Apr. 1, 1918 



Capacities of Soils for Irrigation Water 



23 



the difficulty in wetting these compact impervious soils. This high 

 ratio may also be the result of difference in volume weight between 

 the soil in the field and in the perforated cup of the centrifuge.* The 

 probable error of a single comparison in the first group is ±0.06 for 

 both foot sections; for the second group ±0.12 in the first foot and 

 ± 0.04 in the second ; for the third group it is ±0.11. 



Table X. — Comparison of the maximum quantities of water contained after irrigation 

 by the first- and second-foot sections of soil in place with their moisture equivalents 



SOILS HEAVILY IRRIGATED 



Name of tract. 



First foot of soil. 



Moisture 

 equivalent. 



Per 

 cent. 



Inches 



per 

 foot of 



soil. 



Maxi- 

 mum 

 quan- 

 tity of 

 water 

 after 

 irriga- 

 tion 

 (inches 

 per 

 foot 

 of soil). 



Ratio, 

 moisture 

 equivalent 

 to maxi- 

 mum 

 quantity 



after 

 irrigation. 



Second foot of soil. 



Moisture 

 equivalent. 



Per 

 cent. 



Inches 



per 

 foot of 



soil. 



Maxi- 

 mum 

 quan- 

 tity of 

 water 

 after 

 irriga- 

 tion 

 (inches 

 per 

 foot 

 of soil). 



Ratio. 



nioisture 

 equivalent 

 to maxi- 

 mum 

 quantity 



after 

 irrigation. 



Wigno 



Griffes 



Himdy 



Hof henke 



Hughson 



Huartson 



O'Hair 



Geer 



University farm 



Average. . 



34.18 

 30.64 

 28.63 



32. 13 



32. 10 

 31.46 

 33-87 



24-75 

 23-88 



3.18 



3.98 



4.48 



3-45 



3-21 



3-38 

 3- 18 

 3-78 

 3-67 



3.63 

 2.58 

 3-50 

 3-27 

 2.87 

 3.92 

 3-14 

 3-67 

 3-25 



I- IS 

 1.28 

 I- OS 



1.03 

 I- 13 



24.4s 



21. 22 

 26.92 



22. 13 

 21. 70 



23. 10 

 31. 70 

 36. 71 

 31.90 



3-06 



3-45 

 3- IS 

 3-48 

 2.89 

 4.08 

 3-37 



23-52 



3-48 



3-09 



I- 13 ±0.03 



23-20 



2-73 

 2-S7 

 3.62 

 3- 29 

 2.94 

 2.90 

 2.51 

 3-86 



1.18 

 1. 19 



1. 16 

 I. OS 

 1.07 

 I. 20 

 I- IS 

 1.06 



SOILS MODERATELY IRRIGATED 



Guile 



Jackson- Woodard 



Beck 



Wright 



Average 



Purdy 



Tuttle 



Willows' experimental tract, 



plots 3 and 4 



Willows' experimental tract, 



plots 6 and 7 



Willows' experimental tract, 



plots II and 12 



Average 



24.18 

 30.31 



25.68 

 37.72 



26.97 



31.02 

 19.30 



19.70 



22.59 



20. 70 



30.66 



4.07 

 4S3 

 4.07 



4.14 

 4- 03 



4-14 



4-75 



4-35 



4.38 



4.00 

 4.04 

 2-97 

 3-83 



3-71 



3-03 

 3-09 



2.40 



2-97 



2.91 



2.i 



I- 13 



1-37 

 1-30 



1-37 

 1-34 



1.72 



I. 60 



1.50 



J±o. 05 



28.74 

 31-65 

 35.18 

 27-54 



28.28 



4-83 

 4-79 

 3-99 

 4.96 



4.64 



3-34 



3-52 



3- 76 



3-36 



1-44 

 1.36 

 1-40 

 1-32 



I.38±0. 03 



The impervious nature of these 

 soils prevented the irrigation 

 water from wetting the second 

 foot; therefore comparisons are 

 not made. 



a Moisture-equivalent sample for first foot determined on soil from second foot. 



The comparisons made in Table X suggest that the moisture equiva- 

 lent may be made a means of judging the maximum capillary capacity 



* That the volimie weights of these clay soils are higher in the field than in the ordinary air-dry con- 

 dition in the laboratory has been determined beyond reasonable doubt. If the same relative condition 

 exists between the volume weights in the field and in the perforated cups of the centrifuge the increase 

 of the ratio with increase of fineness of soil would be readily accounted for. However, volume-weight 

 determinations were not made upon the soils after rotation in the centrifuge; nor have any such deter- 

 minations been made, so far as known to the writer. 



