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UBC Theses and Dissertations

Determining the moisture holding capacity of soils, some modifications of the tube drainage method Wilcox, John Cameron 1933

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I.ULB.C. LIBRARY { . C A T . m + J k l i J W d b L & L J L * --SSTSRMIMIIsG THE MOISTURE HOLDIHG- CAPACITY OF SOILS Some l i o d i f i eat Ions of the Tube Drainage Method. by .John. Oar mas. Wtieox A T h e s i s s u b m i t t e d f o r the Degree of .MASTER GIf SCIENCE- III AGB2CULTUBE j i a t h e D e p a r t m e n t of H o r t i c u l t u r e THE UNIVERSITY OF BRITISH COLUMBIA APRIL, 1033* The w r i t e r w i s h e s t o e x p r e s s h i s a p p r e c i a t i o n o f t h e h e l p a n d 'guidance g i v e n by D r . H, R» M e L a r t y , o f t h e Dominion, F i e l d L a b o r a t o r y o f P l a n t P a t h o l o g y a t S u m m e r land, i n t h e p l a n n i n g a nd e x e c u t i o n o f t h e e x p e r i m e n t a l w o r k r e p o r t e d h e r e i n ; a n d o f t h e s u g -g e s t i o n s a n d a d v i c e o f D r . .0.. H. H a r r i s , o f t h e De-p a r t m e n t o f H o r t i c u l t u r e i n t h e U n i v e r s i t y o f B r i t -i s h C o l u m b i a , i n c o m p i l i n g t h e r e s u l t s . He i s a l s o i n d e b t e d t o M r . If. S, B a r n e s , o f t h e D o m i n i o n D e p a r t ment o f A g r i c u l t u r e , f o r d e t e r m i n a t i o n s o f m o i s t u r e e q u i v a l e n t s , and t o Mr. C . 0 . K e l l e y o f t h e P r o v i n -c i a l D e p a r t m e n t o f A g r i c u l t u r e , f o r m e c h a n i c a l a n a l ? / s e s b y the h y d r o m e t e r m e t h o d . TJkBlM O F O O H T M T S • P A R T A . . . I n t r o d u c t o r y Page 1.' M o i s t u r e h o l d i n g c a p a c i t y i m p o r t a n t ' . . v . . . . I Zi Reason f o r experiment •»..»......... ...-...» • • • « .... 2 PARI? Bw ••PART Gi 4 r . S o i l s tTsedj and T h e i r P r e p a r a t i o n .......... 8 PART D . T e s t s o f Method 5 « 3^ 3? © X X2XX JJLCL3^  3* fcS^XSL'X.'S « « • ••* •# « * • e • » o o o • « « « « o * • .a .« 3-0 6 « X^©,.C l^X X I 0 S O 1 XX » e » ®• » ' * • » . ' » » • » •*• » « :« «»• B id . a> <« « o « •» a * v X 0 *7 ^ fc U X£l (3) "Ull 0 S O XX #• * .» :a 9' 'ft • '9 a » a. a •» •• • » © » * » «• c •« e « X 3 •«?• O O-jT X IIS. ^ 0 • e -« • •©••© e- <s 9 « « -ft- •« » » * *• * * © X 5 9„ C o r r e c t i n g f o r e v a p o r a t i o n ................. 19 X0 ^. X*GJI^J"fcii o x coXxxnxn <> * •«. .©•» *• «» «•».«a• • . « « « « « • » » o • «* S o PART JS.^ D i s c u s s i o n and Recommendations 11. Re 1 x&hi J.i t»y of ps.clci.ng . .«.... .... ». » . «.. « .. •« n>c? 12. Lie an i n g of m o i s t u r e h o l d i n g c a p a c i t y ....... 28 13. Comparison o f methods, and reeomaendations „ 29 Sli'^iilvi.A.Iri^r a m o o • 0. 0 * « * . » e o 4 *- -© c & » « 9 * « • » o a « 9 « © 1 » * © » » * * & 3 X ' T T* fTJ ' " | " A » p-^  t 'r V N iwfl. J»5 p-j f y i» X? X X JitHxk X' Uxt-CJ v i i a e » e a o « - o o o o c o 00 «. c a e « e « « c o- -« © -•©. © * « 0 » o » a « o O — A p PRISTS T T - *^  17-THE MQISTUBE H O L D I K G - CAPACITY 0? S O I L S  Some M o d i f i c a t i o n s o f t h e Tube D r a i n a g e ISethod PAST A . , I n t r o d u e t o r y 1» M o i s t u r e H o l d i n g C a p a c i t y I m p o r t a n t The s o i l may be c o n s i d e r e d a s t h e s o u r c e o f s u p p l y b o t h f o r t h e m i n e r a l n u t r i e n t s a n d f o r t h e w a t e r r e . q u i r e m e a t s o f t h e p l a n t . I n t h i s l a t t e r c a p a c i t y i t i s e s s e n t i a l t h a t i t c o n t a i n n e i t h e r t o o much n o r t o o l i t t l e w a t e r , s i n c e t h e one c o n d i t i o n I s a c c o m p a n i e d by a l a c k o f o x y g e n , t h e o t h e r by a l a c k o f m o i s t u r e , f o r t h e p l a n t r o o t s . B e t n e e n t h e t i ? o e x t r e m e s t h e r e i s a r a n g e o f m o i s t u r e c o n t e n t s f o r a n y one s o i l T ; h i c h may be t e r m e d t h e "optimum" r a n g e j a n d i t i s i m -p o r t a n t t h a t c u l t u r a l o p e r a t i o n s a n d i r r i g a t i o n p r a c t i c e s be s u c h t h a t a s f a r a s p o s s i b l e , t h e m o i s t u r e c o n t e n t be a t a l l t i m e s m a i n t a i n e d w i t h i n t h a t r a n g e . I t i s o b v i o u s t h a t s o i l s s r i l l v a r y i n t h e i r u p p e r and l o T v e r l i m i t s o f o ptimum r a n g e , and i n t h e r e l a t i o n s h i p o f t h e i r m o i s t u r e h o l d i n g c a p a c i t i e s t o t h e s e l i m i t s . A v e r y l i g h t s o i l , f o r e x a m p l e , may h a v e a l o t ? m o i s t u r e h o l d i n g c a p -a c i t y , "with a c o n s e q u e n t n a r r o w m a r g i n o f s a f e t y b e t w e e n t h i s a n d t h e w i l t i n g c o e f f i c i e n t a t t h e l o w e r l i m i t o f t h e o p t i m u m r a n g e . A v e r y h e a v y s o i l , on t h e o t h e r h a n d , may h a v e a m o i s -t u r e h o l d i n g c a p a c i t y e v e n a b o v e t h e u p p e r l i m i t o f t h e optimum, f r i th a wide range between t h i s and the w i l t i n g c o e f f i c i e n t . Such d i f f e r e n c e s a r e , of c o u r s e , taken i n t o account i n i r -r i g a t i n g s o i l s of d i f f e r e n t t y p e s : i n the one c a s e , f o r e x -ample, s m a l l amounts o f water would need to be a p p l i e d at f r e -quent i n t e r v a l s ; and i n the o t h e r c a s e , l a r g e r amounts o f water s h o u l d be a p p l i e d a t l e s s f r e q u e n t i n t e r v a l s . I n d e t e r m i n i n g the s u i t a b i l i t y o f a s o i l f o r growing c rops under i r r i g a t i o n c o n d i t i o n s i t i s therefor© impor tan t t h a t among o t h e r t h i n g s , the m o i s t u r e h o l d i n g c a p a c i t y be d e t e r m i n e d . T h i s measurement i s a l s o u s e f u l when i n f o r m a t i o n i s r e q u i r e d on the amount o f water n e c e s s a r y f o r a c e r t a i n fa rm or d i s t r i c t d u r i n g the grow-i n g season, on the bes t s i z e o f f l u m i n g , or oa the most d e s i r -a b l e p e r i o d s o f water d i s t r i b u t i o n . £, Heason f o r Exper iment . I n 'the'.'Okanagaii V a l l e y ±n'the ftr-ovinee- o f B r i t i s h Co lumbia , i t has been found n e c e s s a r y to i r r i g a t e i n p r a c t i c a l -l y a l l d i s t r i c t s . Thus f.ar.9 water has i n many cases been s u p -p l i e d to the growers end a p p l i e d by them, n o t so much i n a c c o r d -ance w i th the a c t u a l mo i s tu re r e q u i r e m e n t s d u r i n g the growing season as t?ith the ease o f d i s t r i b u t i o n and a p p l i c a t i o n . • 171th an i n c r e a s e i n the c o s t o f the crater, however, and w i t h a g r e a t e r p r e v a l e n c e o f c e r t a i n t r o u b l e s which appear to be a s s o c -i a t e d r/ith i r r e g u l a r i t y o f m o i s t u r e c o n d i t i o n s i n the so i l , i t has become apparent t h a t i n c r e a s i n g s t r e s s must be l a i d on the s c i e n t i f i c a p p l i c a t i o n o f i r r i g a t i o n w a t e r . I t i s d e s i r a b l e , t h e r e f o r e , tha t i n v e s t i g a t i o n s be conducted i n t o water r e q u i r e -ments o f the v a r i o u s s o i l s notr b e i n g i r r i g a t e d , and tha t as a ' p a r t o f t l iess I n v e s t i g a t i o n s , the m o i s t u r e h o l d i n g c a p a c i t i e s be d e t e r m i n e d . V a r i o u s schemes have a l s o been proposed f o r s u p p l y i n g water to c e r t a i n d i s t r i c t s which a re n o t now i r r i g a -t e d , and i t i s f e l t tha t p l a n s c o u l d be made more s p e c i f i c a l l y f o r o b t a i n i n g j u s t the r e q u i r e d amounts of water and f o r d i s -t r i b u t i n g the f lura ing c o r r e c t l y i f the m o i s t u r e h o l d i n g c a p -a c i t i e s o f the s o i l s are knovm ahead o f t ime• For the most p a r t , the a r e a s UOTT b e i n g i r r i g a t e d i n the Okanagan are p l a n t e d to o r c h a r d s . So a l s o are the d i s -t r i c t s above mentioned which i t i s proposed to i r r i g a t e . I t i s p r e f e r a b l e , t h e r e f o r e , , t h a t whatever method i s used f o r de-t e r m i n i n g the m o i s t u r e h o l d i n g c a p a c i t y be a p p l i c a b l e to o r -c h a r d c o n d i t i o n s . S ince the r o o t s o f t r e e s go down to v a r y i n g depths* — as much as 10 o r IS f e e t i n some c a s e s , — the •method s h o u l d ;. p r e f e r a b l y - a l l o w f o r such •vsariat•lousy, a t l e a s t to a p r a c t i c a l depth f o r i r r i g a t i o n . Another p o i n t t o be h e l d i n mind i s tha t under Okanagan c o n d i t i o n s a water t a b l e i s s e l -dom to be found c l o s e enough to the s u r f a c e to I n f l u e n c e the m o i s t u r e h o l d i n g c a p a c i t y w i t h i n the spread of the r o o t s * I n any p a r t i c u l a r o r c h a r d , the most a c c u r a t e method i s cb v i o u s i y to app ly an i r r i g a t i o n to the r e q u i r e d depth and determine the m o i s t u r e con ten ts to tha t depth at i n t e r v a l s • a f t e r the i r r i g a t i o n has s t o p p e d , " h e r o , however, there i s a g r e a t d e a l o f v a r i a t i o n i n the s o i l , or a l a r g e number o f o r -chards to work o n , such that a g r e a t many d e t e r m i n a t i o n s a re r e q u i r e d to a f o u r o r six. f o o t d e p t h , i t vras thought t h a t s u f -f i c i e n t l y a c c u r a t e r e s u l t s might be o b t a i n e d much more r e a d i l y by making compos i tes and t e s t i n g f o r m o i s t u r e h o l d i n g c a p a c i t y i n the l a b o r a t o r y . Moreover.,, i n a reas where vrater i s n o t now a v a i l a b l e f o r i i r r i g a t i o n p u r p o s e s , i t ^as f e l t tha t making de-t e r m i n a t i o n s i n the f i e l d as no ted above would be r a t h e r a t e d i o u s p r o c e s s . I t was a c c o r d i n g l y proposed to r e v i e w and t e s t such l a b o r a t o r y methods as appeared to approximate f i e l d c o n d i t i o n s , so tha t a r a p i d and s imple procedure c o u l d be adopted f o r d e t e r m i n i n g the m o i s t u r e h o l d i n g c a p a c i t y w i t h s u f f i c i e n t a c c u r a c y f o r p r a c t i c a l a p p l i c a t i o n to the above con d i t ions. . . -PART B i 3 . Review of l i t e r a t u r e . P i o n e e r wox'k was done on l a b o r a t o r y techn ique i n o b -t a i n i n g the m o i s t u r e h o l d i n g c a p a c i t y by T io l lny i n 1 8 8 5 . H i s method, as c i t e d by 7/iley ( 3 4 ) , c o n s i s t e d o f f i t t i n g toge ther a s e r i e s o f tubes of 4 cm., d i a m e t e r , f i l l i n g them w i t h s o i l by g e n t l y tamping, w e t t i n g f rom above u n t i l water appeared a t the bottom, and a l l o w i n g to:- d r a i n over wi re s c r e e n . The amount o f m o i s t u r e at the end o f 36 hours was c o n s i d e r e d to be the m o i s -t u r e h o l d i n g c a p a c i t y . W i l e y a l s o d e s c r i b e e severa lmother methods which 'have been a d v o c a t e d . W o l f f ' s method tas, to pack the c y l i n d e r s -with s o i l by g e n t l y j a r r i n g d u r i n g t h e f . i l l i n g . 9 and to p l a c e the bottoms o f the c y l i n d e r s i n water u n t i l no . more -water was taken u p . The m o i s t u r e con ten t o f the s o i l would then r e p r e s e n t the m o i s t u r e h o l d i n g c a p a c i t y . The method of Petermann \ras somewhat s i m i l a r , ezeept t h a t the tubes were a l l o w e d t o d r a i n f o r a few h o u r s b e f o r e d e t e r m i n i n g t h e m o i s -t u r e , c o n t e n t • E a r l y w o r k was a l s o done by K i n g ( I S ) i n 1 8 8 9 . He o b t a i n e d s a m p l e s i n t h e f i e l d b y d r i v i n g o n e - f o o t t u b e s i n t o t h e s o i l , The s o i l c o l u m n s t h u s o b t a i n e d w e r e s o a k e d i n w a t e r f o r f i v e d a y s , d r a i n e d o v e r p e r f o r a t e d t i n f o r f o u r , d a y s , and t h e r e m a i n i n g m o i s t u r e d e t e r m i n e d a s r e p r e s e n t i n g t h e m o i s t u r e h o l d i n g c a p a c i t y . A somewhat s i m i l a r m e t h o d was u s e d b y W i d s t o e a n d M c L a u g h l i n ( 2 S ) i n 1912,. T h e y f o u n d t h a t a f t e r d r i p p i n g s t o p p e d t h e m o i s t u r e c o n t e n t i n t h e b o t t o m end o f t h e t u b e was s t i l l above t h e t r u e m o i s t u r e h o l d i n g c a p a c i t y . L a t e r e x p e r i m e n t s by M c L a u g h l i n ( 1 8 ) o n t h e movement o f s o i l m o i s -t u r e i n l a r g e c o l u m n s showed t h a t t h e amount o f w a t e r r e t a i n e d a g a i n s t g r a v i t y v a r i e d w i t h the l e n g t h o f t h e c o l u m n , and t h a t i t was i n c r e a s e d d e f i n i t e l y by t h e p r e s e n c e o f a w a t e r t a b l e b e l o w . He f o u n d f u r t h e r t h a t a s i s - f o o t c o l u m n r e t a i n e d l e s s m o i s t u r e a g a i n s t g r a v i t y t h a n d i d s m a l l c o l u m n s when, a l l o w e d t o come t o e q u i l i b r i u m o v e r a w a t e r t a b l e . In. a f u r t h e r s e r i e s o f e x p e r i m e n t s ( 1 9 ) , he f o u n d t h a t u n i f o r m i t y i n p a c k i n g o f t h e s o i l c o u l d be o b t a i n e d i n any one o f v a r i o u s ways, b u t t h a t a l l m e t h o d s d i d n o t r e s u l t i n e x a c t l y t h e same m o i s t u r e h o l d i n g c a p a c i t y , • O t h e r p i o n e e r w o r k e r s i n t h i s f i e l d i n c l u d e d L o u g h -r i d g e a n d H i l g a r d . L o u g h r i d g e {16) p o i n t e d o u t i n 1894- t h a t when a t u b e o f s o i l was p l a c e d o v e r w a t e r , t h e w a t e r r o s e i n t h e t u b e , u n t i l a f t e r a l o n g p e r i o d o f t i m e ( t h i s t i m e d e p e n -d i n g on t h e t y p e o f s o i l ) a n e q u i l i b r i u m was a r r i v e d a t . 'Th© m o i s t u r e c o n t e n t o f t h e s o i l was t h e n c o n s i d e r e d t o be a t t h e "maximum" w a t e r h o l d i n g c a p a c i t y i m m e d i a t e l y above t h e water, usi fac'el, -and a t t h e "minimum" w a t e r h o l d i n g c a p a c i t y a t o r n e a r t h e t o p o f t h e w e t t e d p o r t i o n . A s a more p r a c t i c a l m e t h o d o f d e t e r m i n i n g t h e s e two p o i n t s , H i l g a r d l a t e r ( 9 ) u s e d a b r a s s c y l i n d e r 1 em. h i g h and o f s u c h w i d t h a s t o h o l d 25 o r 50 c c . o f a i r d r y s o i l . The c y l i n d e r ( w i t h a p e r f o r a t e d b o t t o m ) was f i l l e d w i t h s o i l , s t r u c k l e v e l , a n d p l a c e d i n 1 mm, o f w a t e r f o r 1 h o u r . The m o i s t u r e c o n t e n t was t h e n e o n s i d e r e d t o be a t t h e "maximum"• M o i s t u r e was t h e n r e m o v e d b y a d d i n g s o i l o n t o p a t t h e h y g r o s c o p i c c o e f f i c i e n t a n d l a t e r r e m o v i n g t h i s s o i l . I'hc m o i s t u r e s t i l l r e m a i n i n g was c a l l e d t h e "minimum" w a t e r h o l d i n g c a p a c i t y . I t was l a t e r c l a i m e d by B o u y o u c o s (4) t h a t t h e s e m e t h o d s were u n r e l i a b l e . H a r d y (8) p o i n t e d o u t i n 1923 t h a t t h e maximum w a t e r h o l d i n g c a p a c i t y a s o b t a i n e d a b o v e c o u l d be a p p r o x i m a t e d w i t h t h e s t i c k y - p o i n t m e a s u r e m e n t . A l w a y and M c D o l e ( 2 ) i n 1917, p a c k e d t h e i r s o i l s I n t u b e s by means o f a g a s p i p e c a p p e d w i t h a r u b b e r s t o p p e r , t a m p i n g t h e s o i l c o n t i n u a l l y a s i t was a d d e d . Z3ach s o i l was t e s t e d a t t h r e e i n i t i a l m o i s t u r e c o n t e n t s , 0.5, 1.0 a n d 1.5' t i m e s t h e h y g r o s c o p i c :eo e f f i c i e n t r e s p e c t i v e l y . Once i n c h i n d e p t h o f w a t e r was a d d e d a t t h e t o p o f e a c h t u b e . One h o u r a f t e r t h i s w a t e r had a l l s o a k e d i n t o t h e s o i l , i t was f o u n d t h a t t h e w e t t e d p o r t i o n c o n t a i n e d o n l y a b o u t one h a l f a s much w a t e r a s t h e s a t u r a t i o n c a p a c i t y . V a r y i n g t h e i n i t i a l m o i s -t u r e c o n t e n t up t o 1.5 t i m e s t h e h y g r o s c o p i c c o e f f i c i e n t made no c o n s i s t e n t d i f f e r e n c e i n t h e f i n a l p e r c e n t a g e o f w a t e r r e -t a i n e d . I t was f o u n d f u r t h e r t h a t t h e m o i s t u r e h o l d i n g c a p -a c i t y o b t a i n e d i n t h i s way showed a f a i r l y c o n s t a n t r e l a t i o n to both- t />. e h. y groSc&/> I C C6effic.ie.Kt a n d tko v>v e i t>fc-Keen and P.aezkovrski (11} i n 1921 f o l i o vied the s u g -g e s t i o n o f H i l g a r d .and used a s m a l l b r a s s c y l i n d e r o r "box*1 w i t h p e r f o r a t e d bottom* I t was compacted w i t h s o i l by t a p p i n g on the bench a f t e r eaeh a d d i t i o n o f 10 grams s o i l , : I t was then p l a c e d w i t h the bottom i n water o v e r n i g h t , the s w e l l i n g at the top removed, ana the rema in ing s o i l t e s t e d f o r m o i s t u r e c o n t e n t . The method was improved r e c e n t l y by C o u t t s ( 5 ) . Keen ( i s ) has p o i n t e d out tha t the amount o f m o i s t u r e h e l d i s a f -f e c t e d by the ,degree o f p a c k i n g . Teihmeyer (20) found i n 1927 that o r d i n a r i l y , i r r i -gat ion. water had a lmost s topped i t s downward movement 24 to 48 hours a f t e r tho a p p l i c a t i o n was f i n i s h e d . He c o n s i d e r e d the m o i s t u r e c o n t e n t a t tha t t ime to be the t r u e " f i e l d c a p a c i t y . " With loam s o i l s (but not w i t h sandy s o i l s ) , t h i s f i e l d c a p a c -i t y was found (21 ,22) t o agree v e r y c l o s e l y w i t h the m o i s t u r e equ iva len t . , l abedef f (15) i n 1927 a l s o found a cons tant r a t i o between h i s ^maximum molecular'-' m o i s t u r e h o l d i n g c a p a c i t y " and the m o i s t u r e e q u i v a l e n t . L'ebedeff (15) p o i n t e d out that when a one metre column o f s o i l i s s a t u r a t e d and a l lowed to d r a i n , the upper p o r t i o n lowers t o the maximum m o l e c u l a r m o i s t u r e h o l d i n g c a p a c -i t y , wh i l e the lower p a r t o f the column r e t a i n s a l a r g e r p e r -centage o f m o i s t u r e . He a l s o noted (14) as d i d Alway and McDole ( l ) , t ha t the water h e l d by a s o i l v a r i e s w i t h the type o f s o i l a d j a c e n t : i t r e t a i n s l e s s water as the a d j a c e n t s o i l becomes h e a v i e r * In the above o u t l i n e , the work o f a few o u t s t a n d i n g s o i l p h y s i c i s t s h a s b e e n b r i e f l y m e n t i o n e d . A g r e a t d e a l o f a d d i t i o n a l work h a s b e e n done o n the m o i s t u r e h o l d i n g c a p a c i t -i e s o f s o i l s , b u t i n g e n e r a l t h e m e t h o d s u s e d a r e t h e same as o r s i m p l e m o d i f i c a t i o n s o f t h o s e n o t e d . A t t h e p r e s e n t t i m e i t a p p e a r s t h a t t h e m e a s u r e m e n t s most p o p u l a r l y u s e d a r e t h o s e o b t a i n e d b y t h e K e e n b o s m e thod o r b y t h e P e t e r m a n n t u b e d r a i n a g e m ethod* o r s i m p l e m o d i f i c a t i o n s t h e r e o f : . I t m i g h t be n o t e d t h a t no c l a i m i s made t h a t a c t u a l f i e l d c a p a c i t i e s a r e o b t a i n e d b y e i t h e r m e t h o d ; i n . f a c t , i t i s p o i n t e d o u t b y some i n v e s t i g a t o r s ( 1 8 , 6 , 2 4 ) t h a t s u c h i s n o t t h e c a s e . T h e i r c h i e f v a l u e l i e s i n t h o l r u s e a s b a s e s o f c o m p a r i s o n i n t e s t i n g t h e r e s u l t s o f v a r i o u s t r e a t m e n t s i n t h e l a b o r a t o r y , • ? A B T 0* 4. S o i l s Ifeedfr, a n d T h e i r P r e p a r a t i o n . . • S o i l was c o l l e c t e d f r o m e a c h o f f i v e l o c a t i o n s , t o a t o t a l o f s i x s a m p l e s . " T h r o e w e r e f r o m t h e s u r f a c e o r A h o r i z o n , two were from., t h e B h o r i z o n , and one was f r o m t h e C h o r i z o n . E a c h s a m p l e was p l a c e d i n b o x e s a n d a l i o wed t o a i r -d r y u n t i l i t was i n a c r u m b l y c o n s i s t e n c y . I t was t h e n w o r k e d by hand t h r o u g h a 5 mm. s c r e e n , t h o r o u g h l y m i s e d , r e t u r n e d t o t h e b o x e s and" a l l o w e d t o a i r - d r y c o m p l e t e l y b e f o r e u s i n g * S u n d r y d e t e r m i n a t i o n s were made on e a c h s a m p l e , o f s t i c h a n a t u r e a s i t was deemed w o u l d a s s i s t i n c l a s s i f y i n g i t . T h o s e i n c l u d e d t h e m e c h a n i c a l a n a l y s i s , .tho m o i s t u r e e q u i -v a l e n t , t h e s t i c k y p o i n t " , t h e s p e c i f i c g r a v i t y , t h e volume w e i g h t and t h o p e r c e n t a g s a i r s p a c e . The r e s u l t s a r e sum-m a r i s e d i n T a b l e I , TABLE I. S o i l Humber 1 2 3 • .4 "'5 6 M e c h a n i c a l A n a l y s i s : $> S&nd & g r a v e l % s u t # C l a y C o l l o i d 92.0 7,4 0,6 3.8 67.9 6.9 11.8 10,8 55.8 35,4 5 7 . *d 34.2 53.4 12.4 2 1 . 8 76 .8 19.2 4.0 10,4 27.8 63.8 8.4 8.4 Moisture e q u i v a l e n t S t i c k y p o i n t q An 2.63 1 3 . 7 1 84,4 26.8 33.08 •iii £rf «g. *B 91.00 S p e c i f i c G r a v i t y Vo luiae VJ eigh.t a i r s p a c e 2,41 1.6 5 •3-1.8 2.35 1.46 •38 ,.7 • 2.40 1.34 44.3' 2*39 1.43 39. 3 3.41 1.75 27.4 1.85 0.69 62.5 "The m e c h a n i c a l a n a l y s e s t r e r e d e t e r m i n e d b y Mr* C»C« J C e l l e y , o f the. P r o v i n c i a l D e p a r t m e n t o f A g r i c u l t u r e . , by t h e B o u y o u e o s h y d r o m e t e r m e t h o d ( 3 ) , The m o i s t u r e e q u i v a l e n t s w e r e d e t e r m i n e d b y Mr. .S.. .Barnes o f t h e D o m i n i o n D e p a r t m e n t o f A g r i c u l t u r e , 30 grams o f ©oil b e i n g s a t u r a t e d a n d c e n t r i f a g e d a t 1000 t i m e s g r a v i t y ' f o r 30 m i n u t . e s . The s t i c k y p o i n t , as a d v o c a t e d b y H a r d y ( 7 ) , was o b t a i n e d f o r o n l y t h r e e o f t h s s o i l s , t h e t w o s a n d y s o i l s a n d t h e p e a t ' s o i l : no t b e i n g . s u i t -a b l e f o r t h i s m e a s u r e m e n t . The s p e c i f i c g r a v i t y , t h e v o l u m e w e i g h t a nd t h e p e r c e n t a g e a i r s p a c e w e r e d e t e r m i n e d a s f o l l o w s ; a t u b e 2 i n c h e s i n d i a m e t e r a n d 3 i n c h e s i n h e i g h t , o f known v o l u m e , was p a c k e d w i t h a i r d r y s o i l a s n o t e d i n t h e n e x t s e c t i o n . I t was s a t u r a t e d hj i m m e r s i o n i n w a t e r , w i t h s u f -f i c i e n t w e i g h t o n t o p .tec p r e v e n t e x t e r n a l s w e l l i n g , a n d t h e n o v e n - d r i e d . The voltirae o f tho- t u b a 9 and t h e w e i g h t s o f t h e s o i l w h e n - s a t u r a t e d a nd when o v e n - d r i e d s u p p l i e d t h e n e c e s s a r y - 10 -PAST D.» T e s t s o f Method 5 . P r e l i m i n a r y T r i a l s . I t has been noted ( 9 , 1 1 ) tha t the H i l g a r d or Seen "bos" method i s c l o s e r to s a t u r a t i o n o r to maximum c a p i l l a r i t y than i t i s to f i e l d c a p a c i t y . P r e l i m i n a r y t e s t s by the w r i t e r a l s o showed t h i s to be the c a s e . I t has f u r t h e r been demon-s t r a t e d {18} tha t the use o f s o i l columns over a water t a b l e w i l l g i v e h i g h e r r e s u l t s than they w i l l i n the absence o f the water t a b l e ; which the w r i t e r l i k e w i s e found i n p r e l i m i n a r y t r i a l s to h o l d t r u e . For f i e l d d e t e r m i n a t i o n s , moreover, i t was c o n s i d e r -ed i m p r a c t i c a b l e to a l low the water to r i s e i n a column to i t s h i g h e s t p o s s i b l e r i s e , as t h i s t a k e s too l o n g ; and even were t h i s done, i t would not r e p r e s e n t t r u l y the p a r t i c u l a r f i e l d c o n d i t i o n s under c o n s i d e r a t i o n . I t was a c c o r d i n g l y d e c i d e d to t e s t i n some d e t a i l the techn ique o f the "tube d r a i n a g e " method, — i . e . , w e t t i n g a column of s o i l and a l l o w i n g i t to d r a i n . 6 . P a c k i n g the Sol l« G a l v a n i z e d i r o n tub ing two i n c h e s i n d iameter was used i n a l l the work here r e p o r t e d . As an i n i t i a l t e s t o f p a c k i n g , two tubes six i n ches l o n g were shoved i n t o the s o i l a t a depth o f one f o o t , and the weight o f s o i l i n them d e t e r -mined a f t e r a i r - d r y i n g . From the same p l a c e a sample o f s o i l was t a k e n , a i r - d r i e d , and packed by three methods, as f o l l o w s ; ( a ) As t h e s o i l was s i f t e d i n t o t h e t u b e , t h e l a t t e r was j a x ' r e d c o n t i n u o u s l y b y t a m p i n g o n t h e b e n c h ; ( b ) a b o u t 1 i n c h d e p t h o f s o i l was a d d e d w h i l e b e i n g J a r r e d , a n d t h e n tamped t e n t i m e s w i t h a s t e e l b a r 1 7 /8 i n c h e s i n d i a m e t e r a n d w e i g h i n g c l o s e t o 4,000 grams? ( c ) t h e s o i l was tamped a s a b o v e a f t e r eaeh a d -d i t i o n o f 20 c e . B e f o r e t a m p i n g i n ( b ) and ( e ) , t h e b a r was p l a c e d u p r i g h t on t h e s o i l s u r f a c e and g i v e n a h a l f t u r n e i t h e r way t o l e v e l i t o f f . I t was t h e n r a i s e d a nd d r o p p e d f r o m a h e i g h t o f 1 t o 1-g- i n c h e s , t h e t e n tamps b e i n g g i v e n I n c o n s e -c u t i v e o r d e r a r o u n d t h e i n n e r s i d e o f t h e t u b e . The same m e t h o d s o f p a c k i n g were t r i e d o n S o i l s 1 e n d 4. The r e s u l t s a r e g i v e n i n T a b l e I I . TA3L3 I I . M e t h o d s o f P a c k i n g T u b e s ( S h o w i n g T/eight o f S o i l i n Grams) S o i l Number A i r - d r y w e i g h t of s a m p l e s t a k e n w i t h t u b e i n t h e •9 -*' .»' .-••:* •« • « •» « « 9 (a) J a r r i n g only (b) J a r r i n g & tamping .. a f t e r e a e h l p w a d -d i t i o i i *. . . Cc) Tamping a f t e r e a c h 20 c c . a d d i t i o n ... 498 .0 496 .0 4 9 8 . 0 421.9 418.5 5 4 5 . 5 401.0 415.0 535 - .0 393.0 403.0 S i n c e the t h i r d method was a p p a r e n t l y c l o s e s t to the f i e l d c o n d i t i o n s t e s t e d , i t was the one used throughout these e x p e r i m e n t s . I t might he noted., o f c o u r s e , t h a t ' i n the f i e l d the s o i l Is not a l l packed to the same d e g r e e , The s o i l a t or near the s-urface Is much, l e s s compact than t h a t f a r t h e r down. T h i s can r e a d i l y be seen by s h o v i n g a 3^ tube i n t o the s o i l for- j u s t the 3 i n c h e s : — i f the sample i s taken a t a d e p t h , say , o f 4 f e e t , the tube w i l l be found to be n i c e l y f i l l e d ; w h i l e i f taken at the s u r f a c e , i t w i l l d e f i n i t e l y l a c k some p a r t o f b e i n g f i l l e d . I n spit© o f these n a t u r a l v a r i a t i o n s i n the f i e l d , i t was f e l t tha t i n the l a b o r a t o r y c l o s e u n i f o r m i t y o f p a c k i n g should be a t t a i n e d f o r most r e l i a b l e r e s u l t s . I t n&s found tha t h e a v i e r p a c k i n g reduced th,e percen tage water o f s a t u r a t i o n and a l s o the m o i s t u r e h o l d i n g . c a p a c i t y . S i m i l a r r e s u l t s were a l s o o b t a i n e d by McLaugh l in ( 1 9 ) , Keen (12) and .others..* •  By the- t h i r d method,, t h r e e - i n c h tubes and s i x - i n c h tubes were packed w i t h each o f the s ix . SiOlls, and. i n . a l l cases, the s i x - I n c h tubes were found to c o n t a i n a g r e a t e r weight per u n i t volume than d i d the t h r e e - I n c h t u b e s . I t was found that the tamping done on the upper p a r t of th© s i x - i n c h tube caused some f u r t h e r compact ing o f the s o i l i n the .lower p a r t . The c o n c l u s i o n was a c c o r d i n g l y draun tha t compar isons of mo i s tu re h o l d i n g c a p a c i t y c o u l d no t be made between columns of d i f f e r -i n g l e n g t h u n l e s s they were packed i n u n i t s o f e q u a l l e n g t h . The u n i t chosen f o r f u r t h e r work was the t h r e e - i n c h l e n g t h , t h i s b e i n g cons idered s h o r t enough to a l i a ? d i v i s i o n of c o l -- 1 9 -PLATS I. M a t e r i a l s Used i n P a c k i n g Tubas w i t h S o i l . J From l e f t t o r i g h t a r e shown: pan o f a i r - d r y s o i l and 20 c c . v i a l f o r measuring each a d d i t i o n ; 3 - i n c h tub© i n p r o c e s s o f f i l l i n g , w i t h e x t e n s i o n above to guide the tamper when the s o i l s u r f a c e i s n e a r i n g the top o f the t u b e ; k n i f e f o r l e v e l l i n g th© s o i l s u r f a c e ; s t e e l bar used f o r tamping; and two 3 - i n c h t u b e s , one empty and one packed w i t h s o i l . umns i n t o s m a l l p a r t s f o i * i n d i v i d u a l v - e i g h i n g s , and l a r g e e n o u g l i t o a l l o w f o r v a r i a t i o n s due t o l a r g e r p a r t i c l e s i n c o a r s e l y - s c r e e n e d s o i l s . The m a t e r i a l s u s e d i n p a c k i n g a r e I l -l u s t r a t e d i i i P l a t e I , V. l e t t i n g t h e S o i l . The s o i l was w e t t e d by i m m e r s i o n i n w a t e r . A t f i r s t , t h e d e p t h o f w a t o r was i n c r e a s e d g r a d u a l l y , t o e n s u r e t h a t w e t -t i n g w o u l d t a k e p l a c e f r o m t h e b o t t o m u p w a r d a nd t h u s t r a p v e r y l i t t l e I f a n y a i r . C o m p a r i s o n o f t h i s , h o w e v e r , w i t h i m -m e d i a t e c o m p l e t e i m m e r s i o n , showed no d i f f e r e n c e i n r e s u l t s . I t u a s f o u n d t h a t when t h e t u b e was c o v e r e d w i t h w a t e r , w e t t i n g s t i l l t o o k p l a c e c o n s e c u t i v e l y f r o m t h e b o t t o m u p . T h i s m e t h o d was a c c o r d i n g l y a d o p t e d . When t h e c o l u m n v?as t h u s s a t u r a t e d i t was f o u n d t h a t some s w e l l i n g t o o k p l a c e a t t h e t o p o f t h e s o i l and t h a t t h e m o i s t u r e h e l d b y t h e u p p e r p o r t i o n was t h e r e b y c o n s i d e r a b l y i n -c r e a s e d . F o r u n i f o r m i t y i n r e s u l t s a n d f o r c o m p a r i s o n w i t h f i e l d c o n d i t i o n s , i t was f e l t t h a t i t should be a d v i s a b l e t o t r y t o p r e v e n t t h i s s w e l l i n g . The t e s t s w e r e a c c o r d i n g l y r e p e a t e d , w i t h v a r i o u s w e i g h t s o n e a c h o f S o i l s 1 t o 5, and i t was f o u n d t h a t w e i g h t s o f f i v e p o u n d s o n e a c h t h r e e - I n c h c o l u m n e n t i r e l y p r e v e n t e d e x t e r n a l s w e l l i n g . A p p a r e n t l y t h e s o i l s w e r e n o t so t i g h t l y p a c k e d b u t t h a t w h a t e v e r s w e l l i n g t h e r e was c o u l d t a k e p l a c e i n t e r n a l l y , and w o u l d do s o w i t h o n l y a c o m p a r a t i v e l y s m a l l p r e s s u r e a b o v e . S o i l Ho. 6 was f o u n d l a t e r t o r e q u i r e s t i l l m o r s p r e s s u r e t o p r e v e n t e x t e r n a l s w e l l i n g . I n a l l t h e o t h e r t e s t s q u o t e d h e r e i n , s w e l l i n g was p r e v e n t e d by w e i g h t i n g . I n t h e a b o v e t e s t s , : t h e l e n g t h , o f t i m e r e q u i r e d t o s a t u r a t e e a c h s o i l was d e t e r m i n e d . S o i l Ho. 5, "which t o o k l o n g e s t t o w e t , g a i n e d no more i n w e i g h t a f t e r 2-> t o 3 h o u r s . A s a m a t t e r o f ' c o n v e n i e n c e , h o w e v e r , t h e t u b e s w e r e ' i a sub*-s e q u e n t w o r k l e f t i m m e r s e d o v e r n i g h t . 8. Type, o f D r a i n a g e * A s a l r e a d y n o t e d ( 2 4 , 1 8 , 4 , 1 4 , 1 ) , v a r i o u s means h a v e b e e n e m p l o y e d by i n v e s t i g a t o r s f o r r e m o v i n g t h o d r a i n a g e w a t e r f r o m t h e b o t b om o f t h e s o i l s o l x u u n . D r a i n a g e o v e r a. w i r e s c r e e n i s commonly u s e d * D r a i n a g e h a s a l s o been, t r i e d i n t o a i r - d r y s o i l , b o t h o f t h e same l:5.,nd a n d o f d i f f e r e n t k i n d s . The q u e s t i o n was, i s d r a i n a g e o v e r a w i r e s c r e e n t h e most s a t i s f a c t o r y method? W i t h e a c h o f t h e s i s s o i l s , , t e s t s o f d r a i n a g e were made b y p a c k i n g and s a t u r a t i n g t h r e e 5 - i n c h t u b e s , and d r a i n -i n g one o v e r w i r e s c r e e n , one o v e r a i r - d r y s o i l o f t h e same ki n d , , a nd one o v e r S o i l Ho. 5 air-&rie&» I n t h e l a s t t w o , t h e s o i l , b e l o w was p a c k e d i n . e x a c t l y t h e same m a n n e r a s t h e s o i l a b o v e * I t was t h o u g h t t h a t t h e s e t e s t s w o u l d r e p r e s e n t ' t h r e e d i s t i n e t l i n e s o f a p p r o a c h . D r a i n a g e o v s r a w i r e s c r e e n , i s q u i t e commonly u s e d i n l a b o r a t o r y work, and s h o u l d a p p r o x -i m a t e more c l o s e l y t o t h a t f i e l d c o n d i t i o n where t h e s o i l i s u n d e r l a i n b y g r a v e l * D r a i n a g e i n t o s o i l ' o f t h e same k i n d s h o u l d r e p r e s e n t t h a t f i e l d c o n d i t i o n w h e r e t h e s o i l i s u n i -f o r m and i s d e e p e r t h a n t h e r e q u i r e d s p r e a d o f i r r i g a t i o n w a t e r . And d r a i n a g e I n t o one common s o i l w o u l d r e p r e s e n t a common o r u n i f o r m p u l l i n a l l c a s e s w h i c h m i g h t be c o r r e l a t e d w i t h t h e common p u l l o f t h e c e n t r i f u g e . T h i s p u l l h a s b e e n found' t o i n c r e a s e a s t h e s o i l becomes h e a v i e r (14,13,9,17), a n d a s I t was t h o u g h t t h a t p e r h a p s b e t t e r c o m p a r i s o n s c o u l d be made w i t h a l a r g e r p u l l , t h e h e a v i e s t o f t h e f i v e I n o r g a n i c s o i l s was u s e d i n m a k i n g t h e t e s t . v,'ith e a c h s o i l , t h e t h r e e t u b e s w e r e s t a r t e d a t t h e same t i m e , a n d w e i g h e d p e r i o d i c a l ! ; / t o d e t e r m i n e t h e l o s s o f m o i s t u x ' e . The o v e n - d r y w e i g h t was l a t e r o b t a i n e d , and t h e p e r c e n t a g e m o i s t u r e c a l c u l a t e d i n e a c h c a s e on t h a t b a s i s . The r e s u l t s a r e g i v e n i n T a b l e v., I n t h e A p p e n d i x . T hey a r e a l s o i l l u s t r a t e d g r a p h i c a l l y i n C h a r t I . The c u r v e s f o r S o i l 2Jo.. 1 a r e - n o t i n c l u d e d , as t h e y o v e r l a p t h o s e f o r S o i l Ho* 2» They a r e , h o w e v e r , v e r y s i m i l a r t o t h o s e o f S o i l Sov -2.4- I t w i l l be s e e n t h a t t h e c u r v e s f o r S o i l Ho. 4 h a v e b e e n r a i s e d b y 2 f j s t o s a v e o v e r l a p p i n g * An e x a m i n a t i o n o f t h e c u r v e s w i l l r e v e a l t h e f o l l o w -i n g f a c t s ? ( l ) T h e r e was v e r y l i t t l e l o s s o f m o i s t u r e when d r a i n a g e t o o k p l a c e o v e r a w i r e s c r e e n . ( I t m i g h t be n o t e d t h a t c o r r e c t i o n s h a v e b e e n made f o r e v a p o r a t i o n . , a s e x p l a i n e d I n S e c t i o n 9 below)-. ( 2 ) The c u r v e s o f d r a i n a g e i n t o t h e same s o i l b e l o w a s a b o v e a r e d i s t i n c t l y l o x ? e r i n e v e r y c a s e . ( 3 ) D r a i n a g e i n t o S o i l Ho-, 5 c a u s e d t h e l o s s o f a a u c h l a r g e r p e r c e n t a g e o f w a t e r t h a n d r a i n a g e i n t o t h e same s o i l b e l o w , when t h e s o i l above h a d a l o w s a t u r a t i o n c a p a c i t y ( i . e . . , S o i l s i f o . 1 and 2,) A s t h e s a t u r a t i o n c a p a c i t y o f t h e s o i l above i n c r e a s e d , h o w e v e r , t h e s e d i f f e r e n c e s d i s a p p e a r e d . A l t h o u g h i n t h e f i e l d t h e r e a r e f r e q u e n t c h a n g e s i n - 17 -CHART X . COMPARISON OF DRAINAGE OVER A WIRE SCREEN AND DRAINAGE INTO AIR-DRy SOIL. - DRAINA&E OVER WIRE SCREEN -DRAINAeE OVER SAME SOIL AIR-DRIED -DRAINAGE OVER SOIL NO. 5 AIR-OHIED SO I L NO. S. «—(M.TUALIM %7. LOWER THAN SHOWN) SOIL NO. 1. o\ , , , , . , , , , . , _ J 0 2. Y b 8 10 12. HOURS ORAININO s o i l t y p e , w i t h c o n s e q u e n t e f f e c t s . o n t h e m o i s t u r e h o l d i n g c a p -a c i t y o f a n y p a r t i c u l a r s o i l , i t was f e l t t h a t c o r r e c t i n g f o r s u c h c h a n g e s I n t h e l a b o r a t o r s r w o u l d he impo ssibie» I t was a l s o t h o u g h t t h a t t h e s l i g h t l o s s o f w a t e r b y d r a i n a g e o v e r a w i r e s c r e e n d o e s n o t e v e n c l o s e l y r e p r e s e n t a c t u a l f i e l d c o n ^ d l t i o n s i n t h e m a j o r i t y o f e a s e s . A n d so i t was d e c i d e d t o assume- a u n i f o r m s o i l deeper' t h a n n e c e s s a r y t o I r r i g a t e , and t o d r a i n i n a l l c a s e s i n t o t h e same s o i l b e l o w a s a b o v e * Vihere s o i l was u s e d t o d r a i n i n t o , i n t h e a b o v e t e s t s , i t was p a c k e d i n t h e same s i z e t u b e s a s t h e s o i l a b o v e . I t s p u l l was a c c o r d i n g l y s t r a i g h t down. I n t h e f i e l d , how-e v e r , t h e w a t e r s p r e a d s f r o m t h e I r r i g a t i o n f a r r o w i n . somewhat th e s h a p e o f a s e m i c i r c l e . To f i n d o u t i f t h i s makes a d i f f e r -e n c e I n r e s u l t s , two s e t s o f t u b e s o f e a c h s o i l w e r e d r a i n e d o v e r S o i l Ho• 5, — one s e t o v e r t u b e s a s a b o v e , and t h e o t h e r s e t o v e r a f l a t s u r f a c e . T h e r e was p r a c t i c a l l y no d i f f e r e n c e i n t h e r e s u l t s ( S e e T a b l e Y) „ S i n c e i t was f o u n d e a s i e r t o m a i n t a i n u n i f o r m i t y b y p a c k i n g i n t u b e s , t h i s method was a c c o r d ifegEy ' r e t a i n e d * A n o t h e r p r o b l e m r e q u i r i n g a t t e n t i o n w a s t h a t w h e r e a s i n t h e above t e s t s , a i r - d r y s o i l was u s e d f o r d r a i n a g e p u r -p o s e s , i n t h e f i e l d s u c h i s n o t t h e c a s e . u n d e r o r d i n a r y c o n -d i t i o n s . The m o i s t u r e I n t h e s o i l b e l o w u n d e r t h e o r c h a r d c o n -d i t i o n s b e i n g i n v e s t i g a t e d i s i n d e e d g e n e r a l l y f o u n d t o be q u i t e l o w d u r i n g t h e summer m o n t h s ; b u t i t i s d o u b t f u l i f i t a c t u a l l y d e c r e a s e s t o t h e w i l t i n g c o e f f i c i e n t . I n f a c t , t h e r e w o u l d be d a n g e r i n a l l o w i n g i t t o g e t t h a t l o w . The q u e s t i o n was t h e n , w o u l d s u c h an i n c r e a s e i n t h e m o i s t u r e c o n t e n t o f t h e s o i l b e l o w a f f e c t t h e m o i s t u r e h o l d i n g c a p a c i t y o f t h e s o i l a b o v e ? To t e s t t h i s out., t h r e e t u b e s were d r a i n e d o f e a c h , s o i l , one i n t o o v e n - d r y s o i l , one i n t o a i r - d r y s o i l , and one i n t o s o i l w e l l a bove t h e w i l t i n g c o e f f i c i e n t . I t was f o u n d ( S e e T a b l e 7) t h a t when t h e m o i s t u r e I n t h e s o i l b e l o w was i n -c r e a s e d t o a b o v e t h e w i l t i n g c o e f f i c i e n t , t h e m o i s t u r e h o l d -i n g c a p a c i t y was i n m o s t c a s e s l e s s e n e d somewhat, b u t n o t e n ough t o be o f much p r a c t i c a l I m p o r t a n c e . I t was a c c o r d i n g l y d e c i d e d t o c o n t i n u e w i t h t h e u s e o f a i r - f e y s o i l b e l o w . I t i s i n t e r e s t i n g t o n o t e t h a t s i m i l a r r e s u l t s w e r e o b t a i n e d b y A l w a y and J.:.cI>ole ( 2 ) ; a l t h o u g h , o n t h e o t h e r h a n d , I t h a s b e e n f o u n d by v a r i o u s i n v e s t i g a t o r s (10) t h a t s t i l l h i g h e r m o i s t u r e c o n t e n t s i n a s o i l w i l l a p p r e c i a b l y l o w e r i t s p u l l i n g p o w e r • 9. C o r r e c t i n g f o r E v a p o r a t i o n . A s f a r a s was c o n v e n i e n t l y p o s s i b l e , e v a p o r a t i o n was p r e v e n t e d d u r i n g t h e p r o c e s s o f d r a i n a g e . The top o f e a c h c o l u m n was c o v e r e d I n s u c h a manner* a s t o a l l o w t h e e n t r y o f a i r , b u t p r e v e n t d r y i n g . The 3 - i n c h u n i t s w e r e f i t t e d ' t o -g e t h e r c a r e f u l l y . ' And t h e l o n g e r c o l u m n s w e r e e a c h e n c l o s e d i n a wooden box, as i l l u s t r a t e d i n P l a t e I I . I n s p i t e o f t h e s e p r e c a u t i o n s , h o w e v e r , some m o i s -t u r e was l o s t b y e v a p o r a t i o n . The amount o f s u c h l o s s c o u l d e a s i l y be c a l c u l a t e d b y a d d i n g t o g e t h e r t h e w e i g h t s o f a l l u n i t s o f t h e c o l u m n -- b o t h wet a n d d r y -- a f t e r e a c h w e i g h i n g . And f r o m t h e s e f i g u r e s c o u l d be o b t a i n e d t h e r e s p e c t i v e p e r -~ 20 PLAT a I I Four Foot Column Set up f o r Drai n a g e , The b ox I s j u s t l a r g e e nough to h o l d n i c e l y t h e 2- i n c h d i a m e t e r c o l u m n , t h e d o o r being o p e n e d t o show t h e 3- i n e h u n i t s as s e t up f o r d r a i n a g e . Of t h e s e u n i t s , t h e t o p 16 h a v e b e e n s a t u r a t e d , and t h e b a l a n c e w e r e s t a r t e d a i r . d r y . N o t e t h e s q u a r e b o a r d a n d s m a l l w e i g h t a t t h e t o p o f t h e c o l u m n . c e n t a g e s o f l o s s . I t was found t h a t a l t h o u g h t h e s e l o s s e s were not l a r g e , s t i l l t h e y d i d a f f e c t the shape o f the d r a i n -age c a r v e --- more p a r t i c u l a r l y w i t h the l o n g e r columns ( S e c -t i o n 10 below) which v e r s d r a i n e d f o r l o n g e r p e r i o d s . Some o f the l o s s between the f i r s t and second weigh-i n g s was due to d r a i n a g e onto tho pan o f the b a l a n c e . A f t e r t h a t , however, a l l the l o s s i n t o t a l weight was due to evap-o r a t i o n * I n f a c t . , i t was found t h a t a l t h o u g h t h i s l o s s was n o t l a r g e , and a l t h o u g h i t d e c r e a s e d s t e a d i l y w i t h an i n c r e a s e i n time o f d r a i n a g e , s t i l l i t ?;as umeh l a r g e r l a t e r on i n the d r a i n a g e p e r i o d than was the l o s s f r o m the s a t u r a t e d p a r t o f the column by d r a i n a g e . I t was- f e l t t h a t t h e s o i l s s e r e a c -t u a l l y b e i n g d r i e d out more r a p i d l y than, would have been the case i f no e v a p o r a t i o n had t a k e n p l a c e , and t h a t a c c o r d i n g l y . i t would o n l y be f a i r to make correction®- f o r t h e s e evapor-a t i o n l o s s e s . Tho method f i n a l l y used f o r making c o r r e c t i o n s was to s t a r t w i t h the second w e i g h i n g as a b a s i s f t o c a l c u l a t e th© l o s s o f water from the column as a whole,, at eaeh w e i g a i a g , t o t u r n t h i s l o s s i n t o a p e r c e n t a g e of the weight o f s o i l i n t h e wet t e d p a r t o f the column, and to add t h i s p e r c e n t a g e t o t h a t a c t u a l l y o b t a i n e d f o r each u n i t o f the column. T h i s c o r r e c -t i o n has been made l a a l l p e r c e n t a g e s quoted i n t h i s r e p o r t . By way o f i l l u s t r a t i o n , the p e r c e n t a g e l o s s by e v a p o r a t i o n i s c a l c u l a t e d i n T a b l e I I I f o r the 4 8 - i n c h column o f S o i l Ho . 1. The r e s u l t i n g e f f e c t s on the shape o f the curve a r e shown In G h a r t I I . C o r r e c t i o n s a r e a l s o i l l u s t r a t e d i n t h i s c h a r t f o r ~ 22 -CHART H . ^^^^^^^ 'EFFECT OF CORRECT IONS FOR EVAPORATION • DM C U A D r n r- n n A I », A ^ r~ ~ . . „ . . _ NO. 3. SOIL NO. 2, SOI L NO. 1. ON SHAPE OF DRAINAGE CURVE. • — RESULTS ACTUALLY OBTAINED x— AS CORRECTED FOR EVAPORATION. -CwTlMLLy x % LOWER THAU SHOWN) , , ... I A 0 S ''''(»'''' (f ' 20 ' ' ' ' 25 ' ' ' ' 30' ' ' ' 35' ' ' ' T'O ' ' ' <fs ' ' ' Vo^H WOWSS DRAINING the 4 8 - i n c h columns o f each of the o t h e r f i v e s o i l s . TABL15' I I I CORHSCIIH& FOE EVAPORATION. S O U 50. 1, 48-IKOH COLUMU Hours d r a i n i n g ....... 2 4 S 12 24 T o t a l w e i g ht o f column .•.6443.7 0427.5 6422.6 6418.8 6399.4 •in -gria. • •loss -by-• evaporation a f t e r f i r s t 2 ho u r s , i n gm. - 18.2 21..1 24.9 44.3 Oven-dry weight o f s a t u r a t e d s o i l , i n gia. 4047*8 4047.8 4047,8 4047.8 4047.8 l o s s by e v a p o r a t i o n - 0,4 0,5 0.6 1.1 10• L e n g t h o f Column, As a l r e a d y n o t e d , i t was d e c i d e d t h a t i n v a r y i n g the l e n g t h o f column, the s o i l s h o u l d be packed uniformly i n t h r e e -I n c h u n i t s . In d o i n g t h i s p a c k i n g , i t was o f co u r s e found ne-cessary to c o v e r the bottom of the tube w i t h some m a t e r i a l t h a t would h o l d the s o i l and y e t a l l o w the passage o f w a t e r . A t f i r s t s f i n e w i r e s c r e e n i n g "was s o l d e r e d on the bottom o f each piece.' Further t e s t s , however, showed t h a t when the tubes were d r a i n e d i n t o s o i l , b e t t e r c o n t a c t was made with cotton be-tween; and so a l l the work throughout the e x p e r i m e n t s was done with c o t t o n t i e d o v e r the bottom o f each t u b e . ' That p a r t of t h e c o t t o n o v e r l a p p i n g the s i d e of the tube (^hers i t was t i e d ) was t r e a t e d w i t h b l a c k enamel t o p r e v e n t e v a p o r a t i o n . When l o n g e r columns of s a t u r a t e d s o i l were s e t up, i t was found t h a t the d r y i n g o f the s o i l .caused s h r i n k a g e * which i n some cases was s u f f i c i e n t to break the c o n t a c t a n d so a p i e c e o f b l o t t i n g pep»3? wao ul&o i n t r o d u c e d between each two u n i t s , w i t h apparently s a t i s f a c t o r y r e s u l t s . The q u e s t i o n then arose, doe® t h i s i n s e r t i o n of c o t -ton aad c l o t t i n g paper prevent tho downward flow of water? T h i s was t o s t e d out by pack ing two tubos, ono with end on© without c o t t o n end b l o t t i n g papor h a l f way up, and then d r a i n -i n g thorn i n the u s u a l way, Tm c o n s i s t e n t d i f f e r e n c e s woro found , I t was decided a c c o r d i n g l y to continue w i t h tho use of the c o t t o n and b l o t t i n g paper as n o t e d , Under orchard conditions,, i r r i g a t i o n i s r e q u i r e d at depths v a r y i n g q u i t e commonly from o n l y two to over ois: f o e t . I t wee t h e r e f o r e 'Considered, d o e i r o b l o t h a t under tho p a r t i c -u l a r d r a i n a g e c o n d i t i o n s "being used, the e f f e c t o f v a r i a t i o n s i n l e n g t h o f column on th© r e t e n t i o n o f moisture should, bo understood, i n a g e n e r a l way a t l e a s t . i^c cord i n g l y , a s e r i e s of t e s t e was run o f I E - i n c h and 4 8 - i n c h columns of each s o i l . These v»ero s a t u r a t e d In 3 - i n c h u n i t s , s e t up and d r a i n e d i n t o a i r - d r y s o i l t?el©ir4 o f the same fclad^ and packed- i n a s i m i l a r manner, A s u f f i c i e n t numbor of a i r - d r y 3-irich u n i t s was p l a c e d c o n s e c u t i v e l y hole®, such that i n no cane wore they tall wotted by the water r e c e i v e d from above. Tho 12-inch and 48 -Inch columns were weighed p e r l o o l o e i l y i n 3-inoh end 1 2 - l R e h s e c t i o n s r e s p o c t i v o l y , Tho r e s u l t s a rc t a b u l a t e d i n T a b l e s ¥1 and V"II in tho .Appendix, and the averages a re compared g r a p h i c a l l y i n Chart I I I w i t h the f i g u r e s from Tublo V...for. the dra inage o f 3 - ineh columns i n t o a i r - d r y s o i l of tho samo k i n d boloK. The complete curves f o r tho 4 9 - i n c h columns are a l s o shotva'ia Char t II..-- 85 -EFt CHART IE. FECT ON DRAINAGE CURVE OF VARYING THE LENG OF COLUtIN OF WETTED SOIL ,.. 26.-.- .. ...... -An e x a m i n a t i o n o f t h e t a b l e s and c h a r t s w i l l r e v e a l t h e f o l l o w i n g * -( a ) The i n i t i a l r a t e o f l o s s o f w a t e r was i n n e a r l y a l l e a s e s r a p i d , W i t h t h e i n o r g a n i c s o i l s i t was l e s s a s t h e s o i l s became h e a v i e r . A l s o , a s t h e c o l u m n i n -c r e a s e d i n l e n g t h , t h e r a t e o f i n i t i a l l o s s o f w a t e r l e s s e n e d , ( b ) W i t h a l l b u t t h e p e a t s o i l s , t h e m o i s t u r e s o o n r e a c h e d c o m p a r a t i v e e q u i l i b r i u m . I n g e n e r a l , t h e h e a v i e r t h e s o i l t h e l o n g e r t h i s t o o k , The 4 8 - i n c h c o l u m n s h ad a p p a r e n t l y a l l a r r i v e d a t e q u i l i b r i u m a t t h e ends o f t h e i r r e s p e c t i v e t e s t s e x c e p t i n t h e c a s e o f S o i l Ho. 6 ( C h a r t II) , {c) A f t e r t h e i n i t i a l p e r i o d , v a r y i n g t h e l e n g t h d i d n o t a p p e a r t o a f f e c t t h e r a t e o f l o s s o f w a t e r , The i n -d i c a t i o n s a r e t h a t d e c r e a s e i n l e n g t h o f c o l u m n w i l l d e c r e a s e t o some e x t e n t t h e u l t i m a t e m o i s t u r e h o l d -i n g c a p a c i t y . The d i f f e r e n c e s due t o v a r i a t i o n s i n l e n g t h a r e , h o w e v e r , n o t l a r g e when c o m p a r e d w i t h t h e d i f f e r e n c e s b e t w e e n s o i l s , * ( d ) No c o n s i s t e n t d i f f e r e n c e s a r e t o b e f o u n d b e t w e e n t h e m o i s t u r e c o n t e n t s o f t h e d i f f e r e n t p a r t s o f t h e 1 2 -i n e h and o f t h e 4 8 - i n c h c o l u m n s . T h i s means t h a t t h e r e was a t e n d e n c y f o r t h e l o w e r p a r t s o f a c o l u m n t o l o s e j u s t a s much w a t e r a s t h e u p p e r p a r t s , and i n a d d i t i o n , t o p a s s on an amount o f w a t e r e q u a l t o t h a t r e c e i v e d f r o m a b o v e . D i s c i s s i o n a n d R e c o m m e n d a t i o n s 11. R e l i a b i l i t y o f P a c k i n g . I t was s u s p e c t e d t h a t sine© t h e d e g r e e o f p a c k i n g . ( S e c t i o n 6) d e p e n d e d t o some e x t e n t on t h e p r e s s u r e o f t h e h a n d when p o u n d i n g , some v a r i a b i l i t y i n t h i s r e s p e c t m i g h t be expected« An e x a m i n a t i o n o f t h e d a t a o b t a i n e d I n t h e t e s t s showed t h i s t o be t h e c a s e . A s e r i e s was c h o s e n a t random o f 17 p a i r s o f d o u b l e f i l l i n g s o f t h e same t u b e w i t h t h e same s o i l a nd d i f f e r e n c e s w e r e f o u n d i n t h e w e i g h t s o f t h e two u n i t s o f ea c h p a i r . T a k i n g t h e f i r s t w e i g h t a s 100 i n e a c h c a s e , a n d t h e r a t i o o f t h e o t h e r i n p r o p o r t i o n , I t was f o u n d t h a t t h e p r o b a b l e e r r o r was 0.22$« T h a t i s , t h a t f o r e a c h 100 grams o f a i r - d r y s o i l i n t h e f i r s t t u b e p a e k e d ? a s e c o n d p a c k i n g w i t h t h e same s o i l w o u l d h a v e a 50-50 c h a n c e - o f c o m i n g v / i t h i n t h e l i m i t s 99,78 a n d 100,22 g r a m s . T h i s i s n o t l a r g e , b u t t h e v a r -i a b i l i t y b e t w e e n o p e r a t o r s w o u l d l i k e l y b e g r e a t e r . I t i s p r o -p o s e d therefo3.*e t o a t t e m p t t o d e v e l o p a s m a l l m a c h i n e t o r e -p l a c e t h e u s e o f t h e h a n d i n d o i n g t h e p a c k i n g . I t w i l l be n o t e d a l s o t h a t t h e l a b o r a t o r y p a c k i n g was com p a r e d w i t h f i e l d p a c k i n g i n t h e c a s e o f o n l y one s o i l . I t i s f e l t a c c o r d i n g l y t h a t f u r t h e r t e s t s o f t h i s n a t u r e s h o u l d be made w i t h o t h e r t y p e s o f s o i l ; b u t t h a t p e n d i n g s u c h f u r t h e r t e s t s j one w i l l n o t go f a r a s t r a y i n u s i n g t h e t h i r d m e t h o d ' a s d e s c r i b e d i n S e c t i o n 6* An examinat ion o f the c u r v e s as c o r r e c t e d f o r e v a p o r -a t i o n i n Char t I I w i l l r e v e a l tha t i n a l l but the peat s o i l , a p o i n t i s sooa r e a c t e d where the l o s s by d ra inage i s ve ry s l i g h t The percentage m o i s t u r e at t h i s p o i n t may s a f e l y be c a l l e d the m o i s t u r e h o l d i n g c a p a c i t y . I t i s p o s s i b l e tha t i f l e f t i n p o s -i t i o n , the wetted p o r t i o n o f the column would con t inue to l o s e m o i s t u r e to the d r i e r p a r t i n d e f i n i t e l y : but such f u r t h e r l o s s e s would , i n the f i e l d , be n e g l i g i b l e i n comparison wi th l o s s e s by t r a n s p i r a t i o n , and may fo r p r a c t i c a l purposes be d i s -regarded. , O b s e r v a t i o n s made i n the f i e l d indeed p o i n t e d to the e s t a b l i s h m e n t , i n a c o m p a r a t i v e l y s h o r t time a f t e r i r r i g a t i n g . , o f a s t a t s of e q u i l i b r i u m between the wet and dry s o i l s , such t h a t the l i n e o f demarca t ion between them moved downward v e r y s l o w l y i f a t a l l . Veihmeyer {20)„ and o t h e r s have made s i m -i l a r o b s e r v a t i o n s . The i n i t i a l o r more r a p i d s tage o f the d r a i n a g e l a s t -ed o n l y a v e r y shor t time w i t h those s o i l s h a v i n g a low m o i s -t u r e h o l d i n g capac i t y , , w h i l e i t l a s t e d much l o n g e r where the m o i s t u r e h o l d i n g c a p a c i t y was h i g h . T h i s r e l a t i o n s h i p i s a l s o found to h o l d i n the f i e l d . . Indeed, when f i e l d d e t e r m i n a t i o n s o f the m o i s t u r e h o l d i n g c a p a c i t y a re b e i n g made, i t i s very. i d i f f i c u l t to know j u s t how l o n g a f t e r an i r r i g a t i o n the s o i l samples shou ld be c o l l e c t e d . I t was no ted tha t as the column becomes l o n g e r , the m o i s t u r e h o l d i n g c a p a c i t y i n c r e a s e s somewhat, but tha t t h i s i n c r e a s e i s not l a r g e i n comparison w i t h the d i f f e r e n c e s b e -t w a e n s o i l s . I t i s f e l t t h a t f o r t h e p a r t i c u l a r c o n d i t i o n s u n d e r c o n s i d e r a t i o n , t h e r e s u l t s o b t a i n e d w i t h t h e 4 8 - i n c h c o l u m n s c a n be c o n s i d e r e d t o be v e r y c l o s e t o t h e a c t u a l m o i s t u r e h o l d i n g c a p a c i t y , A p o s s i b l e e x c e p t i o n may be n o t e d i n t h e c a s e o f S o i l S o . 8; t h e f a c t t h a t d r a i n a g e was s t i l l in p r o g r e s s a t t h e end o f t h e t e s t w o u l d I n d i c a t e t h a t t h e m o i s t u r e c o n t e n t a t t h a t t i m e was s t i l l somewhat a b o v e t h e m o i s t u r e h o l d i n g c a p a c i t y , 1 3 . C o m p a r i s o n o f M e t h o d s o f D e t e r m i n a t i o n . , , .and H e c o m m e n d a t i o n s I f we a c c e p t t h e r e s u l t s o f t h e 4 8 - i n c h c o l u m n s a s b e i n g a c c u r a t e , t h e q u e s t i o n i s , how c a n wo a p p r o x i m a t e t h e s e r e s u l t s b y some s h o r t e r m e t h o d? O b v i o u s l y i t i s n o t p r a c t i c -a b l e i n m a k i n g a l a r g e number o f d e t e r m i n a t i o n s t o s e t up 4 8 -i n c h c o l u m n s o f e v e r y s o i l . V a r i o u s o t h e r m e a s u r e m e n t s a r e c o m p a r e d I n T a b l e IV w i t h t h e m o i s t u r e h o l d i n g c a p a c i t i e s o f t h e 4 8 - i n c h c o l u m n s . I t w i l l bo s e e n t h a t d r a i n a g e o f 3 - i n c h c o l u m n s f o r o n e - h a l f h o u r gave a l m o s t e x a c t l y t h e same r e s u l t s . The m o i s t u r e e q u i -v a l e n t was c l o s e in t h e e a s e o f two s o i l s o n l y . The p e r c e n t -age c o l l o i d showed e v e n g r e a t e r d e v i a t i o n f r o m t h e m o i s t u r e h o l d i n g c a p a c i t y t h a n d i d t h e m o i s t u r e e q u i v a l e n t . W i t h t h o s e s o i l s o n w h i c h the s t i c k y p o i n t c o u l d be o b t a i n e d , i t a p p r o x -i m a t e d v e r y c l o s e t o t h e 4 8 - i n c h c o l u m n r e s u l t s . The p e r -c e n t a g e a i r s p a c e shows a f a i r l y c o n s t a n t r a t i o t o t h e m o i s t u r e h o l d i n g c a p a c i t y w i t h most s o i l s , b u t t h e p e r c e n t a g e s a t u r a t i o n , shows a much c l o s e r r a t i o s t i l l * The m o i s t u r e e q u i v a l e n t , t h e p e r c e n t a g e c o l l o i d a nd t h e p e r c e n t a g e a i r s p a c e a r e a p p a r -e n t l y n o t r e l i a b l e f o r u s e I n d e t e r m i n i n g t h e m o i s t u r e h o l d i n g TABLE IV._ COMPARISON OF VARIOUS MSASPR-SMSNJS. S o i l N o . 1 3 4 5 6 7. rith 43-inch, c o l u m n s at e q u i l i b r i u m 14,2 17.1 24.3 26.9 34.4 89 .4 i V i t h 3 - i n c h c o l u m n s a f -t e r II- hour 14,6 1 7 . S 24. 5 26.8 34.3 87.7 M o i s t u r e e q u i v a l e n t ' S-,4 13.7 18.6 53.1 91.0 P e r c e n t a g e c o l l o i d 10.4 3.6 11.8 S I . 6 o7 8.4 S t i c k y p o i n t 24.4 2 6 8 52.8 P e r c e n t a g e a i r space £7.4 31.7 38.4 39.3 44.3 62,5 P e r c e n t a g e s a t u r a t i o n 19 .,-4 28.7 35.6 92.7 c a p a c i t y 'With s o i l s o f t h ese t y p e s * The s t i c k y p o i a t shows p r o mi sc., but is- n o t a p p l i c a b l e t o a l l s o i l s , The p e r e e n t a g © s a t u r a t i o n l i k e w i s e shows p r o m i s e , a n d f o r p r a c t l & a I p u r p o s e© may g i v e v e r y s a t l s . f a . e t o r y r e s u l t s . , t h a t i e # i t ja&y s i m p l y be n e c e s s a r y t o p a c k t h e s o i l , . Immerse i t i n w a t e r t i l l s a t -u r a t e d , d e t e r m i n e t h e p e r c e n t a g e m o i s t u r e a n d f r o m t h i s f i g u r e d e d u c t say Z% t o o b t a i n t h e m o i s t u r e h o l d i n g c a p a c i t y . I n t h i s r e s p e e t , i t i s w e l l t o n o t e (See: S e c t i o n 3} t h a t q u i t e d i f f e r -e n t r e s u l t s w e r e o b t a i n e d b y A1way and MeBol© ( 2 ) , A t t h e p r e s e n t t i m e i t i s f e l t t o be s a f e r t o d r a i n t h e 3 - I n c h c o l u m n s f o r o n e - h a l f h o u r t?hen more a c c u r a t e r e s u l t s a r e r e q u i r e d ; a n d t h i s a c c o r d i n g l y i s t h e m e t h o d recommended. W I t h a l i t t l e more s t a n d a r d i s a t i o n p e r h a p s i n t h e p a c k i n g , I t m i g h t pro\-p v e r y u s e f u l , m o r e o v e r , i n t e s t i n g t h e e f f e c t s o f such f a c t o r s a s o r g a n i c m a t t e r c o n t e n t , s o d i u m and c a l c i u m b a l a n c e , and c u l t u r a l t r e a t m e n t s o n t h e m o i s t u r e h o l d i n g c a p -a c i t y o f a. s o i l . I t s h o u l d be much more c o n v e n i e n t i f t h e same m e t h o d c o u l d be u s e d b o t h f o r d e t e r m i n i n g a c t u a l f i e l d c a p a c i t y a n d f o r c o n d u c t i n g r e s e a r c h w ork o n m o i s t u r e r e t e n t i o n i n t h e l a b o r a t o r y . * T o • s u m m a r i & e , t h e p r o c e d u r e recommended i s a s f o l l o w s : (1) A i r - d r y the s o i l - , s c r e e n out l a r g e r s t o n e s a n d r o o t s , , a n d m i x t h o r o u g h l y . Use e q u a l p o r t i o n s b y v o l u m e when m a k i n g c o m p o s i t e . (2 ) Use tubes S inches i n diameter and 3 inches h i g h , w i th c o t t o n ox^or t h e i r bottoms.. I t w o u l d be w e l l a c t u a l l y t o m e a s u r e t h e i r v o l u m e . Pa-ck two t u b e s w i t h t h e so .11$ by t h e t h i r d m e t h o d d e s c r i b e d i n S e c t i o n 6 o r b y some s t a n -d a r d i s e d v a r i a t i o n o f t h i s m e t h o d . ( 3 ) S a t u r a t e one c o l u m n b y i m m e r s i o n i n w a t e r f o r a t l e a s t t h r e e h o u r s . C o v e r w i t h a w e i g h t o f f i v e p o u n d s o r l a r g e r w h i l e s a t u r a t i n g , t o p r e v e n t s w e l l i n g . Y i e i g h . (4) P l a c e w o t t e d c o l u m n o v e r a i r - d r y c o l u m n f o r o n e h a l f h o u r * w i t h s m a l l w e i g h t a b o v e t o e n s u r e g o o d c o n t a c t . T/©igh t h e t o p • c o l u m n * (5} D r y a t 105° G* f o r 24 h o u r s , w e i g h and c a l c u l a t e ' the-'vol-ume w e i g h t , s p e c i f i c g r a v i t y , , p e r c e n t a g e a i r spa-so, p e r -c e n t a g e s a t u r a t i o n and m o i s t u r e h o l d i n g c a p a c i t y . SUMMARY L a b o r a t o r y t e s t s were c o n d u c t e d o n e a c h s u c c e s s i v e s t e p o f t h e p r o c e d u r e f o r d e t e r m i n i n g 1 : t h e m o i s t u r e h o l d i n g c a p a c i t y o f a s o i l i n the l a b o r a t o r y . That f i e l d c o n d i t i o n which i t was at tempted to approximate was an i r r i g a t e d o r c h a r d s o i l , u n i f o r m i n p h y s i c a l c o m p o s i t i o n to a depth g r e a t e r than r e q u i r e d to i r r i g a t e . The f o l l o w i n g r e s u l t s may be n o t e d : (1) Of those methods t r i e d f o r o b t a i n i n g the m o i s t u r e : h o l d i n g c a p a c i t y , , w e t t i n g and d r a i n a g e o f a column o f s o i l a p -peared to approx imate most, c l o s e l y to the above c o n d i t i o n s , (2) The degree of p a c k i n g Is o f g r e a t importance i n i t s e f f e c t on the amount o f s o i l , i n the ^ibe and c o n s e q u e n t l y on the m o i s t u r e h o l d i n g c a p a c i t y . To approximate f i e l d p a c k i n g below the s u r f a c e foot* a c o n s i d e r a b l e amount of tamping i s n e c e s s a r y i n the l a b o r a t o r y r I t was found that the same method' o f p a c k i n g r e s u l t e d i n g r e a t e r compact ing as the column was i n -c r e a s e d i n l e n g t h , (5) S p e l l i n g a t the top of the column d u r i n g the p r o c e s s o f n e t t i n g causes the r e t e n t i o n o f too much m o i s t u r e i n the upper p a r t o f the co lumn. Hence i t , Is a d v i s a b l e to p revent s t r o l l i n g . T h i s can be done by p l a c i n g a s u i t a b l e weight on top o f the eolt ima, {4} When c o r r e c t ions wore made f o r e v a p o r a t i o n , d r a i n a g e over a wire s c r e e n tras found to be very SIO T C , Dra inage over an a i r - d r y s o i l o f the same k i n d caused g r e a t e r l o s s e s , . S t i l l l e s s m o i s t u r e was r e t a i n e d i f the s o i l b elov? was h e a v i e r i n type than tha t b e i n g d r a i n e d , kn i n c r e a s e i n the i n i t i a l m o i s t u r e content of the s o i l below f rom sere to above the w i l t i n g c o e f f i c i e n t i n c r e a s e d s l i g h t l y the m o i s t u r e h o l d i n g c a p a c i t y of the s o i l above . (5) An i n c r e a s e i n t h e l e n g t h , o f c o l u m n w e t t e d i n c r e a s e d s l i g h t l y t h e m o i s t u r e h o l d i n g c a p a c i t y a n d a l s o i n c r e a s e d t h e t i m e r e q u i r e d f o r t h e m o i s t u r e c o n t e n t t o come t o c o m p a r a t i v e e q u i l i b r i u m , T h e r e a p p e a r e d t o be l i t t l e v a r i a t i o n i n t h e m o i s t u r e r e t a i n e d i n t h e d i f f e r e n t s e c t i o n s o f t h e l o n g e r c o l -umns, (6 ) C o m p a r i s o n s a r e made b e t w e e n t h e d r a i n a g e o f a 4 8 -i n c h c o l u m n a n d v a r i o u s o t h e r m e t h o d s o f o b t a i n i n g t h e m o i s t u r e h o l d i n g c a p a c i t y . I t I s c o n c l u d e d t h a t d r a i n a g e f o r o n e - h a l f h o u r o f a 3 - i n c h c o l u m n I n t o t h e same s o i l b e l o w a s a b o v e , s h o u l d . g i v e r e l i a b l e r e s u l t s . - 34 ~ LITEBATUBS CITED A l w a y , ' ? . J . a n d H e D o l e , C-.R. 1917* R e l a t i o n o f t l i e w a t e r - r e t a i n i n g c a p a c i t y o f t h e s o i l t o i t s h y g r o s c o p i c c o e f f i c i e n t . J . A g r . R e s , £ % 2 7 - 7 1 , A l w a y , F. J , a a t I c B o i e , & , , B , 1917, The r e l a t i o n o f movement o f w a t e r i n a s o i l t o i t s ' h y g r o s c Q p i c i t y a n d I n i t i a l m o l s t n e s s , J , A g r , R e s . 10 : 391 -428 , Bouyoucos,. (5.1* 1927 . The h y d r o m e t e r a s a new and r a p i d method f o r d e t e r m i n i n g t h e c o l l o i d a l c o n t e n t o f s o i l s . S o i l Se*. 25 3 1 9 - 3 3 2 , B o u y o u c o s , G-.J. 1 9 2 9 . A new, s i m p l e a n d r a p i d m e t h o d f o r d e t e r m i n i n g t h e m o i s t u r e e q u i v a l e n t o f s o i l s , and t h e r o l e o f • s o i l c o l l o i d s , o n t h i s m o i s t u r e e q u i -v a l e n t . S o i l S c . 27 : 2 3 3 - 2 4 0 . ,Contt%. '-J*-H*-H.* . • • - . • . ' . • * ' . • • ' 1950* S i n g l e v a l u e s o i l p r o p e r t i e s . 111.. H o t e o n t h e t e c h n i q u e o f t h e K e e n - R a c z k o w s k i b ox e x p e r i -ment . X . A g r . S c . 20 : 4 0 7 - 4 1 3 . Frap.s^ G*-S*...... 1915 . M o i s t u r e r e l a t i o n s o f some T e x a s s o i l s . T e x a s A g r . -Sxp. S t a . B u i . 1 8 3 . Hardy.,. , 'F. 1923 . The p h y s i c a l s i g n i f i c a n c e o f t h e s h r i n k a g e c o -e f f i c i e n t o f e i a y s and s o i l s . J . A g r , S c . 13 i . 2 4 3 - 2 6 4 . H a r d y , I 1 , 1923. The minimum w a t e r - r e t a i n i n g c a p a c i t y o f c o l l o i d a l s o i l s , t h e i n t e r p r e t a t i o n o f t h i s a n d o f c e r -t a i n o t h e r s o i l m o i s t u r e c o n s t a n t s . J . A g r , Sc.. 13 : 3 4 0 - 3 5 1 . H l l g a r d , E * JJ*. .' 1914 . S o i l s . The M a c M I l l a n Co. . J o f f s , J . 8 . and McLean,. H. 0 . 1Q25. C o l l o i d a l b e h a v i o r o f s o i l s and s o i l f e r t i l i t y * . I , S u c t i o n f o r c e o f s o i l s a s a n i n d e x o f t h e i r c o l l o i d c o n t e n t . S o i l S c . 20 : 169 -176 . - . 3 5 -1 1 . • K e e n , B.A. a n d R a e z k o v / s k i , H. 1 9 2 1 , The r e l a t i o n b e t w e e n t h e c l a y c o n t e n t a n d c e r -t a i n p h y s i c a l p r o p e r t i e s o f t h e s o i l , T. A g r . S c . 11 : 4 4 1 - 4 4 9 . 1 2 . K e e n , B.A, . , • 1 9 3 0 , S i n g l e v a l u e s o i l p r o p e r t i e s . . I T , A f u r t h e r n o t e o n t h e t e c h n i q u e o f t h e b o x e x p e r i m e n t . , J» A g r * S C . 20 4. 4 I 4 - 4 1 S . 1 3 . K i n g , P*H. . 1 8 8 9 . D e t e r m i n a t i o n s o f w a t e r - h o l d i n g c a p a c i t y o f t h e u p p e r f i v e f e e t o f s o i l . T£is. A g r . E x p . S t a . ; B p t . 1 8 3 9 , 1 4 . .Labedef f.,, A*F . . . 1 9 2 7 . The movement o f g r o u n d and s o i l w a t e r s . P r o c . F i r s t I n t . Gong. S o i l S c . 1 : 4 5 9 - 4 9 4 . 1 5 . t e h e d 0 f f 9 A . f . 1 9 2 7 . M e t h o d s o f d e t e r m i n i n g t h e maximum m o l e c u l a r m o i s t u r e h o l d i n g c a p a c i t y o f s o i l s . P r o c . F i r s t I n t . . .Gong* B o i l S o . . 1 ••: 5 5 1 - 5 8 0 . 16.. L o u g h r i d g e , R.,H,. , 1894. I n v e s t i g a t i o n s i n s o i l p h y s i c s . G a l . A g r . 3xp« S t a . Hp i s . 1 8 9 3 - 9 4 . 1 7 . L y n d e , 0,3", a n d D u p r e , H..A. 1 9 1 3 . On a new method o f m e a s u r i n g t h e c a p i l l a r y l i f t : o f s o i l s . J . Am. S o c . A g r , _5 ; 1 0 7 - 1 1 6 . 1 8 . M c L a u g h l i n , - .^.W* 1 9 2 0 . C a p i l l a r y movement o f s o i l m o i s t u r e . U.S.is .A. B u i . 8 3 5 . 1 9 . M c L a u g h l i n , 1 9 2 4 . The c a p i l l a r y d i s t r i b u t i o n o f m o i s t u r e i n s o i l c o l u m n s o f s m a l l c r o s s s e c t i o n . U.S.3.A. D e p t . Bul» 1 2 2 1 . 2 0 . V e i h m e y e r , P . J . 19 2 7 . Some f a c t o r s a f f e c t i n g t h e I r r i g a t i o n r e q u i r e -m e nts o f d e c i d u o u s o r c h a r d s . H i l g a r d l a _2 j 1 2 5 - 2 8 4 . 2 1 . V e i h m e y e r , IT.T., O s k e r k o w s k y , J . a n d T e s t e r , K,B. 1 9 2 7 . Some f a c t o r s a f f e c t i n g t h e m o i s t u r e e q u i v a l e n t o f s o i l s . P r o c . F i r s t I n t . C o n g . S o i l . S c . .1 ; 512-534. - 5 0 22„ Yeihrneyer* and H e a d r i e k s o n , A..H, 1931. The mo is tu re e q u i v a l e n t as a measure o f the f i e l d c a p a c i t y e f s o i l s . S o i l S c . 3J2 : .23. ' Widstoe , 3" .A., and M c L a u g h l i n , 1?.W, 1912,, The movement o f water i n i r r i g a t e d s o i l s . Utah A g r . Go 1 1 . I2sp. St a . B u i . 1 1 5 . 24 . W i l e y , 'H..W. 1926. P r i n c i p l e s and p r a c t i c e s of a g r i c u l t u r a l a n a l y s i s , T o l . 1 , The Chemica l P u b l i s h i n g 'Co, A P P E B S Z X , A d d i t i o n a l Tables R e f e r r e d to i a Test., Comparison o f D r a i n a g e o v e r T/jre S c r e e n a n d . O v e r S o i l ; * ( C o r r e c t i o a s ^ .-Percentage l l o l s - t t t r e S o i l No-. 1 D r a i n a g e over S a t a . T 1 h r 2 h r 3 h r "5 h r 9 h r . Tv'Ire s c r e e n 17..0 16.9 16 .6 16 , 6 16,5 16.4 16.3 S o i l 1 o v e n - d r i e d 15.1 14.0 13,9 13,7 13.4 " 1 a i r - d r i e d ( 1 * 3 $ ) 16.9 14*6 14*1 13 . . , 7 13.5 13,2 13.0 s' 1 abov e iV.C^U .0£) 15* 4 14.3 14.0 13.6 13.5 " 5 i n t u b e 16.1 1 3 , 1 124 5 11.4 10.9 10.2 9,9 " 5 i n can* 16.. 0 12.. 8 12.3 11.5 10.9 10.1 9-, 7 S o i l Ho.. 2 D r a i n a g e o v e r S a t n . i " hr 1 h r 2 h r 4 h r 6 hr 8 h r . W i r e s c r e e n 19 .5 19.2 19.. 1 19.0 19.0 19 .0 18.9 S o i l 2 o v e n - d r i e d 17.9 15.1 15.8 15.6 15.2 S o i l 2 a i r - d r i e d ' ( 0 , 7 j i ) 10.8 17.2 17.0 16.7 16.6 1 6 . 4 16.4 S o i l 2 a b o v e Y/.C.(3.9}j) 18.. 4 16,5 16.3 1 6 . 1 15,9 16 .0 S o i l 5 i n t u b e 20.2 11.3 9.. 5 8.1 7,2 6.6 6.4 S o i l 5 i n c a n 19.5 9.6 S-.4 8.7 5.8 5.6 5.5 S o i l Up. 5 D r a i n a g e o v e r S a t n . 1 h r 2 h r 3 h r 4 h r 5 h r . V.'ire s c r e e n 26 .6 26.5 26.3 26.3 26,1 26.1 S o i l 5 o v e n - d r i e d 24.8 22 . 8 22.4 21.8 S o i l 3 a i r - d r i e d ( l . 6 f i ) 26.3 24.6 24.5 24,5 24.2 2 4 . 1 24.1 S o i l 3 a b o v e Y/.C. (3-. 0 5 s ) 26 .3 2 5 . 1 ,.2 5 » X 25,1 25,0' S o i l 5 i n t u b e 25,8 24.4 24.3 24.2 24,1 24,1 24.1 S o i l 5 i n c a n 26 . 8 24,2 2 4 . 1 34.0 24,0 24.0 23.9 1. S a t n . - P e r c e n t a g e s a t u r a t i o n 2. V?„G*- W i l t i n g C o e f f i c i e n t 3. I n c a n - i . e . , on a f l a t s u r f a c e . W i r e s c r e e n 26*6 28.4 20,4 38.3 28 * X 28.0 27 ,6 S o i l 4 o v e n - d r i e d 26.4 24.5 25.9 23,7 2o .2 S o i l 4 a i r - d r i e d (1.5$) 28 ,2 26,8 26.6 26.4 26 .3 26 .3 26.2 S o i l 4 a b o v e W.C. (13,2<>;) 27.3 25.2 24.9 24..6 24 .4 24.4 24.3 S o i l 5 i n txibe 28.6 26.1 25 *4 25.1 S o i l 5 i n c a n 29.1 26.4 26 ,2 26 . 2 try ^ . 1 2 5.. 9 25.9 S o i l ITo. 5 , D r a i n a g e over , J S a t n . 1 h r 2 h r 3 h r 5 hr 9 'for »ire s c r e e n 5 6 , 1 3 6 * 0 3 6 . 0 3 5 . 9 3 5 , 7 3 5 . 7 3 5 , 5 S o i l 5 o v e n - d r i e d 5 3 . 3 3 1 , 8 3 1 , 2 3 1 . 0 3 0 1 5 S o i l 5 a i r - d r i e d ( 2 . 4 ^ ) 5 6 , 5 3 4 . 5 3 4 . 2 3 3 . 9 3 3 . 5 3 3 , 3 3 3 . 0 S o i l 5 a b o v e Y ',.C. ( 2 1 . 6 ^ ' ) 3 6 , 2 3 4 . 5 3 4 . 1 5 4 . 0 3 3 . 7 3 3 , 6 3 3 . 5 S o i l 5 i n c a n 5 6 , 4 3 4 . 2 3 5 . 3 3 3 , 6 3 3 , 3 3 3 , 0 5 2 , 8 S o i l Ho . 6 . s l a l ^ ' l T ^ Iir W i r e s c r e e n 9 0 . 5 9 0 . 4 9 0 . 4 9 0 . 4 9 0 . 5 9 0 , 5 90 . 2 S o i l 6 o v e n - d r i e d 8 6 . 6 82*4 8 3 . 7 8 1 . 8 8 0 , 1 S o i l 6 a i r - d r i e d (lO.Oyi) 9 1 . 6 87 . 7 8 6 . 1 8 5 . 1 8 3 . 5 8 2 . 0 8 0 . 7 So i l a a b o v e Y7.C. (46,95:- ) 9 5 - . 1 9 1 . 5 9 0 . 1 8 9 . 3 8 7 . 0 8 5 . 6 8 3 , 6 S o i l 5 i n t u b e 9 1 . 5 8 8 . 0 8 5 . 3 8 4 . 4 8 2 . 7 8 1 . 5 8 0 .0 S o i l 5 i n c a n 8 9 . 1 8 5 . 1 8 2 . 6 8 1 . 7 7 9 . 5 7 9 . 0 7 7 . 8 D r a i n a g e o v e r ----- - -*fbmuam>~- ~—— - 39 -S o l i Ho. TABLE Y I . D r a i n a g e o f 1 2 - I n c h Columns ( C o r r e c t e d f o r E v a p o r a t i o n ) P e r c e n t a g e Moisture Depth I n I n d i e s S a t n . 1 h r . 2 h r . 4 h r . 8 h r . 0-3 1 6 . 5 1 5 . 5 15 .0 1 4 . 7 14 .6 3-6 1 5 . 8 1 4 . 4 1 4 . 1 13 , 6 1 3 . 4 6—9 1 5 . 8 14 ,2 13 ,8 13 .3 13 .2 9 -12 , 1 5 , 8 14.. 6 14 .2 1 3 , 8 1 3 . 5 Average • 1 6 . 0 14 .6 1 4 . 3 1 3 . 8 13 .7 S o i l I.o. 2 Percentage Moisture Depth i n Inches. S a t n . 1 hr* 2 h r . 5 hr . 7 hr , 11 hr 0-3 1 9 , 7 17 ,7 17 .7 17*4 17 .3 17 .1 3-6 19 ,6 17 .6 17 . 5 1 7 . 1 17 .0 15 ,9 6-9 19 . 4 18*0 17 .8 17 .7 17 .7 9-12 1 9 . 5 1 7 . 8 17 .8 17.6 17 .6 1 7 . 7 Average 1 9 . 5 1 7 , 8 17 .7 1 7 . 5 1 7 . 4 17 , 4 S o i l Ho. P e r c e n t a g e M o i s t u r e Depth i n i n c h e s , Satn. 1 hr.. 2 h r . 5 hr... 4 hr... . 5 hr 0-3 3-8 6-9 9-12 Averase 26 .6 25 .0 24 .7 24 .6 2 4 . 5 2 6 . 4 25 ,0 2 4 , 8 24 .7 24 .6 24*6 26.7 25 .0 24 ,7 24.6 24 .6 2 5 . 5 24*0 23 .7 25 ,6 26 « 3 24*8' 24 .6 2 4 . 4 24 .3 24 .2 - 40 --TABL5 71 (Continued) S o i l Ko• 4 Percentage 1 .ioisture 6 hr. . 10 h r Denth i n I n c h e s ' , Satn » 1 h r . 2 h r . ''4 h r . 0-3 27 .4 3 o »• V 25.. 4 25.1 24.8 24.6 3-6 27.7 26.1 25.8 25.4 25.0 6-9 29.6 27 .4 3 *7 » 0 26.5 26.1 25.3 9-12 29.4 27 ;s 25,9 26 .5 26.5 25.9 A v e r a g e 23.5 26 . 6 26 a 2 25.9 25,6 2o»o S o i l No. 5 • J5ejpth Satn-*5 Percentage M o i s t u r e 1 hr, << jLlJ. , 3 hr , 5 hr. 7 hr. " ~ 1 0 l h r 0-3 36 «5 35.8 3 o. 2 34.8 34,6 34.4 34.1 3-6 35.7 35.0 3 4 . 6 34,4 34.0 53 . 9 33.8 6-9 35.8 54.7 34.4. . 34.2 53 . 8 55.7 33.4 • 9-12 3-6.0 . 54,3 • 34.1 34. 1 33 . 3 33.7 33.4 Ave . 56.0 35.0 ' 3 4 . 6 ' 34.3 3,4.1 ' 53.9 - 55.7 S o i l K o , 6 'Percen t a g e '. Faoistur e Depth i n I n c h e s S a t n * 1 hr. 2 hr . 3 hr. 5 hr, 8 hr«, 0-3 3-6 ' 6 -9 • . . 9-12 92.5 94.4 95.1 91.3 91.2 93.0 93.6 88.8 90.6 92.2 93.0 88.6 90.2 91.6 92.4 88.2 39 .4 90.8 91.7 87.6 08,7 90.1 91.0 87 ,3 . A v e r a g e 93.4 91.3 91.2 90 ,6 89.9 89 .4 ; TABLZ 711. Drainage,, of 43-Inch Coluians. (Corrected for 3vapora t ion) S o i l ilo. 1 Pe r c e n t a g e -Moistare' Dentil i n Feet -Sa.fcsu •. 2 hr. • § h r . 7 hr. 20 h r . 0-1 15.8 14.3 14.6. 14,5 14.4 1-2 15.0 14.1 13.9 13.7 13,7 3-3 15.6 14.. 5 14.3 14.1 13.9 ._ 3-4 15,7 .. 14.5 14. 5 14.4 .14,4 Average IS.5 14.4 14.3. 14.2 14.1 S o i l Ko. 2 P e r c e n t a g e Moisture.; Denth i n F e e t Satri.. ' 2 hr. 4 h r . 8 hr. 12 hr. 24 hr 0-1 • 19.4 16.7 16.5 16.5 16.6 16.5 1-2 18,9 15.9 16,4 16.4 16.4 16.3 2-5 18.9 17.5 •17.2 17.0 16.9 16,8 3-4 . 20.2 18.9 18.9 18.8 18.9 Average , 19.4 17.5 17,3 17.2 17.1 17.2 S o i l llo. 5 Per c e n t a g e Moistnre' Depth i n F e e t . S a t n , 2 hr... 4 hr. 8 hr. 24 hr.. ' 0-1 26.7 25.6 2 5.3 25.0 24.7 1-2 25.3 25.2 24,8 24.5 24.5 2-3 25.5 24.4 24,0 S3.8 23.7 3-4 . 26.1 24.7 24.6 24.5 24.6 Average 26.1 24.9 2,4.6 24.4 24.3 - 42 -TABXS 111 (OonT-lnticft) t a r e 0 - .1 SB iS 37 ,S S6.4 ^6,5 1- 2 23.U E7.X S7*0 86 40 .8-5- SS^S g © . # B 2^*5 &l1*g M,*S .. S f i , S . . . . . . , . » • » . . « • . . . . . . . . . „ . r » ^ , I .Mill i Ii II. ,. i . . , , . , . .•,«..•, i a t t ire ^ _ 1-2 3-3 $-4 35.4 35.4 33.8 35.8 3 35*0 35.0 35.0 34.0 34*S 34.4 34.G 34.6 34.6 S4*4 34*13 34.4 34.1 , 34.0 34.5 34.2 84*4 353 „0 34.5 34,3 34.4 33*9 34.3 AvoroKP 35.6 34.9 34.6 34.5 34.4 54.3 S o i l IIo. 5. Farcontape Holeture .uoptii i n li'eet .4 h % 24 nr. .30 hr., 0-1 01.3 90.8 .50 *9 90.4 f»0 *I G9.5 en. 5 • 1-2 92. 2 92.0 01.1 90.4 90 ..3 93.5 91*1 90.6 90.5 ^ 3-4 , 9S.1 , , qo." 09,0 88.8 88.4 , 88.0 5 S - I _ 91.2 90.6 . PP.2 J s ! £ . * B 

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