LIME CONTENT OF SOIL IN RELATION TO CROP RESPONSE TO MAGNESIUM By BISHWANATH SAHU A THESIS S u b m itte d to th e S ch o o l of G ra d u ate S t u d i e s of M ichigan S t a t e C o l l e g e o f A g r i c u l t u r e and A p p l i e d S c i e n c e i n p a r t i a l f u l f i l l m e n t of t h e r e q u i r e m e n t s f o r th e d e g re e of DOCTOR OF PHILOSOPHY D epartm ent of S o i l S c ie n c e 1949 ACKNOWLEDGEMENTS 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 s i n c e r e g ratitu d e a nd a p p r e c i a t i o n t o D r . L . Ivl. T u r k f o r h i s c o n s t a n t g u i d ­ a n c e and v a l u a b l e s u g g e s t i o n s c o n c e r n i n g t h e c o n d u c t o f i n v e s t i g a t i o n r e p o r te d in t h i s p a p er and p r e p a r a t i o n of the m a n u s c rip t. I am i n d e b t e d t o D r . C. E . M i l l a r , D r . R. L. Cook and D r . K. L aw to n f o r t h e i r s y m p a t h e t i c i n terest, _ a d v i c e and e n c o u r a g e m e n t d u r i n g t h e c o u r s e of in v estig atio n . T h a n k s a r e a l s o d u e t o M i s s Naomi B e r t h a A bling f o r re n d e rin g help in the greenhouse and la b o r a ­ t o r y work. A ll p h o to g rap h s i n c o n n e c tio n w ith the t i o n w e r e k i n d l y t a k e n by- D r . R. L . Cook. in v estig a­ CONTENTS Page 1. I n t r o d u c t i o n .......................................... 2. The O b j e c t o f t h e 3. Review o f L i t e r a t u r e ................................................... 3 4. P l a n o f t h e I n v e s t i g a t i o n ......................................... 5 $. D e s c r i p t i o n of S o i l T y p es Used . . . . 7 6. S o i l S a m p l i n g a nd P r e p a r a t i o n . . . 8 7* A n a l y t i c a l Methods 8. P h y s i c a l C om position and Chemical C h a r a c t e r ­ i s t i c s of th e S o i l s . . . . . . 11 E xperim ental Procedure i) F e r t i l i z e r A p p licatio n . . . i i ) ' C u l t u r a l Methods i i i ) P r e p a r a t i o n of P l a n t M a t e r i a l . . iv) N itrogen F ractio n s . . . . 15 16 18 19 9. 10. 11. 12. . In v estig atio n . . . . . . 1 . . 2 . 8 . . . . P r e l im i n a r y Experim ents M o b i l i t y of a p p l i e d Ca a n d Mg I o n s i n t h e D ifferen t S o ils ............................................................ 25 E f f e c t o f C o n c e n t r a t i o n of M a g n es iu m on t h e S t r u c t u r e o f S o i l ............................................................ 30 E xperim ental R e su lts i) Grow th R e s p o n s e ii) Gro w th R e s p o n s e iii) Growth R e s p o n s e iv) Growth R e s p o n s e 36 40 45 45 in in in in Q,ua rtz S a n d C u l t u r e . W isner S o i l . . P l a i n f i e l d an d F o x Sand H ills d a le S ubsoil . 13. F o lia r A nalysis of C r o p s D u r i n g Growth . 14. Crop Y i e l d s i) Q u a r t z Sand C u l t u r e ........................................ i i ) "W isner . . . . i i i ) P l a i n f i e l d a n d Fox S a r d iv) H ills d a le Subsoil . . . . . . . . . . . . . . . 51 57 61 65 71 ii Page 15. P l a n t C om position i) Calcium . 75 ii) M a g n e s i u m .......................................................... . . . 8 6 iii) P o t a s s i u m ............................................................................ 92 16. Ca:Mg R e l a t i o n s h i p i n P h o s p h o r u s N u t r i t i o n . . 17. C a tio n E q u iv a le n t Constancy . . 103 18. C a l c i u m and M agnesium C o n t e n t of Soils a t t h e End of C ro p H a r v e s t ..............................................105 19. D i s c u s s i o n .................................................. .......... 20. Summary and C o n c l u s i o n .........................................................117 21. . . . L i t e r a t u r e C i t e d .............................................................. 98 109 . 120 LIME CONTENT OF SOIL IN RELATION TO CROP RESPONSE TO MAGNESIUM B i s h w a n a t h Sa hu INTRODUCTION M a g n e s iu m i s a n i m p o r t a n t c o n s t i t u e n t of c h l o r o ­ p h y l l and i t c o n s t i t u t e s a b o u t 2 . 7 p e r c e n t of t h e ch lo ro p h y ll m olecule. Proper fu n c tio n in g and e f f ic ie n c y o f t h e l e a f , t h e r e f o r e , d e p e n d s t o a l a r g e e x t e n t on t h e p r e s e n c e of a n a d e q u a t e a m ou n t of m a g n e s i u m . p r o p e r u t i l i z a t i o n of B e t t e r and the f e r t i l i z e r s a p p l i e d to q u i r e s a l a r g e and e f f i c i e n t l e a f a r e a . so il re­ The p r e s e n c e of a d e q u a t e a m o u n t of m a g n e s i u m p l a y s an i m p o r t a n t p a r t i n th is regard. phosphorus. M a g n es iu m i s a l s o c o n s i d e r e d a s a c a r r i e r o f I t is a s s o c i a t e d w i t h seed fo rm a tio n ; h y drate p ro d u c tio n and t r a n s p o r t . carbo­ A ccum ulation of n i t r o ­ gen by l e g u m e s i s i n c r e a s e d b y t h e p r e s e n c e of m a g n e s i u m . T h u s , t h e i m p o r t a n c e of an a d e q u a t e s u p p l y o f m a g n e siu m i n p l a n t a n d f e r t i l i z e r economy i s e v i d e n t . L im e — M a g n e s i a H y p o t h e s i s An e x c e s s of m a g n e s i u m i s h i g h l y t o x i c t o g r e e n p l a n t C alcium i n s u i t a b l e c o n c e n t r a t i o n c o u n t e r a c t s t h i s t o x i c i t y Loew ( 3 5 , 3 6 ) * i n 1 8 9 2 , d e v e l o p e d t h e e s i s and p ro p o se d t h a t "L im e—m a g n e s i a ” h y p o t h c a l c i u m a n d m a g n e siu m s h o u l d be ^F igures in p a re n th e s is r e f e r to " L ite r a tu r e C ite d ." p r e s e n t i n a d e f i n i t e r a t i o f o r t h e p r o p e r f u n c t i o n i n g and g r o w t h o f p l a n t s a l t h o u g h t h e op tim um r a t i o w o u ld v a r y w ith th e plant species. gations in s o i l , T h i s h a s p r o m p t e d many i n v e s t i ­ s a n d and w a t e r - c u l t u r e s . Lipman (34 ) in an e x h a u s t i v e summary h a s shown t h a t a l l t h e s e i n v e s t i g a ­ t i o n s h a d n o t l e d t o a g e n e r a l a g r e e m e n t on the i n t e r p r e ­ t a t i o n of t h i s h y p o t h e s i s . In a l l these in v e s tig a tio n s very l i t t l e p a i d t o t h e d e g r e e o f s a t u r a t i o n of t h e a t t e n t i o n was exchange complex o f s o i l i n d e t e r m i n i n g t h e optim um Ca:Mg r a t i o f o r t h e g r o w t h o f p l a n t s a n d t o w h a t e x t e n t t h e v a r i a t i o n i n t h e Ca:Mg r a t i o -influenced t h e m in e r a l and o rg a n ic c o m p o sitio n o f the p l a n t s . There i s a grow ing te n d e n c y to a sso c ia te the h e a l t h a n d w e l l - b e i n g o f man a n d a n i m a l s w i t h t h e f o o d they e a t . S o i l i s one of t h e p o t e n t f a c t o r s i n d e t e r m i n i n g the co m p o sitio n o f p l a n t s . ratio So a n y v a r i a t i o n i n t h e Ca:Mg i n t h e s o i l may i n f l u e n c e t h e c o m p o s i t i o n o f p l a n t s . Thus a s t u d y of t h e Ca:Mg r a t i o f r o m t h e s e two a s p e c t s appears t o be w a rra n te d . THE OBJECT OF THE INVESTIGATION The o b j e c t o f t h e p r e s e n t i n v e s t i g a t i o n i s t o s t u d y t h e i n t e r a c t i o n of C a l c i u m a n d Magnes ium a s i n f l u e n c e d b y t h e d e g r e e o f s a t u r a t i o n of t h e e x c h a n g e c o m p l e x i n r e ­ l a t i o n t o c r o p r e s p o n s e t o m a g n e s i u m and t h e e x t e n t t o w h i c h t h e m i n e r a l c o m p o s i t i o n o f c r o p s a r e i n f l u e n c e d by such i n t e r a c t i o n s . REVIEW OF LITERATURE G edroiz ( 2 0 ) w a s one of t h e f i r s t t o p o i n t o u t t h e i m p o r t a n c e of c a l c i u m i n th e n u t r i t i o n of p l a n t s . I t was found t h a t o a t s could n o t d e v e l o p i n a H - s a t u r a t e d s o i l . He t h e n s a t u r a t e d t h e s o i l w i t h s i x t e e n d i f f e r e n t c a t i o n s and b r o u g h t them to n e u t r a l r e a c t i o n s . None of t h e m c o u l d s u p p o r t t h e g r o w t h o f o a t p l a n t s b u t a s l i g h t a d d i t i o n of lim e improved t h e growth t o a g r e a t e x t e n t . velopm ent of th e W ith t h e d e ­ c o n ce p t t h a t e x c h a n g e a b le c a t i o n s h e ld on t h e s u r f a c e of s o i l c o l l o i d s a r e g e n e r a l l y a v a i l a b l e t o p l a n t s , i t h a s b e e n o b s e r v e d t h a t t h e d e g r e e of s a t u r a t i o n of th e ion d e term in es i t ’ s a v a i l a b i l i t y fa c to rs are co n sta n t. Even th o u g h th e c a t i o n s a r e a s s i m i ­ l a t e d d i r e c t l y by p l a n t s , low ering th e w ith r e s p e c t to th e o t h e r w i l l d e c re a s e J e n n y and Cowan ( 2 7 ) f o u n d t h a t grow when t h e provided a l l o th e r s a t u r a t i o n o f on e its a v a ila b ility . soybeans d id n o t c a l c i u m s a t u r a t i o n i n a Ca-H s y s t e m f e l l b e ­ low 30 p e r c e n t of t h e t o t a l exchange c a p a c i t y . R atner (1+8) d id not succeed in grow ing o a t s i n a so d iu m -ca lc iu m c la y s y s t e m when c a l c i u m s a t u r a t i o n f e l l b e l o w 30 - 40 p e r c e n t . A l b r e c h t an d M a c C a l l a (2) f r o m t h e i r s a n d - c o l l o i d fo u n d t h a t t h e a v a i l a b i l i t y cu ltu res of Ca f r o m Ca-H s y s t e m i n c r e a s e d re g u la rly w ith in c re a s e in p e r cent C a -s a tu ra tio n . Thorne ( 58) i n a s o d iu m -c a lc iu m s y s te m fo u n d t h a t growth of to m a to p l a n t s was r e d u c e d m a r k e d l y when t h e c a l c i u m s a t u r a t i o n f e l l b e l o w 50 p e r c e n t o f t h e t o t a l s a tu ra tio n cap acity . Arnon 4 and G r o s s e n b a c h e r (4)> i n a m b e rl i t e - s a n d m i x t u r e s , f o u n d t b a t p o o r gr owth, o f t o m a t o w a s a s s o c i a t e d w i t h low s a t u r a ­ t i o n of d i v a l e n t c a t i o n s . fa ile d to E ven 4 6 . 6 p e r c e n t s a t u r a t i o n i n d u c e go od g r o w t h . shown t b a t a l k a l i Bower a n d T u r k (1 0) h a v e s o i l s w i t h h ig h sodium s a t u r a t i o n f a i l e d to supply calciu m to p l a n t s d e s p i t e th e p resen c e of f r e e CaCo^. The Ca-Mg i n t e r a c t i o n may a l s o b e i n f l u e n c e d b y t h e k i n d of c o m p l e m e n t a r y i o n s p r e s e n t . h a v e shown t h a t Je n n y and A yres (26) u p ta k e of K by e x c i s e d b a r l e y r o o t s was i n f l u e n c e d b y t h e p r e s e n c e o f NH4 , C a , Na and H i o n s . n iu m i o n h a d t h e g r e a t e s t and calciu m the Ammo­ le a st effect w h i l e s o d i u m and h y d r o g e n o c c u p i e d i n t e r m e d i a t e p o s i t i o n s . Yan I t a l l i e little (61) show ed t h a t e x c h a n g e a b l e c a l c i u m h a d v e r y i n f l u e n c e o n t h e u p t a k e o f p o t a s s i u m by t h e I t a l i a n Rye g r a s s w h i l e m a g n e s i u m d i s t i n c t l y d e p r e s s e d t h e a b s o r p ­ t i o n of p o t a s s i u m . A v ailab ility of exchangeable c a tio n s i n d i f f e r e n t s o i l s t h a t a r e a t a g i v e n d e g r e e of the n a t u r e o f c o l l o i d s i n e a c h s o i l . s a tu ra tio n v a rie s w ith A llw ay (1) and M e h l i c h and C o l w e l l .( 4 2 ) h a v e shown t h a t g r e . a t .e r p e r c e n t a g e o f r e l e a s e of c a l c i u m was o b t a i n e d f r o m c o l l o i d s o f 1 : 1 la ttic e type t h a n from the 2 : 1 t y p e . have a l s o shown t h a t t h e i n f l u e n c e on th e uptake M e h l i c h a n d Reed ( 43 ) organic c o llo id s e x e rt g r e a te r of n u t r i e n t s of e i t h e r 1 :1 or 2 :1 ty p e s . than m in e ra l c o l l o i d s Thus t h e m u t u a l r e p l a c e m e n t o r a n t a g o n i s m b e t w e e n c a l c i u m and magnesium, d o e s no t d e p e n d u p o n a d e f i n i t e r a t i o o f t h e two b u t r a t h e r on t h e d e g r e e of s a t u r a t i o n , n a t u r e o f c o m p l e m e n t a r y i o n s , a n d t h e t y p e of c o l l o i d s p r e s e n t i n t h e so i l . PLAN OF THE EXPERIMENT • No a t t e m p t w a s made t o p r e p a r e Ca o r Mg s a t u r a t e d c l a y s and d i l u t i n g them w ith in ert q u a r t z sa n d t o g e t t h e d e s i r e d d e g r e e of b a s e s a t u r a t i o n . Such p r e p a r e d c u l t u r e m e d i a do n o t a p p r o a c h t h e m i c r o b i o l o g i c a l a n d n a t u r a l p r o p ­ e r t i e s of s o i l d u r i n g t h e g r o w t h of t h e crop. A lk alin e c alcareo u s s o i l r e l a t i v e l y r i c h in changeable calcium and a c id exchangeable sandy s o i l s ex­ r e l a t i v e l y low i n c a l c i u m an d m a g n e s i u m w e r e u s e d f o r t h e p r e s e n t in v estig atio n . W isner loam r e p r e s e n t s t h e f i r s t ty p e w h ile P l a i n f i e l d a n d F ox s a n d r e p r e s e n t t h e l a t t e r t y p e of s o i l . A s u b s o i l w i t h v e r y low c a t i o n exchange c a p a c i t y and c o n ­ t a in in g very . l i t t l e c o l l o i d a l m a t e r i a l , e i t h e r m in e r a l or o r g a n i c , w a s t a k e n a s an i n t e r m e d i a t e b e t w e e n t h e loam an d the sandy s o i l s . Due t o t h e i s i n f l u e n c e d by t h e f a c t t h a t t h e d e l i v e r y of c a t i o n s o r i g i n a l c a t i o n exchange c a p a c i t y of s o i l s t h e s e t h r e e k i n d s of s o i l p e r m i t t e d f u r t h e r i n v e s t i ­ g a t i o n of . t h i s p o i n t . o r d e r to w ith th a t Q u a r t z s a n d c u l t u r e was i n c l u d e d i n compa re t h e u p t a k e o f n u t r i e n t s f r o m a s o l u t i o n from the s o i l s . The e f f e c t o f V a r y i n g c a l c i u m l e v e l s on p l a n t g r o w t h 6 and c o m p o s i t i o n was d e t e r m i n e d w i t h f o u r d i f f e r e n t l e v e l s of c a lc iu m s a t u r a t i o n in com bin atio n w ith fo u r d i f f e r e n t l e v e l s o f m ag n e siu m s a t u r a t i o n a t e a c h l e v e l of c a l c i u m satu ratio n . C alcium w as a p p l i e d i n amounts to s u p p l y 50, 7 5 , 100 and 150 p e r c e n t s a t u r a t i o n w h i l e m a g n e s i u m was a p p l i e d i n a m o u n t s t o s u p p l y 1 0 , 2 5 , 5 0 , 75 a n d 100 p e r c e n t s a t u r a t i o n of t h e c a t i o n e x c h a n g e c a p a c i t y o f e a c h s o i l . The p e r c e n t a g e c a l c i u m a n d m a g n e s i u m s a t u r a t i o n s w e r e made up by a d d i n g q u a n t i t i e s "of t h e s e two e l e m e n t s t h r o u g h s u i t ­ able s a l t s t o th e am ounts a lr e a d y c o n ta in e d i n the exchange c o m p l e x of e a c h s o i l . C a l c i u m a n d m a g n e siu m w e r e a p p l i e d t o the sand c u l t u r e on a m i l l i e q u i v a l e n t b a s i s w i t h i n a c e r t a i n r a t i o com parable to t h a t resu lts can b e e v a l u a t e d on t h e of e a c h s o i l . Thus t h e b a s is of (1 ) in c re a sin g a m o u n t s of m a g n e s i u m w i t h a c o n s t a n t c a l c i u m l e v e l a n d ( 2 ) t h e ch an g es cau se d by v a r i a t i o n s i n th e p r o p o r t i o n of t h e two c a t i o n s a t c o n s t a n t l e v e l s of b a s e s a t u r a t i o n . The c o rn p le m e n ta iy c a t i o n s , as w e ll a s a l l other n u t r i e n t s , w e r e k e p t c o n s t a n t and i n e ac h t y p e of c r o p g r o w n . s u f f i c i e n t amount f o r The l e v e l of N - P - K was k e p t c o n s t a n t by c h e c k i n g w i t h t h e Spurway t e s t [5 k ) a t i n t e r ­ v a l s of two w e e k s d u r i n g t h e g r o w t h of t h e crops. c i e n t a m o u n t s w ere a d d e d i n o r d e r t o b r i n g t h e to the s a m a - l e v e l a s t h e y w e r e a t the e x p e r iment . S u ffi­ n u trien ts s t a r t of t h e 7 DESCRIPTION OF SOIL TYPES USED FOR THE INVESTIGATION D e t a i l e d d e s c r i p t i o n of t h e s o i l t y p e s u s e d f o r t h e g ree n h o u se e x p e r i m e n t s a r e to b e found i n the S o i l Survey R e p o r t S e r i e s No. 19 o f 193 3 , No. 27 of 1 9 2 9 , a n d No. 12 o f 1936 o f S a g i n a w , S t . C l a i r a n d C l i n t o n C o u n t i e s o f M i c h i g a n , resp ectiv ely . A b r i e f d e s c r i p t i o n o f e a c h s o i l t y p e is. p re s e n te d below . W i s n e r Sandy Loam. The s o i l i s d e r i v e d f r o m t h e o l d b e d s of t h e g l a c i a l l a k e s . I t is s i t u a t e d in th e r i v e r f l o o d p l a i n and i s v e r y young a n d p o o r l y d e v e l o p e d . s o il co n tain s f r e e l i m e c a r b o n a t e and i s d a r k e n e d w i t h a r e l a t i v e l y s m a l l amount of o r g a n i c m a t t e r . s o i l is The The s u r f a c e o r d i n a r i l y a l k a l i n e and lim e i s i n v a r i a b l y a b u n d a n t a t d e p t h s o f 18 - 2 4 i n c h e s . P l a i n f i e l d Sand. v alley tr a in d ep o sits; The s o i l i s l a r g e l y o u t w a s h a n d is lig h t g r a y i s h - b r o w n loam y f i n e sand p o o r l y s u p p l i e d w ith o r g a n i c m a t t e r . la y e r is The s u r f a c e u n d e r l a i n b y i n c o h e r e n t l i g h t y e l l o w i s h brown fine sand. The s o i l i s § t r o n g l y a c i d i n r e a c t i o n a nd t h e c a p a c i t y f o r r e t e n t i o n of w a t e r i s l o w . F o x Sa n d y Loam. w a sh p l a i n s , t e r r a c e s , I t o c c u p ie s l e v e l to u n d u l a t i n g o u t ­ v a lle y -tra in dep o sits. throughout the s o i l m ass. medium t o It G ravel occurs i s low i n o r g a n i c m a t t e r a nd stro n g ly a c id in r e a c tio n . The' r a t h e r strongly a c i d r e a c t i o n of the s u r f a c e s o i l i n h i b i t s th e grow th of some p l a n t s , p a r t i c u l a r l y the leg u m es. 8 H illsd ale S u b so il. T his s o i l was o b t a i n e d fro m a q u a r r y a t a d e p t h of 40 - 50 i n c h e s . At t h i s depth th e m a t e r i a l c o n s i s t s o f l i m y y e l l o w i s h g r a y f r i a b l e s a n d y lo a m o r c l a y e y s a n d y loam of g l a c i a l d r i f t . c a rb o n a te s and is a l k a l i n e I t co n tain s fre e in r e a c t i o n . S o i l Sam pling and P r e p a r a t i o n The s a m p l e s of W i s n e r , P l a i n f i e l d a n d Pox s o i l s w e r e s e c u r e d fro m t h e A h o r i z o n fro m a d e p t h of 0 to 8 i n c h e s , w hile the H illsd ale s u b s o i l was ta k e n from t h e B h o r i z o n a t a d e p t h of 40 - 50 i n c h e s . The b u l k s a m p l e s w e r e a i r - d r i e d and p a s s e d t h l o u g h a o n e - f o u r t h in c h s i e v e a n d w e r e m ix e d th o roughly. The Q u a r t z s a n d was s o a k e d w i t h 0 . 0 5 N H01 f o r a p e r i o d of f o r t y - e i g h t h o u r s a f t e r w h i c h i t was w a s h e d w i t h d i s t i l l e d w a t e r u n t i l f r e e of c h l o r i d e i o n s . The w a s h e d sand was t h e n d r i e d b e f o r e u s e . A n a l y t i c a l Methods The m e c h a n i c a l c o m p o s i t i o n of t h e s o i l s was d e t e r ­ m in e d by t h e h y d r o m e t e r m eth o d a s d e s c r i b e d b y B o u y o u c o s (13). B e c a u s e of t h e p r e s e n c e o f f r e e c a r b o n a t e s i n t h e H illsd ale s u b s o i l a nd t h e W i s n e r s o i l t h e y w e r e f i r s t s a t u ­ r a te d w ith hydrogen. These hydrogen s a t u r a t e d s o i l s were u se d f o r t h e d e t e r m i n a t i o n of t h e i r m e c h a n i c a l c o m p o s it i o n . P r e e c a r b o n a t e s w e r e d e t e r m i n e d b y t h e m ethod d e s c r i b e d by Piper ( 4 6 ) and o r g a n i c m a t t e r c o n t e n t w a s d e t e r m i n e d b y a d o p t i n g W a lk le y and B l a c k ’ s r a p i d t i t r a t i o n method (46). E x c h a n g e a b l e h y d r o g e n w a s d e t e r m i n e d by u s i n g T r i e t h a n o l a m i n e b u f f e r e d a t pH 8 a s d e s c r i b e d b y M e h l i c h ( 4 1 ) . W isner and H i l l s d a l e of fre e c arb o n ate s. of f r e e s u b s o i l c o n t a i n a l a r g e amount B e c a u s e of t h e p o s s i b l e in terferen ce c a r b o n a t e s w i t h t h e d e t e r m i n a t i o n of B a s e E x c h a n g e C a p a c i t y b y t h e N e u t r a l Ammonium A c e t a t e m eth o d d e s c r i b e d b y S c h o l l e n b e r g e r and Simon ( $ 2 ) , t h e p o t e n t i o - m e t r i c t i t r a t i o n m e t h o d s of P u r i a n d U p p a l (4 7) w e r e u s e d . s u l t s o b t a i n e d b y t h e two m e t h o d s w e r e m illieq u iv alen ts. w ith in The p r o c e d u r e a d o p t e d f o r The r e ­ 0.5 - 0.8 the p o t e n t i o - m e t r i c t i t r a t i o n was a s f o l l o w s : F i f t y gram p o r t i o n s o f a i r - d r i e d s o i l s w e r e t r e a t e d w i t h 2 N HC1 t o d i s s o l v e a l l leach ed w ith s u c c e s s iv e carbonates. The s o i l was t h e n 50 c c p o r t i o n s of 0 . 0 5 N HCl. The e x c e s s a c i d was washed w ith d i s t i l l e d w a t e r u n t i l t h e l e a c h ­ a t e s w ere f r e e from c h l o r i d e i o n s a n d f i n a l l y w a sh e d w i t h 100 m l of The h y d r o g e n - s a t u r a t e d s o i l s 95% e t h y l a l c o h o l . w e r e d r i e d a t 80°C f o r 12 h o u r s . One gram o f b a r i u m c h l o r i d e w a s a d d ed to each of t h e h y d r o g e n s a t u r a t e d s o i l s a n d made i n t o a p a s t e w i t h 25 m l . of d i s t i l l e d w a t e r . E a c h sa m p le was t h e n t i t r a t e d w i t h 0 . 1 N Ba(0H) s o l u t i o n u sin g the g l a s s e l e c t r o d e . The t i t r a t i o n curve f o r each s o i l i s r e p r e s e n t e d i n F i g . 1 . The m i l l i - e q u i v a l e n t s o f b a s e n e c e s s a i y t o a d j u s t t h e pH t o 7*0 was i n t e r p o l a t e d from the t i t r a t i o n c u r v e . To a v o i d t h e d e p r e s s i n g i n f l u e n c e of c a l c i u m i n OJ L, 6 8 10 12 14 M i l l i e q u i v a l e n t s of b a s e pel* 100 gms. s o i l F ig . 1. E le c tro m e tric t i t r a t i o n f o r "B ase-exchange” and b u f f e r i n g c a p a c i t y of t h e s o i l s . 16 18 if o so lu tio n , in th e s o ils c o n ta in in g f r e e carbonates, upo n c a lc iu m rep lacem en t fro m th e c o l l o i d a l complex, e x t r a c t i o n o f c a l c i u m and m a g n e s i u m vsas made by u s i n g n o r m a l s o d i u m c h l o r i d e s o l u t i o n a s s u g g e ste d by H i s s in k (2 3 ). f e r e n c e i n t h e c a l c i u m a n d m ag n e siu m c o n t e n t and s e c o n d l i t e r The d i f ­ of t h e f i r s t p o r t i o n s w a s t a k e n to be t h e e x c h a n g e a b l e c a lc iu m and magnesium. C a l c i u m w a s p r e c i p i t a t e d a s o x a l a t e on t h e 1 0 ml a l i q u o t and was e s t i m a t e d w ith p o t a s s i u m p e rm a n g an a te fo llo w in g the p r o c e d u r e of Chapman ( 1 4 ) . determ ined p h o t o c o l o r im e tr i c a l ly , Magnes ium was u s i n g $20 m/w f i l t e r i n s u i t a b l e a l i q u o t w ith p ro p e r d i l u t i o n by T ita n yellow m eth o d o f P e e c h and E n g l i s h (44). E x c h a n g e a b l e p o t a s s i u m was e x t r a c t e d b y l e a c h i n g 50 gms of s o i l w i t h n e u t r a l n o r m a l ammonium a c e t a t e s o l u t i o n (pH 6 . 9 ) a s d e s c r i b e d b y S c h o l l e n b e r g e r and Simon ( 5 2 ) a n d was d e t e r m i n e d v o l u m e t r i c a l l y b y t i t r a t i o n of t h e p o t a s s i u m c o b a l t i n i t r i t e p r e c i p i t a t e w ith s t a n d a r d p o t a s s i u m perman­ g a n a t e a c c o r d i n g t o t h e m e t h o d of V o lk a n d T ru og ( 6 2 ) . P h o s p h o ru s was d e te r m i n e d b y m olybdenum -reduced p h o sp h o m o ly b d ate b lu e c o l o r m ethod ( 3 2 ) . A ll c o lo rim e ter readings were tak e n w ith E v ely n P h o t o e l e c t r i c C o l o r im e te r . PHYSICAL COMPOSITION AND CHEMICAL CHARACTERISTICS OF THE SOILS The p h y s i c a l a n d c h e m i c a l d e t e r m i n a t i o n s w e r e c a r r i e d o u t on e a c h s o i l i n an e f f o r t to e v a l u a t e t h e i r resp ectiv e 12 c a l c i u m and magnesium s t a t u s a s w e l l a s t h e f e r t i l i t y lev els. The r e s u l t s o f t h e a n a l y s e s a r e p r e s e n t e d i n T a b l e s I a nd I I . The p r e d o m i n a t i n g s o i l s e p a r a t e i s s a n d where,as t h e silt f r a c t i o n i s v e r y low. D a ta p r e s e n t e d i n Table I I show show t h a t a l l the s o i l s h a v e a h i g h e r c o n t e n t of c a l c i u m t h a n of m a g n e s i u m . In t h e W isner, th e r a t i o of c a l c i u m t o m a g n e s i u m i s 1 7 : 1 w hile in th e p o d so liz e d P l a i n f i e l d , s u b s o il the Fo x and t h e H i l l s d a l e r a t i o 'is v e r y narrow , v a ry in g from 2 :1 to 4 : 1 . The W i s n e r a n d t h e H i l l s d a l e su b so il a re a lk a lin e . This c o n d i t i o n i s g e n e r a l l y f a v o r a b l e f o r c a l c i u m s u p p ly but u n fa v o ra b le f o r p h o sp h a te a v a i l a b i l i t y . The p r e s e n c e of e ig h t to nine per cent f r e e calcium c a rb o n a te f u r t h e r r e ta r d s phosphate a v a i l a b i l i t y . P l a i n f i e l d an d Fox s a n d y lo a m a r e a c i d i n r e a c t i o n an d h a v e a low d e g r e e of b a s e sa tu ratio n . These c o n d i t i o n s a r e not f a v o r a b l e f o r th e s u p p l y of b a s e s o r f o r k e e p i n g p h o s p h o r u s a v a i l a b l e . They need lim e and f e r t i l i z e r s f o r s u c c e s s f u l growth of c r o p s . < TABLE I Some M e c h a n i c a l and C h e m i c a l C h a r a c t e r i s t i c s o f S o i l s Used H illsd ale su b so il W isner P lain field Fox sand * % fo 1o S a n d 3- 71.2 82 . 8 8 7 .8 ‘ 9 1 .8 S ilt2 5.6 6.0 5.0 2.0 C lay3 23.2 11.2 7.2 6.2 F i n e Clay^" 19.2 9.2 5.2 . 5.2 0.07 0.08 0.03 N il 9.05 Organic M a t t e r 4.3 -Free C a r b o n a t e 9.5 1 2 . 0 - 0 . 0 2 mm ^ 0 . 0 2 - 0 . 0 0 2 mm 3 . 0 0 2 mm ^ 2 h r s . reading N il Table I I Chemical C h a r a c te r is tic s o f th e S o il s Used S o il PH B ase Exchange C apacity M.E. per 100 gm. S o il R e la tiv e p roportion o f b a se s. P ercen t o f t o t a l R eplaceable Bases M.E. per 100 gm. S o il Ca K H Ca K_ Ca T otal N Total P ppm H Mg Wisner 7 .5 1 8 .3 2 1 6 .7 5 0 .9 8 0 .1 5 0 9 1 .4 3 5 .3 5 0 .8 2 P l a in f ie ld 5 .3 3.56 1.10 0 .6 3 0 .0 8 1 .7 30.89 1 7 .6 9 Fox Sand 6.0 3 .3 9 1 .2 4 0 .3 1 0 .0 3 1.8 36.57 H ills d a le S u b so il 8.-3 1 .3 2 0 .9 2 0 .3 0 0.02 0 69.69 (1) R atio o f th e C ations ( l ) K_ _Ca Mg Mg 0 17:1 0 .1 6 :1 0 .0 0 8 :1 0 .25 0 .5 5 2 .2 4 47.75 1 .7 4 :1 .1 3 :1 0 .0 7 :1 0 .0 4 0 .0 5 9 .1 4 0.88 53.1C 4:1 0 .02:1 0 .0 5 0 .0 6 22.72 1 .5 1 0 3:1 .02:1 0.02 L ess than 0 .0 2 1:1 .0 7 :1 C alcu lated on b a s is o f m illigram e q u iv a le n ts, r a th er than w eight e q u iv a le n ts. H EXPERIMENTAL PROCEDURE F e r t i l i z e r A p p licatio n A summary o f t h e t r e a t m e n t s f o r t h e f o u r d i f f e r e n t s o i l s and the q u a rtz sand c u ltu r e is given in Tables I I I , I V , V, VI a M V I I . C a l c i u m w a s a p p l i e d a s c a l c i u m h y d r o x i d e , m agn esiu m as t h e s u l f a t e and p o ta ssiu m a s th e c h l o r i d e . The r a t e o f a p p l i c a t i o n of p o t a s s i u m w a s 10 P . P . M . f o r t o m a t o and 15 P.P .M . f o r to b ac co and c o r n . N itrogen was a p p lie d a t th e r a t e of 90 m i l l i g r a m s f o r t e n p o u n d s of s o i l w h i l e P h o s ­ p h o r u s w a s a p p l i e d a t t h e r a t e of 2 4 P . P . M . N i t r o g e n was s u p p l i e d p a r t l y a s ammonium n i t r a t e a n d p a r t l y a s mono­ ammonium p h o s p h a t e . S o l u t i o n s of s o d i u m i o d i d e , copper s u lf a te , fe rro u s s u l f a t e , m a n g a n o u s s u l f a t e a nd s o d i u m b o r a t e w e r e a p p l i e d to th e q u a r t z san d to g i v e c o n c e n t r a t i o n s of 2 , 4 > 8 , 1 0 , 2 and 8 P . P . M . o f i o d i n e , copper, i r o n , manganese, zinc and b o r o n , r e s p e c t i v e l y . E i g h t a p p l i c a t i o n s of t h e s e m i n o r e l e m e n t s w e r e made d u r i n g t h e g r o w i n g p e r i o d o f t h e crop. P r o p e r a m o u n t s of c a l c i u m h y d r o x i d e and m a g n e siu m s u l f a t e fo r e a c h tr e a tm e n t were th o r o u g h ly i n c o r p o r a te d w i t h r e q u i r e d amount of s o i l b e f o r e p l a c i n g t h e s o i l i n t o the p o t s . The n i t r o g e n , p h o s p h o r u s and p o t a s s i u m f e r t i l i z e r s were a p p l i e d in s o l u t i o n . grade. A l l c h e m i c a l s u s e d w e r e of C . P . A f t e r t h e a p p l i c a t i o n of f e r t i l i z e r s t h e s o i l s w e r e 16 k e p t i n a m o i s t c o n d i t i o n f o r two w e e k s t o p e r m i t e q u i l i ­ brium a d ju s tm e n t s b e f o r e p l a n t i n g th e c r o p s . C u l t u r a l Methods G lazed e a r th e n w a r e j a r s w e r e employed t h r o u g h o u t th e in v estig atio n . One t r i a l s e r i e s w a s c a r r i e d o u t i n one g a l l o n j a r s , e a c h f i l l e d w i t h t e n p o u n d s of s o i l o r q u a r t z sand. ity , Two c r o p s w e r e grow n i n c o n t a i n e r s of 2 g a l l o n c a p a c ­ e a c h f i l l e d w i t h t w e n t y p o u n d s of s o i l o r q u a r t z s a n d . Throughout t h e e x p e rim e n ts , the m o istu re c o n te n t of the s o i l s w as m a i n t a i n e d a t a p p r o x i m a t e l y t h e i r m o i s t u r e e q u i v a l e n t c a p a c i t y w h i l e i n t h e c a s e of q u a r t z s a n d , t h e m o i s t u r e was m a i n t a i n e d a t 8 per c e n t by w e i g h t . A pproxi­ m a t e l y e q u a l m o i s t u r e c o n d i t i o n s w e r e m a i n t a i n e d by w e i g h i n g the p o t s . D i s t i l l e d w a t e r w a s u s e d a n d n o d r a i n a g e was p e r ­ m it t e d from t h e p o t s . Usual p r e c a u t i o n s w ere ta k e n to e q u a l- l i z e lig h t and tem perature c o n d itio n s in th e greenhouse. The t r e a t m e n t s on w h i t e q u a r t z s a n d w e r e r e p l i c a t e d t h r e e t i m e s a n d a l l o t h e r t r e a t m e n t s on m i n e r a l s o i l s w e r e re p lic a te d f i v e tim es. A ll th e r e p l i c a t e s fo r a p a r t i c u l a r s o i l were a r r a n g e d i n a random ized m anner. rep licatio n s fo r eqch of - t h e Of t h e f i v e t r e a t m e n t s , two w e r e u t i l i z e d f o r e i t h e r greentii'aBare s t u d y o r f o r s t u d y of a n y n u t r i t i o n a l diso rd ers. G row th a n d y i e l d d a t a w e r e r e c o r d e d f r o m t h r e e r e p l i c a t e s of each t r e a t m e n t . T h r e e c r o p s , t o m a t o , t o b a c c o and c o r n , w e r e grown in the four m in e ra l s o i l s as w e l l as in q u a r tz san d . These c r o p s w e re n o t grown in s u c c e s s io n . E a c h c r o p w a s g ro wn in f r e s h ly p re p a re d s o i l and q u a rtz sand. The e x p e r i m e n t s w e r e c a r r i e d o u t d u r i n g t h e s p r i n g , summer an d e a r l y grown i n t h e f a l l of t h e y e a r 1 9 4 8 . Tomatoes w e re p e r i o d fro m A p r i l 5th to J u l y 3 0 t h , 1948; to b a c c o fro m J u l y 1 5 th to October 5 th , 1948; w h i l e corn w a s g row n f r o m A u g u s t 1 5 t h t o O c t o b e r 1 5 t h , 1 9 4 8 . a rtific ia l No i l l u m i n a t i o n of t h e g r e e n h o u s e w a s u s e d . As i t was n o t p o s s i b l e t o g r o w e a c h c r o p i n t h e f o u r d i f f e r e n t s o i l s and i n q u a r t z s a n d a t t h e same t i m e , s e e d i n g w a s so a d j u s t e d t h a t t h e p e r i o d o f g r o w t h of a p a r t i c u l a r i n e a c h s o i l was t h e s a m e . h a r v e s t i n g of each cro p i s crop The e x a c t d a t e o f s e e d i n g and shown i n T a b l e s I I I , I V , V, VI and V I I . T om ato. Tom ato, M a s te r M arglobe v a r i e t y p r o c u r e d f ro m t h e H o r t i c u l t u r a l D e p a r tm e n t, M . S . C . , was t h e f i r s t crop grow n. after T h r e e s e e d s w e r e sown i n e a c h p o t . Two w e e k s g e r m i n a t i o n t h e p l a n t s w e r e t h i n n e d t o one p e r p o t . The p l a n t s w e r e a l l o w e d t o grow f o r 1 0 5 d a y s . Tobacco. Y ellow s p e c i a l , a f l u e - c u r e d to b a c c o s e ­ c u r e d from B r i g h t Tobacco F i e l d S t a t i o n , Chatham, V i r g i n i a , was g r o w n a s t h e s e c o n d t e s t crop. S u fficien t seedlings were grown i n q u a r t z sand to p e rm it s e l e c t i o n f o r u n iform ity. The s e e d l i n g s w e r e t r a n s p l a n t e d a f t e r v e l o p m e n t of t h e s e c o n d p a i r of l e a v e s . was g r o w n i n e a c h p o t . p e r i o d o f 70 d a y s . s i z e and the de­ A sin g le plant H a r v e s t i n g w a s do n e a f t e r a g r o w t h Corn. M ichigan h y b r id 51B, a mid s e a s o n v a r i e t y o f c o r n , was sown a s t h e t h i r d c r o p . Three g ra in s of co rn of u niform w e ig h t w ere p l a n t e d i n each pot.. th in n ed to The s t a n d w a s o ne p l a n t p e r p o t o n e w e e k a f t e r g e r m i n a t i o n . The c r o p w a s a l l o w e d t o g ro w f o r a p e r i o d of e i g h t w e e k s , a f t e r which t h e above ground p o r t i o n w a s h a r v e s t e d . S o i l s a m p l e s w e r e t a k e n f o l l o w i n g t h e r e m o v a l of each crop. S o i l s of t h e t h r e e r e p l i c a t e d p o t s w e r e m ix ed t o g e t h e r a n d a c o m p o s i t e sa m p le f r o m t h i s w a s t a k e n f o r analysis. P r e p a r a t i o n of P l a n t M a t e r i a l s A f t e r t h e h a r v e s t of t h e c r o p s , t h e m a t e r i a l s w e r e d r i e d i n p a p e r b a g s f o r two d a y s i n t h e g r e e n h o u s e a n d t h e n d r i e d a t 70°C f o r t h r e e d a y s , a f t e r w h i c h t h e d r y w e i g h t s were t a k e n . U s u a l l y two w e i g h i n g s a t a n i n t e r v a l d a y s w e r e made a s a c h e c k t o of two in su re c o n sta n t w eight. The d r i e d p l a n t m a t e r i a l s o f t h e t h r e e r e p l i c a t e d p o t s f o r e a c h t r e a t m e n t w e r e m i x e d a n d g r o u n d i n a W il e y m i l l t o p a s s t h r o u g h a 40 m esh ‘s i e v e . T h e s e w ere t h e n c a r e f u l l y m ix e d and s a m p l e d f o r a n a l y s i s . t i o n s of t h e oven d r y t i s s u e w e r e d r y - a s h e d i n a n e l e c t r i c f u r n a c e a t 3 50 ° C f o r e i g h t h o u r s . i n h y d r o c h l o r i c a c i d and t h e lite rs. Two g r a m p o r ­ A l i q u o t s of t h i s The' a s h w a s t a k e n up e x t r a c t d i l u t e d to 50 m i l l i ­ e x t r a c t w ere ta k e n f o r a n a l y s i s o f c a l c i u m , m a g n e s i u m , p o t a s s i u m and p h o s p h o r u s . C a l c i u m and m a g n e s i u m w e r e d e t e r m i n e d b y t h e m e t h o d s 19 d e s c r i b e d u n d e r t h e " A h a l y s i s of S o i l . ” d e te r m in e d by t h e d i p i c r y l a m i n e P o t a s s i u m was procedure as d e sc rib e d by L aw to n ( 3 3 ) • N itrogen F ra c tio n s T otal n i t r o g e n , i n c l u d i n g n i t r a t e s , was d ete rm in e d in a p p ro p r ia te a l i q u o t s of d r i e d t is s u e K j e l d a h l - G - u n n i n g me t h o d . t i s s u e were u se d f o r n itro g en . by t h e m o d i f i e d Hot w a t e r e x t r a c t s of t h e d r i e d t h e d e t e r m i n a t i o n of t o t a l soluble The e x t r a c t s w ere o b t a i n e d b y b o i l i n g a p p r o ­ p r i a t e a l i q u o t s i n a b o u t 60 ce o f w a t e r f o r f i v e m i n u t e s . The s u s p e n s i o n was c o o l e d , a l l o w e d t o stand overnight and t h e s u p e r n a t a n t l i q u i d was f i l t e r e d t h r o u g h a d r y f i l t e r paper. filtra te A t o t a l n i t r o g e n a n a l y s i s w a s made on t h e rep resen tin g th e t o ta l soluble n itro g e n (15)• 20 TABLE I I I Summary o f T r e a tm e n ts o f t h e G re e n h o u s e E x p e r im e n ts on Q u a r tz S and T reatm ent M.E. o f Mg Ca , Ca :Mg 2.25 3.00 9.4 6.6 0.06 0.12 6.4 6.2 6.2 0.24 0.60 1.50 3.00 At s t a r t 9.0 9.2 9.2 0.75 1.50 0.75 ' pH-* At H a r v e s t Tomato T ob ac co 0.06 0.12 1 2 .5:1 0.24 0.60 8.2 8.1 8^.4 8.3 8.5 8.3 8.4 8.8 6.5 6.3 6.2 6.2 6.5 6.2 6.2 6.2 Co rn Cl ? 0 Cf t»Q -P O a cl fH 0 0 6.7 7 .4 6.5 6 .25:1 9.4 9.2 6.7 6.5 3 .1 :1 9.3 6.3 7 .4 7.0 1.25:1 9.3 6.5 7.5 0.06 25:1 8.7 7.5 8.5 0.12 12.5 :1 7.4 8.3 0.24 6 .25:1 8.7 9.0 7.3 8.3 8.4 8.2 0.60 2 .5 :1 9.0 7.3 8 .4 8.2 0.06 50:1 9.0 8.1 8 .5 8.6 0.12 8.9 8.8 8 .0 8.7 0 .24 25:1 12:1 8.0 8.7 8.4 8.6 0.60 5:1 8.8 7 .9 8.6 8.6 C r o p s Grown: Tomato - 5 t h A p r i l t o 1 9 t h J u l y Tobacco - 2 1 s t J u l y t o 2 8 t h Sept C o r n - 2 0 t h Aug. t o 1 4 t h O c t . E q u i v a l e n t amount o f f e r t i l i z e r a p p l i e d : l / 2 t o n CaCQo 0 . 7 5 M.E. Ca 1.50 « 1- 1/2 » " 2.25 " 3.00 " 2 ,f 100 l b . MgSo 0 . 0 6 M.E.-Mg 200 " ,f 4 0.12 " 400 » « 0.2 4 " 1000 ” » 0.60 « 6.9 6.9 8.0 i 21 TABLE IV Summary o f T r e a tm e n ts of t h e G -reenliouse E x p e r im e n ts on W is n e r S o i l pH Degree of S atu ratio n Ca 1o Mg At s t a r t Ca:Mg At H arvest Tobacco lom ato Corn 1o 91.43 5.35 17:1 7 .8 7.2 7.4 7.2 100 10 10:1 8.3 7 .5 7.5 7 .4 25 4:1 o• to 7 .4 7.3 7.4 50 2:1 8.0 7 .4 7.4 7.4 1 .3 :1 1:1 8 .1 7.2 7 .4 7 .4 8 .1 7 .3 7 .4 7.7 10 15:1 8 .8 7 .7 7.8 7.7 25 50 6:1 8.6 7-7 3:1 8.5 7.5 7.6 7.5 7.5 7.6 75 100 2:1 8.7 7.8 7.7 1 .5 :1 8.7 7.7 7 .8 7.8 7.7 75 100 150 C r o p s Grown: Tomato - 5 t h A p r i l . t o 1 8 t h J u l y Tobacco - 1 5 th J u l y to 2 1 s t S e p t. Corn - 1 0 t h Aug. t o 4 t h O c t o b e r Amount of f e r t i l i z e r a d d e d p e r a c r e t o b r i n g t o d e s i r e d s a tu ra tio n percentage: 1 0 0 $ Ca S a t . = 150 $ » 1 0 $ Ma S a t . 25$ ” 50$ " 75$ " 100$ " = 960 l b . Ca(OH) 6 ,5 8 0 " = 1,488 = 6,312 =14,271 =22,291 -30,253 lb ” " " ” 2 MgS04 3H2 0 TABLE V - Summary o f T r e a tm e n ts of t h e G re e n h o u s e E x p e r im e n ts on P l a i n f i e l d D egree of S atu ratio n 5 -3 4 .1 5.1 k.,6 25 1 .7 4 :1 2:1 5.5 4.5 5.0 4.9 50 1:1 5.3 4.5 4.7 4.8 75 .7 5 :1 5.3 4* 6 5.1 4.9 .5:1 5.3 4 .7 4.7 4.7 5.4 5.5 5.3 5.3 25 50 3:1 6.1 1 .5 :1 6.0 5.3 512 75 1:1 5.9 5.0 5.2 5.3 .7 5 :1 5.9 5.1 5.1 5.9 4:1 2:1 6.6 5.6 6.0 5.9 6.5 6.3 5.5 5.5 5.6 5.9 6.1 5.9 5.8 5.9 5.7, 6.5 6.5 6.4 6.5 6.6 6.5 6.4 6.9 100 100 25 50 75 100 150 Corn At s t a r t 100 75 PH At H a rv e st Tomato T obacco Ca:Mg Ca Mg 1o $ 30.89 17.69 50 Sand 25 50 75 100 C r o p s Grown: 1 .3 :1 6.5 1:1 6:1 7.1 3:1 2:1 7.1 7.0 6 .4 ^6.1 6.2 7.0 6.2 1 .5 :1 " Tomato - 1 7 t h A p r i l t o 3 0 t h J u l y Tobacco - 3 1 s t J u l y t o 9 t h O c to b e r C o r n - l $ t h A u g u s t to 1 5 t h O c t o b e r Amount of f e r t i l i z e r a d d e d p e r a c r e t o b r i n g t o d e s i r e d s a tu r a tio n percentage: 400 l b . Ca(0H)~ 50$ Ca S a t . = tt ^ it 960 tt 75$ » tt i i ~ 1 , 5 0 0 100$ tt tt n = 2,580 150$ 453 l b . MgS04 3H20 2 5 $ Mg S a t . = « n = 2 , 0 00 50$ tt tt tt = 3,550 75$ tt tt tt = 5,112 100 $ TABLE VI Summary o f T r e a t m e n t s o f t h e G r e e n h o u s e E x p e r i m e n t s on F o x Sand ' Degree of S atu ratio n Mg Ca % 36*. 57 9 . 1 4 50 At s t a r t Tomato Tobacco Corn 5.3 5.0 5.5 25 2:1 5.9 5.0 5.1 5.4 50 1:1 5.9 4.9 5.1 5.3 -.7 5 :1 5.7 5.1 5.4 5.3 .5:1 5.7 5.0 5.3 5.1 3:1 6.6 6.0 6.0 1 .5 :1 1:1 6.5 5.7 5.6 5.9 6.0 5.5 ^ 5.9 6 .4 5.6 5.7 6.4 6.5 25 50 ~ - .75:1 6.4 6.5 25 4:1 7.1 5.4 6.2 50 2:1 7.0 6.0 6.4 6.3 75 1 .3 :1 6.9 6 .0 6.5 6.3 100 1:1 6.9 6.0 6.4 6.5 25 6:1 7.7 6.9 7.1 7.1 50 3:1 2:1 7.6 7/0 7.0 7.5 6.7 6.8 6.9 7.2 1 .5 :1 7.5 6.7 7.0 7.1 75 100 150 Ca:Mg 5.6 100 100 At H a r v e s t 4:1 75 75 pH 75 100 C r o p s Grown: Tomato - 1 5 t h A p r i l t o 2 8 t h J u l y Tobac co - 2 5 t h J u l y t o 5 t h O c t o b e r Corn - 1 5 t h A u g u s t to 1 5 t h O c t o b e r Amount o f f e r t i l i z e r a d d e d p e r a c r e t o b r i n g t o d e s i r e d s a tu ra tio n percentage: 50$ Ca S a t . = 336 l b . C a (0 H )2 75$ *» = 963 ” " 100% " = 1 ,5 9 1 " " 150% '*» = 2,845 " "2595 Mg S a t . = 937 l b . MgSO 13H2 0 50% " = 2,416 " " 75% " = 3,695 ” " 100% " = 5,373 " " 24 TABLE V I I Summary o f T r e a t m e n t s o f t h e G r e e n h o u s e E x p e r im e n ts on H i l l s d a l e Degree o f S atu ratio n Ca % Mg % 150 Ca:Mg At S t a r t At H a rv e s t Tomato . Tobac co 8.0 7.6 7.4 50 1 .5 :1 7.9 7.7 7.6 75 1:1 7.9 7.7 7.6 .75 :1 7.7 7.6 7.3 50 2:1 8.1 7.8 7.6 75 1 .3 :1 8.0 7.7 7.5 100 1:1 7.8 7.7 ' 7.4 50 3:1 8.7 7.8 7.6 75 2 :1 8.4 7.9 7.7 1 .5 :1 8.2 7.8 7.6 100 100 -pH 3 :! -69 . 6 9 2 2 . 7 4 75 S ubsoil 100 C r o p s Grown: Tomato - 1 8 t h A p r i l t o 2 9 t h J u l y Tobacco - 7 th A ugust t o 1 5 th O cto b er Amount o f f e r t i l i z e r a d d e d p e r a c r e t o b r i n g t o d e s i r e d s a tu r a tio n percentage: 7 5 $ Ca S a t . = 51 l b . C a ( 0 H ) P 100% » = 296 l b . " 150% '» - 784 l b . " 50% Mg S a t . = 645 l b . MgS0,3Ho 0 75%- " = 1,2 2 0 l b . ^ 100% " = 1,796 l b . " 25 PRELIMINARY EXPERIMENTS - M o b i l it y o f A p p l i e d C alciu m a n d Magnesium Ions in th e D iffe re n t S o ils The r e l a t i v e c o n c e n t r a t i o n of e x ch a n g ea b le c a t i o n s a n d t h e i r m o b i l i t y or r e a c t i v i t y g r e e of s a t u r a t i o n on t h e is a ffe c te d by t h e i r d e ­ a b s o r p t i o n complex (2 5 )* The a c t i v i t y i s a l s o a f f e c t e d by t h e c o n c e n t r a t i o n o f t h e in th e s o i l s o l u t i o n and t h e i r io n izatio n . ions The c a t i o n s a d d e d t o a s y s t e m do n o t n e c e s s a r i l y r e a c t w i t h t h e e x c h a n g e com plex. Some o f t h e m m i g h t e x i s t i n t h e c a t i o n s an d would n o t b e a b s o r b e d by th e changeable c a t i o n s . system a s -fre e c o llo id s as ex­ In a n . e f f o r t to d e te r m in e the a c t u a l amount of a d s o r p t i o n of c a l c i u m and magnesium a d d ed t h r o u g h f e r t i l i z e r s by d i f f e r e n t were c a r r i e d in th e s o i l s , th e fo llo w in g exp erim ents lab o rato ry . C a l c u l a t e d a m o u n t s of c a l c i u m h y d r o x i d e a n d mag­ n e s i u m s u l f a t e w e r e m i x e d w i t h 2 50 g r a m s of e a c h s o i l o n t h e b a s i s of d e g r e e of s a t u r a t i o n of t h e exchange complex d e sire d fo r the They w e r e k e p t a t greenhouse e x p e rim e n ts. t h e i r p r o p e r m o i s t u r e e q u i v a l e n t s f o r a p e r i o d of two weeks. C o m p le m e n t a i y p o t a s s i u m i o n s w e r e n o t a d d e d t o the s o i l . A f t e r t h i s p e rio d th e s o i l s were a i r d r i e d and b o th exchangeable c a lc iu m and magnesium w ere d e t e r m i n e d by t h e p r o c e d u r e s a l r e a d y d e s c r i b e d . The r e s u l t s o f t h e a n a l y s e s a r e p r e s e n t e d i n T a b l e s V I I I and I X . From T a b l e s V I I I and I X , i t is ev id en t t h a t a p p lic a tio n s TABLE V I I I E x t e n t of I o n i c E x c h a n g e R e a c t i o n s F o l l o w i n g t h e A p p l i c a t i o n o f C a l c i u m an d Magnes ium t o t h e S o i l a f t e r two w e e k s o f I n c u b a t i o n . P ercentage S atu ratio n Ca Mg Ca:Mg C heck 100 150 4:1 ' M .E.added Ca Mg W isner pH a f t e r ineubatio n ■ ' m VE. Recovered Ca Mg 16.75 0 .9 8 7.6 16.58 0.95 18.30 4 .58 7.6 16.2 3.0 H illsd ale. S ubsoil pH a f t e r M.E . M .E.added in c u b a - ; R ecovered Ca Mg t i o n Ca Mg 0.92 0.03 8.1 0.9 0.029 25 50 2:1 « 9.16 7.6 15.8 5.5 1.32 0.66 8.1 1.3 0.32 75 1 .3 :1 " 13.74 7.5 15.5 6.8 n 0.99 8.1 1.2 0.49 » 1.32 7.9 1.1 0.95 0.99 1.50 0.28 1.40 0.68 100 1:1 25 50 6:1 75 100 3:1 2:1 1.5 :1 18.32 7.5 15.0 9s '. 0 27.48 4 .58 7.9 20.8 2.9 5.0 1.98 0.66 6.3 n 0.99 8.7 8.3 8.8 n 1.32 8.3 " « " " 9.16 13.74 18.32 7.9 7.8 7.8 . 16.8 16.7 18.8 0.47 ON TABLE IX E x t e n t o f I o n i c Exchange R e a c t i o n s f o l l o w i n g th e A p p l i c a t i o n of C a l c i u m and Magnes ium t o t h e S o i l a f t e r two weeks of I n c u b a t i o n Percentage S atu ratio n Ca Mg Ca:Mg C he ck 50 25 2:1 50 1:1 75 100 100 150 .75:1 .5 :1 25 4:1 50 2:1 ■ P lain field pH a f t e r M.E. M .E . a d d e d i n c u b a ­ R e c o v e r e d Ca Mg Ca Mg t i o n 1.1 0.63 5.2 1.05 0.60 1.78 «» 0.89 1.78 5.2 1.3 0.80 5.2 1.5 it it 2.67 3.57 4.9 4.9 3.56 tt 0.89 o .3 l 0.92 1.24 1.70 tt 1.5 1.56 1.60 2.20 tt tt 5.8 2.49 0.92 1.78 5.6 1.00 2.67 5.5 3.3 3.2 1.65 3.40 tt tt 3.57 5.4 3.1 4.2 1.75 rt 0.85 1.70 2 . 50 2.90 75 100 1 .3 :1 1:1 tt tt 25 6:1 1 3:1 2:1 0.89 L.78 6.1 50 5.34 it » 2 .67 5.9 n 3.57 5.9 75 100 1 .5 :1 M .E.added Ca Mg 6.0 4.4 4.9 4.8 Eox pH a f t e r in cu b a­ tio n M.E. Recovered Ca Mg 5.7 5.6 1.24 1.70 0.31 0.60 5.6 1.62 0.80 2.55 3.40 5.5 1.60 1.16 1.20 0.85 1.70 6.7 6.6 2.88 0.61 3.20 2.55 3.40 6.3 6.1 3.40 0.85 1.3 3.30 1.25 5.10 tt tt 0.85 1.70 7.0 3.2 0.62 2.55 6.8 6 .8 3.5 3.9 0.85 1.30 tt 3.40 6.7 4.2 1.28 0.85 1.70 5.4 1.40 ■ 28 o f c a lc iu m h y d r o x id e a n d magnesium s u l f a t e i n v a r ia b ly r a i s e d t h e pH. At each l e v e l of c a l c i u m s a t u r a t i o n th e c h a n g e i n pH -was i n f l u e n c e d b y t h e c o n c e n t r a t i o n of mag­ nesium io n s . The v a r i a t i o n i n pH was o n l y one t e n t h u n i t w i t h W i s n e r s o i l w h i l e i t was two t o th re e te n th s u n its w i t h P l a i n f i e l d , F o x sand a n d H i l l s d a l e (3) and K a r d o s a n d I o f f e h i g h SiO / r 0 'r a tio su b so il. (30) h a v e shown t h a t Anderson c o llo id s w ith show g r e a t e r v a r i a t i o n i n pH when s a t u r a t e d w i t h Ca a n d Mg i o n s t h a n t h o s e w i t h a low r a t i o . C o l l o i d s s a t u r a t e d w i t h Ca h a d a l o w e r pH t h a n t h a t o f t h e c o l l o i d s s a t u r a t e d w i t h Mg. f o r the silic ate The s t r o n g e r a f f i n i t y of Mg i o n a s c o m p a r e d w i t h t h e Ca i o n makes t h e form er more e f f e c t i v e i n r e d u c i n g the q u a n t i t y of s i l i c a t e a v a i l a b l e f o r h y d r o l y t i c c le av a g e a s m easured by the i n ­ c r e a s e i n pH. The d a t a p r e s e n t e d i n T a b l e I show t h a t t h e W isner h a s l e s s or the H i l ls d a l e s a n d i n compar i s o n wi t h P l a i n f i e l d , Fox su b so il. T h e r e f o r e , t h e r e d u c t i o n i n pH d ue t o c o n c e n t r a t i o n of m a g n e s i u m i o n s i s l e s s i n t h e W i s n e r th an in the o th e r th r e e s o ils m atter. t h a t h a v e more s i l i c e o u s Thus t h e r e i s a t e n d e n c y f o r t h e c o n v e r s i o n o f th e magnesium io n s i n to m a g n e s i u m m s il i c a te s w i t h i n c r e a s i n g c o n c e n t r a t i o n of t h e f o r m e r i n t h e s o i l s o l u t i o n . i s f u r t h e r s u p p o r t e d b y t h e a m o u n t of This t o t a l magnesium r e ­ c o v e r e d a f t e r a n i n c u b a t i o n p e r i o d of two w e e k s a s shown by t h e d a t a i n T a b l e s V I I L a n d I X . The r e c o v e r y of add ed m ag n e siu m i o n was l e s s i n p r o p o r t i o n t o t h e a m o u n t ad d ed i n th e c a s e o f th e W isner s o i l . T h e r e was l e s s m ag ne sium 29 r e c o v e r e d with, t h e h i g h e r c o n c e n t r a t i o n s of c a l c i u m a n d h i g h e r pH. Ray a n d G a n g u l y (4 9 ) h a v e d e m o n s t r a t e d t h a t s i l i c i c a c i d s o l becomes v e r y u n s t a b l e i n th e r a n g e o f pH 6 t o 9 a n d t h e s e n s i t i v i t y r a n g e n a r r o w s a s t h e c o n ­ c e n t r a t i o n of s i l i c a t e d e c r e a s e s . t r a t i o n o f Ca i n t h e increases W ith i n c r e a s i n g c o n c e n ­ e x ch a n g e complex, (T ab les V I I I and IX).. nesium combines w ith s i l i c a t e Thus a t h i g h p.H more mag­ io n s and a r e t i e d u p . may be a n e x p l a n a t i o n why i n a l k a l i n e o f m agnesi um i s t h e pH o f t h e medium s o i l the T his a v aila b ility low a s n o t e d b y Bower and T u r k ( 1 0 ) . T h e r e was l e s s r e c o v e r y of a d d e d Ca f r o m t h e a c i d th a n the a lk a li n e s o i l s . was a d d e d i n e x c e s s of t h e ch an ge c o m p l e x . I n some i n s t a n c e s t h e calcium s a t u r a t i o n c a p a c i t y of th e e x ­ I t sh o u ld be r e c a l l e d t h a t the soils are v e r y low i n o r g a n i c a s w e l l a s m i n e r a l c o l l o i d s . G enerally the added c a lc iu m r e a c t s w i t h o r g a n i c o r th e m i n e r a l c o l ­ lo id s. I n the a b s e n c e o f t h e s e su b stan ces, t h e Ca r e a c t s w i t h t h e H^SiO^ w h i c h i s i n g r e a t e r c o n c e n t r a t i o n a nd r e - . p l a c e s t h e H i o n s , CaSiO^ i s f o r m e d , a n d t h e pH i s creased. in ­ T h e s e f a c t s e m p h a s i z e t h e i m p o r t a n c e of t h e d e g r e e of c a lc iu m s a t u r a t i o n or t h e av ailab le calcium co n ten t of the s o i l a s a m ajor f a c t o r i n f l u e n c i n g the e f f e c t of m ag nesiu m i n p l a n t g r o w t h a n d n u t r i t i o n . 30 E f f e c t o f M a g n esiu m o n t h e S t r u c t u r e o f S o i l s I n c r e a s i n g a m o u n t s of m a g n e s i u m a t a c o n s t a n t l e v e l of c a lc iu m s a t u r a t i o n was found t o b r i n g ab o u t a p u d d le d a n d c o m p a c t c o n s i s t e n c y of t h e W i s n e r s o i l . The s o i l w a s s t i c k y and w a t e r t i g h t when m o i s t b u t became v e r y h a r d on drying. I t r e s e m b l e d somewhat t h e m o r p h o l o g i c a l c h a r a c t e r ­ i s t i c s of a s o l o n e t z s o i l . in p r o p o r tio n to the change i n t h e S w e l l i n g of s o i l on w e t t i n g was c o n c e n t r a t i o n of m agnesium . s t r u c t u r e o f t h e s o i l was r e f l e c t e d Such a in poor g r o w t h of t o m a t o s e e d l i n g s a s c a n b e s e e n f r o m t h e p h o t o ­ graph in F ig . 2 . The ’’check'* p l a n t s w h i c h d i d n o t c a l c i u m or m a g n e s i u m g r e w b e t t e r th a n t h o s e w hich r e c e i v e d i n c r e a s e d a m o u n t s of m a g n e s i u m a t a c o n s t a n t l e v e l McGeorge and B r e a g e a l e receive of c a lc iu m . (4 0 ) h a v e s u g g e s t e d o x y g e n d e f i c i e n c y as a f a c t o r r e s p o n s i b l e f o r poor grow th and w i l t i n g of p la n ts in a puddled s o i l . P l a i n f i e l d , F o x s a n d and H i l l s d a l e s u b s o i l w i t h low o r g a n i c m a t t e r and c l a y c o n t e n t showed co m p actio n n e a r t h e surface. A c o a rse r te x tu re d s o i l w ith larg e pores is u s u a l l y a s s o c i a t e d w i t h e a s y p e r m e a b i l i t y of w a t e r . w h i t e i n c r u s t a t i o n w a s f o u n d when t h e a f t e r each w a te rin g . The i n t e n s i t y t a t i o n in cre ased a s the D u r i n g t h e g r o w t h of t h e n o ticed th a t s o il sta rte d A drying of t h e w h i t e i n c r u s ­ c o n c e n t r a t i o n of m a g n e s i u m i n c r e a s e d . t o m a t o a n d t o b a c c o p l a n t s i t was a lt h o u g h a l l t h e t r e a t m e n t s were m a i n t a i n e d a t a uniform m o istu re lev el, p l a n t s r e c e iv in g a high r a t e 31 W ISNER F ig . 2. Growth, o f 17 d a y s o l d t o m a t o s e e d l i n g s s h o w in g t h e e f f e c t of p o o r t i l t h of W i s n e r s o i l a s a r e s u l t of i n c r e a s i n g Mg s a t u r a t i o n a t a c o n s t a n t l e v e l of Ca s a t u r a t i o n . W.SWER. I307.C . isi M . CHECK F i g . 3* T o b a c c o s e e d l i n g s a f t e r f o u r w e e k s o f t r a n s p l a n t a t i o n show ing th e e f f e c t o f poor p h y s i c a l c o n d i t i o n of s o i l a s a r e s u l t o f i n c r e a s i n g Mg s a t u r a t i o n a t a c o n s t a n t l e v e l o f Ca s a t u r a t i o n . 32 o f m ag n e siu m showed symptoms of more m ark e d m o i s t u r e s t r e s s t h a n the p l a n t s r e c e i v i n g s m a l l am o u n ts o f m a g n e s i u m . The p r o n o u n c e d r o l l i n g of l e a v e s o f c o r n and w i l t i n g of t h e l e a v e s o f t o b a c c o were e v i d e n t symptoms of m o i s t u r e s t r e s s . R e c o v e r y f r o m s u c h m o i s t u r e s t r e s s was q u i c k w i U u a l l o f t h e s a n d y s o i l s b u t v e r y slow w i t h W is n e r upon w a t e r i n g . E lectrical c o n d u c t i v i t y m e a s u r e m e n t s w e r e made on 1:2 e x t r a c t s (1 p a r t of s o i l t o 2 p a r t s of on a l l s o i l s after t h e a p p l i c a t i o n of t h e d i s t i l l e d w ater) r e q u i r e d a m o u nt o f c a l c i u m h y d r o x i d e a n d m ag n e siu m s u l p h a t e . The m e a s u r e ­ m ents were c o n fin e d to th e c l e a r s u p e r n a ta n t l i q u i d w ith " S o lu b r id g e ." The e l e c t r i c a l t a i n e d w e r e c o r r e c t e d t o 2 5°C. i n T a b l e X. B radfield r e s is ta n c e re a d in g s thus ob­ The r e s u l t s a r e s u m m a r i z e d (11) h a s shown t h a t a f t e r t h e s a t u ­ r a t i o n p o i n t i s r e a c h e d an y a m o u n t of c a l c i u m a d d e d i s c o n ­ v e r t e d t o so l i d - p h a s e c a l c i u m c a r b o n a t e a n d t h e calcium io n c o n c e n t r a t i o n , a s m e a s u r e d b y t h e c o n d u c t i v i t y of t h e s o l u ­ t i o n , b ecom es c o n s t a n t and i s i n d e p e n d e n t o f t h e amount o f c a lc iu m h y d r o x id e added to the sy s te m . T a k i n g f o r g r a n t e d t h a t t h e same s i t u a t i o n h o l d s t r u e f o r magnesium a s f o r c a l c i u m , any e x c e s s magnesium added above the s a t u r a t i o n c a p a c i t y of the exchange complex, w i l l b e p r e c i p i t a t e d a s m a g n e siu m c a r b o n a t e o r r e a c t s w i t h s ilic a to f o r m i n s o l u b l e m agn e siu m s i l i c a t e . l a t t e r p r o c e s s i s slow . a m o u n t s of Mg s a l t , But t h i s Hence, a f t e r a p p l i c a t i o n of h i g h the t e n d e n c y i s f o r th e conversion of TABLE X E l e c t r i c a l C o n d u c t i v i t y o f S o i l S o l u t i o n a s I n f l u e n c e d b y t h e C a l c i u m and M ag nesiu m R a t i o i n S o i l s . Degree of S a t­ u ration Ca Mg Ca:Mg % 1o W isner Con­ duc­ tiv ity M. E,. o f Ca Mg C heck 50 tt tt 100 tt 25 2 : 1 50 1 : 1 75 . 7 5 : 1 100 . 5 : 1 25 4 : 1 50 2 : 1 tt 75 1 : 3 tt 100 1 : 1 150 25 6 : 1 tt tt tt 50 3 : 1 75 2 : 1 100 1 . 5 : 1 ( C o n d u c t i v i t y v a l u e s e x p r e s s e d a s MhoSxlO — P lain field Con­ M. E. o f duc­ tiv ity Ca Mg 52 1.10 0.63 - - 1.78 0.89 1.78 3 10 16 2.67 3.56 28 42 0.89 1.78 10 it — — — — . - - tt — tt 18.32 4.58 160 It 9.16 380 tt 13.74 It 18.32 ■ 2 7 . 4 8 4,. 58 440 tt 575 360 tt 9.16 13.74 18.32 380 450 tt 475 tt ft tt « tt 3.56 5.34 tt 2.67 3.56 0.89 1.78 2.67 3.56 24 40 40 16 Eox M. E . o f Mg Ca 1 .2 4 0.31 1 . 7 0 0185 tt 1.70 tt Con­ duc­ tiv ity 3 . 4 0 0185 tt 1.70 22 » 2.55 3.40 42 55 , 50 5.10 ,0.85 24 1.70 2.55 3.40 36 44 48 26 38 it 55 tt tt 12 14 20 34 36 tt H illsd ale Con­ M. E • of duc­ tiv ity Ca Mg 5 2.55 3.40 tt a t 25 C ) . 1.32 0.66 tt tt 1.98 tt tt 0.99 19 20 1.32 24 0.66 0.99 1.32 20 22 36 the s a l t t o the c a rb o n a te form . In a system w ith calcium and m ag n e s i u m c a r b o n a t e , t h e l a t t e r i s 1 0 t i m e s m o r e s o l u b l e th an the f o r m e r , (16). M agn esiu m s u l p h a t e i s 25 t i m e s m o r e s o l u b l e t h a n the c alciu m s u l f a t e , . a lth o u g h c alciu m c h l o r i d e i s more s o l u b l e t h a n m a g n e s i u m c h l o r i d e . 1.5 tim e s Thu s i n t h e s o i l s o l u t i o n a t e q u a l t o t a l c o n c e n t r a t i o n s of Ca and-Mg s a l t s t h e r e i s a p r e p o n d e r a n c e of m ag n e siu m i o n s and m a g n e s i u m sa lts. The c o n d u c t i v i t y v a l u e w a s, t h e r e f o r e , to magnesium s a l t . l a r g e l y due T h u s , h i g h a p p l i c a t i o n s of m a g n e s i u m , i n e x c e s s of c a lc iu m , i n c r e a ® t h e s a l t t h e r e b y t h e osm otic v a lu e of t h e c o n c e n t r a t i o n and s o il so lu tio n . (50) h a s s t a t e d t h a t t h e r a n g e i n R ichards ’c a p illa r y ’ fo rce w ith w h i c h w a t e r i s h e l d by s o i l p a r t i c l e s b e t w e e n f i e l d cap acity and p e r m a n e n t w i l t i n g p o i n t i s a p p r o x i m a t e l y 0 . 1 - 1 . 5 a t ­ m ospheres of t e n s i o n . I f w ater is held above t h i s i t w i l l not be e q u a lly a v a i l a b l e in the c a p a c i t y and w i l t i n g p o i n t . ten sio n r a n g e betw een f i e l d Thus t h e a m o u n t o f s o l u b l e s a l t a f f e c t s t h e amount of w a t e r a v a i l a b l e t o p l a n t s . This a c c o u n t s f o r t h e i n c i p i e n t w i l t i n g of t h e t o m a t o a n d t o ­ bacco p l a n t s i n the h i g h c o n c e n t r a t i o n o f m a g n e s i u m s a l t s i n the W i s n e r s o i l . The amount of w a t e r a d d e d a t e ac h w a t e r i n g , to b rin g the s o i l m o i s t u r e to t h e so a s o r i g i n a l l e v e l , was l e s s w i t h high, m a g n e s i u m a p p l i c a t i o n t h a n t h a t w i t h low mag­ nesium a p p l i c a t i o n . H i g h e r c o n c e n t r a t i o n s of m a g n e s i u m r e s u lte d i n a corresponding re d u c tio n in p la n t growth, th ereb y low ering th e r a t e F r e q u e n c y of of w a t e r r e m o v a l f r o m the s o i l . i r r i g a t i o n was c l o s e l y r e l a t e d to c e n t r a t i o n of m a g n e s i u m i n t h e m e d iu m . the con­ EXPERIMENTAL RESULTS Growth. R e s p o n s e i n Q ,u artz Sand C u l t u r e M a g n esiu m w i t h o u t C a l c i u m * s e e d s a p p e a r e d to b e n o r m a l i n t h e G e r m i n a t i o n of t o m a t o sand c u l t u r e s i n th e a b s a n c e of c a l c i u m b u t a f t e r tw o weeks t h e s e e d l i n g s s t a r t e d t o damp o f f . The young l e a v e s on t h e upper p a r t of th e tom ato a s w e l l a s to b acco p l a n t s tu r n e d yellow w h ile the low er l e a v e s rem a in e d g r e e n . d i e d and n o f u r t h e r growth to o k p l a c e . a l l the n u t r i e n t s except calcium . The t e r m i n a l bud The s e r i e s r e c e i v e d H e n c e , m a g n e siu m i n t h e a b s a n c e of c a l c i u m d o e s n o t i n s u r e t h e h e a l t h y g r o w t h of p lan ts. ( F i g . U) C a l c i u m wi t h o u t M a g n e s i u m . and to b a c c o p l a n t s was v e r y slow a n d r e t a r d e d i n the a b ­ s e n c e of m a g n e s i u m . and v e ry ro u g h . came b l a n c h e d . off. layed. Growth of b o t h t o m a t o L eaves were d u l l g r e e n , s m a ll , narrow As g r o w t h a d v a n c e d t h e l o w e r l e a v e s b e ­ Some o f t h e m t u r n e d b r o w n , Flow er d i f f e r e n t i a t i o n d i e d , and f e l l of t o m a t o p l a n t s was much d e ­ The f e w f r u i t s w h i c h d e v e l o p e d w e r e s m a l l , t o u g h , and c o n t a i n e d few s e e d s . High C a l c i u m a n d Low M a g n e s i u m . R etarded grow th was n o t i c e d w i t h h i g h c a l c i u m a n d low m a g n e s i u m a p p l i c a ­ t i o n s j. Tomato s e e d l i n g s show ed p h o s p h o r u s d e f i c i e n c y symptoms an d i t was i n t e n s i f i e d w i t h w i d e r a t i o s of c a l ­ c iu m t o m a g n e s i u m . As g r o w t h ”a d v a n c e d , p o t a s s i u m d e f i c i e n c y symptoms b e g a n t o a p p e a r . The y o un g l e a v e s o f t o m a t o a n d t o b a c c o b e ca m e c r i n k l e d , w h e r e a s t h e o l d e r l e a v e s t u r n e d g r a y i s h g r e e n w ith a yellow t i n g e a lo n g t h e m a rg in . a 50:1 and 2 5 :1 r a t i o W ith of c a l c i u m t o m a g n e s i u m a b r o n z i n g o f l e a f t i s s u e s w a s f o l l o w e d by many l i g h t co lo red sp o ts betw een t h e l a r g e r v e i n s . Low C a l c i u m a n d H ig h M a g n e s i u m . With a n a r r o w r a t i o of c a l c i u m t o m a g n e s i u m , t o x i c i t y symptoms b e g a n to a p p e a r four weeks a f t e r g r o w th . The y o u n g l e a v e s of b o t h t o m a t o and to b a c c o showed c u r l i n g and r o l l i n g of t h e l a m i n a w i t h many s u n k e n brown p a t c h e s . * A c a r e f u l e x a m i n a t i o n of t h e c r o s s s e c t i o n of t h e a f f e c t e d l e a f t h r o u g h t h e brown b l o t c h e s showed t h e l o w e r e p i d e r m i s a n d s p o n g y r e g i o n s t o be somewhat d i s o r g a n i z e d a n d c o l l a p s e d . The p a l l i s a d e r e g i o n i n t h e s e a r e a s was n o t m a r k e d ly a f f e c t e d . s i d e of t h e The l o w e r l e a f i n t h e s e a f f e c t e d a r e a s was som ewhat d e ­ p r e s s e d b e lo w t h e l e v e l of t h e a d j a c e n t a r e a s . Sorokin and Sommer (55) w o r k i n g w i t h P i s u m S a t i v u m f o u n d t h a t t h e absence o f c alciu m had a d i r e c t g r a t i o n of t h e c e l l - w a l l . e f f e c t fim t h e d i s i n t e ­ They h a v e s u g g e s t e d t h a t t h e a b s e n c e of c a l c i u m d i s t u r b s t h e n o r m a l m i t o s i s o f t h e m eristem atic c e l l s and t h e a p p e a r a n c e o f a b e r r a n t t y p e o f d i v i s i o n a s calcium i s w ithdraw n. s m a l l a m o u n t of c a l c i u m i s This i n d i c a t e s t h a t a needed a s a c o n s t i t u e n t of t h e * T h is m i c r o t o n i c c r o s s s e c t i o n and e x a m in a tio n was done i n t h e l a b o r a t o r y of Dr. E . E. Woodcock of t h e D e p a r t m e n t of B o t a n y . Fig. 4 . Growth of k w e ek s o l d t o m a t o s e e d l i n g s w i t h i n c r e a s i n g a m o u n t of Mg i n a b s e n c e o f Ca a p p l i c a t i o n . ■Fig. 5 . Tomato l e a v e s u n d e r l o w Ca a n d h i g h Mg t r e a t m e n t s , show ing sunken p a t c h e s on the l a m i n a . N arrow r a t i o of Ca:Mg b r o u g h t a b o u t d i s o r g a n i z a t i o n of c e l l w a l l s due t o w h i c h t h e s u n k e n p a t c h e s became p r o m i n e n t . 39 F ig . 6. Growth o f f l u e c u r e d t o b a c c o a t t h e end o f 7 t h w e ek a s r e l a t e d t o th e i n t e r a c t i o n o f C a l c i u m and M a g n esiu m i n Q u a r t z s a n d c u l t u r e . T r e a t m e n t s of 1. 2. 3. 4. 5. 6. jars, fro m l e f t to 100 l b s . of MgSO. ( 0 . 0 6 M . E . Mg) . 4 400 l b s . of MgSO^ ( o . 2 4 M . E . M g ). 1 / 2 t o n CaCo 1 '» ” 1-1/2 " « 2 " " 400 l b . MgSO " " " " " " " " rig h t: No C a l c i u m . " (Ca:Mg ( " ” ( ” »* = 3 .1 :1 ) = 6.2 5 :1 ) = 9 :1 ) = 12:1) p ro to p la sts of the w h ile c e llw a lls. n e s i u m i n tJn e in t h e a (F ig . calciu m :m ag n esiu m th e 5). s J n o w e d t o x i c i t y sy m pto m s w i t h t h e n a r r o w ra tio . fo u r t h basal p o rtio n . leaf T h is Old l e a v e s e x h ib ite d the r o l l e d le a v e s ro lle d w ere c a lle d of c a l c i u m , a lso to x ic in creased . to G ro w th The p o o r p h y sic a l h ig h in the of to m a to , of t h e c o n ten t w i t h a r e l a t i v e l y low c o n c e n t r a t i o n c o n d i t i o n of th e W isner s o i l , c o n c e n t r a t i o n s of Mg, w a s r e f l e c t e d t o b a c c o and c o rn p l a n t s . by phonographs -There a p p e a r e d t o to m ato , of t h e be a to b ac co s o il. Thus, a h ig h c o n c e n tr a tio n R e s p o n s e i n W isner S o i l by illu stra te d As t h e a v a i l a b l e p l a n t grow th. brought a b o u t grow th l e v e l s o f m agnesium s a t u r a t i o n , i n c r e a s e d t h e a b s o r p t i o n of magnesium a sso c ia te d is Due t o t h e f a c t t h a t m agnesium t o x i c i t y . s u p p l y of m a g n e s i u m w a s of m agnesium , ap ices. o b s e r v e d u n d er a c o n s t a n t l e v e l of th is w as em e rged w i t h a t i g h t l y r o l l e d a w i d e r c a l c i u m to magnesium r a t i o . in c re a sin g p lan ts calcium in th e r o l l i n g was more pronounced t h a n t h e calciu m , w ith by t h e W i t h h i g h l e v e l of lea f grow n w i t h co u ld b e needed f o r ttie f o r m a tio n T h u s , a n a r r o w r a t i o o f c a l c i u m t o m ag­ Corn, p l a n t s norm al amount i s s u b s b r a t u r n , b r o u g h t a b o u t magnesium t o x i c i t y p lan t. su b stratu m la rg e of t h e s e p l a n t s This i s ( F i g . 2 , 9, 1 0 ) . d i r e c t r e l a t i o n s h i p betw een th e c o lo r a n d c o r n l e a v e s w i t h t h e m ag n e s i u m W i t h t h e w i d e r Ca:Mg r a t i o s t h e l e a v e s 41 W/SNER U-1301 M»-100 C.-IOO CHECK F i g . 7* Tomato c r o p a t the end o f f i f t h week of g e r m i n a t i o n s h o w i n g t h e e f f e c t of i n c r e a s i n g s a t u r a ­ t i o n o f Mg a t a c o n s t a n t l e v e l of Ca s a t u r a t i o n . ( I n c r e a s e d a m o u n t of Mg a p p l i c a t i o n i s f r o m l e f t to r i g h t ) . WISNER livion.v-u F ig . 8. G row th o f t o m a t o p l a n t s j u s t b e f o r e b l o s s o m i n g a s i n f l u e n c e d by d i f f e r e n t l e v e l s o f Ca a n d Mg s a t u r a t i o n . From l e f t t o r i g h t : J a r ” ” " " _ 2 3 45 - £Jj^L0 clC 1 5 0 $ Ca s a t . 100$ 100$ " 150$ " 1 0 $ Mg s a t . 25$ " 100$ " 100$ " (Ca:Mg ( " ( ,? ( " 15:1) 4:1) 1: 1 ) 1.5:1) 42 F i g . 9 . G ro w th of t o m a t o crop b e fo re h a r v e s t a s r e l a t e d t o v a r y i n g Ca and Mg s a t u r a t i o n . Top row 100% Ca s a t . w i t h v a r y i n g amount of Mg s a t . , from, l e f t t o r i g h t : Jar 1 10 % (Ca:Mg 1 0 : 1 ) '» 2 - 25% ( " 4:1) » 3 - 50% 2 : 1) 1 .3 :1 ) " 4 - 75% 1: 1) " 5 - 100% B o t t o m row, l e f t t o r i g h t J a r 1 - Chech '» 2 - 100% Ca 10% Mg XKJU /O M " 3 - ioo% »» 10 % " 4 - 150% 100 % » 5 - 150% As Ca:Mg be co m es n a r r o w e r , t h e r e i s more v i n e g r o w t h and l e s s f r u i t i n g . .,st> O I I 100 ry u\' u uv u cv la r- o 150 F i g . 2 2 . E f f e c t of d e g r e e of Ca a n d Mg s a t u r a t i o n on t h e y i e l d of tom ato crop i n W isner s o i l . 0 Gr CV 100 I>- O i— I T7 ■u\ o —u tr r i— I N 1A O 150 F i g . 2 3 . E f f e c t of d e g r e e o f Ca and Mg s a t u r a t i o n on t h e y i e l d i8f 1 T obacco c r o p i n W i s n e r s o i l . ON VjJ 60i 40 30 20 Yield of dry matter in grams 50 AJ O A O >-A O (V 1A (N O i—I I 75 100 TA <_) u\ (V A A 150 DOT 0 L Mg fo CA VO F i g . 26;. The e f f e c t of d e g r e e of Ca and Mg s a t u r a t i o n on t h e y i e l d of t o m a t o i n Fox s o i l . gram s 100-r- 80 80 - 60 60 - 40 40 =r 20 20 - Yield of dry matter in 100 0 o Mg' % Ca fo Che ck -y o 0 x! UN O UN O CV UN [>- Q r— I 0 UN cv O un UM N O O - e rr T T UN o UN O CV U N C * - O 50 100 H 150 F i g . 2 7 . E f f e c t of d e g r e e of Ca and Mg s a t u r a t i o n on t h e y i e l d of c o r n in P la in f ie ld s o i l . cv i—1 F ig .2 UN us o [>- o t— I u \ C X ' T V U CV UN O [>- ' 1—I trv cv T T UN O UN r- O 1—I 50 100 150 E f f e c t of d e g r e e of Ca and Mg s a t u r a t i o n on the y i e l d o f co rn i n Fox s o i l . -a o c a t i o n c o n c e n t r a t i o n i n e a c h of t h e t r e a t m e n t s w a s t h e same w hile the r a t i o tiv ely . 4 .9 , o f Ca:Mg was 0 . 6 6 : 1 , 1 . 5 : 1 a n d 4 : 1 , r e s p e c ­ The pH o f t h e s o i l r e c e i v i n g s u c h t r e a t m e n t s w a s 5 .4 a n d 5 . 8 , r e s p e c t i v e l y . R e d u c t i o n of a c i d i t y was i n f l u e n c e d m o re b y Ca t h a n b y Mg. The y i e l d s o f t h e t o ­ m a t o c r o p w i t h t h e s e t r e a t m e n t s w e r e 30 , 37 a n d 40 gms, resp ectiv ely . Y i e l d s of t o b a c c o f o l l o w t h e same p a t t e r n . The same r e l a t i v e 3r i e l d s w e r e o b t a i n e d w i t h Fo x s a n d . Thus, in a c i d s o i l s , pressed the low c a l c i u m a n d h i g h m a g n e s i u m d e ­ y i e l d w h i l e h i g h c a l c i u m a n d low m a g n e s i u m in creased th e y ie ld . The r a t i o o f Ca:Mg g i v i n g h i g h e s t y i e l d was 4 :1> b u t b e y o n d t h i s r a t i o , a s w i l l be s e e n f r o m T a b l e XVI a n d X V I I , y ie ld s f e l l sharply, in d ic atin g th a t h i g h c a l c i u m s a t u r a t i o n o v e r s h a d o w e d t h e e f f e c t o f mag­ nesium a p p l i c a t i o n . Y i e l d s of c o r n , a s p r e s e n t e d i n T a b l e s XVI and X V I I , showed a d i f f e r e n t t r e n d f r o m t h a t o f t o m a t o an d t o b a c c o . H igher y i e l d s w ere o b t a i n e d w ith h ig h e r c o n c e n t r a t i o n of m a g n e s i u m a t a c o n s t a n t l e v e l of calcium s a t u r a t io n . Bender anri :..E is e n m e n g e r (9) h a v e show n t h a t t h e e f f e c t o f one c a t i o n on t h e a b s o r p t i o n of a n o t h e r c a t i o n w a s d e p e n d a n t up on p l a n t sta n t. the s p e c ie s p ro v id e d th e s o i l c o n d itio n s rem ain con­ Growth a n d y i e l d of c o r n , tom ato and to b a c c o a t i n c r e a s i n g l e v e l of m a g n e s i u m s a t u r a t i o n a t a c o n s t a n t l e v e l of c a l c i u m s a t u r a t i o n e m p h a s i z e t h a t p o i n t . H illsd ale S u b so il. Y i e l d s o f t o m a t o and t o b a c c o a r e g i v e n i n T a b l e - X V I I I a n d a r e shown i n F i g s . 29 a n d 3 0 . 72 Compared w i t h t h e y ield o b t a i n e d f r o m no a p p l i c a t i o n o f Ca o r Mg, t h e r e s p o n s e of c r o p s t o Mg a p p l i c a t i o n was v e r y l i t t l e when t h e p e r c e n t a g e o f c a l c i u m s a t u r a t i o n was i n ­ creased to 150. O verlim ing i n t e r f e r e d w ith th e a v a i l a b i l i t y of o th e r n u t r i t i v e e l e m e n t s and t h e r e s p o n s e t o magnesium f e r t i l i z a t i o n was n o t w e l l m a r k e d . A c o m p a r i s o n of t h e h e i g h t of t o m a t o p l a n t s a s a f f e c t e d b y v a r i o u s t r e a t m e n t s g i v e s a n i n d i c a t i o n o f t h e i n f l u e n c e o f m a g n e s i u m on t h e v e g e t a t i v e g r o w t h o f t o m a t o , b u t t h e r e w a s p r a c t i c a l l y no d i f f e r e n c e in t h e y i e l d of f r u i t s , in d ic a tin g a d istu rb ed c a r b o h y d r a t e h i t r o g e n m e t a b o l i s m so e s s e n t i a l f o r s a t i s ­ f a c t o r y r e p r o d u c t i v e p h a s e of t h e p l a n t . 73 TABLE X V I I I E f f e c t o f D i f f e r e n t L e v e l s of Lime a nd M a g n es iu m F e r t i l i z e r on t h e Y i e l d of Tomato and Tobacco i n H i l l s d a l e S u b s o i l * Degree o f S atu ratio n Mg Ca Tomato Ca:Mg Vine F r u it T otal cm 1o * H t. Tobacco H t. Y ield cm 69.6 22.7 3 .1 :1 35 11.8 2.3 1 4.1 77 15 75 50 1 .5 :1 42 12.6 3.3 15.9 75 18 75 1:1 46 17.5 2.0 19.5 75 20 0 .7 5 :1 38 12.2 3.9 16.1 82 22 50 2:1 40 14.2 2.0 16.2 67 19 75 1 .3 3 :1 42 15.1 2.2 17.3 64 23 100 1:1 39 1 6 .6 1.9 18.5 68 25 50 3:1 40 11.5 1 .0 12.5 44 14 75 2:1 37 12.1 2.0 14.1 48 i4 1 .5 :1 39 11.1 2.5 13.6 • 50 15 100 100 150 100 * F i g u r e s r e p r e s e n t a v e r a g e of t h e t h r e e r e p l i c a t i o n s . W eights a r e d ry w e ig h ts in gram s. 25 2C- 20 r 15- 15- 1C 10 Yield of dry matter in grams 25r o M £ xj o o Ca fo a t> o <— i 75 "O *A 'VTv O I>- O I 100 “cr u=C I O I— I o >a i—I 150 F i g . 3 0 . E f f e c t of d e g r e e o f Ca and Mg s a t u r a t i o n on t h e y i e l d s o f tobacco in H ills d a le s u b s o il . P l a n t C om position D a t a p r e s e n t e d i n T a b l e s XIX t h r o u g h . X X I I I show t h e amou nt a n d p r o p o r t i o n of c a l c i u m , m a g n e s i u m and p o t a s s i u m i n t o m a t o , t o b a c c o and c o r n c r o p s i n r e l a t i o n t o the con­ c e n t r a t i o n of t h e s e i o n s i n s o i l . C alcium . From F i g s . 31 t h r o u g h 4 0 , ' i t t h e c o n c e n t r a t i o n of m a g n e s i u m i n t h e a b s o r p t i o n of c a l c i u m b y t h e p l a n t . is seen t h a t s o il in flu en ced th e When t h e c o n c e n t r a t i o n o f m a g n e s i u m was low t h e c a l c i u m c o n t e n t of t h e crop i n ­ creased f a i r l y c o n s i s t e n t l y w i t h i n c r e a s e d a p p l i c a t i o n of c alciu m to the s o i l , although th is p o r tio n a l to the o f the i n c r e a s e i n no way 4jv a.s -p ro ­ i n c r e a s e d amounts t h a t w ere a d d e d i n e x c e s s o r i g i n a l amount p r e s e n t in t h e s o i l . As t h e d e g r e e o f m a g n e s i u m s a t u r a t i o n i n c r e a s e d f r o m 25 p e r c e n t t o 1 0 0 p er.cen t of t h e t o t a l e x c h a n g e c a p a c i t y o f t h e s o i l , c a l c i u m c o n t e n t of t h e crop s i g n i f i c a n t l y d e c re a s e d . the E v en t h e t r e a t m e n t s w i t h e q u i m o l e c u l a r c o n c e n t r a t i o n of c a l c i u m and magnesium r e s u l t e d i n a lo w e r c o n t e n t of c a l c i u m a n d a h i g h e r c o n t e n t of m a g n e s i u m i n t h e p l a n t s . M o b ilizatio n of calcium in th e p la n t w as, t h e r e f o r e , b y t h e c o n c e n t r a t i o n of m a g n e s i u m i n th e g r e a tly influenced so il. I n a l l of t h e s o i l s a n d w i t h a l l t h r e e c r o p s s t u d i e d i t was e v i d e n t t h a t magnesium a c t e d a s a r e t a r d i n g i o n t o c a l c i u m u p ta k e and t h e r e t a r d i n g i n f l u e n c e in c re a s e d w ith in c re a s e d con­ c e n t r a t i o n of t h e m a g n e s i u m i o n . TABLE XIX i E f f e c t of C a l c i u m and M a g n es iu m on t h e M i n e r a l C o m p o s i t i o n o f T o m a to , T obac co a n d Corn C r o p s i n Q u a r t z S a n d . ( I n M i l l i e q u i v a l e n t s p e r 100 gm. d r y m a t t e r ) . M.E. of c a tio n s applied Ca Mg 0 .7 5 1 .6 0 0 .0 6 0 .1 2 0 .2 4 0 .6 0 0 .0 6 0 .1 2 0 .2 4 0 .6 0 3 .0 0 0 .0 6 0 .1 2 0 .2 4 0 .6 0 Ca:Mg Ca Tomato Mg K 1 2 .5 :1 90 27 6 .2 5 :1 74 57 61 81 3 .1 :1 1 .2 5 :1 48 101 92 2 5 :1 27 1 2 .5 :1 85 47 6 .2 5 :1 75 54 58 90 2 .5 : 1 5 0 :1 26 101 42 2 5 :1 85 1 2 :1 49 85 70 1 94 5 :1 61 60 69 51 61 57 60 47 64 54 48 47 T otal Ca 178 191 211 200 180 189 189 195 185 182 183 211 84 78 55 43 87 75 67 60 105 100 87 68 Tobacco K Mg 32 40 50 60 30 51 61 65 25 25 37 37 58 60 69 71 84 87 92 97 66 69 89 79 T otal Ca 174 178 174 174 201 213 220 222 196 194 213 184 38 33 24 22 36 27 21 18 41 30 27 23 C o rn Mg 17 30 36 40 19 21 33 52 25 30 35 40 K T otal 64 119 135 124 121 134 122 136 140 130 124 132 128 72 64 59 69 74 82 70 64 64 70 65 -< 3 ON TABLE XX E f f e c t o f D i f f e r e n t L e v e l s o f C a l c i u m a n d M agn esiu m on t h e C o m p o s i t i o n of T om a to, T o bac co a n d Corn C r o p s i n W i s n e r S o i l . (M.E. p e r 100 gms d r y m a t t e r ) . M .E .o f c a t 1*0a s added"12 Ca Mg Ca:Mg Ca Tomato Mg K 1 6 .7 5 0 .9 8 1 7 :1 86 70 1 8 .3 2 2 .2 9 1 0 :1 101 4 .5 8 4 :1 9 .1 6 2 7 .4 8 Ca G orn Mg K Tot a l Ca Tobacco Mg K T o ta l 16 172 138 38 27 203 61 38 43 142 77 11 189 101 61 43 20 5 61 42 27 130 98 95 13 206 101 81 31 213 52 62 28 142 2 :1 82 110 14 206 76 88 41 205 58 68 34 160 1 3 .7 4 1 .3 : 1 69 129 14 212 66 144 45 255 52 72 28 152 1 8 .3 2 1 :1 58 145 10 213 48 156 i 35 239 51 83 20 154 2 .2 9 1 5 :1 109 87 11 207 138 68 64 270 72 50 20 142 4 .5 8 6 :1 92 110 15 217' 120 90 73 283 66 56 27 149 9 .1 6 3 :1 74 124 19 217 106 129 81 316 58 53 29 140 1 3 .7 4 2 :1 60 20 220 106 ,141 82 323 56 66 30 152 1 8 .3 2 1 .5 :1 59 14 228 85 169 69 323 54 66 27 147 140 145 T o ta l TABLE XXI E f f S c t o f D i f f e r e n t L e v e l s of C a l c i u m an d M agn esiu m on t h e C o m p o s i t i o n of T o m a to , T o b a c c o and C orn C r o p s i n P l a i n ­ f i e l d S o i l . (M.E. p e r 100 gms d r y m a t t e r ) . M .E.of ea-tions Ca 1 .1 0 1 .7 8 ' 2 .5 6 3 .5 6 5 .3 4 ad ri fid Mg 0 .6 3 0 .8 9 1 .7 8 2 .6 7 3 .5 6 0 .8 9 1 .7 8 2 .6 7 3 .5 6 0 .8 9 1 .7 8 2 .6 7 3 .5 6 0 .8 9 1 .7 8 2 .6 7 3 .5 6 Ca:Mg Ca 2 :1 1 :1 0 .6 6 :1 0 .5 : 1 3 :1 1 .5 : 1 1 :1 0 .7 5 :1 4 :1 2 :1 1 .2 5 :1 1 :1 6 :1 3 :1 2 :1 1 .5 : 1 72 73 54 46 43 82 72 56 52 88 72 61 58 98 86 75 65 Tomato Mg K 29 46 80 95 100 42 84 93 j 97 42 77 85 88 33 66 100 100 11 8 12 14 10 10 12 14 9 9 10 12 8 8 10 10 6 Tot a l 112 127 146 155 153 134 168 163 158 139 159 158 154 139 162 185 171 j Ca 101 107 59 56 49 78 84 57 55 87 54 52 40 95 72 42 46 Tobacco Mg K 35 49 80 108 114 51 78 98 112 44 71 93 113 53 68 65 100 45 45 49 51 84 47 47 57 72. 33 43 47 40 37 34 34 24 T otal Ca 181 201 188 215 247 176 209 212 239 164 168 192 193 185 174 111 170 29 48 36 28 22 56 23 23 22 60 32 23 26 46 j 41 32 29 Co rn Mg 18 22 21 50 55 28 47 50 55 40 50 53 53 33 33 59 62 K 36 21 29 34 48 49 51 51 42 31 42 46 47 38 31 47 55 T otal 83 91 86 112 122 133 121 124 119 131 124 122 126 117 .■ 105 138 146 TABLE XXII j E f f e c t of D i f f e r e n t L e v e l s of C a l c i u m and M agnesium on t h e C o m p o s i t i o n of T o m a to , T o b ac co a n d Corn C r o p s i n Fo x S a n d . (M.E. f o r , 100 gms s o i l ) . 1 .2 4 1.70 2.55 3.40 5.10 0.31 0.85 1.70 2.55 3.40 0.85 1.70 2.55 3.40 0.85 1 .70 2.55 3.40 0.85 1.70 2.55 ' 3.40 Ca :Mg Ca 4:1 2:1 1:1 0.75:1 3:1 3:1 1 .5 :1 1:1 64 68 60 42 42 78 69 58 i—1 ir\ • call ions--- .add ed Ca Mg 54 90 85 80 4 :1 1 2:1 1.33:1 1:1 69 6:1 104 88 3:1 2:1 74 65 1 .5 :1 Tomato K Mg 30 52 21 61 84 27 112 30 127 27 16 94 18 99 119 24 132 20 68 : 14 92 17 109 19 121 20 56 14 16 89 103 29 124 20 T o b a c c o _______________ Co rn___________ Mg K T otal Ca Mg K T otal Tota. Ca 146 150 171 174 196 188 186 40 46 45 27 33 55 43 35 13 77 92 102 105 49 73 81 34 60 48 35 26 102 191 206 172 194 208 210 1 74 193 206 77 66 39 1 44 55 71 90 32 49 66 209 35 68 37 49 77 80 60 50 66 70 52 52 58 70 90 172 21 4 209 195 154 182 186 188 156 161 176 181 65 55 65 68 164 180 173 62 165 24 49 40 40 32 ' 51 35 34 30 58 52 44 34 70 52 46 46 30 48 51 58 64 37 53 56 71 39 48 62 83 36 51 44 59 41 57 52 53 62 34 48 68 56 95 154 143 151 158 122 136 158. 49 60 65 57J 52 48 52 157 136 160 171 174 158 151 142 41 146 80 TABLE X X I I I E f f e c t of D i f f e r e n t L e v e l s o f C a l c i u m a n d M a g n e s i u m on t h e C o m p o s i t i o n o f T om ato and Tobacco i n H i l l s d a l e S u b s o i l . (M.E. p e r 100 gms d r y m a t t e r ) M . E . o f CafKTrmc, -ahripfl ' c a ' J mg Ca:Mg Ua Tomato Mg- K Tot a l 100 59 13 172 Tobacco Mg K T o ta l 87 35 71 193 Ha 0.99 0.66 1 . 5 : 1 63 73 16 157 81 61 71 213 0.99 1 :1 57 80 11 148 85 79 79 243 41 87 10 138 82 61 71 214 0.66 2 :1 60 40 15 115 82 30 71 183 0.99 133:1 58 80 17 155 67 60 70 197 1.32 I : 1 47 85 15 147 54 75 71 200 0.66 3 :1 107 63 15 185 104 30 82 216 0.99 2 :1 68 59 15 142 95 44 78 217 1.32 1 . 5 : 1 48 62 14 124 77 64 78 219 1.32 1 .32 1.198 i—I «• ir\ C'• 0.30 3:1 O 0 .9 2 81 75 M .E . C a l c i u m 3 .0 IO C M.E. Ca/lOO gm. dry matter 130 7C 06 12 M .E. F ig . 24 o f M a g n es iu m 3 1 . The e f f e c t of i n t e r a c t i o n of Ca an d Mg s a t u r a t i o n on t h e Ca c o n t e n t of t o m a t o p l a n t s i n Q u a r t z sand c u l t u r e . 60 .E. Ca/lOO gm. dry matter 7 5 M.E. C a l c i u m < 40 20 O 12 M. E . o f Ma gne s i urn F ig . 3 2 . The e f f e c t of i n t e r a c t i o n of Ca a n d Mg s a t u r a t i o n on t h e Ca c o n t e n t of c o r n p l a n t s i n Q u a r t z sa n d c u l t u r e . 82 110 ' M.E. Ca/lOO gm. dry m atter Ca S a t u r a t i 10 °/o Mg S a t u r a t i o n F ig. 80 33* The e f f e c t o f d e g r e e of Ca and Mg s a t u r a t i o n on t h e Ca c o n t e n t of t o m a t o p l a n t s i n V /isn er s o i l . M.E. Ca/100 gm. dry matter 100 fo Ca S a t u r a t i :>n 150 10 100 llg s a tu ra tio n F ig . 3 4 . The e f f e c t of d e g r e e of Ca and Mg s a t u r a t i o n on t h e Ca c o n t e n t of c o r n p l a n t s i n V /isn e r s o i l . 83 m atter 100 dry / 80 y r jr / gm. / i N ' M.E. / / / Ca/lOO / 60 ---------------------. c r\n1 Ca s a t u r a t i i >n »» -------------- 100$ tt » » » — x— X— 150$ 40 0 25 50 100 75 $ Mg s a t u r a t i o n E ig . 3 5 . The e f f e c t of d e g r e e of Ca and Mg s a t u r a t i o n on .the Ca c o n t e n t o f tom ato p l a n t s in P l a i n f i e l d s o i l . j \ j -------------------V gm.dry matter \ ^_ --“V. Ny. y Ca/100 0 M.E. ___ _ __— • — -------------- 1 0 q$ o —x— X— 150$ Ca s a t u r a t i on it it tt tt °Jo Mg S a t u r a t i o n F i g . 3 6 . The e f f e c t Of d e g r e e of Ca and Mg s a t u r a t i o n on t h e Ca c o n t e n t of c o r n p l a n t s in P l a i n f i e l d s o i l . 84 \ r gm.dry m atter > * Ca/lOO ) M.E. --------------50% (3a S a t u r a t i o n Tt tt ------------1 0 0 # Tt tt —x— * - 1 5 0 # — ................. ^ # Mg S a t u r a t i o n F i g . 3 7 . The e f f e c t of d e g r e e o f Ca a n d Mg s a t u r a t i o n on t h e Ca c o n t e n t of t o m a t o p l a n t s i n Fox s o i l . 70 ^ — X'*y 50 dry matter X *_ ^ r — X— X— X— Ca/lOO gm. ' 30 M.E. c n .n 7 /o Da S a t u r a t i o r ♦T tt — ------ 1 0 0 # tt T t 0 — »>—Xr-150# # Mg S a t u r a t i o n F i g . 3 8 . The e f f e c t of d e g r e e o f Ca a n d Mg s a t u r a t i o n on t h e Ca c o n t e n t o f c o r n p l a n t s in Fox s o i l . i S5 100 \ \ + \ -+ \ gm. Ca/lOO M.E. + \ 80 dry m atter \ r . 6C 4d >V . .... . . >- -------------- 7 5 $ Ca s a t u r a t i o a tt ------------- 100$ »» »* — x— x—-1 5 0 $ »t 0 50 75 °jo Mg s a t u r a t i o n M.E. Ca/lOO gm. dry matter F i g . 3 9 . The e f f e c t o f d e g r e e o f Ca a n d Mg s a t u r a t i o n on t h e Ca c o n t e n t of tom ato p l a n t s in H i l l s d a l e s u b s o i l , °Jo Mg s a t u r a t i o n F ig. 4 0 . The e f f e c t o f d e g r e e o f Ca a n d Mg s a t u r a t i o n on t h e Ca c o n t e n t of tobacco p l a n t s in H i l l s d a l e s u b s o i l . 100 86 M agnesium . The g r a p h s ( F i g s . 4 1 th r o u g h 5 0 ) , show ing t h e m a g n e s i u m c o n t e n t o f t o m a t o , t o b a c c o and c o r n grown i n q u a r t z s a n d c u l t u r e an d i n t h e f o u r d i f f e r e n t s o i l t y p e s , a r e a lm o s t s t r a i g h t l i n e s i n d i c a t i n g t h e r e b y t h a t by i n ­ c r e a s i n g t h e d e g r e e of m a g n e s i u m c o n c e n t r a t i o n a t e a c h l e v e l o f c a l c i u m c o n c e n t r a t i o n i n c r e a s e d a m o u n t s of m a g n e s i u m was d e l i v e r e d to .the crop. From an e q u i m o l e c u l a r c o n c e n t r a t i o n o f c a l c i u m a n d m a g n e s i u m , e . g . 1 8 . 3 2 m . e . of Ca and 1 8 . 3 2 m . e . o f Mg ( T a b l e X X ) ; 1 . 7 8 , 2 . 6 7 , 3 . 5 6 m . e . o f Ca and Mg ( T a b l e Z Z I ) ; and 1 . 7 0 , 2 . 5 5 a nd 3*54 m . e . of Ca a n d Mg ( T a b l e 2XEI) m o r e m a g n e s i u m t h a n c a l c i u m h a s b e e n t a k e n up by t h e p l a n t . At low c o n c e n t r a t i o n s of m a g n e s i u m , e i t h e r a t 10 p e r c e n t s a t u r a t i o n i n W i s n e r s o i l o r 25 p e r c e n t s a t u r a t i o n i n P l a i n f i e l d and Fox sa n d , t r a t i o n of c a l c i u m i n t h e of calcium by p l a n t s . s o i l r e s u l t e d in g r e a t e r uptake At h i g h e r m a g n e s i u m c o n c e n t r a t i o n s t h e u p t a k e of c a l c i u m was s u p p r e s s e d . ratio T h u s , when t h e Ca:Mg i n t h e s o l u t i o n was n a r r o w , m a g n e s i u m h a d a s u p p r e s ­ s i v e e f f e c t on t h e on the in c r e a s in g concen­ uptake uptake of c a l c i u m a n d t o c e rta in ex ten t of p o t a s s i u m . The a b s o r p t i o n of i n c r e a s e d i n c r e m e n t s ' of m a g n e s i u m n e i t h e r i n d u c e d go o d g r o w t h n o r p r o d u c e d a n y i n c r e a s e i n y ield . Such a n a b s o r p t i o n of m a g n e s i u m i s c o n s i d e r e d a lu x u ry consum ption. At t h e l o w e r r a n g e of c o n c e n t r a t i o n s o f t h e e l e m e n t i n t h e s o i l t h e r e se em ed t o b e e c o n o m i c a l u t i l i z a t i o n of n u t r i e n t s a n d h e n c e b e t t e r g r o w t h and y i e l d of the crops. 4 B7 J "— i m atter — tt— =; # J P XVI E . C a l c i u m I *— . 3 I 0 * // // // * 1 . . gm .dry . tt tt M.E. Mg/100 £/ .06 . 0 2 72TT ' 76t) M.E. o f M agnesium F i g . 41* The e f f e c t of i n t e r a c t i o n of Ca and Mg s a t u r a t i o n on t h e Mg c o n t e n t of t o m a t o p l a n t s i n Q u a rtz sand c u l t u r e . \ \ 40 gm.dry Mg/100 M.E. ' \ tatter ............... • / J lvl . E . C a l c i u m » II ------------------------------i . 5 tr tt ----# --- * — *---- 3 . 0 „ 25 ------X— ^ *.*’ <■ / 10 M.E. o f Magnes ium F i g . 4 2 . The e f f e c t of i n t e r a c t i o n of C a 'a n d s a t u r a t i o n on t h e Mg c o n t e n t of c o r n p l a n t s i n Q u artz sand c u l t u r e . i 88 M.E. Mg/100 gm. dry m a t te r 100% 0a S a t u r a t i o n 150% " " 10(^ 0 10 25 50 75 100 % Mg s a t u r a t i o n F i g . 4 3 . The e f f e c t o f d e g r e e of Ca a nd Mg s a t u r a t i o n on t h e Mg c o n t e n t of tomato p l a n t s i n W isner s o i l . matter ------------ 100% 3a S a t u r a t i o n --------- ------------150% n t? / M.E. Mg/100 gin. dry s/ / ' / 1 ■ 0 10 25 50 75 % Mg s a t u r a t i o n F i g . '4 4 . The e f f e c t of d e g r e e o f Ca and Mg s a t u r a t i o n on t h e Mg c o n t e n t o f c o rn p l a n t s i n W isner s o i l . 100 89 120 m atter ' 3U '/O Ca S a t u r a t i (>n tt --------------1 00 % IT " _ tt '■* 1 5 0 % i gm. dry 90 M.E. Mg/lOO --- if---- X—— if —^ << ---- — 60 / ✓ / / X>- y . yp* " V / 3QL % Mg s a t u r a t i o n F i g . 4 5 . The e f f e c t of d e g r e e o f Ca a n d Mg s a t u r a t i o n on t h e Mg c o n t e n t of tom ato p l a n t s in P l a i n f i e l d s o i l . -/O, o 0 ---------------------100; 1 0 — * — X.— 150; 1 Ca S a t u r a t i " tt 4 m " tt 60 gm. dry m atter 80 / ------------------- / " + Mg/100 / / / ✓ 40 x ' -— 20 0 25 i.-----X— X — X- / > / / ft 50 75 % Mg s a t u r a t i o n F i g . 4 6 . The e f f e c t of d e g r e e of Ca and s a t u r a t i o n on t h e Mg c o n t e n t of corn p la n ts in P l a i n f i e l d s o i l . 100 90 ' jKJjo Da s a t u r a t i o r tt ------------- 1 0 0 o/Q T? tt tt —*— *--- ]_50$ 110 . M.E. Mg/lOO gm dry m atter 140 7 BO ^ X — - C. . 50 aJ0 Mg s a t u r a t i o n F ig . 4 7 . The e f f e c t of d e g r e e of Ca and Mg s a t u r a t i o n on t h e Mg c o n t e n t of tom ato p l a n t in Fox s o i l . 90 ----------------------5 0 $ — «— . — 100 / * — 150$ 60 Mg/100 M.E. > • ... -- -~^tr ^ _ _ __y- gm dry matter — *— Ca s a t u r a t i c n II It II t! X« 30 - 0 50 75 fo Mg s a t u r a t i o n F i g . 4 8 . The e f f e c t of d e g r e e of Ca and Mg s a t u r a t i o n on t h e Mg c o n t e n t of c o r n p l a n t s ill F o x s o i l . TOO 4 91 -7 yk c a s a t u r a t i o n 100/ ° *-*-150% 80 M.E. Mg/lOO gm. dry m atter 100 100 ■fo Mg s a t u r a t i o n F ig. 49 . The e f f e c t of d e g r e e of Ca and Mg s a t u r a t i o n o n t h e Mg c o n t e n t of tom ato p l a n t s i n H i l l s d a l e s u b s o i l . ------------75% C a s a t u r a t i o n n ------ -— 100% tt u tt —*—*—150% 71 dry m atter 9 q A v gm. < M.E. .........- A T*\ Mg/100 / 5C / / 3 Cl O' A / 25 50 * - " ' 75 b Mg s a t u r a t i o n F ig. 5 0 . The e f f e c t of d e g r e e of Ca and Mg s a t u r a t i o n on t h e Mg c o n t e n t of tobacco p l a n t s in H i l ls d a l e s u b s o il . 100 I n t e r m s o f m a g n e s i u m c o n c e n t r a t i o n s and t o t a l mag-> n e s i u m c o n t e n t of t h e c r o p s , t h e y w e r e g r e a t e r i n t h e soils than i n the c a l c a r e o u s s o i l s . acid Thus, th e a b s o r p t i o n o f b o t h c a l c i u m a n d m a g n e s i u m d e c r e a s e d a t t h e h i g h e r pH v alu es. When a c i d s o i l s , s u c h a s P l a i n f i e l d and Fo x s a n d , w e r e l i m e d t o a n e u t r a l c o n d i t i o n t h e b a s e s t a t u s of t h e so ils and t h e m o b i l i t y of t h e c a l c i u m a s w e l l a s m a g n e s i u m was i n c r e a s e d . P otassium . As i n d i c a t e d i n F i g s . 51 t h r o u g h 6 0 , the p o t a s s i u m c o n t e n t , of t o m a t o , t o b a c c o and c o r n a p p e a r e d t o be i n f l u e n c e d more b y the magnesium th an t h e t e n t of t h e in so il. I n c r e a s i n g c o n c e n t r a t i o n s of c a l c i u m the s o i l had b u t l i t t l e t a s s i u m by t h e p l a n t s . in th e s o i l , the calcium con­ i n f l u e n c e on t h e uptake o f p o ­ W i t h .a c o n s t a n t a m o u n t o f p o t a s s i u m p e r c e n t a g e as w e l l as th e t o t a l amount of p o t a s s i u m a b s o r b e d b y t o m a t o , t o b a c c o and c o r n i n c r e a s e d w i t h i n c r e a s i n g magnesium c o n c e n t r a t i o n s , o f c a l c i u m rem ained c o n s t a n t . when t h e c o n t e n t Thus, t h e r e i s a p p a r e n t l y a " s y n e r g i s t i c ' e f f e c t " of magnesium on p o t a s s i u m inasm uch a s t h e f o r m e r i s a s s o c i a t e d w i t h t h e movement of t h e p o ­ tassiu m in to the p l a n t . B ut t h i s to be r e la te d to a d e f i n i t e sy n erg istic e f f e c t seemed c o n c e n t r a t i o n of m a g n e siu m w i t h r e s p e c t t o t h e s a t u r a t i o n c a p a c i t y of t h e e x c h a n g e c o m p l e x . In the presen t stu d ie s t h is t o b e 75 p e r c e n t of t h e s a t u r a t i o n of t h e o r i g i n a l e x ­ c h a n g e c a p a c i t y of t h e s o i l . tiv e effect a ris e s , c o n c e n tra tio n le v e l appeared B e yo n d t h i s l e v e l a com peti­ t h e u p t a k e of m a g n e s i u m i n c r e a s e s w h i l e m atter 93 / —* — 1 / ' gm. dry » ' n K/l.00 _ ‘ ----- M.E. • 7j U .E. C alcium tt t* !t tt — * — » ------ 3.’ o .06 .12 * ---- xV .24 .60 M.E . o f Magnesium F ig. 5 1 . Tiie e f f e c t of i n t e r a c t i o n of Ca and Mg s a t u r a t i o n on t h e K c o n t e n t of t o m a t o p l a n t s i n Q u a r t z sa nd c u l t u r e . \ 80 \ V 1 1 70 li m atter \ i \ r gm. dry f X--Jt i 4 M.E. K/lOO 60 50 — — — — *— *----. 06 M ,E . C a l c i u m » »t t t» 3.0 . 75 1 .5 .1 2 .24 M.E. of Ma gne s i um F ig. 5 2 . The e f f e c t of i n t e r a c t i o n of Ca and Mg s a t u r a t i o n on t h e K c o n t e n t o f c o r n p l a n t s i n Q u a rtz sand c u l t u r e . .60 94 20 gm. dry m atter a satu ratio n M.E. K/lOO 10 100 10 °]o Mg s a t u r a t i o n F ig . 5 3 . The e f f e c t of d e g r e e of Ca a n d Mg s a t u r a t i o n on t h e K c o n t e n t of tomato p l a n t s in W isner s o i l . matter a sa tu ratio n gm. dry i M.E. K/100 20 10 100 cf0 Mg s a t u r a t i o n F ig . 5 4 . The e f f e c t o f d e g r e e of Ca and Mg s a t u r a t i o n o n t h e K c o n t e n t of c o r n p l a n t s in W isner s o i l . 95 m atter 15 ....... M.E. K/100 gm. dry 1 X 1 X '] ... ... JV /» 12a s a t u r a t i o n t» ---- •------- 1 0 0 # i* tt tt — *—*—1 5 0 # . ......... -------------------1 fiA # Mg s a t u r a t i o n F ig. 5 5 . The e f f e c t of d e g r e e o f Ca a n d Mg s a t u r a t i o n on t h e K c o n t e n t of t o m a t o p la n ts in P la in f ie ld s o il. matter * 0* 1■ M.E. K/lOO gm. dry - --------------- 50# Ca s a t u r a t i c n tt — — — 1 0 0 # tt tt tt -=r-*— *— 15 0 # °/o Mg s a t u r a t i o n F ig. 5 6 . The e f f e c t of d e g r e e of Ca and Mg s a t u r a t i o n on t h e K c o n t e n t of c o r n p lan ts in P la in fie ld s o il. 20 10 Ca S a t u r a t i c M.E. K/lOO gm. dry m atter 96' TOO 0/q Mg S a t u r a t i o n F ig. 57 . The e f f e c t of d e g r e e of Ca and Mg s a t u r a t i o n on t h e K c o n t e n t of t o m a t o p l a n t s in Fox s o i l . M.E. K / 100 gm. dry m atter i *-----------------50°p Ca S a t u r a t i 100>? " ” *— *— 150?) " ' " % Mg s a t u r a t i o n F ig. 5 8 . The e f f e c t of d e g r e e of Ca and Mg s a t u r a t i o n on t h e IC c o n t e n t o f c o r n p l a n t s i n Fox s o i l . 97 20" Ca s a t u r a t i o © —. i 15 m T3 o o I— I 10- 100 °/o I£g s a t u r a t i o n F ig. 5 9 . The e f f e c t of d e g r e e of Ca a n d Mg s a t u r a t i o n on t h e K c o n t e n t of t o m a t o p lan ts in H illsd ale su b so il. Ca s a t u r a t i o n © -p -p 80 * > !>> u O O i—1 70- 100 c/o Mg s a t u r a t i o n F i g . 6 0 . The e f f e c t of d e g r e e of Ca a n d lug s a t u r a t i o n on t h e K c o n t e n t of t o b a c c o p lants in H illsd ale su b so il. 98 the uptake of potassium d e c r e a s e s . here that, as -was shown i n T a b le s It XI, may be mentioned X II and XIII, there was increased accumulation of n i t r o g e n when the concentra/ tion of magnesium went beyond 75 p e r c e n t sa tu ra tion l e v e l of the exchange capacity of Jarmesem (6) , working w ith the so il. to m a to p l a n t s , nitrogen and potassium b e a r an in verse percentage of one i s a s s o c i a t e d w i t h other in the plant. Bartholomew and Under t h e tions, the suppressive e f f e c t - justment results in i n j u r y to relationship; a high low percentage of the present experimental condi­ of Mg i s maintenance of a p h y s i o l o g i c a l have found t h a t probably towards the b alan ce, p lan ts although th is ad- by r e ta r d i n g growth and depressing yields. In comparing the K content and corn crops grown i n t h e acid soils. with Ca:Mg R e l a tio n s h ip (8) have and Fox sand, fixed much l a r g e r form than did e f f e c t on the absorp­ e f f e c t was noticed more tom ato . i n P h o s p h o r u s Nutrition shown t h a t of tomato le a fle ts was a s s o c i a t e d while P content of the so ils a b en eficial b en eficial with corn and tobacco t h a n Beeson et a l Wisner and H illsda le n o n e x c h a n g e a b le Magnesium had tion of K; although t h i s tomato, tobacco P lain field ca lcareo u s amounts of potassium i n t o the h ig h -lim e subsoil with the base u n s a t u r a t e d i t becomes apparent t h a t of le a fle ts w ith magnesium content a Mg-Ca in te r a c tio n was a s s o c i a t e d with Mg— P t in te rac tio n . Truog e t a l (60) h a v e shown t h a t i n c r e a s i n g s u p p l i e s of a v a i l a b l e Mg i n c r e a s e d t h e P c o n t e n t of t h e p e a s much m o r e t h a n d i d i n c r e a s i n g s u p p l i e s of a v a i l a b l e P. They c o n c l u d e d t h a t e fficien t use of P . a v a i l a b l e Mg i n s o i l s p r o m o t e s K e l l o g (3 1 ) h a s s t a t e d t h a t in c a l ­ c a r e o u s s o i l . Mg d e f i c i e n c y l i m i t s t h e P f e r t i l i z a t i o n and P n u t r i t i o n c o u l d b e i m p r o v e d b y a p p l y i n g Mg f e r t i l i z e r . B u t S t u r g i s a nd Reed (5 7 ) c o u l d n o t f i n d a n y c o r r e l a t i o n b e t w e e n t h e Mg a n d P c o n t e n t of r i c e s t r a w and g r a i n s . W illis et a l (6 3) c o u l d n o t f i n d a n y d i f f e r e n c e i n t h e i n f l u e n c e of Ca a n d Mg on P a b s o r p t i o n . from h is s t u d y of u t i l i z a t i o n B a r th o l o m e w (5) of p h o s p h a t i c f e r t i l i z e r s d i d n o t f i n d a n y p r o n o u n c e d r e l a t i o n s h i p b e tw e e n Mg a n d P u tiliza tio n . So t h e c o r r e l a t i o n b e t w e e n Mg a n d P u t i l i ­ zatio n is q u estio n ab le. The p e r c e n t a g e c o m p o s i t i o n of p h o s p h o r u s i s p r e s e n t e d i n T a b l e s XXIV and XXV and shown i n P i g . 6 1 . show t h a t t h e r e was v e r y l i t t l e i n f l u e n c e of The r e s u l t s exchangeable Mg i n t h e s o i l a t a n y g i v e n l e v e l o f Ca s a t u r a t i o n on t h e uptake o f P by p l a n t s . D e c r e a s i n g t h e Ca:Mg r a t i o t o 0 . 7 5 : 1 0 . 5 : 1 did not a p p r e c i a b l y i n c r e a s e th e P c o n t e n t . Thus, t h e r e a p p e a r e d t o b e no c l o s e c o r r e l a t i o n b e t w e e n t h e Mg c o n t e n t of s o i l and u p t a k e of P by t h e p l a n t . S e i f r i t z (53) a r r a n g e s th e ratd..) o f p e n e t r a t i o n a s f o l l o w s : a n io n s a c c o r d i n g to t h e 100 T a b l e SZIY P h o s p h o r u s C o n t e n t of T om a to , T o b a c c b a n d C o r n grown on S o i l s w i t h D i f f e r e n t D e g r e e s o f Ca a n d Mg s a t u r a t i o n . % ofi. Dry M a t t e r . Degree o f S atu ratio n Ca Mg Ca :Mg C he ck 100 Tobacco H illsd ale W isner s u b s o i l 0.12 0.10 0.09 0.08 Corn Wisne] 0.12 10 10:1 0.11 — 0.08 — 0.14 25 4:1 0.12 — 0.08 — 0.15 50 2:1 0.12 0.11 0.09 0.10 0.15 75 1 .3 :1 0.11 0.10 0.08 0.10 0.13 1:1 0.10 0.10 0.09 0.09 0.13 10 15:1 0.09 _ _ 0.08 ■— 0.12 25 6:1 0.11 -- 0.09 _ _ 0.12 50 3:1 0.11 0.09 0.10 0.09 0.12 75 2:1 0.10 0.10 0.08 0.09 0.13 1 .5 :1 0.09 0.10 0.08 0 .-08 0.13 100 150 Tomato H illsd ale W isner su b so il 100 101 TABLE XXV P h o s p h o r u s C o n t e n t o f T o m a to , T obacco a n d C o r n g r o w n on S o i l s w i t h D i f f e r e n t D e g r e e fo on d r y m a t t e r . o f Ca a n d Mg S a t u r a t i o n , Degree of S atu ratio n Ca Mg Ca:Mg Check 50 150 Corn P lain ­ field Fox 0.06 0.0 8 0.09 0.10 0.11 0.12 2:1 0.08 0.08 0.08 0.10 0.10 0.10 50 1:1 0.09 0.08 0.10 0.12 0.11 0.12 75 0 .7 5 :1 0.09 0.10 0.10 0.11 0.11 0.11 .5 :1 0.08 0.09 0.11 0.10 0.10 0.11 25 3:1 0.11 0.13 0.09 0.08 0.09 0.10 50 1 .5 :1 0.10 0.12 0.10 0.12 0.12 0.11 75 1:1 0.11 0.09 0.08 0.09 0.10 0.12 0 .7 5 :1 0.10 0.10 0.09 0.10 0.09 0.10 25 6:1 0.12 0 .14 0.12 0.10 0.12 0.12 50 2:1 0.13 0.13 0.12 0.12 0.12 0.13 75 1 .3 :1 0.13 0 .1 4 0.11 0.12 0.11 0.13 100 1:1 0.12 0.12 0.10 0.10 0.11 0.11 25 6:1 0.13 0 .1 4 0.13 0.12 0.12 0.10 50 3:1 0.14 0 .14 0.13 0.11 0.12 0.12 75 2:1 0.13 0.13 0.12 0.12 0.11 0.12 1 .5 :1 0.12 0.13 0.12 0.11 0.10 0.10 100 100, Tobacco P lain ­ field Fo x 25 100 75 Tomato P lain ­ Fox field 100 4 W isner H illsd ale Sub s o i l Fox ■P l a i n f i e l d 50% Ca s a t u r a t i o n \ 1;. of Dry M a t t e r — o*; 55 75 Too 0 75 100 0 F i g . 6 1 . P h o s p h o r u s c o n t e n t of t o m a t o p l a n t a s i n f l u e n c e d b y t h e v a r y i n g l e v e l of Ca a n d Mg s a t u r a t i o n i n s o i l . 50 7 102 cjo Mg s a t u r a t i o n 25 103 H oagland e t a l (2 2 ) p o s t u l a t e t h a t t h e r e e x i s t s a d e f i n i t e c o m p e titio n betw een a n io n s , r e p r e s s i n g the a c c u m u la tio n of the l e s s a c t i v e i o n . a lso suggest th a t about t h e m o re a c t i v e a n i o n They s i m i l a r i t y of e l e c t r i c a l c h a r g e b r i n g s c o m p e t i t i v e e f f e c t on t h e a c c u m u l a t i o n of a n i o n s . D a t a p r e s e n t e d i n T a b l e s X I , X I I and X I I I show t h a t t h e r e i s a d i r e c t r e l a t i o n s h i p b etw een th e a c c u m u la tio n of N w i t h i n c r e a s i n g c o n c e n t r a t i o n of m a g n e s i u m a t a g i v e n c a l ­ c iu m s a t u r a t i o n . p r e s s e s the The a c c u m u l a t i o n of n i t r a t e a c c u m u l a t i o n , o f HoP 0 - n e g ativ e charge. an ion d e ­ t o b a la n c e the t o t a l L ike c a t i o n e q u iv a le n c y , a n io n e q u iv a ­ l e n c y may p r e v a i l . T h i s i n v e r s e r e l a t i o n s h i p b e t w e e n N0^ and H P 0 can e x p l a i n th e n e g a t i v e 2 /.(. m a g n e s i u m and p h o s p h o r u s u p t a k e . c o r r e l a t i o n betw een C a tio n E q u iv a le n t Constancy The q u a l i t y an d q u a n t i t y of p l a n t g r o w t h i s g r e a t l y i n f l u e n c e d by t h e p h y s i o l o g i c a l b a l a n c e o f t h e t h r e e b a s i c c a t i o n s C a , Mg a n d K. A lth o u g h each c a t i o n has a s p e c i f i c f u n c t i o n i n t h e p l a n t , t h e r e a r e some p h y s i o l o g i c a l f u n c ­ t i o n s t h a t a r e p e r f o r m e d i n common b y t h e s e c a t i o n s . tio n in th ese th re e a f f e c t the V aria c a t i o n s w i t h i n a c e r t a i n r a n g e may n o t growth and q u a l i t y of t h e c ro p , but any extrem e v a r i a t i o n t h a t r e s u l t s f r o m l u x u r y c o n s u m p t i o n of o n e c a ­ t i o n w i l l be r e f l e c t e d i n t h e grow th and c o m p o s i t i o n of the c ro p , becau se Lucas e t a l B ear and P r in c e (7) a n d H u n t e r ( 3 7 > 3 8 ) , Van I t a l l i e (6i), (24) h a v e shown t h a t when t h e i n d i v i d u a l c a t i o n c o n t e n t o f p l a n t s a r e e x p r e s s e d on a n e q u i v a l e n t b a s i s , t h e sum of t h e e q u iv a le n ts tends t o be c o n s t a n t . The sum o f t h e m i l l i e a u i v a l e n t s of Ca, Mg and K in tom ato, tobacco a n d corn c ro p s a r e p r e s e n t e d in T ab les XIX t h r o u g h X X I I I . erab le v a ria tio n The d a t a show t h a t t h e r e i s a c o n s i d ­ i n t h e C a , Mg a n d K c o n t e n t s o f p l a n t s w i t h i n c r e a s i n g Mg s a t u r a t i o n a t e a c h l e v e l of s a t u r a t i o n of t h e e x c h a n g e c o m p le x i n s o i l . o f i n d i v i d u a l c a t i o n , of type. calcium The c o n t e n t e a c h crop v a r i e s w i t h t h e s o i l N o tw ith s ta n d in g such v a r i a t i o n of th e i n d i v i d u a l c a t i o n , the m aterial sum of t h e t h r e e c a tio n s per u n it of p l a n t t e n d s to b e c o n s t a n t . The r a n g e o f v a r i a t i o n i n t h e sum f o r a g i v e n c r o p i s b e t w e e n 20 and 3 0 , d e p e n d i n g upon t h e s o i l ty p e c o n s i d e r e d . th a n for e a c h of t h e T h i s v a r i a t i o n was s m a l l e r i n d i v i d u a l Ca and Mg i o n s , w i t h i n ­ c r e a s i n g Mg s a t u r a t i o n a t a c o n s t a n t l e v e l of Ca s a t u r a ­ t io n in the so il. The m u t u a l r e p l a c e m e n t of b o t h t h e i o n s i s g r e a t b u t the t o t a l c a t i o n e q u iv a le n c y rem ains c o n s ta n t. Such a c o n sta n c y i n e q u iv a le n c e does not r e s u l t y i e l d due t o l u x u r y c o n su m p tio n of magnesium. T his b r i n g s out. t h e tratio n s in high of t h e s e t h r e e i m p o r t a n c e of b a l a n c e d c o n c e n ­ c a tio n s in the s o i l . t e n t of a n y one i s h i g h t h e I f the con­ r e s e r v e of t h e o t h e r two s h o u l d be b ro u g h t up t o s u c h a l e v e l a s t o m a i n t a i n a p h y s i o l o g i c a l b a l a n c e of the t h r e e c a t i o n s . This a l s o em phasizes t h e im p o r ta n c e o f lim e c o n t e n t of s o i l f o r th e m a in te n a n c e of 105 a p h y s i o l o g i c a l b a l a n c e i n t h e Mg n u t r i t i o n of crops. Ca a n d Mg C o n t e n t of S o i l s a t t h e End o f Crop H a r v e s t The Ca and Mg c o n t e n t of e a c h s o i l a t t h e s t a r t a n d a t t h e h a r v e s t of t h e t o m a t o c r o p i s p r e s e n t e d i n T a b l e s XXVI a n d XXVII. The t o t a l exchange c a p a c i t y of s o i l s seems t o b e i n c r e a s e d and t h i s may p r o b a b l y be d u e t o in ­ c o r p o r a t i o n o f o r g a n i c m a t t e r 'thr ough t h e p l a n t r o o t s d u r i n g t h e g r o w t h of t h e c r o p . tbat in a s o i l w ith d e f i n i t e However, t h e d a t a show exchange c a p a c i t y , any c h a n g e i n t h e a m o u n t of o n e e x c h a n g e a b l e c a t i o n i s a c c o m p a n i e d by a r e c i p r o c a l c h a n g e of t h e o t h e r c a t i o n a nd a l s o a d e f i n i t e amount o f ‘ each i s p r e s e n t in t h e a d s o r b e d s t a t e , w h ile th e r e s t rem ains a s f r e e s a l t or r e a c t s w i t h o t h e r s o i l c o n s t i t u e n t s t o f o r m i n s o l u b l e c o m p ou n ds. From T a b l e s XXVI a n d XXVII, i t so ils is seen t h a t in a c i d l i k e P l a i n f i e l d a nd F o x a d s o r p t i o n of m a g n e siu m h a v e i n c r e a s e d w i t h i n c r e a s i n g l e v e l s of Ca s a t u r a t i o n . T his may b e due t o a d s o r p t i o n o f m ag n e siu m i n r e p l a c e m e n t o f a d s o rb e d c a l c i u m a s r e p r e s e n t e d below . Ca ® 4 h 2s 0 4 Mg Lime r e a d i l y r e p l a c e s h y d r o g e n of t h e c l a y and t h e a d s o r b e d calcium c o n te n t is th ere b y in c r e a s e d . This a d s o rb e d c a l ­ c iu m i n t u r n i s r e p l a c e d by m a g n e s i u m . T h u s, i n c r e a s e in l i m e c o n t e n t of an a c i d s o i l h e l p s t h e r e t e n t i o n o f m a g n e s i u m 106 of t h e is in added f e r t i l i z e r i n t h e a d s o r b e d s t a t e . l i n e -with t h e o b s e r v a t i o n s W i s n e r and H i l l s d a l e of P e e c h ( 4 5 ) . s u b s o i l show v e r y l i t t l e c r e a s e i n e x c h a n g e a b l e m a g n e siu m . d i t i o n of t h e s o i l s T his r e s u l t The h i g h a l k a l i n e in­ con ­ h a v e f a v o r e d f i x a t i o n o f m ag n e sium a s i n s o l u b l e m a g n e s i urn s i l i c a t e . 107 TABLE XXVI E x c h a n g e a b l e C a l c i u m a n d M a gn esiu m a t t h e S t a r t a n d a t H a r v e s t o f JTomato C r o p . M.E. p e r 100 gm. S o i l r '" - W isher At s t a r t Ca Mg H illsd ale At end Mg Ca S ubsoil At s t a r t Ca . Mg A t end Ca Mg 16.75 0.98 13.1 0...20 0.92 0.30 0.7 8 0.92 13.32 1.33 12.2 0.09 0.99 0 .6 6 0.78 0.12 n 4.58 15 . 2 2 .5 tt 0 .99 1.2 8 0.21 tt 9.16 16 .0 5.7 ii 1.32 1.1 7 0.33 tt 13.74 15 .0 6 .4 0 .66 0 .8 1 0.24 tt 18.32 14.0 9.2 it 0.99 1 .30 0 .48 27-48 1.83 12 . 8 1.0 it 1.32 1.2 9 0.84 ii 4.58 12 . 7 2.3 0 .66 0 .4 1 0.2 4 ii 9.16 19.3 5.9 it 0 .99 0 .75 0^ 4 8 •t 13 .7 4 1 8.3 8.0 tt 1.32 0.49 0.63 n 18.32 21.3 8.1 1.32 1 .9 8 " 108 TABLE XXVII ' E x c h a n g e a b l e Calciu m , and M a gn esiu m a t S t a r t a n d a t H a r v e s t o f Tomato C r o p . M.E. f o r 100 gm. S o i l P la in field At S t a r t A t H arvest Ca Mg Mg Ca Fox At H a r v e s t At S t a r t Mg Mg Ca Ca 0.6 3 0 .9 3 0 .1 4 1.24 0 .31 0.91 0.19 1.78 0.8 9 1 .1 6 0.73 1.70 0.85 1.02 0.60 2 .6 7 0 .8 9 1 .7 4 0.75 2.55 0.85 2.00 0.69 3.56 0.89 2 .9 2 0.77 3.40 0.85 2.90 - 0.71 5 .34 0.8 9 4 .1 0 0.78 5.10 0.85 3.00 0.75 1.78 1.7S 1 .1 7 0.90 1.70 1.70 1.01 1.20 2.67 1 .7 8 1 .9 2 1.10 2,55 1.70 2.05 1.30 3.56 1 .7 8 2 . 58 1.20 3.40 1.70 2.76 1.33 5.34 1 .7 8 3 .9 0 1.40 5.10 1.70 2.96 1.35 1 .78 2 .6 7 1 .6 0 1.07 1.70 2.55 1.30 2.00 2.6 7 2 .6 7 1 .9 8 1.90 2.55 2.55 2.08 1.90 3.56 2 .6 7 3 .0 0 2.07 3.40 2.55 2.90 1.93 5 .34 2 .6 7 3.9 0 2.10 5.10 2.55 2.98 1.92 1.78 3.5 6 1.4 5 2.38 1.70 3.40 1.05 2.20 2.67 3.-56 2 .7 8 2.40 2.55 3.40 , 2.02 2.25 3.56 3.-5 6 2 .00 2.43 3.40 3.40 2.92 2.18 5-34 3 .5 6 3-00 2.45 5.10 3.40 3.01 2.27 - i DISCUSSION The r e s u l t s i n t h i s s t u d y show t h e i m p o r t a n c e o f l i m e c o n t e n t o f s o i l i n r e l a t i o n t o c r o p r e s p o n s e t o mag­ nesium . A l t h o u g h t h e a m o u n t o f magne siu m u s e d i n t h i s i n v e s t i g a t i o n was f a r i n e x c e s s o f t h a t u s e d i n o r d i n a r y agronom ic p r a c t i c e , y e t the r e s u l t s d e m o n s tr a te the harm ­ f u l e f f e c t s o f m a g n e s i u m when i t e x c e e d s t h e satu ratio n c a p a c i t y of t h e e x c h a n g e c o m p l e x b e y o n d a c e r t a i n l i m i t . T h i s l i m i t of s a t u r a t i o n d e p e n d s up o n t h e n a t u r e of c o l l o i d and a l s o t h e i n i t i a l s a t u r a t i o n of b a s e s a s w a s i l l u s t r a t e d by t h e P l a i n f i e l d a n d F o x s a n d w h i c h a r e a c i d i n r e a c t i o n . At a low l e v e l of b a s e s a t u r a t i o n , m a g n e s i u m i n c r e a s e s t h e e f f i c i e n c y of t h e p l a n t a n d t h e r e b y t h e e l e m e n t s s u p p l i e d t h r o u g h N-P-K f e r t i l i z e r s a r e more e c o n o m i c a l l y u s e d a n d crop p r o d u c t i o n i s i n c r e a s e d . the u p ta k e of m agnesium i s from the e x c e s s magnesium. of t h e At h i g h m agn esium l e v e l s in cre ased but the crop s u f f e r s Above 75 p e r c e n t s a t u r a t i o n exchange c a p a c i t y w ith m agnesium i n th e c ase of W i s n e r and H i l l s d a l e s u b s o i l t h e c r o p g r o w t h was i n c r e a s e d b u t t h e n u t r i e n t b a l a n c e was s u c h t h a t t h e s u p p l y o f t h e other n u tr itiv e e le m e n ts and o r g a n ic fo o d s w e re in a d e q u a te f o r p r o d u c t i o n of f r u i t s a n d f o r m a i n t a i n i n g a h e a l t h y p lan t co n d itio n . S o i l s f a i r l y r i c h i n b o t h m i n e r a l and o r g a n i c co llo id s become h i g h l y d i s p e r s e d a s t h e m ag n e s i u m c o n c e n t r a t i o n i s in cre ased . No s u c h e f f e c t was n o t i c e d a s l o n g a s c a l c i u m was th e p re d o m in a tin g i o n i n t h e e x c h a n g e co m p lex and c o n ­ c e n t r a t i o n of magnesium was low. e s i s of R u s s e l ( 5 1 ) A c c o rd in g to t h e h y p o t h ­ th e c l a y p a r t i c l e s a r e held t o g e t h e r b y o r i e n t e d m o l e c u l e s of a p o l a r l i q u i d . These p o l a r m o l e ­ c u l e s l i e betw een n e g a tiv e c h a rg e s on t h e clay su rfa ce and the exchangeable c a t i o n s t h a t have d i s s o c i a t e d fro m t h e c la y s u r f a c e and a r e s t r o n g l y o r i e n t e d i n t h e e l e c t r o s t a t i c f i e l d betw een t h e s e charges. C a l c i u m h a s o n l y one m o l e c u l e o f w a t e r of h y d r a t i o n w h i l e m a g n e s i u m t a k e s up n i n e m o l e c u l e s o f w a t e r of h y d r a t i o n i n s t e a d of b eing (19). The w a t e r d i p o l e m o l e c u l e s , o r ie n te d betw een th e c la y p a r t i c l e s , b e ­ come o r i e n t e d a r o u n d m a g n e s i u m i o n s and r e m a i n a s b o u n d w a t e r w ith l o s s of f r e e e n erg y t o w i t h t h e l o s s of forces fo r act. Thus t h e p a r t i c l e s o r i e n t a t i o n become d i s p e r s e d . I o f f e and Zimmerman (29) a l s o f o u n d t h i s sa m e d i s p e r s i v e e f f e c t of m a g n e s i u m o n t h e s o i l c o l l o i d s a n d came t o t h e c o n c l u s i o n t h a t t h e r e m u st b e s u f f i c i e n t a c t t h i s d i s p e r s i v e e f f e c t of m a g n e s i u m . calcium to cou nter­ No s p e c i f i c r a t i o o f Ca:Mg c a n b e g i v e n a s r e p r e s e n t i n g m o s t f a v o r a b l e o n e f o r a l l c o n d i t i o n s , b u t i n c a s e of a low Ca:Mg r a t i o ap p ears to b e the it low c o n t e n t of Ca r a t h e r t h a n t h e h i g h c o n t e n t of m a g n e s i u m t h a t i s h a r m f u l to t h e p l a n t . Any a p p l i c a t i o n o f m a g n e s i u m a b o v e t h e s a t u r a t i o n c a p a c i t y o f a s a n d y s o i l i s b e l i e v e d to b e p r e c i p i t a t e d a s co m p lex s i l i c a t e s . This is i n d i c a t e d from th e amount a p p l i e d a t t h e s t a r t and t h e a m o u n t of e x c h a n g e a b l e m a g n e s i u m Ill r e c o v e r e d a t t h e e n d of t h e i n v e s t i g a t i o n , a s p r e s e n t e d i n T a b l e XXVI. The r e m o v a l of m ag ne sium b y t h e c r o p s w a s n o t v e r y h i g h a n d , t h e r e f o r e , a l a r g e p e r c e n t a g e of t h e a d d e d m agnesium r e a c t e d w i t h s i l i c i c a c i d . f a v o r e d by a h i g h pH o f t h e s o i l T his r e a c t i o n i s (49). So o v e r l i m i n g o f an a c i d s o i l w i l l p r e c i p i t a t e m agnesium a s i n s o l u b l e cate. T h is p o s s i b l y a c c o u n t s f o r t h e arid T u r k (10) . sili­ o b s e r v a t i o n of Bower t h a t a l k a l i n e s o i l s may show a d e f i c i e n c y o f a v a i l a b l e magnesium. I f we assu m e t h a t t h e p e r c e n t a g e n u trien t c o m p o s i t i o n of the e l e m e n t s i n a p l a n t r e f l e c t s "the p h y s i o l o g i c a l a c t i v i t y of t h e p l a n t d u r i n g t h e g r o w t h , t h e n t h e v a r i a t i o n in th e u p t a k e of Ca, Mg, and K f r o m a c o n s t a n t c o n c e n t r a ­ t i o n o f c a l c i u m a n d v a r y i n g c o n c e n t r a t i o n of m a g n e s i u m m u s t have b e e n i n f l u e n c e d by the l a t t e r . The d i f f e r e n c e i n m i n e r a l c o m p o s itio n i s not the r e s u l t grow th. The t o t a l of d i f f e r e n t i a l p lant q u a n t i t i e s of a n i o n a b s o r b e d by t h e p l a n t f o l l o w s t h e same t r e n d a s t h e c o n c e n t r a t i o n o f t h e ion i n the p l a n t . by t h e p l a n t i s T h u s , the. t o t a l a m o u n t of a n i o n a b s o r b e d d e p e n d e n t upon t h e r e s p e c t i v e r a t e of a b ­ s o r p t i o n t h a t o c c u r r e d d u r i n g t h e g r o w t h of t h e p l a n t . r a te and quantity The of a b s o r p t i o n i s m o d i f i e d b y t h e c o n c e n ­ t r a t i o n of m ag nesiu m i n the s o i l . If it i s assumed t h a t a p l a n t r o o t absorbs the ion f r o m t h e s o l i d p h a s e of s o i l b y t h e p r o c e s s o f " c o n t a c t e x c h a n g e ” a s a d v a n c e d by J e n n y and A y r e s (26) , t h e a m o u n t o f a n ion t h a t c a n b e rem oved d e p e n d s up on t h e o s c i l l a t i o n v o l u m e of t h a t ion. calcium is ■I n t h e H o f m e i s t e r S e r i e s H>Ca>Mg>K>Na, c h a r a c t e r i z e d by a h i g h e r e n e r g y of a d s o r p t i o n w hich i n d i c a t e s t h a t i t ha.s a l e s s e r a m p l i t u d e of o s c i l l a ­ t i o n , w h ile m agnesium h a s a lo w e r a b s o r p t i o n e n e r g y or l a r g e r a m p l i t u d e of m o t i o n . Mg i o n s , T h u s , i n a m i x t u r e o f Ca a n d t h e l a t t e r w i l l r e m a i n a t t h e p e r i p h e r y of t h e i o n i c a t m o s p h e r e , a n d h e n c e m o re c o n t a c t e x c h a n g e of mag­ nesium w ith the r o o t h a i r . I f the c o n c e n t r a t i o n of mag­ nesium io n s i s h ig h e r th an t h a t o f Ca, t h e f o r m e r w i l l n o t o n l y be a t t h e p e r i p h e r y of t h e io n ic atm osphere but w i l l p e n e t r a t e d e e p e r a n d w i l l b e a d s o r b e d o n the c o l l o i d a l surface h i s was e v i d e n c e d f r o m t h e d a t a i n T a b l e s XX t h r o u g h X X I I I , w h e r e i t was shown t h a t , t h e e x c h a n g e a b l e m a g n e s i u m i n c r e a s e d and e x c h a n g e a b l e c a l c i u m d e c r e a s e d , w h e n t h e c o n c e n t r a t i o n of a d d e d m a g n e s i u m was i n c r e a s e d w ith a c o n sta n t the uptake c o n c e n tra tio n o f calcium . of magnesium was g r e a t e r th a n t h a t D a ta p r e s e n te d in the a n a l y s i s ( T a b le s X I , X II and X I I I ) n e s i u m c o n t e n t of t h e o f m agnesium i n t h e p lan t c e lls . of g r e e n instance of c alciu m . leaf tis s u e show t h a t t h e w a t e r s o l u b l e mag­ le a f in creased as the c o n c e n tra tio n s o il in creased . t i o n of m a g n e s i u m i o n s e n t e r i n t o t h e nehium , i t In t h i s Due t o t h e The e x c e s s c o n c e n t r a ­ d e e p e r l a y e r of t h e g r e a t e r h y d r a t i o n e f f e c t of m a g - h a s a g r e a t e r c o a g u l a t i n g e f f e c t on t h e c e l l p ro to p la s m th a n , e i t h e r p o ta ssiu m or calcium . This coagu­ l a t i n g e f f e c t of t h e p r o t o p l a s m was r e f l e c t e d b y t h e 113 re d u c e d g ro w th of t h e p l a n t . t r a t io n s in the At h ig h e r calciu m concen­ s u b s t r a t e , t h e a b s o r p t i o n of i n c r e a s e d and t h a t c a l c i u m was of m a g n e s i u m w a s d e c r e a s e d . Thus, a t h i g h c a l c i u m c o n c e n t r a t i o n s , magnesium had l e s s o p p o r t u n i t y to i n h i b i t p l a n t grow th. T his em ph asizes t h e im p o rtan c e o f c a l c i u m , i n t h e m a g n e s i u m n u t r i t i o n of t h e p l a n t . C al­ c iu m m u s t b e a t a h i g h e r c o n c e n t r a t i o n t h a n t h a t o f mag­ nesium i n th e s o i l com plex. I f t h e p r o c e s s o f uptake of t o be due to io n s by p l a n t s i s assumed i o n i c o r m o l e c u l a r movement i n t h e s o i l s o l u ­ t io n , then the r a t e of e n t r y o r i n t e r c h a n g e of i o n s w i l l b e d e t e r m i n e d by t h e p o s i t i o n o f t h e i o n i n t h e l y o t r o p i c s e r i e s and i t s c o n c e n t r a t i o n i n th e so il so lu tio n . There a r e n o e l e c t r o s t a t i c a t t r a c t i v e f o r c e s of t h e s o i l p a r t i c l e s t o r e s t r a i n t h e m o v e m e n t of t h e i o n s . fre e in th e s o i l s o lu tio n , on t h e Su c h i o n s moving o th e r hand, are surrounded by a la y e r of o r ie n te d w ater m o lecu les. So i n a n e q u i m o l a r s o l u t i o n of Ca a n d Mg i o n s , t h e c o n c e n t r a t i o n of s o l u t i o n w i l l be h i g h e r f a i t h r e s p e c t t o Mg t h a n Ca b e c a u s e t h e w a t e r of h y d r a t i o n of Mg i s m ore t h a n t h a t ^resu lt, of Ca. As a t h e b o m b a r d m e n t of m a g n e s i u m i o n s a t t h e r o o t s u r ­ f a c e w i l l b e m ore f r e q u e n t t h a n t h a t of t h e Hence, t h e calcium io n s . c h a n c e of e n t r y of m a g n e siu m i o n s f r o m t h e s o l u ­ t i o n i n t o t h e r o o t i s g r e a t e r t h a n t h a t f o r calcium-. i s e v id e n t from th e T his i o n c o m p o s i t i o n of t o m a t o , t o b a c c o an d c o r n c r o p s g rown i n Q u a r t z s a n d an d p r e s e n t e d i n T a b l e s XX, 2X1, 2 X I I and X X I I I . The i n e r t q u a r t z sand h a s v e r y 114 little e l e c t r o s t a t i c a t t r a c t i v e f o r c e s on i t s surface. The a d d e d i o n s a r e i n t h e l i q u i d p h a s e and t h e a b s o r p t i o n of t h e . ions i s a lso from th is liq u id phase. To r e d u c e t h e u p t a k e of m a g n e s i u m t h e c o n c e n t r a t i o n of c a l c i u m i o n s s h o u l d be much g r e a t e r t h a n t h a t of m a g n e s i u m i o n s . A b s o r p t i o n of i o n s i s c o n d i t i o n e d , a s p o s t u l a t e d byM arshall rium t h a t and (39) b y two f a c t o r s , e x i s t s betw een the (2) the s t e a d y s t a t e t h a t The m a i n t e n a n c e of t h e v iz. (1 ) t h e c h e m i c a l e q u i l i b ­ i n n e r and o u t e r e n v i r o n m e n t , i s m a in ta in e d betw een them . steady s t a t e c h e m i c a l p o t e n t i a l of t h e i s c o n d i t i o n e d by t h e s o l v e n t o u t s i d e and th e t h e c h e m i c a l p o t e n t i a l s of t h e s o l u t e i n s i d e . sum o f The c h e m i c a l p o t e n t i a l of a s o l u t i o n c o n t a i n i n g a l a r g e p r o p o r t i o n o f c a l c i u m io n s a n d l e s s e r amount o f magnesium i o n s w i l l be g r e a t e r th a n t h a t of a s o l u t io n w ith h ig h e r c o n c e n tr a tio n o f m a g n e s i u m a n d l o w e r c o n c e n t r a t i o n of c a l c i u m . To m a i n ­ t a i n e q u i l i b r i u m -between s u c h o u t s i d e s o l u t i o n s and i n s i d e s o l u t e c o n c e n t r a t i o n p o t e n t i a l s , m o r e - c a l c i u m w i l l h ave t o be a b s o r b e d from th e s o l u t i o n w i t h h i g h e r c o n c e n t r a t i o n o f c a l c i u m w h i l e more m a g n e s i u m f r o m t h e h ig h er co n cen tratio n s of m a g n e s i u m . s o lu tio n co n tain in g As s u c h a b s o r p t i o n o f magnesium r e s u l t s i n p o o r g r o w t h , y i e l d and u n b a la n c e d c o m p o s itio n of p l a n t , the c o n c e n tr a ti o n o f c alciu m should a l w a y s be h i g h e r t h a n m a g n e s i u m to m a i n t a i n h i g h c h e m i c a l p o t e n t i a l a n d g r e a t e r a b s o r p t i o n of c a l c i u m t h a n m a g n e s i u m . I t has been su g g e ste d t h a t i o n a b s o r p t i o n may t a k e p l a c e e i t h e r b y f r e e d i f f u s i o n o r by c h e m i c a l i n t e r a c t i o n 115 with, t h e membrane o f t h e r o o t h a i r s . suggest th a t m eab ility H ansteen-G arner (21) l i p o i d and p e c t i c m a t e r i a l s govern the p e r ­ of t h e and c a l c i u m a s cell w a ll. coagulants. A lk alis a c t as d isp e rsa n ts T h u s , t h e s t a b i l i t y of t h e c a l c i u m p e c t a t e t h a t c o n s t i t u t e s t h e m a j o r p a r t of t h e c e l l w a l l i s m a i n t a i n e d when s u f f i c i e n t c a l c i u m i o n s a r e present. P e r m e a b i l i t y an d d i f f u s i o n of i o n s a r e e a s y . W ith m a g n e s i u m p r e d o m i n a t i n g , t h e p e r m e a b i l i t y of c e l l w a l l is d istu rb ed . u n stab le. The w a l l s a r e h i g h l y h y d r a t e d and become T h i s was e v i d e n t f r o m t h e e x a m i n a t i o n of t h e m i c r o e h e m i c a l c r o s s s e c t i o n of t h e l e a f w h ic h h ad r e c e i v e d - l a r g e a p p l i c a t i o n s of m a g n e s i u m . p erm eability of t h e of t h e When t h e s ta b ility of c e l l w a ll i s d is tu r b e d , the e q u ilib riu m p ro to p la sm w ith w hich i t i s c h e m i c a l l y and b i o l o g ­ i c a l l y a s s o c i a t e d i s d i s r u p t e d , t h e n o r m a l g r o w t h of t h e plant is in h ib ite d . In c o n clu sio n , i t c a n be said t h a t , from t h e - s t a n d ­ p o i n t of n u t r i e n t s u p p l y , , two f a c t o r s d e t e r m i n e t h e y i e l d , a n d c o m p o s i t i o n of p l a n t s . grow th, T h e s e two f a c t o r s can be d e s i g n a t e d a s " i n t e n s i t y " a nd " c a p S c i t y f a c t o r s . " A ddi­ t i o n o f m a g n e siu m i n v a r i a b l y i n c r e a s e d t h e p r o d u c t i v e c a p a c i t y of t h e p lan ts. This i s e v i d e n t f r o m t h e g r o w t h a n d y i e l d o f p l a n t s w h i c h r e c e i v e d no a d d e d m ag n e s i u m b u t d e p e n d e d e n ­ tire ly on s o i l m ag n e sium f o r t h e i r s u p p l y of t h i s e l e m e n t . Low m a g n e s i u m was a s s o c i a t e d w i t h low y i e l d s . 'W ith i n ­ c r e a s e d m a g n e s i u m , p l a n t g r o w t h i m p r o v e d b u t when t h e 116 q u a n t i t y o f magnesium was i n c r e a s e d beyond a c e r t a i n p e r ­ centage o f s a t u r a t i o n of t h e e x c h a n g e c o m p l e x , t h e r e -was l u x u r y c o n s u m p t i o n of m a g n e s i u m and p h y s i o l o g i c a l d i s t u r ­ bance s e t in . u tilize d . The o t h e r e s s e n t i a l e l e m e n t s c o u l d n o t be The ’’q u a l i t y f a c t o r ” o r n u t r i e n t b a l a n c e i n t h e p l a n t w a s d i s t u r b e d and t h e co ntent of "quality" Hence, r e s u l t w a s low y i e l d . the m e d ia l a r g e l y c o n t r o l s t h i s The l i m e " i n t e n s i t y ” an d f a c t o r i n t h e m a g n e s i u m n u t r i t i o n of p l a n t s . t h e b e s t g r o w t h r e s p o n s e a n d n u t r i t i o n of p l a n t c a n b e a c h i e v e d o n l y w he n t h e p e r c e n t s a t u r a t i o n and t o t a l c o n c e n t r a t i o n of c a l c i u m e x c e e d s t h a t of m a g n e s i u m . T h e s e r e s u l t s i n d i c a t e t h a t f r o s t r e s u l t s f r o m mag­ nesium f e r t i l i z a t i o n c a n b e o b t a i n e d o n l y when i t accom panied by lim e a p p l i c a t i o n . h ow e v er, should is The l i m e a p p l i c a t i o n , n o t be i n e x c e s s a s was d e m o n s t r a t e d by t h e g ro w th and y i e l d of c r o p s grown i n H i l l s d a l e s u b s o i l thafei c o n t a i n s a h i g h p r o p o r t i o n o f f r e e c a l c i u m c a r b o n a t e w hic h m a s k s t h e . b e n e f i c i a l e f f e c t of m a g n e siu m a p p l i c a t i o n . 117 SHvHvIARY T h i s i n v e s t i g a t i o n was u n d e r t a k e n t o s t u d y by m eans of p o t c u l t u r e th e l im e c o n t e n t of s o i l i n r e l a t i o n to crop r e s p o n s e t o magnesium. Four s o i l s w ere used fo r th e t h e W i s n e r and- H i l l s d a l e stu d y i n c l u d i n g two, s u b s o i l , which were a l k a l i n e in r e a c t i o n and c o n t a i n e d f r e e c a r b o n a t e s , a n d t w o , t h e P l a i n f i e l d a n d Fox s a n d , w h i c h w e r e a c i d and low i n d e g r e e of b a s e s a t u r a t i o n . for Q,u artz s a n d c u l t u r e s w e r e a l s o u s e d com parative p u rp o se s. C a l c i u m and m a g n e s i u m a p p l i c a t i o n s w e r e made o n t h e b a s i s of p e r c e n t s a t u r a t i o n o f t h e e x c h a n g e c o m p l e x . The t r e a t m e n t s w e r e d e s i g n e d to e v a l u a t e t h e e f f e c t of i n c r e a s ­ i n g a m o u n t s of m a g n e s i u m when c a l c i u m w a s h e l d c o n s t a n t and t h e c h a n g e s c a u se d by v a r i a t i o n s of t h e two c a t i o n s a t in the p ro p o rtio n s c o n s ta n t l e v e l of b ase s a t u r a t i o n . T o m a to , t o b a c c o a n d c o r n w e r e gro w n a s t e s t c r o p s . G row th, y i e l d and c o m p o s it i o n of t h e c r o p s w e re d e t e r ­ m ined. I n t h e a l k a l i n e W i s n e r s o i l , c o n t a i n i n g a f a i r amount of o r g a n i c m a t t e r and m in e r a l c o l l o i d s , h i g h a p p l i c a t i o n s of m agnesium w ere fo u n d to d e s t r o y t i l t h of t h e s o i l . Mor­ p h o l o g i c a l c t a r a c t e r i s t i c s o f a s o l o n e t z so i l W & r p n o t i c e d . The g r o w t h o f young s e e d l i n g s w a s p o o r due t o t h e h i g h w ater te n sio n . In sandy H ills d a le s u b s o i l very l i t t l e r e s p o n s e to 118 m a g n e siu m w a s n o t i c e d . Due t o t h e h i g h pH t h e r e was c o n ­ s i d e r a b l e f i x a t i o n o f m a g n e s i u m a s i n s o l u b l e m ag nesiu m s i l i c a t e . . T h is w a s i n d i c a t e d b y t h e low r e c o v e r y o f e x ­ ch an g e ab le magnesium a f t e r h a r v e s t i n g th e In the a c id s o i l s , crop. P l a i n f i e l d and Pox, th e r e s p o n s e ' t o m a g n e s i u m was b e s t when t h e b a s e s a t u r a t i o n was h i g h and t h e s o i l r e a c t i o n w a s a b o u t n e u t r a l . I n a l l s o i l s , when t h e c o n c e n t r a t i o n of m a g n e s i u m was h i g h e r t h a n c a l c i u m , m ag n e siu m s i c k n e s s o f t h e p l a n t was c o n s p i c u o u s . T h e r e was s u f f i c i e n t v e g e t a t i v e g r o w t h t o m a i n t a i n a go od h e a l t h y p l a n t b u t t h e g r o w th was i n ­ s u f f i c i e n t to induce f r u i t i n g in tom ato. W ith i n c r e a s i n g c o n c e n t r a t i o n s of m a g n e s i u m , a t - a constant calcium c o n c e n tr a tio n , p lan ts decreased. th e c a l c i u m c o n t e n t of t h e The m a g n e s i u m c o n t e n t i n c r e a s e d w i t h a l i n e a r r e l a t i o n s h i p and p o t a s s i u m c o n t e n t was i n c r e a s e d up t o t h e 75 p e r c e n t s a t u r a t i o n w i t h r e s p e c t o f m a g n e s i u m , b u t be y on d t h i s t h e K c o n t e n t d e c r e a s e d . Growth a n d y i e l d w e re d i r e c t l y p r o p o r t i o n a l t o Ca a n d i n v e r s e l y p r o p o r t i o n a l to magnesium a t high magnesium l e v e l s i n t h e so il. A lth o u g h t h e r e was g r e a t v a r i a t i o n in th e in d iv id u al catio n s, t h e sum t o t a l of t h e sta n t w ith th e d i f f e r e n t treatm ents. uptake of c a t i o n s was c o n ­ This i n d i c a t e s t b a t t h e c a t i o n s p e r f o r m some common f u n c t i o n - i n t h e p l a n t . No d i r e c t c o r r e l a t i o n b e t w e e n t h e m a g n e siu m and p h o s ­ p h o r u s u p t a k e w a s o b s e r v e d w i t h a n y of t h e c r o p s s t u d i e d . The i d e a t h a t Mg i o n s a c t a s a c a r r i e r of PO^ ions 119 is q u estio n ab le. F acto rs i n f l u e n c i n g tJie d i f f e r e n t i a l u p t a k e of cal­ c iu m a n d m a g n e s i u m have been d i s c u s s e d The r e s u l t s of t h i s i n v e s t i g a t i o n it is not the emphasize t h a t calcium :m agnesium r a t i o b u t the c o n c e n t r a t i o n and d e g r e e o f s a t u r a t i o n of t h e c iu m t h a t d e t e r m i n e e x ch a n g e c o m p l e x w i t h c a l ­ th e r e s p o n s e of c r o p s t o t h e a p p l i c a t i o n of magnesium. < 120 LITERATURE CITED 1. A l l w a y , 7/. H. 1 9 4 5 A v a i l a b i l i t y of r e p l a c e a b l e c a l c i u m f r o m d i f f e r e n t t y p e s of C o l l o i d s a s a f f e c t e d 'by d e g r e e o f c a l c i u m satu ratio n . S o i l S c i . 59: 2 0 7 - 2 1 7 . 2. A l b r e c h t , 77. A. a n d M c C a l l a , T. LI. 1938 The c o l l o i d a l c l a y f r a c t i o n of s o i l a s a c u l t u r a l medium. A m er. J o u r . B o t. 25: 403-407* •3* A n d e r s o n , M.' S. 19 2 9 The i n f l u e n c e of s u b s t i t u t e d c a t i o n s on t h e p r o p e r t i e s of s o i l c o l l o i d s . J o u r . A g r . R e s . 38: 564-5 8 4* 4. A r n o n , D. I . and G r o s s e n b a c h e r , K. A. 1 9 4 7 N u t r i e n t c u l t u r e o f c r o p s w i t h t h e u s e of s y n t h e t i c ion-exchange m a te r ia ls . S o i l S c i . 63: 1 5 9 - 1 8 0 . 5. B a r t h o l o m e w , R. P . 1933 The A v a i l a b i l i t y of P h o s p h a t i c F e r t i l i z e r s . E x p t. S t. B ui. 289. A rk. Agr. 6. B a r t h o l o m e w , R. P . a n d J a n n e s e n , G. 19 3 1 The r a t e o f a b s o r p t i o n of p o t a s s i u m b y p l a n t s a nd i t s p o s s i b l e e f f e c t u p o n th e a m o u n t o f p o t a s s i u m r e m a i n i n g i n s o i l s f r o m a p p l i c a t i o n s of p o t a s s i u m f e r t i l i z e r s . A rk . Agr. Exp. B u i. 2 6 5 . 7. B e a r , F . E . and P r i n c e , A. L. C a tio n -e q u ilib ria in a l f a l f a . 37: 217- 2 2 2 . 8. B e e s o n , K. C . , L y o n , C. B . a n d B a r r a n t i n e , M. W. 1944 I o n i c a b s o r p t i o n b y tom ato p l a n t s a s c o r r e l a t e d w i t h v a r i a t i o n s i n t h e c o m p o s i t i o n of t h e n u t r i e n t medium. P l a n t P h y s i o l . 19 : 2 5 8 - 2 7 7 * 9. B e n d e r , W. H. an d E i s e n m e n g e r , W. S . 1 9 4 1 I n t a k e of c e r t a i n e l e m e n t s by c a l c i p h i l i c and c a l c i p h o h i c p l a n t s g r o w n on s o i l s d i f f e r i n g i n pH. S o il S ci. 5 2 : 297-307* 1 94 5 J o u r . A m er. S o c . A g r o n . 10. B o w e r , C. A. and T u r k , L. M. 19 4 6 C a l c i u m a nd m a g n e s i u m d e f i c i e n c i e s i n a l k a l i s o i l s . J o u r . Amer. S o c . A g r o n . 3 8 : 7 2 3 - 7 2 7 * 11. B r a d f i e l d , R. 1 9 4 1 C alcium i n S o i l . I. P hysicochem ical r e l a t i o n s , p r o c . S o i l S c i . S o c . Amer . 6 : 8 - 2 6 . 121 12. B u r k h a r t , L . a n d P a g e , N. R. 1941 M i n e r a l n u t r i e n t e x t r a c t i o n and d i s t r i b u t i o n i n t h e peanut p la n t, l o u r . Am er. S o c . A g r o n . 3 3 : 743-7.$5. 13. B o u y o u c o s , G. '1. 1936 D i r e c t i o n s f o r m a k i n g m e c h a n i c a l a n a l y s i s of s o i l s by h y d r o m e t e r m e t h o d . S o i l S c i . 42: 2 2 5 - 2 2 9 . 14. Chapman, H. D. 1928 The p r e c i p i t a t i o n o f c a l c i u m o x a l a t e i n t h e p r e s e n c e o f i r o n , a l u m i n u m , m a n g a n e s e , m a g n e s i u m and p h o s p h a t e w ith s p e c i a l r e f e r e n c e to the d e te r m in a tio n of t o t a l calcium . S o i l S c i . 26: 4 7 9 -4 8 6 . 15. C l a r k , H. E . 1936 E f f e c t of Ammonium a n d n i t r a t e n i t r o g e n o n c o m p o s i ­ t i o n o f tom ato p l a n t . P l a n t P h y s i o l . 1 1 : 5-2 4* 16. C o o p e r , P . H . , P a d e n , W."R . and G a rm a n, W. H. 1947 Some f a c t o r s i n f l u e n c i n g t h e a v a i l a b i l i t y of mag­ n e s i u m i n s o i l and t h e m a g n e s i u m c o n t e n t of c e r t a i n crop p l a n t s . S o il S c i. 63: 27-42. 17. C l e v e n g e r , C. B. 1 91 9 H y d r o g e n i o n c o n c e n t r a t i o n of p l a n t j u i c e s . II. F a c t o r s a f f e c t i n g t h e a c i d i t y or h y d r o g e n i o n c o n c e n ­ t r a t i o n of p l a n t j u i c e s . S o i l S c i . 3: 2 2 7 - 2 4 2 . 18. E a t o n , F . M. a n d H o r t o n , C. H. 1940 E f f e c t of e x c h a n g e s o d i u m on t h e m o i s t u r e e q u i v a l e n t a n d t h e w i l t i n g c o e f f i c i e n t s of s o i l s . l o u r . Amer. S o c . A g r o n . 62: 4 0 1 - 4 2 5 . 19. F l i n t , L. H. 1932 H y d r a t i o n of s o l u t i o n s of t h e h i g h e r e l e m e n t s . J o u r . Wash. A c a d , of S c i . 2 2 : 9 7 - 20. G e d r o i z , K. K. 1 93 1 E x c h a n g e a b l e c a t i o n s o f t h e s o i l a nd p l a n t s . R elatio n s of p l a n t t o c e r t a i n c a t i o n s f u l l y s a t u r a t i n g t h e s o i l exchange c a p a c i t y . S o i l S c i . 32: 5 1 - 6 3 . 21. H a n s t e e n - G a r n e r , B. 1 9 1 4 Uber d a s V e r h a l t e n d e r k u l t u r p f l a n z e n gu d e n B odensalzen I I I - B e i t r e i g e zu r biochem ie and p h y s io lo g ie d e r zellw and le b e n d e r z e l l e n . Jah rle. W iss. B o t. 53: 5 3 6 -5 9 9 . 22. H o a g l a n d , D. R . , D a v i s , A. R. a n d H i b b a r d , P . L. 1928 G e n e r a l n a t u r e o f p r o c e s s of s a l t a c c u m u l a t i o n by r o o t s w i t h d e s c r i p t i o n of e x p e r i m e n t a l m e t h o d s . P lan t P h y s i o l . 3: 4 7 3 - 4 8 6 . 122 23. H i s s i n k , D. J . 1923 Method of e s t i m a t i n g a b s o r b e d b a s e s i n s o i l s and i m p o r t a n c e of t h e s e b a s e s i n s o i l economy. S o i l S c i . 15: 2 6 9 -2 7 6 . 24. H unter, A lb e rt S. 1949 Y i e l d a n d C o m p o s i t i o n o f a l f a l f a a s a f f e c t e d by v a r i a t i o n s i n th e calciurn-m agnesium r a t i o in the so il. S o i l S c i . 67: 5 3 - 6 2 . 25. J a r u s o v , S . S . 1937 On t h e m o b i l i t y of e x c h a n g e a b l e c a t i o n s i n t h e s o i l . S o i l S c i . 43: 285-303. 26. J e n n y , H. and A y e r s , A. D. 1939 The i n f l u e n c e of d e g r e e o f s o i l c o l l o i d s on t h e n u t r i e n t i n t a k e by r o o t s . S oil S c i. 4 8 : 443-459. 27. J e n n y , H. and Covcan, E . W. 193 3 U be r d i e B e d e w tu n g d e r im b o d e n a d s o r b i e r t e h k a t i o n e n f u r d a s p f l a n z e n wachstum . Z t s c h r P f l a w z e n r n a h r . Dungung H. B o de nk (A) 3 1 : 5 7 - 6 7 . 28. J o f f e , J . S . , K a r d o s , L . T. an d M a t t s o n , S. 193 5 Laws o f s o i l c o l l o i d a l b e h a v i o r XVII Magnesium s i l i c a t e — i t s base exchange p r o p e r t i e s . S o il S ci. 4 0 : 255- 2 6 8 . 29. J o f f e , J . S . a n d Zimmerman, M. 1944 S o d i u m , c a l c i u m an d m a g n e s i u m r a t i o s i n t h e e x c h a n g e c o m p l e x . P r o c . S o i l , S c i . S o c . Amer . 51 -55* 30. K a r d o s , L . T. a n d J o f f e ? J . S . 1938 The p r e p a r a t i o n , c o m p o s i t i o n a nd c h e m i c a l b e h a v i o r o f the complex s i l i c a t e s of magnesium, c a l c i u m , stro n tiu m and barium . S o i l S c i . 45: 2 9 3 -3 0 7 . 31. K e l l o g , C. E . 1 9 3 1 M a g n e s i u m — a p o s s i b l e k e y to t h e p h o s p h o r u s p r o b l e m in c e r t a i n sem i-arid s o i l s . J o u r . Amer. S o c . A g r o n . 23: 494-495. 32. K i n g , E. J . 1932 The c o l o r i m e t r i c d e t e r m i n a t i o n of p h o s p h o r u s . Biochem . J o u r . 2 6 . P a r t I . 2 9 2 -3 0 7 - 33. L a w t o n , K. 1945 The d e t e r m i n a t i o n of e x c h a n g e a b l e p o t a s s i u m i n s o i l s u s i n g h e x a n i t r o d i p h e n y l a m i n e . P r o c . S o c . S c i . Am er. 1 0 : 126- 1 2 8 . 34. L ip m a n , C. B. 1916 A c r i t i q u e of t h e l i m e - m a g n e s i a h y p o t h e s i s . W o r l d . 1 9 : 8 3 - 1 0 5 and 1 1 9 - 1 3 3 . P lant 123 35- L oew , 0. 1892 U b e r d ie p h y s i o l o g is c h e n f u n k t i o n e n d e r k a liu m and m a g n e s ia s a ltz in pflanzer organism s. F lo ral 7 5 : 368-394. 36. L o e m , 0 . and M a y , D. W. 1901 T ± i e r e l a t i o n o f lim e and m a g n e s i u m to p l a n t U . S . D . A . Bur P l a n t I n d u s B u i . 1 . grow th. 37* U a c a s , R . E . , S c a r s e t h , G. D. a n d S e i l i n g , D. H. 1942 S o i l f e r t i l i t y l e v e l s as it i n f l u e n c e s p l a n t n u t r i e n t s o c o m p o s i t i o n a n d consum ption. I n d . Agr. E x p t . S t . 23 m l . 4 6 8 . 38. L u c a s , R . E. a n d S c a r s e t h , G-. D. 1947 u P o t a s s i u m , c a l c i u m and magnesium b a la n c e a n d r e c i p r o c a l ^ re la tio n s h ip i n p lan ts. J o u r . Aruer. S o c . A g r o n . 3 9 : 887-896. 39* L i a r s h a l l , C. E . 1 9 4 4 T i n e e x c h a n g e a b l e b a s e s of two M i s s o u r i s o i l s i n r e l a t i o n b o c o m p o s i t i o n of f o u r p a s t u r e s p e c i e s . ' Mo. A g r . E x p t . S x a . R e s . B u i . 385- 40. I v i c G e o r g e , W. T . a n d B r e a z e a l e , J . F . 1938 S b u d ie s on s o i l stru ctu re. E f f e c t of puddled s o i l s o n p l a n t g r o w t h . A r i z . Agr. E x p t . S t a . T e c h . B u i . 72. 41. 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