FOOD Er AGRICULTURE

ORGANIZATION OF THE

UNITED NATIONS

SOIL MAPPING AND ADVISORY SERVICES

BOTSWANA

PHYSICAL PROPERTIES OF THE

SOILS OF BOTSWANA

GABORONE, 1991

REPUBLIC OF

BOTSWANA

AG : BOT/85/011

FIELD DOCUMENT 33

UNITED NATIONS

DEVELOPMENT

PROGRAMME

Soil Mapping and Advisory Services

Botswana

Physical Properties of thr,

Soils of Botswana

By

Willie D. JoshuaSoil Physicist

an(iç ,. ThE*, C"(

' " H.fp'

1991

The coacJusions given in this report are those considered ap-propriate at the time of its preparation.They may be modified in tho light of furthc?r knowledge gained atsubsequent stages of this project.

ib i ,?` I t- ky0t..ij p " t

pron1N ofFLq.1 C,y(1,a(tHe.,A'

h t FR°, t°,°. ,t,PLIPi tLP(. r r ? t,'-"ot '5, ;'; ° ¡C» t

LOYI P o!'t Cr,

CONTENTS

1 Introduction.---------------------12 Physical PropE of s(

2,i Md,-,ricil,,4 atvi

2.2 RostsPr1,1.ticic!

2.2.2 rulh7.2,3 inf11rali.on-2,2,4 M1.1,r,:- __it

.19.7,cjiab;Thy..

References.... 4 * o 000*V 000.00. 0 0 0 . 0 0 0 . . a 0 O . 024

Appendix Physical properties of soils................ 25

Annex I

,,,, 2

L-LITI;pj dndcontpA,cli,,_.! on ,;-oH phy,i1(2iA:

1;'r rtor rr,,.,I. uvoSeholoj, 1,305W1, ......30

;//I,,/ //1 / /// 0C/di/WI //, $///i1.(0 TV/CÁCi / /C/1 / ......37CH /I/ 4 /..ce/C/ /// IY/ I t //

II CI ditCl//C///u/ ....44

......59

List of Tables

1 par,Lk-ie Jjsirill!Lioo for difEerent..,..............4

2 or(janic Jlarbùr, aTid Oonsit,,,, tor thr,

3 Tuc.nd ir the t_is;lc. irtiltratir)n r,?to2,d.l.fferent :7011

4 :4u tiple regression analysis field -;,'.),.wity

(g) wiLil sand/clay, bulk density and orconicrbon as independentant

5 rgression analysi,s for wl1Linq poot0) with s;ind/clay and .:)i7ganic ,,arbou,ndopondent variables ,.

6 Aveca,it2 and range of ti.el&It-,oinf and evoL.able meistur f,,Dr

soil groups. .....,,,.....,..,

List of Figures

1 Moisture characteristics (FT) curves of sofl12ropresentative soil units in the diffezentsoii groups in Botswana ................................13

1 I NTRODUCT ON

'Ph:13 Bc 31,(1

f Ji' T' H ft tìt soi I uni tsWOtt1.("r. t t.ot ìri to i Lio1 i PAO PONT. i

t,t t Map ( t7t0, I I

vere akr.t.pped as ei 0-).er iz-_Lsoc trit or ,n ," recon,-11,-1 san c'aie. Most f, uho so"t 1 prof c,.,3 h ti wn o s r. r beci

I s o rt.iìpiftd iìr1 c hi:torLori t tt t h t.

r C'; 1tVrH\ ttdf.tz: t 1 H,tt

" \ t', L's 'tt t r, L CH-ttlt,t;t,tx,1H i iri t o vAt,

t,t t ,. I I

Ch44, 4j° hr. o' '0/404 ro4 444H ','!44 h :)Vv\ , ' I , ' '

E''01 ) ,") `' t 0 , ' ' cr

Vt (VC", ." , -

r ;1,' '0' 0 0, 0 ',..'10?),t; !

(' rt-t :" rt7 &I Li s, 1m,

/ " its tt. f-,,t---17: t, t (f,ct, t,tt;h t k t".", ttz n+ I < ,

PC) r V. I ,) .,-", ii ..i) )t: t. '' . i Q .,-Ir r L,,,,t.. -. o",". . 1-. 1,...,...k :,...f.:., ,,'',, ''O,,.. ,, 1-, ,. ,...:,- I, - . , Li ' ;

art Ct it-, k' ('t'q.... i '.: 3. ))' t'...,1" ...".a(..--1- -,...-,,, .-0._),1 I- ht,..t,-, c--- I \,,,, .1.. ' ,t '. 'o )) ') ' V ))'1

s.,i , 1 )). .!° ' ' i V , '') t 1 i i C. ' 11!. ,..('.n.. ',. o t 'Ls, .:".. ?-'..l ..U4..' : --. »I ' I e 't' Lo', ! r ,,

,11' C.: °,1CT''''6.:' , ' ;'.:. tt., ,-) "..,ttr,,,tft t^ts`j -.." t 1 tt, , - t t , " e e M1 e

<t' -) e e e le e e , e ,ee " L,-, r, -0, .. , 0' , ,,,,,, '

h',',..; ' '. "1 ',', '''' `- ,h. i 0 ,s ,: 11 " :, ' ' ., , 0 -0. , , 1 -

, , h .t , ,;,', , ° CC' "

1, - ', ' . 1,0 ';I, h ,.

1 1' » ,, " , ,'. Cc .

I; , , . r '0V V r"t, V

k l' III,

' ''' e e l , , A ' e

, , e

A , t' e. V, oi ° '

h

"b I bII ,k b,,

, 1

b

ób

l'óó b

4 o o

11

2. PHYSICAL PROPERTIES OF SOILS

2.1 Materials and Methods

physir períb(rt W//AY-LA:' "/A! Cin f

,t1s so.:; Witt t ljì ,,,-.0.--)1w1w.t '71v::)n I- ho:;is tr c PiT1 Cut t i1w

".1 1. ::-,u1/1-v oy rri

1.°.Th IÚCIS w, ,Ck Iúkk0;k. i (,) I Ú dorm yi r r Vp,-, 5

. t (tI t n 4 itfiSs ! '.2;, ú '1k sk'ÚtlÚÚJr,i ri t.1 ,"1,,, 'i it t i. -1;n, 5

, -,. zi, , -z z

-k"1° '1H' kúk ' Ú k,i 21 j s," i's,2" v2,1" s, + iv is"

vs;, , o r) v

s, ;,r v ri ,v 11°,'' 1s,t-, ,-1° k 11,

kkÚÚk° Ú úlÚ ú'ú ' ',.° Úúúk '

1111' Úkú 1, '1°' +,1 ' k sk, kk,,Ú Ú , ° 1 kÚ1 kok,° ÚkÚ's r,kÚ S

1Út ° sk,, °k11° út.1111°,°,Ú Úkiit ' ;;,,t Lìr ,1 Jr; Jrviss,

L ; Vo-,rri 1 S. pisivij),0 is is J

t' As` / I /r+0.1./,/0{A',,A"H//../ / ./á^, ////,.; r" //.."1+ /,` A" tr ///

; ; vrrs'iv; ;sr rosiv; , ,JH '''JisJ rit 'L5 L5!HLj';;; ; sií '; r S' s' s;;;.; sr "`; i'/'/A1r t ,°1/

1 r , 4; )ilrri

s

rk 1 Ú

Luvisols and;

5,,11

ú1

o

Th ' 's units i I ded in are as follows:

C.,,tT 1. Arenoso \2 KS09C.roy, 2. l41:\,Lsols:- All, D 107, 7(.1, G09, Gi0v,

SO7Grup 3. Ll,ht A09d, 7.5a, Gl3a, W4aGroup 4. lievy Luvisols:- A07, A7, A16, A4,1, PO6c, 1307, G02e,

G09, Gina, G13, (',14

Group 5. Calcisols:- A04b, A04d, A09, L14Group 6. Saline and Alkali soils:- A09, A5, A37, 1.O2A, [M5Group 7. Vertisols:- A01, L25.2, L25.1)1Group 8. Gleysols:- A31, A47, LO7Croup 9. Regosols:- G02a

All profiles havin9 numbers in Lho 910 cr th;-, Botwano(3,1) DataLase have been oharact2r)7ed Hleir physicat

pr,4)ortio. Some of tho reJevanL proportio5 to aLlqilven in the appendix for Toady reference.Resulto from moisture retention measurements wore statisticallyanalyzed to establish their best possible correlation with tex-ture, bulk density and organic matter content. For this purpose,the soil horizons were grouped into five categories based on tex-ture and organic matter as follows:

All SoilsLight textured soils - clay 40%Heavy textured soils - clay > 40%Soils with high organic matter - org. carbon -ti.Soils with low organic rqattet org. calThor tt O.

17rLpIo n,-i mu 1 tt. Lple rz:rjress cm :2 rtzi rtt t. 1" 9' `'f d capacit v, wi Lt. rIg po ri cr!. ,ut Vu,:;..f. bi r r, .1 1° - °I t, I; ' t

r r I andctrtri L 'ttrr tt tt.tt I rsi y , » rir

Ly arti 1.-Q;1.,(',..t 4," k ° s

t. ho'9,("'":19,,9y i (t.; it t ,°.».°; t , 9, 9', 9',"Kl

L () af , tre.tr-rtrrt) i, rt-ttt r t, '

."k r c h ,'CC." , , ",1G9,) i :9 I H":-, t t-t- rt--;°; ; tt, ott t trt ,` ht 't

ttt.'t AtIo Lk 1

rt

- r Ì r

rl 'rÌflI, ;

Tal L. i ve k Vi .T0

,71vopF. !,-3.t.lri,14:17 ON),ibri3

ierrir

ight A 18.5 , 7

24.1 .):1, T,

17.1 3'3

1,0

A

,

, 1111

1 11

7,7 A 7.9is B 9.7

4

1.3 11

1.2

-

Vertisols,14 ìe g ually

moro periN,k,

Gleysols

ixn Cgtv'e a, -Th)lot 1,", Prr)r, PPP PP:Pi PPP`Pp I P.P.1 ,

Ippp' P``. ` t , .2. `, ` jl.jj`j"`:' 'j'tj''hj ' !"1AqrJ`'`` t``' :` i ``1." ` AA''`,1 .9ì '

' :33 3J 3 ' ' 33, '1 31 44 4UH,,

4 44 tu I

441,t 44: .hu,),141:4,,i,1 2C,''C'1.41' '

2.2.2. Bulk dens tys it '13 1`''` `L..

",- vJ

; . Pirri p-P.P

'/ 1 ' r3r 'Vs 41.41u(44"4 ',V,' I ipPI,PpPr`'- rrPP,4P1

uì h'

1.)' "` , J..") HrY`` '

v

01,1 4 P! tu )2; ,..`k tilt t, I LP, *Pl+.:ro'H P rCirp`P r \PIP, 'P P 'prP r ;'r

,PPr P 1(41-, P/ LsrH' PIPP 1 ,1 PHIp !Pr

PIP\ sP'p -pprg P7( t.' 144,4) I, uP.)IP r 14''4

and -a4b-su-i rpr, p -PP VP(?..Pc,,:r".p.TP sr CP\ 1:),Pr` p '''

showu 11- comparision.

Arenosols

Thf- r=u11 densities z1_ Arenosols vaTy betwecn 1.7, and 1 /cc,ros : et the values ale clustered around dnd 1,5gm/c(% Theorwinic maLLer uoutent of the Arenosols 3F(' tow :n,) and ,As al'esult, the dlfferences in bulk densitieT, f,etween the sur and

hortzon are not aupreciably difforent.

Luvisols -ferricbu. 1 t, SUTrip3C,2 hn; <v1. r

trP ),PP 24i1s't. '; 'aar1and tv;z1-1..;i,.1-",",. LL.?4; Ll 1

6

Luvisols heavy

The 11,k-)Ne fr,tjt,oi ot filso-

!tot', ;.,, I t

I U,tstt

L. 1,r d 'T uu

,

Luv heavy

Calcisol

Vertisol

Gleysol

13

dk

A 4' 4 4

'

A 2; 1

0, ;7 1

A O.

A 0.771,05

A 4.221 .3q ,

,u

- p írp uukkuk, ,

l I (8)

ts't+t +VI tvit\''t '1L tn,", , " I "t ,`''' tt 'Os ttt,t,t tl' t,"

t"tt st'ttit4 Ptt" ,

t\ ", L. +++4 '

:tt "t tt+,'""t+t tt ht. ,,rht N hhho N "'ohtho thh., th'..¡J , ht, thh1;,,, h

hor .11 bt J 4 ;'t tttti t '4,, It t4t- t tt,

u . " `lhotrt't tH tttttt,WtLt th'LTh L :LtL J h

t ;to tchn,),-1 "1.0.4

;ols

; ïï

1;, " - ;;;' ;;;.,";,1, )7)S)1 ))))

'0) )) )7 ')) 1I)*1) )\1).

nd Alkali soils

;

Vr Irra. '

rLt

The .1 P ,h :01 ,, 9.,

1.11;'s dur; ti,"1 ! '

t7;;n;.";, ;;;1ï. Hi71 `;.^,."ï1 6,71,1vy

L"_,,kI.. t",i3.7`",/"1. 71 1 1

'''rQ L:0 I L Jt Of. L. cOlt. ' ,40 tt4

,

Vertisols. 01; \'-.;."1.;`;;-,ï ;;;;"/;""';';

°.;"17L;16,..;" ;).S 1 '1; 51' 11 rs"" CL;f1. ï '1c;" (2,3;34°';111"7.:1-Ci ? )" (7, r?, I (.:` r- -r

t,LIA cont,:,n; ï. , t.th ,lefk.R..?1-,:kil

vary E crt I, o 1i Liiti wt s n1 1.0k41 1110i sture contmlt nc,ai wilt in ,q po n1,

The high amounts uf organic matter and clay in thei=i soils qLvE'to low bulk donsities throughout 1hì profile, Thc_ slTrfac(f

soils have \,ery high ouckint matter and consequnt]y hav-:-, lowbulk 6onsities ci the order 1.1gm/oc.bilvc t)ulk dersitie varying from 0.5gm/c.c to 1.41(111 c dovmoi7v1on -the organic matter content.2.2.3. Infiltration

t R , (A) 1-,J"..;S 1.ve ;1'; 11 r i by t t H'r itit i it: 7,"

)t;ct.?lOt`i ?p ;; f"-; titt ,)

r. r !)f i ,1° 'CY roll., R

ci on...-R, 17: I"C"tt..1"'" 't t; ,""."-;01A1i;; t iat-";, '11"),-; r rr,"

"' t " ; "'77777- I, 11 iriL ,( ("7 7; r

8

Tab e 3.

krenosol

13.7

111 curl!Ra

- 4 . 2

5.

1 10V 0

"

heavy

11

10

k "

tne skk57

Ht, 71'4

"

,

II

rt. r. , rt: writ .-trt t\ttt, S Lt .1

-.tt,rts.tI. tt, tts rr, ^

O 137,4

t ti f 4.' tr,,t/ t3<""i

2.2.4. Moisture retention

111C'oi o;-: 1,1"A 1-41, 1 III'S` I t, t (KtVS7 Lc Itt tv/t !-/ r- o `;. t4",),,r -

t , stt(,..t.T,tr t't- rst. t1, r,t O *r O H'r trt.tt ,k I (r t r555," kk h,

1_,'Aftro, tt..tit.t.r) ILL /71..';`'00t 7or!..°:..1.-ik.',u ttrL r-2'..ttsrtttt. tr.N..tr t H r:t rrt, '5'5Vr k ctt rt/ r

tr o I V O (5ttt.ttit.":, /t. (-tr.( rttt.tritst,r,r, ;It "15t

- )t\t" '""r," "",.r ;e , , (1,

" - r AI" ".`.5

'51 "5

y

u

I;HO '`;; ;, ",; s" , o, kLS

14 ,

,

S

t1C1 tj.,f 1 ra-' 1

,,` ',' 0.. ' 91A9,"A'Y i'999 á , 9 SA, !, "ái1A A, Y's A A A,A

it9 , á AA' A II' á IA!" A!, ,,,,, , t Ay, á 'AA I á ú !!`t"!A st, á A" A9 Al' 9 I A,' A A

I '1 I ) " s! SIL

) , 'III A Al9 á

4 t-d

Arenosols

A ;lJt u, A L'-,-o; \ ;3 11,,ov.; hAcJI J'1 &iY al-Jou t, jj¡...t4? ,

a ut u i u 1-1,1Y? fi 'n i C.11.7121: Tig t I ypctc-, -; tu e1,,ettt un, (;.(e) 1 y '7 9-

t, 191) t..;;-4-,, -Le 't 1:. ti ee;i t' ! r )7, !"1,'1 I. I

01: I U ç tdE'ñ 1-

,

,

9

',11. 'Al' AII99IAI Aá

Iát 119

'At 9 k At, ' ,

12

L L , I 9, A A

á

k ! AAI',

9 ,9 ;qv At 9,"!99

u

IL

IL .J1 ,,) ."

-`; t. iA '91 á sá. 1,»,r,' t). r; s-' LI'70 i 1 Lnipoy. u acyl.. i 1.7u 1 t ut oLu... ;let'

nL (' uni rui:24t srt Tt I.an:11:00-1-i and tu un';'t t

1 (,3 i Vti t ypC J C 1, Riti istU I C chal. ál 9 A C:91

j_ r sonic L;o1, noii Lu in 13,7)1,

111

L

0 9 0O

t? 0G

0Q

lU

Luvisol

t , ;d ; d. 4' 'd '

as. ni ACk.--,/to..kkkkk Lk.r k k kc',1tt i,H.' uti 4.L1k,,,d'r. 41, d 1,11 4, d o '1" T14444

fA. 1-1 L.; '514 1". ^t. a. A. : v ,"*) chinat iiid tt i5it.;int.ti

At ,5L, t..41 ,k g "k,k..kk ,..fAC

1.1

1 41'

A

4

." 1"

S141, 1 9 " 4 I '1 ' 4 ,,

retE LI I (s 1.7,1

; , t ! 1,1R s' t hO. 11a VI ,\ th'11.1,4d; t ; onoI lay

',444:'L44, 4_7(.1,;rTa t t h:H j\tV N .! I i1E in

; rl iiCTS...? .1 ;1 hk..' P1'01-20 t fl1fl icr\-LoJ'ekkeLkCik ki cldsco. hed

t11 k,1;1 t he V()_.,!fl'ieH'1 en t L.,upo? cc,Y51.... fr,i i t 5, P e` f

k, t , J\ t2,,i ;07) H)zz,`,:,, .40P_ ; 4: 44.;"1';,01 (u. L Ukt"1-177.011,

hv

Saline and Alkal

41 '

I 1).`"

td3,1 '41Sd 411 44d 'L. 4 4,''t 4'0 fl'1'{1 I 4'

14

11,

k

d

add

1;1,,L.L't 1: I L 6 r

2.2.5. Moisture availability

15

L ' d)", L n''1

(

1.1

Ulf d., ,t.././LIL L 'LI '3"

J " s

,

''' ,..., , d ", ,,,,' d rk,'dl 'L.,.*, (L. 11.

',, ' ' ' ' ''.

: ': .' ' ,7 ' i ''," ' , ' i. \ ' \ '-: L " II ,» n ' 11 1 ' , I " 'll' 11

II

f..ttt-7o, 333 133 ,3,, " L" L

;ow 13, I .3 1 '" L OV,"i.,', t

314' 33.03LiALI,L3"L'WL3','It Ç

,

," L L T -, °!,I

I X- 3',3 LL 33, H1.3 ,c

.3±1" L Lt T

11 h L'LL

" ,LL'L",`

L3 'LL, w) , ,=-t

t h -utt

)11 ' H-

1 I';

16

of the correlation coefticieot, tiald cepac'ity expgr,ivimet.ric moisture content correiat.es best with clay,sity and organic matter.

Table 4. Multiple regression Analysis for FieldCapacity (g) with sand/clay, Bulk densityand organic carbon as independent variables

17

Table 5 shows the results of regression analysis of wilting pointwith the selected soil physical properties similar to theanalysis on field capacity. Here again the results lead to thesame conclusion as for field capacity in that, grouping horizonsinto different categories did not improve the correlation sig-nificantly. The best and the most convenient correlation of wilt-ing point expressed in gravimetric moisture content was with clayand organic matter when all the horizons were consideredtogether. Thus, it is seen from the above analysis that a singleequation can be established for each, field capacity and wiltingpoint separately, to cover most of the soils of Botswana. Thenecessary inputs are percentage clay, percentage organic carbonand bulk density. The bulk density values are not required forthe wilting point. The equations-are

FC (g) - 51.04 + 0.31CL - 28.9BD 4 3.540C

Standard error = 5.24, correlation coef = 0.90

Soil Category Independent variable Corr. Coef R

Tot.sand bul dens Org.0 Clay

All Soils x x x O. 0do - x x x 0.90

Org. C.> 0.5% x x x 0.89

- do - x x x 0.90

Org. C.< 0.5% x x 0.57

do - x x x 0.67

Clay > 40% x x x 0.86

- do - x x x 0.86

Clay < 40% x x 0.47

- do - x x 0.66

WP(g) -0.64 + 0.32CL + 2.060C

Standard error = 2.77, correlation coef = 0.90

FC(g) - gravimetric niisture percent of soil at field capacity

WP(g) gravimetric moisture percent of soil at wilting point

CL - weight percent of clay fraction

OC - percentage of organic carbon

BD - bulk density in gmVcc

Using the above relationships for field capacity and wiltingpoint, the available moisture can be calculated from the follow-ing equation.

Available moisture = [FC(g) - WP(g)] x BD

Where the available moisture is in volumetric moisture percent.

18

Table 5. Multiple regression Analysis for wiltingpoint (g) with sand/clay, and organic carbonas independent variables

Soil Category Independent Variables

Clay

Corr.Coef R

Tot.sand Org. C.

All Soils x x 0.87

- do - x x 0.90

Org. C.> 0.5% x x 0.92

- do - x x 0.94

Org. C < 0.5% x x 0.76

- do - x x 0.72

Clay > 40% x x 0.81

x x 0.72

Clay < 40% x x 0.54

- do - x x 0.70

Where

Very often quantitative data on organic carbon and bulk densityare not available in respect of soils for which available moisture is to be estimated. The information on soil that is commonlyavailable is either the quantitative data on particle size frac-tions or the textural class to which the soil belongs. In thelatter case, the clay content can be approximated. Under suchcircumstances, the only possible way to estimate available mois-ture very approximately, is through a functional relationship offield capacity and wilting point with either the clay or the to-tal sand content. In order to derive such a relationship, linearregression analysis was carried out on the available data usingclay content as independent variable with field capacity andwilting point as dependent variable separately. The followingresults were obtained.

FC(v) = 9.64 + 0.57 CL

standared error = 6.8, correlation coefficient = 0.80

WP(v) = 1.68 + 0.40 CL

standar d error = 3.3, correlation Coefficient = 0.89

where

FC(v) = Volumetric moisture percent of soil at field capacityWP(v) = Volumetric moisture percent of soil at wilting pointCL = Weight percent of clay fraction

The available moisture in volumetric percent is given by

available moisture = FC(v) - WP(v)

In general, the available moisture of similar soil units fallwithin a characteristic range of moisture contents. The generaltrends in the values of available moisture of the differentcategories of soils that were grouped together are discussedbelow. Table 6 gives the mean values and the range of themeasured field capacity, wilting point and available moisture involumetric moisture percent for the different groups of soilunits.

19

Table 6. Average and range of field capacity,Wilting point and available moisturefor the different soil groups.

Number in parentheses gives the range of values

Arenosols

The Arenosols have very low amount of available moisture due totheir predominantly sandy texture. The available moisture con-tents vary between 5 and 10 percent by volume and seldom exceed10%. The surface horizons have slightly higher available moistureof about 8% compared to that of sub-surface horizons which isusually in the range of 3 -6 percent.

Crop production will be very limited in these soils due to mois-ture stress. Plants can survive only with very frequent rains,even if it is in small amounts.

Luvisols - ferric

The modal value of the available moisture for ferric Luvisol wasabout 10% by volume. More than 80% of the soil samples of ferricLuvisol analyzed had available moisture between 7.5 and 12.5 per-.

20

Luvisol - light

(10.21 - 27.18)

18.09

(12.84 - 25.52)

(4.00 - 16.90)

8.08

(4.78 - 17.12)

(5.43 - 16.92)

10.01

(6.79 - 18.02)

Luvisol - heavy 34.16 17.67 16.79

(12.46 - 50.47) (6.82 - 32.59) (6.56 - 31 60)

Calcisol 26.36 11.12 15.55

(12.46 - 53.92) (5.78 - 17.50) (5.39 - 39.76)

Vertisol 46.32 32.79 13.53

(39.34 - 55.84) (28.38 - 38.45) (10.8 - 16.6)

Gleysol 43.18 22.71 19.59

Soil group Field Capacity % V Wilting point % V Av. Moisture % V

Arenosol 9.74 3.23 6.51

(5.1 - 12.1) (1.6 - 5.0) (3.2 - 8.4)

Luvisol - ferric 18.96 8.96 10.06

(29.81 - 53.99) (15.36 - 30.80) (10.04 - 35.42)

"Che ;,,; n LAii/q,:aoduy w t f i t11vielyi I urouht.3. 13u; Llanin tend

moisturo qulekly frequoutenooqh ropt,-.'n:Lsh

Luvisols - light

The estimation of available moisture made on the light texturedLuvisol showed that they were almost identical to those of ferricLuvisols. These soils too have an avenu - alue of 10% I)Ni volume

of available moisture.

Luvisol - heavy

The heavy textured Luvisols are by far the hest soils in Botswanafor their moisture retention properties and moistureavailability. On an average they have about 18% by volume ofavailable moisture and the modal value is about 15. Onlike theArenosols and ferric Luvisols which can reach field capacity wi,l)less amount of rain, the heavy textured Luvisols wculd requiremore rain to bring the moisture content from air-dry to withiaavailable range. Thus, these soils would h,ive tower planting op-portunities during the growing season. But nc. the sell moisturestorage becomes adequate for planting, pluat growth can be suF,-tained for longer period without rain, thereby reducingchances of crop failure comparod to other

Calcisols

The available moisture holding capacity ot the Calcisols are cc;0-parable to that of the heavy textured Luvisols. Although, boththe field capacity and the wilting point are lower in the Cal-cisols, the relative increase in the pores sizes in the availablerange is such that the available moisture in both these soiJs aresimilar. The field capacity and the wilting point are of the or-der of 26 percent and 11 percent by volume respectively. Theava _Liable moisture is about 16 percent by volume.

Vertisols

Moisture retention in Vertisols is very high but much (

water is in the unavailable form. The available moisture of theVertisols is about 10 to 13 perCent by volume. Due to the highfield capacity of these soils, the soil moisture can reach theavailable range only after large amount of rain if the soil isinitially at air dry moisture content. The cracking nature of thedry Vertisols aggravate the problem as all the initial rains Mow

21

ihrough L.rack:= lowtI I \AT theOnc.: tho ( ,11:4 1,11t, 7407i+ s9, Lot 110

in J raoge, clup vtoduc.-tir.:rn

Gieyso

The average available moisture of 19-20 percent by volume for theGleysols is the highest as compared to other soils. However, thehigh moisture contents of 40-45 percent by volume at fieldcapacity in relation to a total porosity of 50755 percent cancause poor aeration to inhibit plant growth. Thus, the Gleysolshave to dry sufficiently below field capacity for any cropproduction to be successful. In reality therefore, the availablemoisture for plant growth will be lower than the value that isobtained by moisture retention procedures.

2.2.6. Structural Stability

egree to which the soil aggregates withstand the disinter-grating effect of water and mechanical agitation is referred asstructural stability. The relative stability of soil aggregatesto wetting is assessed by comparing the degree of collapse ofair-dried soil aggregates when rapidly wetted as opposed to slowwetting under a tension. When wetted slowly, soil aggregates donot collapse while under fast wetting they collapse and slake ac-cording to their degree of stability. The degree of collapse ofthe fast wetted aggregates is estimated by a measure of the ratioof pore size distribution of the large pores in the two sampleswhich had undeigone the two types of wetting. The pore size dis-tribution in turn is measured by the moisture release charac-teristics of the two samples at low tensions. If the soil ag-gregates are fully stable and do not collapse on fast wetting,the pore size distribution in the fast and the slow wettedsamples will be nearly equal and their ratio will be close tounity. If the soil aggregates are completely unstable, then theywill fully collapse on fast wetting and the ratio will be almostzero. Any intermediate value in the ratio indicates an inter-mediate level in the aggregate stability between the two ex-tremes. Thus, the ratio of the pores size distribution of thefast wetted to the slow wetted aggregates is a measure ofstability and is referred to as the structural stability index of

the soil. Structural stability indices are measured on soilsamples in the size range between 1 and 2mm.

The structural stability index measured by the above method hasto be interpreted in relation to the proportion of single grainsof sizes between 1 and 2mm that are present in the soil sample.In soil samples having both soil aggregates and single grains,only the soil aggregates undergo disintegration on fast wetting

22

ano -,1,1(j, salil1 kJ1,1LC-ct,,,L ;¡,\H.wlth niCAcanr perportion o[ ;;Lnvo t u t rd t o ;how a

'..?dclwural stability indox than wnat t woul,1 have been ir.he srvp i consistod of soil aggrecjates

Only wit.h few exceptions, all the sofl untt., for which struc-tural stability was measured, had structural indices less than0.5. Surface soils on only three profiles showed good aggregatestability with indices between 0.60 and 0.65. These soils werehigh in organic matter content without any single grains in tho1-2mm size range. All the soils which showed high aggregatestability indices above 0.70 were, without exc,,rption, sandy soilswith high percentage of single grains in the 1 -2mm size range.All the results of structural stability index measutements arostored in the soil data base with other soil physi(:al properties.The structural stability of most of the soils ol Botswana can Lwconsidered poor with the attendant erosion and surfacounder rainfall. However the soils with very .iandy surface sil,although do not have any aggregation, can be considored somewhatlike a structurally stable soil. They do rot develop surface soilcrusts beca uso of the loose sands and also do not produce muchrun-oft due to their high infiltration rates. Thus, the soilsshowing very high apparent structural stabili,.:y index due to thepresence of high proportion of I - 2mm single grains, in fact,behave like structurally stable soils under rainfall. Arenosos,some ferric Luvisols and light textured Luvisols belong to classof soils where the surface soils are sandy and show apparentlyhigh structural stability index.

23

P.ErENCE

FAO/188 RPvised Legend of the FAO/Unesco Soil Map of theworld. FAO,Rome.

Joshua, W.D. Methods for the measurements of physicalproperties of soils. Project AG/BOT/85/011. Field Docu-ment 19.

24

L s»

,

Dl0901DI0901DI0901G00902

, pH

n n

Q

5.,)04.1 ;.;

'

4,C

L8.0

,

0,09200,2959

;1;_c

u,:;:c.,o.o.16

4.556.857.08

19.91G0090:: 7,10 0,0 1.48 0.0 0.047g 0.0:401 3.54MW0902 A 4.8C 0.0 4.46 -,..8 0,0565 o.nit-, 2.97KW0902 B 4.90 0.0 1.49 3.8 0.0569 0.01H 4.11MW0902 C 5,00 0.0 1.51 3.8 ,0r,18 3.43PA0901 5.20 3,3 2,71 53 0,1J15 J 329 9.86PA0901 B 71,00 0,'.) 1,73 9.0 0.1142 0-0365P0901 C 4,60 0.0 1,72 9.0 0-1256 0.)301 6.14PA0901 D c,.71 1.59 11.0 0.1013 ","...,572 4,45PAO9CEPA0501

EF 5,?0

0 00.0

1.621,66

11.013.0

0,11990.1428

J.05.8':',''. 0598

6.168.30

SP0904 A 6.70 0.0 1.:,1 7.4 0,081 0,0498 3.17SP0904SP0904TO0903

BCA

i'706. sOb.40

0,1',''';.00.0

1.521.531.63

9.17.50.0

0 0836.",:).oar0.1293

' :0147

J,036::

5.325.518.39

TO0903 S 6_50 0.0 1.51 3.9 0.1,149 0.038t -.31TO0903 C 5. 0.0 1,54 3.5 0,1215 0.0459 7.56

opertl 00avizo1s tur,:,.:

Profile Sample. -lec. Bulk CLay Wlitinci .:0valableNumber Number Cond.

kmS/cmDensity

(977.c1--; .- _ap,ac1ty(c/c) PrDI,nt,

(c..c/oc'A0,4sture

(v)

MA0904 A 6.30 0.0 1.10 14 0 0.2552 1.14.0 11.28MA0904 B 7.50 0.0 1.66 9.0 0.2103 0.1712 3.91MA0904 C 7.30 0.0 1.63 18.0 0.2448 0.1059 13.89MC0901 A 6.90 0.5 1.70 12.0 0.2397 0.0595 18.02MC0901 B 6.70 0.2 1.70 14.0 0.2108 0.0595 15.13MC0901 6.50 .0 1.63 15.0 0.1907 0.0880 10.27MC0901 6.70 ..7 1.59 22.0 0.2115 0.0875 12.40PN0902 5.70 1.44 18.9 0.1343 0.0727 6.21PN0902 6.90 0.0 1.51 19.2 0,1666 0.0933 7.32SP0902 6.10 0.0 1.52 10.1 0.1338 0.0593 7.45SP0902 8.30 0.0 1.51 15.9 0.1284 0.0604 6.79SP0902 6.30 0.0 3.58 15,4 0.1485 0.0679 8.06T00906 6.90 0 0 1.40 p,4 0.1385 0.0470 9.07T00908 7,60 0.0 1.4 9,2 0.1676 0.0976 8.00T0090 3.00 C,.1952 1,99!73 9.2')

The results.[incw that although there is no difference in the maximum rootingdepth, there is a slight increase in root proliferation in the rip line.However this differencP may be either due to lower bulk densities and soilstrength in the rip lines or simply due to crop differences. In any case, tnedifferences are not very large. Definite conclusions on rooting differencesbetween treatments can be obtained only if the control is located in the samefield as the other treatments and with the same crop.

Soil Moisture

One of the important otjectives of the investigations was to measure the

changes in moisture contents in the rip line, traffic line and control andcompare with the amount of rainfall. This data was necessary to check whetherthe increase in moisture content in the rip line is greater than the other twotreatments as well as the amount of rainfall, as expected. Unfortunately, therainfall during the season was far too excessive and masked the difference be-tween treatment by wetting the soil profile equally. However, one set ofmoisute content measurements by neutron probe was possible at the beginning ofthe season after a heavy rainfall of 84mm (Table 4b). At the end of theseason gravimetric sampling was done at 15cms intervals to a depth of 60cms inthe rip line and traffic line (Table 4a).

Table 4a

MOISTURE CONTENT ATEND OF SEASONS

Depth Moisture Content g/gcms-_-_----- ........ -_-----

Rip-line Traffic line"*.no**....4W.* ..... 11WW.mmemmsoom0-15 0.06715-30 0.07330-45 0.1245-60

0,0630.0740.110.14

....... -------

Treatment Mn(RtureIorrenl. cm

Rip lineTraffic lineControl

Table 4b

MOISTURE INCREMENT IN 45CMS OFSOIL DEPTH AFTER 84 MM R/FALL

3.5

1.92.3

From Table 4b, it is seen that there has been an increase in moisture contentin the rip line as compared to the traffic line and control. Apparently the'ais some run-off from the traffic line on to the rip line because the increis more than the control. The result from one set of data cannot be tak,!- asconclusive. Further, the increase in moisture is far less than the ,talrainfall which would also suggest that the moisture increment can be 'hie to

the incident rainfall alone without the effect of run-off. At the end theseason, the moisture contents of soil in rip line and traffic line ar lmostidentical (Table 4a) showing that the rains wetted both the soil ,,zofiles

equally thereby masking the effect of the two treatments. Therefore n order3 evaluate the beneficial effect of rip line - traffic line treatrnt, it is

necessary to repeat the experiment for another season with ade.» measure-ment in the control plo': for better comparison.

SutmwLry ai unclusion

The physical properties of soils that - ripped or t d consecu-tively for three years of the graying measured.

The infiltration in the ripped lines was higher than the normal soil in thebeginning of the season but became similar to that of normal soil at the endof the season. The infiltration rates of the normal soil itself are high.Compaction in the traffic lines reduced infiltration and increased bulk den-sity and induced run-off during rainfall. The reduction in bulk density andsoil strength caused by ripping persisted even after the rainy season and alsoincreased rooting density of plants. The moisture contents in the rip lineswere higher than those of traffic lines and control plots after rainfall. Butthe data are insufficient to conclude that there is definite rainfall run-offfrom the traffic line into the rip line.

-41-ttfiR

,

Traffic I me

Pfgure 'APJATION OF SOIL STRENGTH WITH DEPTH

36

RID t ne

2v 2

AG: BOT/85/

Soil Mapping And Advisory Services

Botswana

PHYSICAL PROPERTIES OF VERTISOLSAND ARENOSOLS OF PANDAMATENGA

^

37

Food and Auriculturak Organization Of The United NationsUnited Nations Development Programne

Gaborone, November 1988

Introduction

The phva cal pronerlos of a typieal er J otiic ordetermined for the purpose cf chafacteriLing those soils. Ilhe major r,Irt et

the Pandamatenga Plains cotsilt, of Vertisols. The data can L Esed aq a

for planning agricultural practices. Some physical property Inensutements were

also carried out on eze Arenosois which occur adjacent ti tne Vertisais on

topographically higher position in the landscape. The Vetrisols profile ha,

a high clay content (>76Z) and is classified as Pellic Vertisol (FAO) whilethe Arenosoi which is very sandy (>90Z) is clas3ified as Ferral]x Areno

Btlik densityV:erriEols:- Due to tho Ihrink-swell and cracking nature or thesp uLls,

bulk density measuremerits by the core-sampling technique was rk)t. posible.Instead, bulk donsitie% were estimated by asing saturated rNoisaure cont,nt

large natural clods and asEaming particle density of 2.65 gris Der cc. * 4)1,-e

these soils expand continuously from air-dryness to saturation, the bulk den-sities thus obtained are that ,)f nearly saturated soils witit rho effect ofoverburden pressure. Blk densities wero also estimated by 7be , q1..atLm iven

for Vertisols by Ausrralran workers (Shaw and Yule, 1_97S) laIng il hlT mclist-

ture content with allowance for overburden pressure. The la ter raPtai i3oor-,s1dered by he ce workers aS most suitable for agricul:_1]7.7. plinhno pur-

pose.;. Tablo 1 ive ahu blilk density valn-, for th

timdted .))r both r.wtho,13.

Table 1

BULK DENSITIES OF VERTISOLS

Arenosols:- Bulk ders.ity measurements were made byth ecre-sampling

techniques at two the Arenosols. Although te=dra11y :hese soils

were very similar at both sites, the soils on the higher topographical posi-

tions were redder and the soils at slightly lower positions were yellowish.The average of five replicate measurements for 0 - 18cms soil death at the up-

per and lower positions of the slope were 1.53gm per cc and 1.16gm per cc

res

Infiltration(a) Vertisol,:- extensive wide cracks devel infIldni-

:to are measured in these .dt'izrdtdon dte,

,sumed to , very high due to the cracks when the are dry and very

as per clays) when the cracks close up in wet soils.

38

Soil Horizon Bulk density (gm/cc)depths (cms) water saturation Australian method

5 - 23 1.30 1.30

23 - 50 1.33 1.35

50 - 85 + 1.32 1.37

ddn:loj j1dt C

,i!uaro, \L.;=nosol- i-o'Alodtc Lvo

, r eld-,:sed Lime or d g grLp;1 rnt n r'straight line was drawn through the lana points r estimate tho infiltrationchaiacreristicfl, Figure I. and Table 2 show the -ele:ant characteristics.

Table 2

INFILTRATION RATE OF ARENOSOLS

The results clearly show that the infiltratio7sandy soils Somewhat lower values of sites I ah:.

tiai variabil:ty the soils.

Ire

Soil Moisture Retention7ertisol:- ,;oil moisture characteristics nriqtrre retos rros)

determined on :arge natural soil clods for at 0, .

and 1 bars. For 3, 5, and 15 bars, 2mm si ai. San

and pressure plate methods were used to -s-4 tension n thesoil samples. Separate samples from each hol..Lat each imposed tension. Figure 2 shows the rdtedtIon dor:s rorhorizons and Appendix Table Al gives the mean gr ric moisture content ateach respective tension.

Arencsols:- Soil moisture characteristics were not measured on theArenosols.

Moisture Availability(a) Vertiscls:- Recent work on Vertisols has shown t}- able :leis-ture estimated by the conventional method as the diff bai aud15 bar moisture contents can be mislead: due to ' a=uie ofthe soil. Although the wilting percent, t !ho 15

bar moisture content, the tension at which _ :Tpr,ximat,,sthe field capacity is very variable. Coi-le,1 oPsd'Te ri=-1dmeasurement, Australian workers (Shaw and Yule,tion using 15 bar'moisture content to estimate ihe it :u

field soils. Table 3 gives the :3ture availabi thismethod.

1 14.7 90

2 41.3 48

3 44.8 60

44.4 54

5 41.2 6

6 22.5 96

Site No Basic Infiltration Time taken to reachRate (cm/hr) basic rate (mine)

2

TablE

MOISTURE AVAILABIL: VTRTISOLS

glg

Available moisturecc/cc cms/m

lye struc .1 stAtlilit7Y r',oils to ,,etti7iF, wa,; ass. ssed by compar-

.e. detroo of ,,)11A-; LI of air drieL.. ,sui1 wettei

opposed t) siow wet,:ing uncie: a tension. The degree oi is es-

timate,: by t1.e relative change pore-size distribut2on which in turn is':he moisture release characteristics of the samples which had

nciergone th nsa kinds of wetting. It is assumed that there will be :ittle

or no colla,Ise of any samole that is wetted under a tension. C,.

stable soi' will hve stability index of 1, whereas a totally unstab soil

n2ex of 0.

1 verti";ois,:- The ,1 stability index of the surface horizon of thewas d2tormined 1r; the above method in duplicate. The average struc-

tural staI).1a.Ly index was 0.4l_ ind±cating that the soil is sti:-turally

unstablt. woala easily a:120 an2er rainfall.Arellos.,:- IIo measurements were done on as

soils wale 'Ioote).

, . D. F. 1978. "rho assosment of soil for irrigation

Emera' Qid. Technlaai, Report No 13. lt)partmens of Primary Industries

F.,:inbane AustraliJ

5 - 23 0.3641 0.2211 0.1859 18.59

23 - 50 0.3212 0.2268 0.1274 12.74

50 - 85+ 0.3135 0.2271 0.1201 12.01

On th lable the Vertisols can be approximated to

12 of soi

(10 Aucno-.Q1s:- No moisturo rel..t.tin measurements were n Arenosols.

ai on simi]at snit in

July .12467 e to be 0.0718 c- oT '!)11

sn,1

`7.4""';

Hor zon depth Upper storage Laver storage

(cms) Limit (g/g) Limit -15bar

ANN1

Appendix 1

Tension(bars)

Table Al

MOISTURE CONTENTS AT IMPOSED TENSIONS - VERTISOLS

Moisture Content (gm/gm)

5 - 23cms 23 - 50cms 50 - 85+ ams

0.03 0.3790 0.3749 .0:36820.05 0.3511 0.3540 0.35670.1 0.3161 0.3160 0.35060.3 0.3060 0.3068 0.30441.0 0.2735 0.2755 0.27783.0 0.2425 0.2447 0.24255.0 0.2308 0.2365 0.236615.0 0.2211 0.2268 0.2271

6000

100

120

140

8O16

0E

LA

M W

A

Fig

ure

1-

INF

ILT

RA

TIO

N R

Ai E

vs

TiM

EA

RE

NO

SO

LS -

MP

AN

DA

MA

TE

NG

A

224

0

o-

= 3 0

E 2-

51

ANNEX 2

23 1 5 - 23 crns.

2 23 - 50 cms.

3 50 - 85-0- cms.

.215

CON7F.N7

I I

1

II

t I

I

\II

IIel

ll

MOIS,TURF: RETENTiC -

43

ANN1

Soil Mapping And Advisory Services

Botswana

PHYSICAL PROPERTIES OF SOILS OCCURRING ADJACENT TO THE MOTLOUTSE RIVERIN THE SELEBI-PHIKWE AREA AND THEIR SUITABILITY FOR IRRIGATION DEVELOPMENT

Food and AgrIcultural Organization Of The United Nations-ti7as Development Programme

e, November 1988

44

AG: BOT/85/011

Technical Paper 4

Results

'

45

46

,

FEASIBILITY OF IRRIGATION DEVELOPMENT ON SELIPHIXWE SOILS

The A71,1

:If` ;, lry generanvSpr/nkL tW.:`0

h13 ;?, ;,;' r r mer.hoo, 01: r ,

(vvestmnr ayd r:tert,,r(--- It1 k,

or lt, ;; '

eptlariLmtor of t taT1O " ,o(i,q;'*1`,)i r rrrn ,` .

- ;; 1 1 ' . , r

r1 rçeu n,

tt9 ,,`\

;s's ` it;p H

I

47

'

,,.

3 11 C ir ( Ti L. ç

mm \'Lçç-sign(1, to ,,--6(.1. Lae(actor ark:! 370 .fte,-,51,:

the sui.120iiity of Lin 1,Arld (Jcil'. tor the parn:cii rrrìn'.vpetw) s'tepi; are aglin Albje(.73ve aad lpc ini rVe

ovai,tation. iz; quaLLtiLarive badasoiglio0, aoht, or

to, la.oa rsnin.7.0. L'I'S:tA,NCO,i ir': im. r,7onr.aiLiJc. nhr 1",F,Cf L mcv SA] nc,( .

OfJ 11.ghLy s2 is moderkels, N

Land (soil) suitability for sprinkler irrigation.

Eutric ambic A er A22 N

2 rosol A36

uvic Xerosol A37 Si

4 XeroF. 7

drair A37a S2

0

2 ^

uaBLxo aaa.4T.ia uo passq

6:661,

'TqUDT

'

é 44 ^4 Cé éé u1 ^ 3'61,1 1, '.(16 ,x

16.1 /6" 16'1 16'62 b.I 0,4 véé

' éITué éé.éé éu 04,444, éu, 1,4 IQ é é é,,u,^,''utUu^ k t,

q 1`;

rk

pU13 sac 44 ap 889II =DE

clITI;; '

A 1 17: LI. ,1 ,

Lr. ir; ;r;'," 21,1 *, ,

111,, rp 7,-)7 -J tqnk.11uk r 1(16,6c/"616(11'6, 66.s.(irk.,', (6 666161,A

'6'16611 - LI 41.4 t pap G.IT1 uo-Fluaqa.1 quaTi;TIN

44i"ld 6V1 166 L 21,0 6 ( 1,61:('''

16:

' 11606' ",61. 1666' 1t"1"..1 6661'I ,VC .it..,CitT 1;1 ' , "ut4u, 4.

.:.uuéé 1.Vu4su é 4+;:,4414, é .u.,1-r,r(;71tC4 u"éu.4 4;4{ 1441,440. é4u, 14 4, 4 4. 44M. 'é ré- "0144 4 ,441.40" ; ?, ,`"'4f

C'I 1réé4 4, ' I 1 ^ ^ 4, 4. éé^, 'L éu4éH4,11 ué4 "4 uu r4; 9

L" éé

él^

6 ,`

, 6;461' .,6 11 ('

' ^

o

(b)

10 - :

TA:PHYSICAL r,rosr,;Cv..°1.70.;',7,;V:q SELEBI-PHIRWE SOILS

a) Profile No Sp11 ivic Xerosols - A37

31. tin

0.2167*

,

(c) Profile No SP143, Solonetz

,

noLizon Moisture Content g g Moisture Availabilitydeneity

1/10bar 1 3bar 15bar

r ° .

o'ks f r,)[... - 0,1

g

1 5

L

- ,

0.1967* 0.1706* 14, 0.0763 76* 1 63

on

t.

1 / Abet,.

'

40.8

O

t

0,1

t

00,0 "vi SS ,

- .7) I.,' r

2 . 6 3.0

Xe:

51

:ial dome.stic

4 LSJLL ,,,ethod ' I aterals

9 rv ,

10

11 To Os

f ytt 11 ttty n

'

13

14 Yj 'actical

.P

'

rqq.,-kcv1(;ATxor, y

52

{

6-3

4-5 >5

100V

>1 0.5-0.2',;4c (CIRO)Yt.(1i1v,:a?r1 of

itrAgaliou (days) >15 15-10 10-5 <5

7 Dr3 :age Grouniw cTe rh

ms) >120 120-90 90-75 <75

6 Erosi 11.:ef -ility 70.75 0.75-0.5 0.5-0.25 <.25

- <1 1-2 2-4 >4

7 7's10., 4 o: CEC ofhot-17.01.i

SCL-C SL LS,S

1A!?,. <5 5-15 >15

,'Of10!

2-4 4-8 >8

CTERISTIC VALUES OF T IL UNITS OF SELEBI-PHIRER

" CFAI Lurl(111 nr.lo Lie 1 i\ Al6 'Y,"6voJot A6i

53

6 6! 6 Nil.»)

7 Av )5 155 155

8 1:16,66 -.HP (basic)40-50 5-10 5-10

9 661:66! 66! !,)1.;;a ET = 4.5

on in, 616,!- t7113

10 Ground water depth >150(cms)

>150

11 St61..ctilral stability 0.64 0.39 0.39Index

12 Slope of land Z 0-1 0-1 0-1

13 TexrA:e6uttacc 0-236m63u0-6u6face 6-1006mo 3-L5or heavier

(1!:: 66av6-6

14 Alkalinity pH <8.5666 <6

15 S! <2 <2

1 depth >75

2 !6.666!!!None

3 bulk55

°

Ora tneF,,,'

bat I i.b i

Nutrient zeta. T.:xt

Salinity & Al

\ t y

"

,

51

siS1

SlSi Si SiSi S1

Si Si Si Si

S1 S152 S2 SI

Si Si S.l Si

S2 Si S2Si Si Si

S1 S1 Si Si

S1 si Si S1Si Si

oz;

-

57

ííiír;

!

!

(t/t'ciS

) eZZ

V;N

RIV

0013LO

3 09

Nati on s

it°

1'1

Introduction

The pnn, OttA 'istt 1L : I 0 to, I ts F- ,n 541 'ToLr4pttLLt ¿ 1 " t t`tiltiO 1 Lt71JJ. Tno t nl - t:P,tZtt , 91 1 t nod , I

prope,!. t In'TA , i c lestiOrl IJ.1 t'LI&t L Y L et ti U L Lct(tt er Ji" /,' t '1,J1»1.

o tttfilirfb,,n, Fni)

Methods

'nn 'Li ) rtiytt nnn°D. ni1LtLir clot no& nn H !

tLt tWht°1s 5iy Jt' ,t2t-t,,,tr.22Al2 t ht,

. 01.221,2 r,1,d1(b) tt t, II°t, t 2 11 II 1 , o:

It' 1,155,),"

1,,¿¿ ,¿,, ;, 111, t2

,t,tt ° Jo; 22 01 2, 5;,'1tttL- °tie 1 t2° ltdit 61011 U/A' p

1.h.11.'..11,?31 rAtd,.t, Lse'ip;tt pruht '''')AAh "k. L,t Iti 1.5 12235°,15 2 2 'V't°' IV 501..

tt St°, It°2,2itttt t tt°2t, ' pet C,,r.t. t.°D.?e, 1r ,

tJ t"",,;,°",8 ,22,27t,t-ttt.' ,0tit

1,11' ,s "t ", it. t t2 ° 2t t.",t itttft, 2i ,

it t 7,1¿. °, " °t°22' i ' ' ,11 22 OA' LS t. I"C» 1

11'',"1,

1 1

'

1,,1.11

S Si

(b L. ; r

o ,ttot.; p /tot,i).,y

'` ,''

LL,)L 1 !1/43

(C) )t T L. 1/N'Avds:,' ,'/4 MOT. 't'L .L L( L. 1217'

, "J1 I'',r i 7 / i

...t..;(..t Inritr)t1 st_!.ro ,:ott otL , HriLrFtt;yot , riakount C t- LL J 0,-,

;") L.:7r Lou, 17,1r , ISTN C, 1 L ! 1.0 L o

C5, p1t, r.3i LA n:J t

\t,t y vz.1, 1.3 :11-1(.1 /.! ' .1` t r. i t l)(°t.tk,,,4 L.sh\;',1 TI.;)1t:1,TtlOi tAv2 tv ;c.v,r sî'T I c'

4.,U '17 I t. ' t , ,

',,' H n

s T, ,

, ;

Table 1. PHYSICAL CHARACTERISTICS OF FERRIC LIXISOI

(a) Moisture retention and Bulk density

".. _Huttltott

deptt

C(.11tYM:

66

7980

CMS ,

;;'

(F) liifilt!F&Fi.ca

and 'n' Are conants in the tquatiou F=atnweeFis the cumulative in-filttat.ion in cms and t is the t.imt in minutes.

* Results of infiltration measurements done after removing surface soilcrusts.

stability

Str.- index = 0.40

62

1*

6

25,243

63,f,

34,2.

15.5

13 z'

0.;.7

L.Ob

57

U.92

0.810.91

Replicate No Initial Basic 'a' 'n'

Infiltration Itfiltration Value ValuemIhr

t. "

0/60-1'

//

/

///

Rer;licate measurements

- /

613

of

e

Y

,

2.

3 5-1

64

KEY

0 - 24 Cms deptr

2 24 - 81) 3andy clay loam

80 - 107,- cms depth - sandy dav 10371

OTE_.

o.:40

Printed By Information SectionMinistry of Agriculture

Private Bag 003 Gaborone, Botswana5191