EVALUATION O F LIME REQUIREMENT METHODS FOR F L O R I D A ' S SANDY S O I L S

BY

THOMAS S . DIEROLF

A T H E S I S PRESENTED TO THE GRADUATE SCHOOL O F THE U N I V E R S I T Y O F FLORIDA I N

P A R T I A L F U L F I L L M E N T - O F THE REQUIREMENTS FOR THE DEGREE OF MASTER O F S C I E N C E

UNIVERSITY OF FLORIDA

EVALUATION OF LIME REQUIREMENT METHODS FOR FLORIDA'S SANDY SOILS

BY

THOMAS S . DIEROLF

A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN

PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE

UNIVERSITY OF FLORIDA

198 6

I n dedication t o Helga, C u r t , Barb, and Sylvia Dierolf

ACKNOWLEDGMENTS

A s with most accomplishments dur ing one ' s l i f e t i m e , a

work, such a s t h i s one, i s poss ib le only through t h e

cooperat ion of many o the r s bes ides t h e one whose s o l e name

appears on t h e cover. I t would not be f e a s i b l e t o thank

everyone ind iv idua l ly a s t h e length of t h i s t h e s i s may then be

doubled.

Many thanks a r e extended t o my major advisor D r . G .

Kidder, f o r always f ind ing t h e time t o work out any problems I

encountered while I was a t t h e Univers i ty of F lo r ida . He was

e s p e c i a l l y he lp fu l during t h e dreaded t h e s i s wr i t ing s t a g e . I

a l s o wish t o thank t h e r e s t of t h e members of my supervisory

committee, D r . Dean Rhue and D r . Pe t e r Hildebrand, f o r

reviewing t h e t h e s i s and o f f e r ing t h e i r he lp fu l suggestions on

improving t h e manuscript.

I am g r a t e f u l t o D r . Dean Rhue, D r . Luther Hammond, t h e

S o i l Charac te r iza t ion Lab, and t h e Extension S o i l Test ing Lab

f o r allowing me t o make use of t h e i r a l ready l im i t ed labora-

t o r y space and f a c i l i t i e s . Thanks a r e a l s o extended t o a l l of

t h e l a b technic ians who l e n t me a hand and put up with my

usurpation of por t ions of t h e l abs . Specia l thanks a r e

o f fe red t o B i l l Reve and Ed Hopwood f o r t h e e x t r a considera-

t i o n they gave me.

iii

For he lp ing me i n i t i a t e and conduct t h e f i e l d t r i a l s i n

Suwannee County I am thoroughly indebted t o D r . Mickey Swisher

who r e a l l y went o u t of h e r way t o accommodate m e . I am thank-

f u l t o D r . T i t o French and t h e r e s t of t h e people involved

with t h e North F l o r i d a FSR/E program f o r p rov id ing l o g i s t i c a l

suppor t . I am a l s o g r a t e f u l t o t h e Andrews, Chamberlain, and

Barr f a m i l i e s f o r a l lowing me t o conduct t h e t r i a l s on t h e i r

farms.

F r i ends a r e e s s e n t i a l i n he lp ing us make our everyday l i f e

b e a r a b l e . The f r i e n d s I ' v e made he re a r e no except ion , and

they a l l w i l l be s o r e l y missed. I hope t h a t I w i l l be a b l e t o

keep i n touch with a l l of them i n t h e f u t u r e . I owe Steve

Grant a l o t of thanks f o r a l lowing me t o t y p e t h i s t h e s i s on

h i s PC, a l though a t t imes I wondered i f i t might of have been

e a s i e r t o h i r e a t y p i s t .

F i n a l l y , t h e r e is a very s p e c i a l f r i e n d , Kate Gieger,

whose love and f r i e n d s h i p have helped make it a l l worthwhile.

TABLE OF CONTENTS

ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v i i LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i x ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x i CHAPTERS

I INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I1 REVIEW OF THE LITERATURE . . . . . . . . . . . . . . . . . . . . . . . . . . . .

I n t r o d u c t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 H i s t o r y o f L i m e Requirement Methods . . . . . . . . . . . . . . . . . 5

Liming P r a c t i c e s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Litmus T e s t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 S o i l - l i m e T i t r a t i o n s . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 S o i l - l i m e P o t e n t i o m e t r i c T i t r a t i o n s . . . . . . . . . . . . 8 Buf fe r Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . '10 Double-buffer Methods . . . . . . . . . . . . . . . . . . . . . . . . . . 13

S o i l A c i d i t y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 4 Forms of S o i l A c i d i t y . . . . . . . . . . . . . . . . . . . . . . . . . . 15 B u f f e r i n g Capac i ty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Role of A1 i n S o i l pH B u f f e r i n g . . . . . . . . . . . . . . . . 16 Base S a t u r a t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 pH-BU R e l a t i o n s h i p . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Measurement o f Base S a t u r a t i o n . . . . . . . . . . . . . . . . . 20 C h a r a c t e r i s t i c s o f F l o r i d a S o i l s . . . . . . . . . . . . . . . 21

Methods o f T e s t i n g L i m e Requirement Methods . . . . . . . . . 22 Re fe rence Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 S a l t Accumulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Comparison of Reference Methods . . . . . . . . . . . . . . . . 25 E f f e c t i v e n e s s o f B u f f e r s i n Measuring T o t a l

S o i l A c i d i t y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 F i e l d C a l i b r a t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 7

. . . . C a l c u l a t i o n o f Adams-Evans L i m e Requirement 28

. . . . P r e v i o u s E v a l u a t i o n s of L i m e Requirement Methods 29 Adams-Evans B u f f e r Method . . . . . . . . . . . . . . . . . . . . . . 30 Yuan Double B u f f e r Method . . . . . . . . . . . . . . . . . . . . . . 31

SMP S i n g l e B u f f e r Method . . . . . . . . . . . . . . . . . . . . . . . 34 SMP Double B u f f e r Method . . . . . . . . . . . . . . . . . . . . . . . 34

I11 INCUBATION STUDY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 I n t r o d u c t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 R e s u l t s and Di scus s ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

. . . . . . . . . . . . . . . . . . . . . . . pH, and Base U n s a t u r a t i o n 46 pHw and pHs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 T i t r a t i o n Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 AE Method and CaC03 I n c u b a t i o n . . . . . . . . . . . . . . . . . . 57 AEmod Method and CaC03 I n c u b a t i o n . . . . . . . . . . . . . . . 59 Yuan DB Method and C a C 0 3 I n c u b a t i o n . . . . . . . . . . . . . 51 A l l Three Methods and BaC12-TEA . . . . . . . . . . . . . . . . . 63 AE T o t a l A c i d i t y and BaC12-TEA . . . . . . . . . . . . . . . . . . 66 BaC12-TEA and CaC03 I n c u b a t i o n . . . . . . . . . . . . . . . . . . . 66 Sugges ted M o d i f i c a t i o n s . . . . . . . . . . . . . . . . . . . . . . . . 68

Summary and Conclus ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 I V FIELD STUDY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

I n t r o d u c t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

D e s c r i p t i o n o f S i t e s and S o i l s . . . . . . . . . . . . . . . . . 76 Exper imenta l Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 Land P r e p a r a t i o n . U s e . and Analyses . . . . . . . . . . . . 80

S i t e 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 S i t e 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1 S i t e 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

R e s u l t s and D i s c u s s i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Obse rva t ions of F i e l d LR Over t h e Length of

t h e S tudy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 C a l c u l a t i o n o f F i e l d L i m e Requirement . . . . . . . . . . 87 Comparison of F i e l d and Labora to ry Data . . . . . . . . 87

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 V CORRELATION STUDY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

I n t r o d u c t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 R e s u l t s and Di scus s ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

V I SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . REFERENCES 103

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BIOGRAPHICAL SKETCH 112

LIST OF TABLES

Table 3-1. C l a s s i f i c a t i o n of 34 s o i l s from which t h e t op 15 c m was used i n t h e incubation s tudy. (So i l Survey S t a f f , 1985) . . . . . . . . . . . . . . . . . . . . 4 0

Table 3-2. Chemical and physical c h a r a c t e r i s t i c s of t h e 34 s o i l s used i n t h e incubation study . . . . . . . . 4 2

Table 3-3. Mean weights and s tandard dev ia t ions of s o i l contained i n an 11 m l scoop. An excess amount of s o i l was scooped i n t o t h e conta iner , t h e s i d e of t he scoop was gen t ly tapped t h r e e t imes, t he s o i l was l eve led o f f , and weighed. 43

Table 3-4. Individual lime r a t e s app l ied t o t h e 34 incubated s o i l s . ESTL measured pHw and AE buf fe r pH. LR ( l b s acre'') was determined from published t a b l e s and converted t o g

. . . . . . . . CaC03 100 9-' s o i l t o a t t a i n pH, 6 .5 . . 45 Table 3-5. Per iod ic pHw (1:2) measurements taken from 1 4

of t h e experimental u n i t s over t h e length of t h e incubation study t o determine when equi l ibr ium pHw was reached . . . . . . . . . . . . . . . . . . 4 7

Table 3-6. Regression equations of f i n a l pH, ( y ) versus g CaC03 kg-' s o i l added (x) used t o compute incubation L R . Also shown a r e t h e comparison of r2 f o r l i n e a r and c u r v i l i n e a r r e l a t i onsh ips and t h e s tandard dev ia t ion ( s ) f o r t h e l i n e a r equations . . . . . . . . . . . . . . . . 56

Table 3-7. Regression s t a t i s t i c s of var ious lime requirement determinations versus t h e BaC12-TEA (pH 8.2) ex t r ac t ab l e a c i d i t y reference method (g CaC03 kg-' s o i l ) . . . . . . . . . . 64

Table 4 - 1 . Selected chemical and physical c h a r a c t e r i s t i c s of t h e top 15 cm of t h e

. . . . . . . . . . t h r e e s o i l s used i n t h e f i e l d study 7 8

Table 4-2 . Average pH, by treatment fo r the three f i e l d s i t e s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Table 4-3. Comparison of various methods of predict ing s o i l LR t o pH, 6 . 0 and 6 . 5 . . . . . . . . . . . . . . . . . . . . 8 9

Table 5-1. Selected cha rac te r i s t i c s of 98 s o i l s used i n the corre la t ion study . . . . . . . . . . . . . . . . . . . . . . . . . 95

Table 5-2. Regression s t a t i s t i c s between AE LR and the BaC12-TEA reference method . . . . . . . . . . . . . . . . . . . . 9 6

LIST OF FIGURES

F i g u r e 3-1.

F i g u r e 3-2.

F i g u r e 3-3.

F i g u r e 3-4.

F i g u r e 3-5.

F i g u r e 3-6.

F i g u r e 3-7.

F i g u r e 3-8.

F i g u r e 3-9. . . .

F i g u r e 3-10

Loca t ion o f Alachua ( A ) and Suwannee (S) . . . . . . . . . . . . . . . . . . . . . . . . . . . Coun t i e s , F l o r i d a 39

R e l a t i o n s h i p between pHw and b a s e u n s a t u r a t i o n f o r 567 F l o r i d a t o p s o i l s ( 0 - 15 c m ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P l o t o f pHs v e r s u s pHw f o r t h e 34 s o i l s u sed i n t h e i n c u b a t i o n s t u d y . . . . . . . . . . . . . . . . . . . . . T i t r a t i o n c u r v e s of f i n a l - pH v e r s u s amount o f CaC03 added f o r s o i l s 7, 8, 17, 18,

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . and 20 T i t r a t i o n c u r v e s of f i n a l pHp v e r s u s t h e amount o f CaC03 added f o r s o l l s 15, 16, 23,

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 and 27 T i t r a t i o n c u r v e s of f i n a l pH, v e r s u s t h e amount o f CaC03 added f o r s o i l s 3 , 5, 11,

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, and 1 4 T i t r a t i o n c u r v e s of f i n a l pHp v e r s u s t h e amount of CaC03 added f o r s o l l s 1 0 , 13, 19,

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20, and 21 T i t r a t i o n c u r v e s of f i n a l pHp v e r s u s t h e amount o f CaC03 added f o r s o ~ l s 1, 2, 4 , 6, and g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

T i t r a t i o n c u r v e s of f i n a l pHp v e r s u s t h e amount o f CaC03 added f o r s o l l s 22, 26, 29,

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . and 3 1 T i t r a t i o n c u r v e s of f i n a l pHs v e r s u s t h e amount o f CaC03 added f o r s o i l s 25, 28, 32, 33, and 34 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F i g u r e 3-11. Reg re s s ion c u r v e s and s t a t i s t i c s o f AE LR v e r s u s i n c u b a t i o n LR. a ) t o pH 5 .5 ; b ) t o pH 6 .0 ; c ) t o pH 6 .5 . . . . . . . . . . . . . . . . . . . . . . .

F i g u r e 3-12. Reg re s s ion c u r v e s and s t a t i s t i c s o f AEmod v e r s u s i n c u b a t i o n LR. a ) t o pH 5 .5 ; b ) t o pH 6.0; c ) t o pH 6 .5 . . . . . . . . . . . . . . . . . . . . . . .

F i g u r e 3-13. Reg re s s ion cu rves and s t a t i s t i c s o f Yuan DB v e r s u s i n c u b a t i o n LR. a ) t o pH 5 .5 ; b ) t o pH 6 .0 ; c ) t o pH 6 .5 . . . . . . . . . . i . . . . . . . . . . . .

F i g u r e 3-14. The r e g r e s s i o n e q u a t i o n and s t a t i s t i c s between t h e t o t a l amount o f a c i d i t y measured by t h e AE b u f f e r (TA) and BaC12-TEA e x t r a c t a b l e a c i a i t y . . . . . . . . . . . . . . .

F i g u r e 3-15. The r e g r e s s i o n e q u a t i o n and s t a t i s t i c s between t h e AE s o i l - b u f f e r e q u i l i b r i u m pH and t h e i n c u b a t i o n LR . . . . . . . . . . . . . . . . . . . . . .

F i g u r e 3-16. The r e g r e s s i o n e q u a t i o n and s t a t i s t i c s between AE-F and i n c u b a t i o n LR t o pH 6 .0 . . .

F i g u r e 4 - 1 . The l o c a t i o n o f t h e t h r e e f i e l d t r i a l s i n . . . . . . . . . . . . . . . . . . . Suwannee County, F l o r i d a

F i g u r e 4-2. The e f f e c t o f l i m e t r e a t m e n t s on s o i l pH,, o v e r t h e t i m e p e r i o d of t h e s t u d y , a t s i t e 1. Each p o i n t r e p r e s e n t s t h e a v e r a g e of f o u r r e p l i c a t i o n s . . . . . . . . . . . . . . . . . . . . . . . . . .

F i g u r e 4-3. The e f f e c t o f l i m e t r e a t m e n t s on s o i l pH,, o v e r t h e t i m e p e r i o d o f t h e s t u d y , a t s i t e 2 . Each p o i n t r e p r e s e n t s t h e a v e r a g e of f o u r r e p l i c a t i o n s . . . . . . . . . . . . . . . . . . . . . . . . . .

F i g u r e 4 - 4 . The e f f e c t o f l i m e t r e a t m e n t s on s o i l pH,, o v e r t h e t i m e p e r i o d o f t h e s t u d y , a t s i t e 3 . Each p o i n t r e p r e s e n t s t h e a v e r a g e of f o u r r e p l i c a t i o n s . . . . . . . . . . . . . . . . . . . . . . . . . .

F i g u r e 5-1. The l o c a t i o n o f t h e 98 s o i l s used i n t h e c o r r e l a t i o n s t u d y . Each number r e p r e s e n t s t h e amount o f samples o r i g i n a t i n g from t h e

. . . . . . . . . . . . . . . . . . . . . . . . . . r e s p e c t i v e county

Abstract of Thesis Presented t o t h e Graduate.Schoo1 of t h e Univers i ty of F lor ida i n P a r t i a l Fu l f i l lment of t h e

Requirements f o r t h e Degree of Master of Science

EVALUATION OF LIME REQUIREMENT METHODS FOR FLORIDA'S SANDY SOILS

THOMAS S . D IEROLF May 1 9 8 6

Chairman: Gerald Kidder

Major Department: S o i l Science

Laboratory and f i e l d s tud i e s were conducted t o eva lua te

two s o i l - t e s t methods used t o determine s o i l lime requirement

( L R ) . The Adams-Evans (AE) LR method which i s c u r r e n t l y used

by t h e Extension S o i l Test ing Laboratory (ESTL) t o make

liming recommendations i n F lor ida and t h e Yuan double buf fe r

(DB) method which was s p e c i f i c a l l y designed t o measure t h e LR

of F l o r i d a ' s sandy s o i l s were compared t o a s tandard CaC03

incubation procedure.

A l abora tory study of 3 4 F lor ida s o i l s , with low organic

mat ter and c l ay contents , ind ica ted t h a t t h e Yuan DB method

was a poor p red i c to r of t h e incubation LR. The AE method was

highly co r r e l a t ed with, but underestimated incubation L R .

An a l t e r n a t i v e method of ca l cu l a t i ng t h e AE LR (AE-F) was

developed from the study d a t a . The AE-F method e l iminated t he

h o n - s p e c i f i c pH-base u n s a t u r a t i o n (BU) r e l a t i o n s h i p and co r -

r e c t e d f o r t h e u n d e r e s t i m a t i o n of i n c u b a t i o n LR by t h e AE me-

t h o d . The a l t e r n a t i v e method used t h e same l a b o r a t o r y d e t e r -

m i n a t i o n s a s the AE method b u t u sed d i f f e r e n t c a l c u l a t i o n s .

The AE method was a l s o e v a l u a t e d u s i n g a g roup o f 98

s o i l s sampled from v a r i o u s a r e a s t h roughou t F l o r i d a . The

s o i l s r e p r e s e n t e d a wider r ange of p h y s i c a l and chemica l

c h a r a c t e r i s t i c s t h a n d i d t h e s o i l s u sed i n t h e i n c u b a t i o n

s t u d y . . R e s u l t s i n d i c a t e d t h a t t h e AE method p r o v i d e d a n

a c c u r a t e i n d e x of t h e s o i l LR on t h e 98 s o i l s s t u d i e d .

F i e l d s t u d i e s r e v e a l e d t h a t c u r r e n t l i m e recommendations

made by t h e ESTL u n d e r e s t i m a t e d a c t u a l f i e l d LR. The AE-F

method a l s o u n d e r e s t i m a t e d f i e l d LR which i m p l i e d t h a t t h e

l i m i n g f a c t o r o f 1 . 5 u sed by t h e ESTL was t o o low. The f i e l d

s t u d y i n d i c a t e d l i m i n g f a c t o r s o f 3 and 5 f o r s o i l s w i t h

r e l a t i v e l y low and h i g h i n i t i a l pH,, r e s p e c t i v e l y . More f i e l d

s t u d i e s a r e needed t o o b t a i n b e t t e r l i m i n g f a c t o r s f o r

F l o r i d a ' s s o i l s .

R e s u l t s i n d i c a t e d t h a t a l t h o u g h t h e AE LR method was

a p p r o p r i a t e f o r u s e on F l o r i d a ' s sandy s o i l s , two ad jus tmen t s

i n t h e c a l c u l a t i o n of AE LR would improve t h e method. F i r s t ,

t h e e q u a t i o n deve loped from t h e i n c u b a t i o n s t u d y shou ld be

employed i n s t e a d o f t h e one from t h e o r i g i n a l AE LR method.

Second, t h e c u r r e n t l i m i n g f a c t o r u sed by t h e ESTL s h o u l d be

i n c r e a s e d t o a t l e a s t 3.

Chairman -

x i i

CHAPTER I INTRODUCTION

P r i o r t o t h e a d o p t i o n o f t h e Adams-Evans ( A E ) l i m e r e -

qu i rement (LR) method by t h e U n i v e r s i t y of F l o r i d a Extens ion

S o i l T e s t i n g Labora tory (ESTL), s o i l l i m e requi rement was

e s t i m a t e d by t h e county e x t e n s i o n a g e n t s . They used s o i l pH,

t e x t u r e , e x t r a c t a b l e Ca and Mg, and o r g a n i c m a t t e r c o n t e n t t o

e s t i m a t e t h e amount of l i m e needed t o accomplish t h e d e s i r e d . pH change (Rhue and Kidder, 1984) .

The desire f o r a q u a n t i t a t i v e method f o r d e t e r m i n i n g s o i l

LR had been d i s c u s s e d s i n c e a t l e a s t t h e e a r l y 1 9 7 0 ' s (Yuan,

1 9 7 0 ) . Unpublished work a t t h a t t i m e had . found t h a t t h e

e x i s t i n g LR b u f f e r methods were n o t s u i t a b l e f o r u se on

F l o r i d a s o i l s . Yuan expres sed a need f o r m o d i f i c a t i o n o f t h e

e x i s t i n g methods, o r t h e development of a new one .

I n r e sponse t o t h e need f o r a new LR method i n F l o r i d a ,

Yuan (1974) c r e a t e d a new b u f f e r employing t h e double b u f f e r

c o n c e p t . Then Yuan (1975) compared h i s b u f f e r w i t h t h r e e o t h e r

methods, i n c l u d i n g among them t h e AE method. Using t h e BaC12-

TEA method a s a r e f e r e n c e method, he found t h e Yuan double

b u f f e r (DB) method t o be p r e f e r a b l e o v e r t h e AE method which

g r e a t l y unde res t ima ted t h e r e f e r e n c e method. Yuan fo l lowed up

t h i s work with f u r t h e r f i e l d s tud i e s (Yuan e t a l . , 1977; Yuan

e t a l . , 1978) .

When t h e decis ion t o adopt a new LR method f o r rou t ine

use by t h e ESTL was made, t h e AE method was chosen over t h e

Yuan DB method. Reasons included were t h a t t h e AE method had

been developed f o r low ca t i on exchange capac i ty (CEC) s o i l s

such a s those which a r e commonly found i n F lo r ida . The

neighboring s t a t e s of Alabama and Georgia had a l s o adopted t he

method thus providing f o r some i n t e r s t a t e co l l abo ra t i on .

F ina l l y t h e AE method used l e s s bu f f e r and required l e s s

determinations than t h e Yuan DB method, making t h e AE method

l e s s expensive and more rap id then t h e Yuan DB method.

Although Yuan (1975) examined t h e AE method he d i d not

g ive t h e method t h e f u l l a t t e n t i o n needed i f a method i s t o be

adopted. Since t he AE method was adopted by t h e Extension

S t a t e S o i l Test ing Laboratory a c r i t i c a l examination of t h e

buf fe r has not been performed.

P r i o r t o t h e adoption of a p a r t i c u l a r s o i l t e s t method,

i n t h i s case t he LR method, s eve ra l methods a r e usua l ly

evaluated i n l abora tory and/or greenhouse s t u d i e s . These a r e

a l s o known a s c o r r e l a t i o n s t u d i e s . A r ep re sen t a t i ve and l a r g e

number of s o i l s f o r a region can be evaluated. This process

allows f o r t h e s e l e c t i o n of t h e method t h a t provides t h e bes t

index of t he s o i l LR.

The next s t e p i s c a l i b r a t i o n . Here f i e l d t r i a l s a r e

conducted t o r e l a t e t h e laboratory values t o a c t u a l f i e l d

va lues . F i e l d recommendations can then be made from these

r e s u l t s .

The o v e r a l l ob j ec t i ve of t h i s t h e s i s was t o eva lua te t h e

AE and Yuan DB methods on F l o r i d a ' s sandy s o i l s . These a r e t he

only two methods being evaluated because of t h e fol lowing

reasons :

1/ There i s a d e s i r e f o r co l labora t ion between s t a t e s o i l

t e s t i n g l abo ra to r i e s , thus t h e d e s i r e t o keep t h e

t e s t s a s s i m i l a r a s poss ib le , poss ib ly s a c r i f i c i n g

some accuracy.

2 / There may be a push i n t h e fu tu re f o r DB methodology,

. so t he se methods should continue t o be evaluated.

The t h e s i s i s divided i n t o f i v e p a r t s . Chapter I1 reviews

t h e l i t e r a t u r e pe r t i nen t t o t h e s tudy. Chapter I11 presen ts

t h e l abora tory incubation s tudy designed t o eva lua te t h e AE

and Yuan DB methods. Chapter I V r e l a t e s t h e l abora tory data t o

a c t u a l f i e l d responses. Chapter V r e l a t e s t h e r e s u l t s from the

incubation s tudy t o a wider range of F lor ida s o i l s t o

determine t h e wider a p p l i c a b i l i t y of t h e AE method. F ina l ly

Chapter V I summarizes t h e study and provides recommendations

f o r f u r t h e r work.

CHAPTER I1 REVIEW OF THE LITERATURE

I n t roduct ioq

The lime requirement of a s o i l can be defined as the

amount of lime or other base required t o neut ra l ize the

undissociated and dissociated ac id i ty i n the range from the

i n i t i a l acid condition t o a selected neutral or l e s s acid

condition (McLean, 1980). The key word in t h i s de f in i t ion i s

' se lec ted ' such t h a t the reason for se lec t ing the desired pH

i s unrelated t o the de f in i t ion . This d i s t inc t ion i s necessary

because some def in i t ions may include the reason fo r a t t a in ing

a ce r t a in pH within the def in i t ion . This i s t r u e of the one

given by Hesse ( 1 9 7 1 ) , where he r e l a t e s lime requirement t o

the amount of lime needed fo r maximum economic return from a

pa r t i cu la r s o i l .

The term pH i s a l so l e f t out of the def in i t ion because

other workers such as Kamprath ( 1 9 7 0 ) have reported t h a t on

highly weathered leached s o i l s exchangeable A 1 was a va l id

c r i t e r i o n on which t o base lime r a t e s .

The remainder of the l i t e r a t u r e review i s divided in to

four sect ions with the purpose of presenting a general

understanding of s o i l lime requirement (LR) methods used t o

predict s o i l LR. The f i r s t section covers a general h is tory

of t h e development and improvement of s o i l LR methods.

Sec t ion two p r e s e n t s a g e n e r a l d e s c r i p t i o n of s o i l a c i d i t y

and r e l a t e d s o i l c h a r a c t e r i s t i c s t h a t i n f l u e n c e s o i l L R .

Sec t ion t h r e e d e s c r i b e s techniques of c o r r e l a t i n g and

c a l i b r a t i n g s o i l LR methods. F i n a l l y s e c t i o n f o u r reviews

f i n d i n g s of previous work e v a l u a t i n g t h e p r e c i s i o n and

accuracy of t h e Adams-Evans ( A E ) , Yuan double b u f f e r (Yuan

DB) , and SMP methods.

f i i s t o r v of Lime Requirement Methods

The methods of l ime requirement de te rmina t ion used today

a r e t h e r e s u l t of an evo lu t ion of methodology and t h e o r y . A

h i s t o r i c a l review of t h e p e r t i n e n t works can l e a d t o a b e t t e r

unders tanding of why t h e c u r r e n t l ime requirement methods a r e

be ing employed.

Limina P r a c t i c e s

Recently, s e v e r a l reviews summarizing t h e e a r l y work

p e r t a i n i n g t o l iming, have been publ ished (Adams, 1984;

Barber, 1984; Lathwell and Reid, 1984; and McLean and Brown,

1984) . References t o t h e use of l ime d a t e back t o t h e f i r s t

and second cen tu ry B . C . . Ruff in, through h i s w r i t i n g s i n t h e

e a r l y and mid 19 th century , promoted t h e use of l ime i n t h e

United S t a t e s by r e p o r t i n g t h a t marl a p p l i c a t i o n s improved

crop y i e l d s on h i s farms.

With t h e advent of a g r i c u l t u r a l r e sea rch s t a t i o n s ,

s e v e r a l s t a t e s i n t h e l a t e 19 th cen tu ry began resea rch on

l iming us ing burned lime, gas lime, o r mar l . Lime had been

used f o r c e n t u r i e s i n Europe and knowledge of i t s b e n e f i t s

were c a r r i e d over t o t h e U.S from previous exper iencs and

a l s o from w r i t i n g s of Europeans on t h e p r i n c i p l e s of p l a n t

growth and n u t r i t i o n . This knowledge was r a r e l y pu t t o use,

however, s i n c e it was e a s i e r f o r t h e farmers t o move t o more

f e r t i l e grounds than t o haul l i m e t h e long d i s t a n c e s u s u a l l y

r equ i red .

Extensive i n v e s t i g a t i o n s on crop responses t o l ime

appeared t o o r i g i n a t e i n t h e Nor theas tern region of t h e U.S..

Near t h e end of t h e 19 th century Wheeler and co-workers

r e l a t e d t h e need f o r l ime on a c i d upland s o i l s i n Rhode

I s l a n d . P r i o r t o t h i s t ime t h e p r a c t i c e of l iming had become

wel l e s t a b l i s h e d i n c e r t a i n l o c a l i t i e s based p r i m a r i l y on

farmer exper ience . It was not u n t i l t h e e a r l y 20th cen tu ry

t h a t e x t e n s i v e l iming t r i a l s were begun i n t h e Southern and

Midwestern U.S..

us T e s r

Although l i tmus was f i r s t used a s an i n d i c a t o r of a c i d i t y

i n 1865, it had no g e n e r a l a p p l i c a t i o n f o r recommending lime

u n t i l many yea r s l a t e r . Wheeler and Tucker (1896) , r e p o r t e d

t h a t s o i l s t e s t i n g more a c i d on l i tmus paper b e n e f i t e d more

from l iming than d i d s o i l s t e s t i n g n e u t r a l o r n e a r l y n e u t r a l .

They c a l l e d f o r a chemical t e s t t h a t , by de termining t h e

r e l a t i v e a c i d i t y of a s o i l , would be a b l e t o p r e s c r i b e t h e

c o r r e c t q u a n t i t y of l ime needed.

ime T i t r a t i o n s So i l -1

The yea r s 1897 t o 1920 were t h e p ioneer ing e r a of t h e

q u a n t i t a t i v e de terminat ion of lime requirement . The e a r l i e s t

methods of de termining s o i l a c i d i t y were based upon t h e

r e a c t i o n of s o i l with excess CaC03. The o l d e s t of t h e s e

methods i s t h a t of Tacke (1897) which c o n s i s t e d of suspending

an excess of CaC03 with t h e s o i l and a s p i r a t i n g t h e evolved

C02 t h r e e hours a t room tempera ture . Shaw (1953) r e p o r t e d

t h a t , i n 1900, Wheeler and h i s co-workers i n v e s t i g a t e d t h e

p o s s i b i l i t y of u t i l i z i n g t h e evolved C02, from t h e r e a c t i o n

of s o i l wi th a suspension of CaC03 a t b o i l i n g tempera ture , as

a measure of l ime requirement . They were unable, though, t o

determine a reasonable t ime l i m i t w i th in which t h e

e l i m i n a t i o n of C 0 2 would be ended and observed.

Veitch (1902) developed a lime-water method based on t h e

Tacke procedure . The Veitch method c o n s i s t e d of a s e r i e s of

CaO e q u i l i b r a t i o n s with t h e s o i l fol lowed by b o i l i n g . The

s m a l l e s t amount of lime-water t h a t gave t h e c h a r a c t e r i s t i c

p ink c o l o r , i n t h e presence of phenolphthale in , was taken a s

t h e a c i d i t y equ iva len t of t h e s o i l . This method was designed

t o b r i n g t h e s o i l pH up t o n e u t r a l i t y because Vei tch f e l t

t h a t an a l k a l i n e s o i l pH was necessary f o r optimum p l a n t

performance. The Veitch method was cons idered t h e most

r e l i a b l e f o r t h e f i r s t two decades of t h e 20th century , but

a t t h e same time was plagued by poor r e p r o d u c i b i l i t y and

cons idered a s t o o l abor ious (Shaw, 1953) .

Hopkins e t a l . (1903) proposed a method in which a

neutral s a l t solution of NaCl was mixed with a s o i l sample.

Their theory held tha t the mineral acids i n the s o i l would

uni te with the mineral bases. A standard f ixed a l k a l i was

then used t o t i t r a t e the l ibera ted mineral acid. In the

laboratory they added quant i ta t ive amounts of lime t o s o i l

samples i n accordance with the method and found tha t

p rac t i ca l ly a l l of the ac id i ty was neutral ized.

Jones (1913) recommended a method in which calcium

ace ta te was used t o ext rac t the ac id i ty . The resul tan t ace t i c

acid was then t i t r a t e d with 0 . 1 M NaOH in the presence of

phenolphthalein. This method was l a t e r shown t o underestimate

the lime requirement because the ext rac tant was most strongly

buffered a t pH 4 . 7 6 which was too low t o e f fec t complete

replacement of exchangeable hydrogen.

MacIntire e t a l . (1917) reacted s o i l s with CaC03 and

MgC03 i n the f i e l d and i n the laboratory. They concluded tha t

s o i l s have capaci t ies t o decompose CaC03 i n the f i e l d grea t ly

beyond the Veitch lime requirement. MacIntire (1915)

developed a method where they evaporated calcium

bicarbonate-soil suspensions t o a t h i n paste on a steam bath

and determined the soil-CaC03 reaction from analysis of the

residual CaC03.

Soil-lime Potentiometric Ti t ra t ions

Sharp and Hoagland (1915) were the f i r s t ones t o use

potentiometric t i t r a t i o n with Ca(OH)2, using the hydrogen

electrode. They added Ca(OH)2 t o s o i l suspensions u n t i l a

d e f i n i t e a lka l ine reaction was obtained. They a l s o

acknowledged t h a t there was incomplete time for complete

neut ra l iza t ion of the s o i l s ac ids .

MacIntire (1920) reported a t a 1 9 1 7 meeting on a

col laborat ive e f f o r t t h a t compared a l l of the aforementioned

methods as well some others . Calcium carbonate-soil incuba-

t ions were used t o assess the predicted lime requirements by

the various methods. Although the lab assigned t o evaluate the

Jones method did not provide any data, MacIntire s t i l l

reported t h a t the Jones method offered the best p o s s i b i l i t i e s

fo r obtaining the coeff ic ient of lime determination.

In 1 9 1 9 , two Danes, Bjerrum and Gjaldbaek, made an

epochal contribution t o the f i e l d when they developed

t i t r a t i o n or buffer curves as determined potentiometrically,

t o study the ac id ic and basic propert ies of s o i l s . They a l so

establ ished the relat ionship between p a r t i a l pressure of C 0 2

and pH values of saturated solutions of CaC03 (Shaw, 1953).

Jensen ( 1 9 2 4 ) and Christensen and Jensen ( 1 9 2 6 ) , a l so of

Denmark, used Ca(OHI2 and CaC03, respectively, t o obtain

soi l -buffer pH curves. P ier re and Worley (1928), in Alabama,

incubated s o i l with increments of Ba(OHI2 f o r three days.

Determinations were made on the c l ea r d i f fusa te by the

colorimetric pH method.

The residual carbonate procedure, developed by Bradfield

and Allison i n 1933, i s the best known t i t r a t i o n procedure

(Thomas-and Hargrove, 1984). They defined a 100% base

saturated s o i l as one which had reached equilibrium w i t h a

surplus of CaC03 a t the p a r t i a l pressure of C02 exis t ing in

the. atmosphere and a t a temperature of 25 C . They determined

tha t the pH of a base saturated s o i l would be approximately

8 . 2 .

Buffer Methods

Schofield (1933) proposed a soi l -buffer method which

required two t i t r a t i o n s . A lime and para-nitrophenol solution

was added t o a s o i l sample and allowed t o equi l ibra te for a t

l e a s t 1 6 hours. Both the o r ig ina l solution and soi l -solut ion

were t i t r a t e d . The difference in cubic centimeters between

the two t i t r a t i o n s was equal t o the milligram equivalents of

lime taken up per 100 g of s o i l .

Mehlich (1938) reported t h a t rapid and accurate analyses

were needed in order t o measure exchangeable H+, base-

exchange reactions, and lime requirement on large numbers of

s o i l samples. He proposed the triethanolamine acetate-barium

hydroxide buffer a t pH 8.15 f o r t h i s . The ~ a ~ + would exchange

the H+ on the s o i l col loids and the hydroxide would neutra-

l i z e the resul tan t ac id i ty . The base exchange could be

measured by t i t r a t i o n of the o r ig ina l buffer and soil-buffer

solut ion and subtract ing the two. T i t r a t ab le ac id i ty was

determined electrometr ical ly by t i t r a t i o n with 0 . 2 M H C 1 t o

approximately pH 6 . 0 . The difference between the t i t r a t i o n

values of a l i k e al iquot of the o r ig ina l ex t rac t ing solution

and the s o i l ex t rac t was equivalent t o the neut ra l iza t ion of

the barium hydroxide by s o i l ac ids .

Mehlich (1942a) proposed an improved buffer consis t ing of

barium chloride-triethanolamine a t pH 8.2.. He subs t i tu ted

barium chloride f o r barium hydroxide because the C02 of the

a i r did not i n t e r f e r e with the t i t r a t i o n s . The base-exchange

capacity and the exchangeable H+ were determined by t i t r a t i n g

one al iquot of ex t rac t .

Dunn (1943) incubated s o i l , Ca (OH) 2 , and d i s t i l l e d water

fo r four days with thorough shaking twice da i ly . He compared

t h i s t i t r a t i o n curve t o f i e l d and laboratory experiments,

where he had added increments of CaC03 or Ca(OH)2 t o s o i l fo r

several months. The t i t r a t i o n curve underestimated the f i e l d

lime requirement but was accurate enough t o bring the f i e l d

s o i l s t o within 0 . 5 pH of the desired pH. .

Brown (1943) f i r s t developed the idea of combining the

use of the g lass e lectrode and the concept of depression of

the buffer pH as a measure of exchangeable H+ present i n the

s o i l . Soi l was added t o e i t h e r neutral normal ace ta te or

normal a c e t i c ac id . The pH was determined in the mixture. The

depression i n pH, in the case of the NH40Ac, or the increase

in pH, in the case of the a c e t i c acid was then read off of a

t i t r a t i o n curve as millequivalents of acid or base,

respect ively.

Woodruff (1948) developed a bu f f e r method, s u i t a b l e f o r

rou t ine t e s t i n g , t h a t required only one pH reading. The

buf fe r so lu t i on cons i s ted of calcium a c e t a t e , para-ni t ro-

phenol, and magnesium oxide. The t i t r a t i o n curve of t h e

bu f f e r was l i n e a r from pH 7.0 t o 6.0.

McLean e t a l . (1958) observed t h a t t h e lime requirements

of Ohio s o i l s were not met a s determined by t h e Woodruff

method. They f e l t t h a t t h e Woodruff bu f f e r method f o r

determining lime requirement genera l ly d id not t ake i n t o

account t h e e x t r a c t a b l e A l .

Shoemaker e t a l . ( 1 9 6 1 ) developed a buf fe r method (SMP)

which cons i s ted of a more d i l u t e mixture of t r ie thanolamine,

para-nitrophenol, potassium chromate, and calcium a c e t a t e

than t h e Woodruff procedure. They found t h a t t h e Woodruff and

Mehlich bu f f e r s were t oo s t rong t o i nd i ca t e by pH change t h e

r e l a t i v e l y weaker a c i d i t y of s o i l s high i n ex t r ac t ab l e A l .

The t i t r a t i o n curve of t h i s bu f f e r was l i n e a r from p H 7 . 5 t o

4 .8 .

Adams and Evans (1962) developed a bu f f e r designed p r i -

mari ly f o r Red-Yellow Podzolic s o i l s with only small amounts

of 2 : l type c l ays . I t had a l a rge buf fe r ing capac i ty r e l a t i v e

t o t h e s o i l but a t t h e same time it was s e n s i t i v e t o t h e

a c i d i t y of s o i l s of low exchange capac i ty . They included

para-nitrophenol i n a g r e a t e r concentra t ion than t he Woodruff

method, and used K-borate ins tead of Ca-acetate. They

employed a pH-base unsatura t ion (BU) r e l a t i o n s h i p i n t h e

c a l c u l a t i o n o f f i e l d l i m e r equ i r emen t . The t i t r a t i o n c u r v e o f

t h e b u f f e r was l i n e a r from pH 8 .0 t o 7 . 0 .

Mehlich (1976) deve loped a b u f f e r f o r t h e r a p i d e s t ima-

t i o n o f u n b u f f e r e d s a l t - exchangeab le a c i d i t y and l i m e

r equ i r emen t . Th i s method was p r i m a r i l y c a l i b r a t e d a g a i n s t

exchangeable a c i d i t y . The l i m e recommendations made a r e based

on t h e n e u t r a l i z a t i o n o f a p o r t i o n o f t h e exchangeable

a c i d i t y r a t h e r t h a n t h e amount needed t o a t t a i n a t a r g e t pH.

T h i s b u f f e r e x h i b i t e d l i n e a r i t y from pH 6 . 6 t o 4 .0 .

Nommik (1983) deve loped a b u f f e r t o measure t i t r a t a b l e

a c i d i t y and LR on Swedish s o i l s . The b u f f e r had a l i n e a r p H

r ange from pH 7 .00 t o 5 . 2 0 . H e found t h e new b u f f e r method

was s a t i s f a c t o r i l y c o r r e l a t e d w i t h b o t h t h e Yuan DB and t h e

SMP methods.

About twenty y e a r s a f t e r 'woodruff mod i f i ed h i s o r i g i n a l

b u f f e r method, work s u p p o r t i n g t h e change was f i n a l l y pub-

l i s h e d (Brown and Cisco , 1 9 8 4 ) . The new b u f f e r was i n t e n d e d

t o more a c c u r a t e l y r e f l e c t t h e c o n t r i b u t i o n of aluminum. They

c a u t i o n e d t h a t t h e method shou ld n o t be adop ted on U l t i s o l s

and O x i s o l s u n t i l it had been p r o p e r l y c a l i b r a t e d f o r t h o s e

s o i l s . The b u f f e r method was d e s i g n e d f o r a c i d s o i l s w i t h a

l i m e r equ i r emen t 1 1 0 cmol (+) kg''.

Double b u f f e r Methods

Yuan (1974) f i r s t p roposed t h e double b u f f e r c o n c e p t . The

method was b a s e d on two s e p a r a t e measurements i n b u f f e r

s o l u t i o n s of t h e same compos i t ion b u t i n i t i a l l y a d j u s t e d t o

pH 6.0 and 7 . 0 . This allowed t h e i n d i v i d u a l b u f f e r i n g

c a p a c i t y of each s o i l t o be determined. The s o i l a c i d i t y t o

be n e u t r a l i z e d was determined by t h e b u f f e r i n g p r o p e r t y of a

s o i l which, i n t u r n , was de f ined by d i v i d i n g t h e d i f f e r e n c e

i n s o i l a c i d i t y n e u t r a l i z e d i n t h e two b u f f e r systems by t h e

d i f f e r e n c e of t h e two equ i l ib r ium pH v a l u e s .

McLean e t a l . (1978) borrowed Yuan's double b u f f e r

concept and a p p l i e d it t o t h e o r i g i n a l SMP b u f f e r method.

They a d j u s t e d t h e two b u f f e r s o l u t i o n s t o i n i t i a l pH va lues

of 6 . 0 and 7 .5 . They found t h e double b u f f e r procedure (SMP

DB) t o be more promising- a s an improved method, e s p e c i a l l y o n

s o i l s of low lime requirement where t h e SMP SB method was

known t o l a c k accuracy.

S o i l Ac ld l tv . .

The forms and sources of s o i l a c i d i t y i n f l u e n c e t h e

b u f f e r i n g c a p a c i t y of a s o i l . Through an i n c r e a s e d under-

s t and ing of s o i l a c i d i t y , s c i e n t i s t s have been a b l e t o

improve t h e r a p i d lime requirement methods.

S o i l s c i e n t i s t s spen t t h e f i r s t h a l f of t h e Twentieth

Century deba t ing t h e n a t u r e of s o i l a c i d i t y . Jenny (1961)

desc r ibed t h i s debate a s a merry-go-round, t h a t began with

Al-clay t h e o r i e s i n i t i a t e d by Veitch i n 1904. In 1922, Van

d e r Spek promoted t h e concept of H-clays . This theory

dominated f o r t h i r t y y e a r s . In t h e e a r l y and mid f i f t i e s , N .

T . Coleman and co-workers a s wel l a s P . L . Low, convinced

Americans once again t o accept the Al-clay theory f i r s t

advanced by Veitch f i f t y years before.

Soi l ac id i ty can be divided i n t o three forms, ac t ive

ac id i ty , exchangeable ac id i ty , and t o t a l a c i d i t y . Active

ac id i ty i s expressed as the pH of a s o i l . I f the s o i l pH i s

7.0 the s o i l i s considered a lka l ine . S o i l pH governs,

among others , nut r ien t a v a i l a b i l i t y t o p lants (Corey, 1973),

as well a s microbial a c t i v i t y in the s o i l (Stotzky, 1 9 7 2 ) .

Exchangeable ac id i ty i s defined as t h a t which is

replaceable by the cation of a neut ra l unbuffered s a l t such

as K C 1 , CaC12, or NaCl (Lin and Coleman, 1 9 6 0 ) . Theoretically t h i s value measures the amount of ac id i ty present in the s o i l

a t the pH of the s o i l or a t l e a s t a t the pH of the s o i l - s a l t

solut ion. Exchangeable ac id i ty i s due almost e n t i r e l y t o

monomeric A13+ (Coleman e t a l . , 1959; Dewan and Rich, 1 9 7 0 ) .

Yuan (1959) observed t h a t H+ dominated over A13+ i n the

exchangeable a c i d i t y f o r some Florida s o i l s , where organic

matter was an important contributor t o the cat ion exchange

capacity (CEC) . Thomas and Hargrove (1984) f e l t t h i s might have been more apparent than r e a l because some of the H+ Yuan

observed was probably from the hydrolysis of A13+ held i n

nonexchangeable form by the organic matter.

Total ac id i ty i s t h a t which i s neutralized a t a

designated pH. Opinion has sh i f t ed toward the use of

BaC12-TEA a t pH 8 .2 (Thomas, 1 9 8 2 ) . T o t a l a c i d i t y g i v e s an

i n d i c a t i o n o f t h e amount o f a c i d i t y t h a t must be n e u t r a l i z e d

t o a t t a i n a pH somewhere between t h e o r i g i n a l s o i l pH and pH

' . 8 . 2 . T h i s v a l u e would g i v e a n i n d i c a t i o n o f t h e l i m e

. r equ i r emen t o f a s o i l .

B u f f e r i n s C a ~ a c i t v

The b u f f e r i n g c a p a c i t y o f a s o i l i s i t s a b i l i t y t o resist

pH change. The g r e a t e r t h e b u f f e r i n g c a p a c i t y o f a s o i l t h e

g r e a t e r i t s l ime r equ i r emen t .

There a r e s e v e r a l ways a s o i l can e x h i b i t b u f f e r i n g

c a p a b i l i t i e s . Most impor t an t i n h i g h l y wea thered s o i l s a r e

c r y s t a l l i n e and n o n c r y s t a l l i n e o x i d e s and hydrous o x i d e s of

A 1 and Fe, k a o l i n i t e , and a l l o p h a n e . The m i n e r a l s have

s u r f a c e hyd roxy l s t h a t p r o t o n a t e o r d e p r o t o n a t e i n r e sponse

t o pH f l u c t u a t i o n s (Keng and Uehara, 1 9 7 4 ) . A c i d i c g roups i n

o r g a n i c m a t t e r , mos t ly c a r b o x y l s , a l s o i o n i z e a t h i g h e r pH

l e v e l s r e l e a s i n g H+ i o n s (Stevenson, 1 9 8 2 ) . The H' i o n s

r e l e a s e d from b o t h t h e m i n e r a l and o r g a n i c m a t t e r can

n e u t r a l i z e any added b a s e s .

Role o f A 1 i n S o i l QH B u f f e r i n q

Aluminum h y d r o l y s i s i s a s s o c i a t e d w i t h b o t h t h e m i n e r a l

and o r g a n i c f r a c t i o n s of t h e s o i l and can be a s i g n i f i c a n t

c o n t r i b u t o r t o t h e b u f f e r i n g c a p a c i t y of a s o i l . Hydrogen

i o n s a r e s u b s e q u e n t l y r e l e a s e d a c c o r d i n g t o t h e f o l l o w i n g

sequence of r e a c t i o n s o c c u r r i n g i n a c i d s o i l s ( T i s d a l e and

Nelson, 1975) :

I / ~ 1 ~ ' + H20 C--> A 1 (OHl2 ' + H+

2 / A 1 (OH) *+ + H20 A 1 (OH) 2f + H' 3 / A 1 (OH) H20 A 1 (OH) + H+

The ~ 1 ~ ' ion i s predominant below pH 4.7, A 1 ( O H ) 2 f

between pH 4.7 and pH 6.5, and A l ( O H I 3 between pH 6 . 5 and pH

8.0 (Bohn e t a l . , 1979) . The r e a c t i o n products of A 1 hydroly- sis may remain i n s o i l s o l u t i o n , be adsorbed a s monomers t o

CEC sites of t h e s o i l , be adsorbed and then polymerized on

s u r f a c e s of c l a y minera ls , o r be adsorbed and then complexed

by o r g a n i c mat te r (McLean, 1976) . The H+ i o n s r e s u l t i n g from

h y d r o l y s i s lower t h e pH of t h e s o i l s o l u t i o n and r e a c t with

s o i l minera l s t o f u r t h e r break them down.

The presence of A 1 and Fe on o rgan ic m a t t e r exchange

s i t e s causes t h e o rgan ic mat te r t o e x h i b i t a g r e a t e r weakness

a s an a c i d . This r e s u l t s i n l e s s c o n t r i b u t i o n t o t h e CEC

determined by e x t r a c t i o n with a n e u t r a l s a l t s o l u t i o n , o r

e f f e c t i v e c a t i o n exchange c a p a c i t y ( E C E C ) , of t h e s o i l ,

e s p e c i a l l y a t low pH values (Hargrove and Thomas, 1 9 8 4 ) . A 1

forms r a t h e r s t a b l e complexes with t h e s o i l o r g a n i c mat te r by

r e a c t i o n p r i m a r i l y with carboxyl groups and t o a l e s s e r

e x t e n t with pheno l i c hydroxyl groups (Hargrove and Thomas,

1984) . The amount of complex formed i s dependent on t h e pH

and t h e ~ 1 ~ ' concen t ra t ion i n t h e s o i l s o l u t i o n (Hargrove and

Thomas, 1984) . Schn i t ze r and Skinner (1963) r e p o r t e d t h a t A1

was predominantly hydroxylated i n o rgan ic mat te r a s A 1 ( O H ) 2'.

Base Saturat ion

The base sa tura t ion (BS) of a s o i l can be expressed i n

several ways. There a re several fac tors which can influence

the reported BS of a s o i l . Base saturat ion and i t s re la t ion-

ship t o s o i l pH plays an in teg ra l pa r t i n the determination

of lime requirement by the Adams-Evans lime requirement

method. There a re several fac tors t h a t influence the measure

of base sa tura t ion i t s e l f as well as the use of the s o i l

pH-base sa tura t ion relat ionship tha t de t rac t from i t s

usefulness i n lime requirement methods.

Percent base saturat ion i s a measure of the amount of

exchangeable bases, mostly Ca, Mg, Kt and Na, t h a t occupy the

cation exchange s i t e s of a s o i l . The other s i t e s a re occupied

by ac id ic cations, mostly A 1 and H . Base unsaturation ( B U ) i s

simply the complement of B S .

- relations hi^

Adams and Evans (1962) used a BU (exchangeable ac id i ty

divided by exchangeable bases plus exchangeable ac id i ty )

versus pH i n water relat ionship from 348 red-yellow Podzolic

s o i l s as a bas is of t h e i r method. The re la t ionship was used

t o describe the general buffering capaci t ies of a group of

s o i l s . Even though they employed t h i s generalized relat ion-

ship, they a l s o s t a t ed t h a t since no constant re la t ionship

exis ted between s o i l pH and BU for a l l s o i l s , pH was

considered t o be a measure of BS only for a pa r t i cu la r s o i l .

The major reason t h a t s o i l s e x h i b i t d i f f e r e n t b u f f e r i n g

c a p a c i t i e s i s t h a t t h e type of base exchange m a t e r i a l

i n f l u e n c e s t h e pH-BS r e l a t i o n s h i p . Mehlich (1942b) us ing

BaC12-TEA a s t h e e x t r a c t a n t , found k a o l i n i t e , which a c t s a s a

weak a c i d , t o be on ly 65% BS a t pH 7 .0 , whereas montmoril-

l o n i t e was 95% BS a t pH 7 . 0 . The BS values f o r o rgan ic mat te r

were between t h e va lues f o r k a o l i n i t e and montmori l loni te f o r

almost t h e e n t i r e pH range.

Base s a t u r a t i o n g e n e r a l l y i n c r e a s e s with an i n c r e a s e i n

s o i l pH f o r a group of s o i l s . Peech (1939) r e p o r t e d on t h e

pH-BS r e l a t i o n s h i p f o r F l o r i d a c i t r u s s o i l s . He determined

CEC by pH 7.0 1MNH40Ac. Base s a t u r a t i o n was determined by

s u b t r a c t i n g exchangeable bases from t h e CEC and d i v i d i n g t h a t

by t h e CEC. He used a non l inea r r e l a t i o n s h i p t o show t h a t

s o i l s were w e l l bu f fe red between pH 5 .0 t o 6 . 5 . Base

s a t u r a t i o n was 25% a t pH 5.0 and 90% a t pH 6 .5 .

Recent l i t e r a t u r e has shown t h a t t h e pH-BS r e l a t i o n s h i p

i s a l i n e a r one (Loynachan, 1981; Magdoff and B a r t l e t t ,

1985) . I n a l l of t h e pH-BS r e l a t i o n s h i p s shown, t h e r e i s a

wide s c a t t e r of p o i n t s about t h e r e g r e s s i o n l i n e , r e g a r d l e s s

of t h e shape of t h e r e g r e s s i o n l i n e . D i f f i c u l t i e s have been

encountered when applying t h i s r e l a t i o n s h i p t o ve ry poor ly

buf fe red s o i l s such a s t h o s e commonly found i n F l o r i d a (Yuan,

1974) .

Use of t h e pH-BS curve impl ies t h a t a l l of t h e s o i l s used

have a t i t r a t i o n curve s i m i l a r t o each o t h e r a s wel l a s t o

the general pH-BS curve. Soi l s ac tua l ly exhibi t widely

d i f fe r ing t i t r a t i o n curves (McLean e t a l . , 1 9 6 0 ; Magdoff and

B a r t l e t t , 1985) . Measurement of Base Saturatioq

Debate a l so occurs as t o what c r i t e r i a a re t o be used t o

determine base sa tura t ion . One way i s t o use a buffered ex-

t r a c t a n t such as BaC12-TEA a t pH 8.2 or NH,OAc a t p H 7.0 t o

measure t o t a l exchangeable cations (Peech, 1939; Mehlich,

1942b) . Coleman e t a l . (1959) proposed determining percent base

sa tura t ion based on the ECEC, where a neut ra l s a l t such as

K C 1 i s used t o ext rac t the exchangeable cations a t the pH of

the s o i l under f i e l d conditions.

Sanchez ( 1 9 7 6 ) reported tha t calculat ing base saturat ion

based on BaC12-TEA a t pH 8.2 or pH 7.0 1 M NH40Ac makes a s o i l

seem more acid than it i s i f the f i e l d pH i s lower than the

pH of the ext rac tant . He c i t ed work by Buol in 1973, where

Buol compared 88 s o i l s from the Midwest, and the Southeast

U.S., and Puerto Rico and found 35% base sa tura t ion a t pH 8.2

was equal t o 55% base saturat ion a t e f fec t ive C E C . For sandy

s o i l s or s o i l s with >1% organic matter, the re la t ionship

would be d i f f e r e n t .

Methods measuring CEC, which a re determined a t pH values

appreciably higher than the s o i l pH, overestimate the

a b i l i t y of var iable charge s o i l t o r e t a in cations i n the

f i e l d (Horn e t a l . , 1982; Gillman e t a l . , 1983) . Methods more

cons i s t en t with f i e l d condi t ions should be used f o r agronomic

eva lua t ion (Gillman e t a l . , 1983) . C h a r a c t e r i s t i c s of F lor ida S o i l 3

A general knowledge of some of t he p rope r t i e s of

F l o r i d a ' s s o i l s can give an i nd i ca t i on of t h e i r buf fe r ing

c h a r a c t e r i s t i c s . Most of F l o r i d a ' s t o p s o i l s a r e sandy. The

p a r t i c l e s i z e f r a c t i o n i s o f t en composed of g r e a t e r than 95%

sand. Clay contents of t h e t o p s o i l s a r e r e s u l t a n t l y a l s o low.

Using published da t a accumulated by t h e S o i l Character-

i z a t i o n Lab a t t he Universi ty of F lor ida (Calhoun e t a l . ,

1974; C a r l i s l e e t a l . , 1978, 1981, and 1985) s eve ra l

gene ra l i za t i ons of t h e p rope r t i e s of F l o r i d a ' s sur face s o i l s

according t o s o i l order can be made. Most of t h e En t i so l s and

Spodosols have a c l ay content of l e s s than 4 % and a CEC (pH

7.0 NH40Ac) of l e s s than 10 meq 100 g'l s o i l . The U l t i s o l s

tend t o have a s l i g h t l y higher c lay content but t h e CEC i s

s t i l l r e l a t i v e l y low. Organic matter content f o r t h e U l t i s o l s

and En t i so l s tends t o range from 1 t o 2 % . The Spodosols tend

t o have a h igher organic mat ter with most s o i l s ranging from

2 t o 3% organic mat te r . The c l ay f r a c t i o n i s usua l ly

dominated by k a o l i n i t e , h a l l o y s i t e , g ibbs i t e , quar tz , and . . .,

vermicul i te ( F i s k e l l and C a r l i s l e , 1963) .

The organic matter i s t h e most important con t r i bu to r t o

t h e CEC of ac id , sandy F lor ida v i r g i n t o p s o i l s (Yuan e t a l . ,

1967) . They found t h a t organic matter con t r ibu ted from 66 t o

96% of t h e CEC depending on t h e s o i l o rde r .

Zelazny e t a l . ( 1 9 7 4 ) found clay content t o give a higher

cor re la t ion coeff ic ient with t o t a l ac id i ty of f i f t e e n surface

s o i l s of Florida Paleudults than organic matter whereas

organic matter gave a higher cor re la t ion coeff ic ient with

exchangeable a c i d i t y .

Methods of Testina .Lime Reauirement Methods

Due t o the d ive r s i ty of forms of s o i l ac id i ty along with

the influence of s o i l solution pH on t h e i r a v a i l a b i l i t y ,

changes i n pH should be gradual so t h a t a l l avai lable ac id i ty

a t a pa r t i cu la r pH i s neutralized (McLean, 1982a). This i s an

important consideration when attempting t o use a quick-test

buffer method, where the s o i l i s subjected t o sudden pH

changes, as a measure of the e f fec t of lime in the f i e l d

where the changes a re much more gradual.

I n cor re la t ion s tudies , the researcher i s attempting t o

discern a lime requirement method t h a t provides an accurate

index of t h e lime needs of s o i l samples representat ive of the

area of i n t e r e s t . Calibration s tudies provide f i e l d r e s u l t s

t h a t a re used as the bas is fo r recommendations (Hanway,

1973) . - McLean e t a l . ( 1 9 6 6 ) l i s t e d the order fo r lime require-

ment t e s t methods,. with respect t o increasing amount of time

needed fo r completion a s : pH measurement < t i t r a t i o n < incu-

bation < f i e l d s tudies . Early researchers r e l i e d primarily on

f i e l d s tudies t o base lime recommendations. Besides requiring

a long time f o r completion, f i e l d t r i a l s a l s o l i m i t t h e re-

searcher a s t o t h e amount and v a r i e t y of s o i l s t h a t can be

s tud i ed . A s they began t o develop labora tory t e s t s they s t i l l

used f i e l d t r i a l s a s well a s pot and labora tory incubations

a s a b a s i s of comparison. With t h e advent of more accura te

and r ap id l abora tory methods, some of t h e o lder more t ed ious

l abora tory methods were used a s t h e b a s i s of comparison o r

" ac tua l lime requirement. "

Examples of commonly used reference methods today include

t h e CaC03-soil incubation method (Webber e t a l . , 1 9 7 7 ;

Shoemaker e t a l . , 1 9 6 1 ) which can l a s t from one month up t o

1 7 months o r more. A second reference method used i s t h e

BaC12-TEA method by Peech, which i s a modificat ion of

Mehlich's e a r l i e r method, and takes one t o two days t o

complete. The Ca(OH)2 t i t r a t i o n method i s a l s o commonly

employed a s reference method. The most recen t modificat ion of

t h e method by McLean e t a l . (1978) t akes s eve ra l days t o

complete. Although they a r e not used a s f requent ly , f i e l d

s t u d i e s a r e s t i l l very important f o r c o r r e l a t i n g labora tory

t e s t da t a with a c t u a l f i e l d response (Yuan e t a l . , 1 9 7 7 ,

1978; Baker and Chae, 1977) .

S a l t Accumula t io~

Although a long term l ime-soil incubation appears t o be

t h e bes t method sho r t of f i e l d t r i a l s , t h e r e a r e some

problems assoc ia ted with i t . Microbial a c t i v i t y i s in tense

under incubation condi t ions where t h e s o i l i s a t o r near

f i e l d c a p a c i t y and a t room t e m p e r a t u r e . S a l t s ( p a r t i c u l a r l y

n i t r a t e s o f Ca, Mg, and K) accumula te i n t h e s o i l (McLean,

1 9 8 2 a ) . These s h o u l d be l e a c h e d o u t o r o t h e r w i s e t a k e n i n t o

accoun t l es t t h e y d e p r e s s t h e s o i l pH.

Dumford (1965) r e p o r t e d t h a t on 38 a c i d s o i l s of t h e

U . S . , w i t h o r g a n i c m a t t e r c o n t e n t s r ang ing from 0.2 t o 6 .0%,

less sa l t was p r e s e n t on t h e ave rage a t t h e end o f t h e

i n c u b a t i o n p e r i o d t h a n t h e e q u i v a l e n t o f 0.02M CaCl*. Baker

and Chae (1977) found t h a t t h e pH i n CaC12 o f t h e i r unl imed

s o i l s dropped d u r i n g i n c u b a t i o n . They s p e c u l a t e d t h a t t h i s

was due t o o r g a n i c m a t t e r decompos i t ion .

Bes ides l e a c h i n g o r measur ing pH i n a s a l t s o l u t i o n some

o t h e r methods have been t r i e d t o overcome t h e s a l t problem.

Some workers have u sed greenhouse p o t t r i a l s p l a n t e d w i t h a

c r o p (Brown and Cisco , 1984; Loynachan, 1 9 8 1 ) . The e f f e c t o f

wa te r l e a c h i n g th rough t h e s o i l a s w e l l a s p l a n t up t ake of

n u t r i e n t s would s e r v e t o p r e v e n t accumula t ion o f s a l t s . Dunn

(1943) u sed t h r e e d rops o f ch loroform, i n 100 c c d i s t i l l e d

water t o 10 g s o i l suspens ion ; i n a f o u r day i n c u b a t i o n s t u d y

t o p r e v e n t m i c r o b i a l a c t i v i t y . Nommik (1983) added 10 ppm

d icyandiamide t o a t e n week i n c u b a t i o n s t u d y t o s u p p r e s s

n i t r i f i c a t i o n . The o r g a n i c m a t t e r c o n t e n t o f t h e s o i l s ranged

from 30%.

An o p p o s i t e e f f e c t o f s a l t accumula t ion r e s u l t s i f t h e

l i m e s t o n e does n o t comple t e ly r e a c t w i t h t h e s o i l , where pH

v a l u e s can b e a r t i f i c i a l l y h i g h . Baker and Chae (1977) found

t h a t l e s s l ime was requ i red when s o i l s and lime were not wel l

mixed due t o t h e presence of s i g n i f i c a n t amounts of unreacted

CaC03 a t a l l but t h e lowest l ime l e v e l s .

Com~ar i son of Reference Methods

A s r e s e a r c h e r s have moved t o us ing r e l a t i v e l y shor t . term

ana lyses a s a measure of a s o i l s l ime requirement , t h e

ques t ion remains a s t o what t h e t r u e lime requirement of a

s o i l i s . Some workers have compared some of t h e r e f e r e n c e

methods o r modi f i ca t ions of them. Yuan (1974) compared t h e

BaC12-TEA method of Peech (1 965) with a Ca (OH) 2-CaC12 one

week incuba t ion on twenty F l o r i d a s o i l s . The mean &R

determined by t h e BaC12-TEA method was 4.54 T / A CaC03 a s

compared t o 4.47 T /A CaC03 f o r Ca(OH)2-CaC12. McLean e t a l .

(1978) r e p o r t e d t h a t Ca(OH)2 t i t r a t i o n t o pH 7.2 with 72

hours of i n t e r m i t t e n t shaking gave va lues an average of 5%

lower than t h o s e f o r CaC03 incubat ion t o pH 6.8 f o r 17 months

Fox (1980) compared t h e BaC12-TEA method of Peech (1965) ,

t h e Ca(OH)2 t i t r a t i o n of McLean e t a l . (1978), and a s i x

month CaC03 incuba t ion . The BaC12-TEA method overes t imated

t h e CaC03 incuba t ion LR below 9.28 meq CaC03 100 g-I s o i l and

underes t imated t h e LR above 9.28 meq CaC03 100 g-I s o i l . The

Ca(OHI2 t i t r a t i o n underest imated t h e CaC03 incuba t ion LR f o r

a l l de te rmina t ions . A t 2 and 4 meq CaC03 100 g-I s o i l , t h e

Ca(OH)2 method es t ima ted only 29% and 39% of t h e CaC03 LR,

r e s p e c t i v e l y .

Brown and Cisco (1984) compared t h e Ca (OH) 2-CaC12

t i t r a t i o n of Benham (1970) t o a CaC03 incubation-cropping

greenhouse method. The LR by t h e CaC03 incubation-cropping

method overest imated Ca (OH) 2-CaC12 LR values of 2 , 4 , and 8

cmol (+) kg-', by 1 9 4 % , 136%, and 1 1 9 % , r e spec t ive ly .

Effect iveness of Buffers i n Measurina Tota l S o i l Aciditv

Tota l s o i l a c i d i t y i s usua l ly defined a s t h e amount of

a c i d i t y t h a t must be neu t r a l i zed t o a t t a i n a p H a t o r near

8 .2 . This i s t h e maximum pH a t t a i n a b l e with CaC03 i n t h e

presence of a i r having a C02 content of 0.03% (Bradf ie ld and

Al l ison, 1933) .

The BaC12-TEA method has been regarded a s t h e rap id

method t h a t most c lo se ly approximates t h e t i t r a t i o n method of

Bradf ie ld and Al l ison (Thomas, 1982) . However, Shoemaker e t

a l . (1961) found t h a t t h e BaC12-TEA buf fe r d id not r e a c t with

a l l of t h e ex t r ac t ab l e A l . Since A 1 i s an important component

of s o i l buf fe r ing , through A 1 hydrolys is , t h i s means t h a t t h e

BaC12-TEA buf fe r does not r eac t with a l l of t h e a c i d i t y

present i n t h e s o i l .

Adams and Evans (1962) repor ted t h a t t h e i r bu f f e r

measured s l i g h t l y more a c i d i t y than was measured by 1 M NH40Ac

(pH 7 . 0 ) e x t r a c t i o n . Acidity, by t h e l a t t e r method, was

ca l cu l a t ed by sub t r ac t i ng t o t a l bases from t h e NH40Ac

measured CEC.

The AE buf fe r measured l e s s a c i d i t y than t h e BaC12-TE~

(pH 8.2) method f o r F lor ida s o i l s (Yuan, 1 9 7 4 ) . This may have

been due t o the a b i l i t y of the stronger BaC12-TEA b u f f e r ' s

a b i l i t y t o react w i t h more s o i l ac id i ty than the AE buffer .

Shoemaker e t a l . ( 1 9 6 1 ) reasoned t h a t buffers weaker than

BaC12-TEA would be expected t o ext rac t l e s s s o i l a c i d i t y .

Field C u r a t i o q

Recommendations based on laboratory analyses a re usually

multiplied by a 'liming f a c t o r ' when making f i e l d liming

recommendations. The liming fac tor accounts fo r the decreased

effect iveness of ag r i cu l tu ra l limestone applied in the f i e l d

versus the f ine ly ground CaC03 used i n laboratory and pot

s tudies . The reduced effectiveness i s due t o the la rger

p a r t i c l e s i z e of ag r i cu l tu ra l limestone and incomplete.mixing

of lime i n the f i e l d . The Adams and Evans method incorporates

a liming fac to r of 1 . 5 based on previous data of P ie r re and

Worley (1928) and Schollenberger and Sa l t e r (1943) . Thomas and Hargrove (1984) s t a t ed t h a t since in pract ice,

lime appl icat ions cannot be made t h a t precisely, inaccuracies

in the method a re not l ike ly t o cause major problems. Adams

(1984) supported the previous point of view, fee l ing t h a t a

high degree of precision i n methods i s usually wasted because

of problems encountered i n the f i e l d appl icat ion of lime.

These problems include s o i l var iat ion, lime spreading

i r r e g u l a r i t i e s , lime qual i ty , and incomplete mixing of the

lime with s o i l . McLean (1982b) countered w i t h h i s argument

tha t the option of taking some addi t ional simple s teps with

the double buffer method a f t e r taking the reading fo r the

s i n g l e b u f f e r method s h o u l d be weighed a g a i n s t t h e i n c r e a s e d

a c c u r a c y of measurement, e s p e c i a l l y f o r s o i l s o f low l ime

r equ i r emen t .

C a l c u l a t i o n of Adams-Evans Lime Requirement

A b r i e f e x p l a n a t i o n o f t h e c a l c u l a t i o n o f t h e AE LR w i l l

b e p r e s e n t e d . A more d e t a i l e d example o f t h e c a l c u l a t i o n i s

g i v e n by Rhue and Kidder ( 1 9 8 4 ) .

De te rmina t ion o f t h e AE LR employs two major s t e p s , one a

l a b o r a t o r y measurement and t h e o t h e r a set o f c a l c u l a t i o n s .

I n t h e l a b o r a t o r y s t e p a known amount o f b u f f e r i s added t o a

known q u a n t i t y o f s o i l . The b u f f e r i s fo rmula t ed w i t h a

b e g i n n i n g pH o f 8 .00 and has t h e p r o p e r t y o f a l i n e a r

d e c r e a s e i n pH between 8 .00 and 7 .00 . Thus t h e amount o f

a c i d i t y n e u t r a l i z e d by t h e b u f f e r i s de t e rmined by measur ing

t h e s o i l - b u f f e r e q u i l i b r i u m pH. The amount o f a c i d i t y

n e u t r a l i z e d by t h e b u f f e r w i l l be h e r e i n r e f e r r e d t o a s t h e

AE t o t a l a c i d i t y (TA) . The c a l c u l a t i o n s t e p of AE LR i n v o l v e s d e t e r m i n i n g t h e

p e r c e n t o f AE TA t h a t must be n e u t r a l i z e d t o a t t a i n a d e s i r e d

s o i l - w a t e r pH (pH,). T h i s s t e p i s n e c e s s a r y because t h e s o i l

b u f f e r e q u i l i b r i u m pH w i l l b e h i g h e r t h a n t h e pH, normal ly

d e s i r e d f o r c r o p s . The b u f f e r t h e o r e t i c a l l y n e u t r a l i z e s more

pH-dependent s o i l a c i d i t y a t t h e h i g h e r s o i l - b u f f e r pH

(between 8 .0 and 7 . 0 ) t h a n would need t o be n e u t r a l i z e d a t

t h e lower pH, v a l u e d e s i r e d f o r p l a n t s . T h i s i s e s p e c i a l l y

important f o r F l o r i d a ' s sandy s o i l s where much of t h e

b u f f e r i n g c a p a c i t y i s pH-dependent.

The c a l c u l a t i o n employs t h e pH-BU r e l a t i o n s h i p found f o r

348 Alabama U l t i s o l s dams and Evans, 1 9 6 2 ) . The BU va lue

f o r a p a r t i c u l a r pH can be determined from t h e c u r v i l i n e a r

r e g r e s s i o n equa t ion t h a t was determined t o g ive t h e b e s t f i t

f o r t h e pH-BU r e l a t i o n s h i p .

Thus, knowing t h e i n i t i a l pH, of t h e s o i l , t h e d e s i r e d

pH, of t h e s o i l , and t h e AE TA, t h e fo l lowing equa t ion of

Adams and Evans (1962) i s used t o determine t h e AE LR:

AE LR = AE TA x (Desired change i n BU) I n i t i a l BU

The AE TA i s c a l c u l a t e d from t h e s o i l - b u f f e r e q u i l i b r i u m

pH. The i n i t i a l BU i s c a l c u l a t e d from t h e i n i t i a l pH, of t h e

s o i l and t h e r e g r e s s i o n equat ion f o r t h e pH-BU r e l a t i o n s h i p .

The d e s i r e d change i n BU i s c a l c u l a t e d by s u b t r a c t i n g t h e BU

va lue corresponding t o t h e d e s i r e d pH, from t h e BU va lue

corresponding t o t h e i n i t i a l pHw of t h e s o i l . The r e s u l t i n g

AE LR i s t h e amount of CaC03 t h a t w i l l n e u t r a l i z e t h e p o r t i o n

of AE TA necessary t o a t t a i n t h e d e s i r e d pH,. The LR may be

p resen ted i n terms of a g r i c u l t u r a l l imestone i f a ' l iming

f a c t o r ' i s a p p l i e d t o t h e CaC03 LR.

Previous Evaluat ions of Lime Reauirement Methods

The va r ious r a p i d s o i l t e s t l ime requirement methods have

been e v a l u a t e d by many workers and on a wide assor tment of

s o i l s . This s e c t i o n w i l l d e t a i l t h e s t r e n g t h s and weaknesses

of the various methods. The Adams-Evans method and the SMP S B

method a re included because they a re current ly being used by

ce r t a in organizations i n Flor ida. The Yuan DB i s included

because it was developed spec i f i ca l ly fo r Florida s o i l s .

Since the SMP DB i s reportedly an improvement of the SMP SB

method it was a l so included i n the review. The reference

methods, t a r g e t pH levels , and the s o i l s used by the workers

d i f fered from experiment t o experiment, making it d i f f i c u l t

t o compare r e s u l t s between experiments. However, general

observations can be made and these a re presented next.

Adams-Evans Buffer Method

Adams and Evans ( 1 9 6 2 ) data showed t h a t the AE method

tended t o underestimate the LR of three s o i l s when compared

t o CaC03-soil incubation. The difference between AE estimated

and incubation predicted LR decreased as the LR decreased.

Although McLean e t a l . ( 1 9 6 6 ) did not publish data for

the AE method, they did evaluate i t . They mentioned t h a t the

AE method predicted l e s s lime than the SMP SB method when

CaC03-soil incubation was used as the reference method. I t

can then be infer red from the published data t h a t the AE LR

underestimated the LR as predicted by the CaC03-soil

incubation.

Fox (1980) reported a high corre la t ion ( r = 0.919) for

the AE versus CaC03-soil incubation. The AE overestimated the

s o i l LR fo r s o i l s requiring

underest imated t h e s o i l LR f o r s o i l s r e q u i r i n g >4.87 meq 1 0 0

g'l s o i l .

Yuan (1975) c o r r e l a t e d t h e AE t o BaC12-TEA method a t pH

8 . 1 ( r = 0.78) f o r 31 F l o r i d a s o i l s . The AE only p r e d i c t e d

1 /3 of t h e LR of t h e re fe rence method. Yuan f e l t t h a t only

p a r t of t h i s d i f f e r e n c e was because t h e AE LR g i v e s t h e

amount of l ime requ i red t o r a i s e t h e s o i l pH t o 6 . 5 , while

t h e BaC12-TEA method e s t i m a t e s t h e t o t a l a c i d i t y . Most of t h e

d i f f e r e n c e was apparen t ly due t o d i s c r e p a n c i e s i n t h e AE LR

method i t s e l f .

Contrary t o t h e f i n d i n g s of t h e previous papers , Tran and

van Lierop (1981) found t h e average AE LR was 145% of t h a t

determined by t h e CaC03-soil incuba t ion . Using a wider

s o i 1 : b u f f e r r a t i o ( 1 : 4 ) expanded t h e b u f f e r range, improved

t h e c o r r e l a t i o n , and was only 1 1 4 % of t h e CaC03-soil

incuba t ion determined LR.

Yuan Double Buffer Method

Yuan (1974) compared t h e Yuan DB method t o both t h e

BaC12-TEA method and t h e Ca(OHI2 t i t r a t i o n - i n c u b a t i o n us ing

20 F l o r i d a s o i l s . The Yuan DB was h igh ly and e q u a l l y cor re -

l a t e d t o both re fe rence methods ( r = 0 . 9 7 ) . Yuan DB method

e s t i m a t e s of 1 .0 , 2 .0, and 4.0 T / A compared t o 1 .38 , 2 . 3 6 ,

and 4.32 T /A a s determined by t h e BaC12-TEA method. The

Ca(OH)2 method gave r e s u l t s comparable t o t h e BaC12-TEA

method.

Yuan (1975) found a v e r y h i g h c o r r e l a t i o n f o r 4 4 F l o r i d a

s o i l s between t h e Yuan DB method and t h e BaC12-TEA method

( r = 0 . 9 9 ) . Yuan DB method LR e s t i m a t e s o f 0 . 37 , 0 . 85 , and

1 . 8 0 T/A compared t o 0 . 5 , 1 . 0 , and 2 . 0 T/A f o r t h e BaC12-TEA

method, r e s p e c t i v e l y .

'Fox (1980) e v a l u a t e d t h e Yuan DB method on 20 Pennsy l -

v a n i a s o i l s . A b e t t e r c o r r e l a t i o n was d e t e r m i n e d when CaC03-

s o i l i n c u b a t i o n ( r = 0 .967 ) w a s u sed a s t h e r e f e r e n c e method

t h a n when C a ( O H ) 2 t i t r a t i o n ( r = 0 .914 ) w a s u s e d a s t h e

r e f e r e n c e method. Using t h e CaC03-soil i n c u b a t i o n a s a

r e f e r e n c e method, t h e Yuan DB method o v e r e s t i m a t e d t h e LR f o r

s o i l s w i t h a LR 7.44 rneq CaCO) 100 9''

s o i l .

Tran and van L i e r o p (1981) worked w i t h 70 Quebec s o i l s

and a n e i g h t week CaC03-soil i n c u b a t i o n . The Yuan DB method

had a h i g h c o r r e l a t i o n c o e f f i c i e n t (r = 0 .959 ) f o r s o i l s

r a n g i n g i n LR from 1 . 4 t o 40 .0 rneq C a C 0 3 100 9-I s o i l t o pH

6 . 5 . A p o o r e r c o r r e l a t i o n was found f o r s o i l s w i t h a LR

was more a c c u r a t e f o r low lime r e q u i r i n g s o i l s than f o r high

lime r e q u i r i n g s o i l s . I t p r e d i c t e d 89% and 73% of t h e LR,

r e s p e c t i v e l y f o r 54 s o i l s from t h e U.S.

Tran and van Lierop (1982) used 37 a c i d , coa r se - t ex tu red

s o i l s . They eva lua ted the.Yuan b u f f e r both a s a double b u f f e r

and a s a s i n g l e b u f f e r (Yuan S B ) . L i n e a r i t y of t h e Yuan SB

method inc reased a s i t s i n i t i a l pH approached t h e d e s i r e d

s o i l pH. The p r e c i s i o n was lower when t h e i n i t i a l pH was 6 .5

versus 6.0 o r 7 . 0 . They f e l t t h i s could be due t o a break i n

t h e t i t r a t i o n curve a t pH 6.2 (Yuan, 1 9 7 6 ) . For a t a r g e t pH

of 5 . 5 (LR5.5) o r a t a r g e t pH of 6.0 (LR6.0) t h e p r e c i s i o n of

t h e r e l a t i o n s h i p was good f o r e i t h e r t h e i n i t i a l b u f f e r pH of

6.0 o r 7 .0 . The DB f o r LR(6.0) had a high c o r r e l a t i o n

c o e f f i c i e n t ( r = 0.97) versus incubat ion wi th CaC03 bu t only

measured an average of 67% of t h e incuba t ion L R . They

proposed us ing a r e g r e s s i o n equat ion t o a d j u s t f o r t h e

d i f f e r e n c e . The DB was l e s s p r e c i s e f o r LR ( 5 . 5 ) ( r = 0.76) . Yet t h e Yuan SB was a s p r e c i s e f o r LR(6.0) and more p r e c i s e

f o r LR(5.5) versus t h e Yuan DB.

Van Lierop (1983) found t h a t t h e Yuan DB performed poor ly

on o rgan ic s o i l s . He f e l t t h i s might be because many of t h e

s o i l - b u f f e r pH values ranged from pH 5 .0 t o 6.0 which f e l l on

t h e c u r v i l i n e a r p o r t i o n of t h e b u f f e r cu rve . A l t e r i n g t h e

s o i l - b u f f e r r a t i o t o 1 : 5 v o l / v o l t o r a i s e t h e s o i l - b u f f e r pH

t o t h e l i n e a r p o r t i o n of t h e curve d i d not t h e improve t h e

precision of the method as it resul ted i n a lowering of the

corre la t ion coeff ic ient .

SMP Sinale Buffer Method

The SMP SB LR method has been evaluated by numerous

researchers. Most of the researchers report tha t the SMP SB LR

method underestimates the LR fo r low lime requiring s o i l s

(Yuan, 1975; Fox, 1980; Brown and Cisco, 1984).

Most of the workers found the SMP SB LR method t o be

s ign i f i can t ly correlated ( r > 0.90) with t h e i r respective

reference methods (Webber e t a l . , 1977; Loynachan, 1981). The

buffer exhib i t s r e l a t i v e l y l i t t l e buffering capacity from an

i n i t i a l buffer pH of 7.5 down t o a pH of 6 . 9 (McLean, 1978).

The v e r t i c a l change in buffer pH in the pH range o f ' 7 . 5 t o 6 . 9

would be too great t o indicate adequate lime fo r acid s o i l s

very low i n cation exchange capacity (McLean e t a l . , 1 9 6 6 ) .

McLean e t a l . ( 1 9 6 6 ) reported t h a t the SMP SB was reasonably

accurate for s o i l s requiring >4000 lb of lime per acre .

SMP Double Buffer Method

McLean e t a l . (1978) found t h a t through the use of the

SMP DB method and regression equations the e r ro r of estimate

fo r low LR s o i l s could be s ign i f i can t ly improved over the SMP

SB method. However, they s t i l l recommended t h a t the SMP SB was

the most sa t i s fac to ry compromise between s implici ty of

determination and reasonable accuracy fo r s o i l s of a wide

range of lime requirement.

Tran and van Lierop (1982) r e p o r t e d t h a t t h e SMP DB was

not s u b s t a n t i a l l y more a c c u r a t e than t h e SMP SB f o r LR 5 . 5 and

6 .0 . I n a previous paper, Tran and van Lierop (1981) found

t h a t t h e SMP DB d i d not s i g n i f i c a n t l y improve t h e c o r r e l a t i o n

a s compared t o t h e SMP SB.

Fox (1980) found t h e SMP DB overes t imated t h e LR f o r

s o i l s wi th a LR of

CHAPTER I11 INCUBATION STUDY

oduct 1 ~n

Rapid s o i l t e s t methods f o r t h e de te rmina t ion of l ime

requ