 



Sample No. 







Mean 







Capil- 



Moist- 



wilting 







lary 



ure 



coeffi- 



Humus 





moist- 



equiva- 

 lent 



cient 



by ig- 



Clay. 



ure 



(spruce 



nition. 





(G). 



(100-G). 



and 

 fir).i 







Per 



Per 



Per 



Per 



Per 



cent. 



cent. 



cent. 



cent. 



cent. 



17.07 



11.68 



3.17 



3.29 



4.5 



20.29 



11.72 



3.00 



3.52 



0.4 



24.06 



14.45 



3.90 



3.00 



2.2 



29.34 



20.32 



6.01 



6.56 



6.7 



33.77 



22.02 



6.02 



7.09 



3.6 



36.16 



19.95 



7.04 



6.04 



4.2 



41.56 



26.30 



8.68 



11.64 



3.4 



49.92 



29.84 



8.60 



9.75 



3.2 



60.00 



42.72 



20.46 



21.10 



2.6 



89.05 



73.50 



21.71 



27.00 



2.7 



Water 2 

 soluble 

 matter. 



Ratio mean 

 wilting coeffi- 

 cient. 



To 

 capil- 

 larity. 



To 

 mois- 

 ture 

 equiva- 

 lent. 



Final 3 

 wilting 

 coeffi- 

 cient. 



Ratio final 

 wilting coeffi- 

 cient. 



To 



capil- 

 larity. 



To 



mois- 

 ture 



equiva- 

 lent. 



539. 

 555. 

 534. 

 547. 

 545. 

 549. 

 544. 

 526. 

 546. 

 538. 



Parts 



per 

 million. 

 305 

 275 

 465 

 270 

 845 

 555 



1,030 

 530 

 200 



1,250 



0. 186 

 .148 

 .162 

 .205 

 .178 

 .195 

 .209 

 .172 

 .341 

 .244 



0.271 

 .256 

 .270 

 .295 

 .273 

 .353 

 .330 

 .288 

 .479 

 .295 



Group averages, granitic loams. 



.204 



.311 



Per 





cent. 





2.56 



0.150 



2.52 



.124 



3.30 



.137 



5.26 



.179 



5.18 



.153 



6.10 



.169 



7.83 



.188 



6.95 



.139 



11.17 



.186 



13.89 



.156 



0.219 

 .215 

 .228 

 .259 

 .235 

 .306 

 .298 

 .233 

 .262 

 .189 



292. 

 37.. 

 235. 

 36.. 

 293. 

 82.. 

 83.. 

 85.. 



11.02 



5.04 



2.73 



1.02 



1.5 



11.48 



3.53 



2.00 



1.33 



0.2 



12.00 



5.06 



3.09 



2.09 



3.1 



12.95 



4.35 



2.47 



1.74 



2.7 



12.96 



5.62 



2.93 



1.79 



1.5 



13.18 



4.86 



2.27 



1.85 



1.9 



13. 61 



5.19 



2.76 



1.76 



2.5 



15.30 



5.57 



2.54 



1.92 



2.1 



15.65 



5.03 



2.54 



1.31 



3.7 



70(1 

 500 

 800 

 500 

 200 

 600 

 500 

 SOU 



.248 

 .174 

 .257 

 .191 

 .226 

 .172 

 .203 

 .166 

 .162 



.542 

 .567 

 .611 

 .568 

 .521 

 .467 

 .532 

 .456 

 .506 



Group averages, granitic gravels . 



Grand averages 



Mean variation of single values. . 



Percentage of mean variation 



Probable error in average 



.200 

 .202 

 .0333 

 16.5 



.0066 



.530 

 .415 

 .1157 

 35.9 

 .0230 



1.79 

 1.18 

 2.25 

 1.64 

 2.06 

 1.85 

 1.76 

 1.62 

 1.62 



158 



,244 



.162 

 .103 

 .188 

 .127 

 .159 

 .140 

 .129 

 .106 

 .104 



.355 

 .334 

 .445 

 .377 

 .367 

 .381 

 .339 

 .291 

 .322 



.135 



.147 

 .0228 

 15.5 

 .0045 



.357 

 .298 

 .0607 

 20.4 

 .0121 



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 

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



8 Average of the moistures existing fcr 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 " Eatio 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. 



