E L 5 E V 1 E R A9f1cu~ure, Ec05y5~m5 and Env1r0nment 54 (1995) 89-101

C0ntra5t1n9 effect5 0f r00t5 and mu1ch fr0m three a9r0f0re5try tree 5pec1e5 0n y1e1d5 0f a11ey cr0pped ma12e

66t2 5chr0th*, J0hanne5 Lehmann ~5~u~ ~ 5011 5c1ence and 5011 ~ r a p ~ Un1ver51~ ~ 8ayreu~ ~ 95440 8ayreu~ ~r~nany

A~e~ed 21 D ~ e m ~ r 1994

A 6 ~ r a ~

1n a9r0f0~ry a550dat10n~ tree m0~ may 1nf1uence cr0p ~dd5 60th ~v0m~y, e5pe~1y ~r0u9h m~ch pr0duct10n and ~e 1mpr0vement 0f 5~1 ~1f1~ thr0u9h r00t effe~5, and un~v0m~y ~mu9h a60ve- and 6e10w-9r0und c0mpet1t10n. A f1dd expedment wa5 c0nduc~d 0n a 5 h ~ w 5andy P11nt~c/Ferdc Acd501 1n the 5u6-hum1d 5avanna 0f centra1 7090 ~ 0rder t0 c0mpa~ ~e c0mpet1t1vene~ 0f 611r1c1d~ 5ep~m, Ca~ndra ca10thyr5u5 and 5enna 5~mea hed9e5 when 9mwn 1n a550c1at10n w1~ ma12~ 7he effect 0f hed9e ~5~nce 0n m~2e y~1d5 wa5 ~5~d 6y mea5ur1n9 y ~ 9md1ent51n u ~ 1 ~ e r ~ 0pen ~ y 5 . 1n ~4-m-w~e a11ey5, m~2e y1dd5 we~ ~wer ~an 1n the 50~ cr0p~n9 c0ntr01 6ecau5e 0f ~e ~ducf10n 1n cr0pped 5urface and a f1dd depre5510n near the Ca111andra hed9e5. W1th 1ncrea51n9 hed9e ~5~nce, y1dd5 per r0w 1ncrea5ed 0ver the c 0 n ~ ~dd51n ~ y cmp~n9 w1th 6 ~ c 1 d ~ , 6ut n0t w1th 5enna and Ca~ndra. R00t 6arr1er5 6etween hed9e5 and cr0p5 1nc~a5ed m~2e y1e1d5 1n the C a ~ n d r a ~0t5, 1n~cat1n9 a ~9h c0mpet1f1vene~ 0f the r00t 5y~em 0f th15 5pe~e~ 1n the 5enna and (n0n- ~9~f1cant1y) 611r1cM~ p~U, m~2e ~dd5 ~ the 1n~rface we~ ~duced r~her than 1nc~a5ed 6y the r00t 6arr1e~. F0r th15, the ~duct10n 0f the cr0p r00t1n9 v~ume and 0f fav0m~e hed9e r00t effec~ 0n 5011 c0n~t10n5 a~ ~5cu~ed a5 p0~1~e ~a50n~ 7ree 5pec1e5 w1th ~9~y c0mp~1f1ve r00t 5y~em~ f1ke Ca~ndra at th15 ~ , 5h0~d 6e u5ed 1n fa110w 1mpmvement 5y9em5 rather than 1n a9r0f0~ry a550~at10n5.

Keyw0rd5: A11ey cr0pp1n9; Ca111andra ca10thyr5u5; C0mpet1t10n; 611r1c1d1a 5ep1um; Ma12e; 5enna 51amea

1.1ntr0duct10n

7he a550c~f10n 0f ~ee5 w1th a9f1cu~ur~ cr0p5 ha5 5ever~ p0mnt1~ advanm9e5.8e5~e ~ e pr0duct10n 0f nutr1ent-r1ch N0ma5~ ~ e pre5ence 0fthe p e r e n ~ r00t 5y5~m5 ~ the cu1t1vated p10t5 may 6e 0ne 0f ~ e m0~ f19~f1cant. 7ree r00t5 may 1mpr0ve ~ e 5~1 5tructure and c~me macr0-p0re5, thu5 1ncrea5~9 water ~f1Rr~ f10n, reduc1n9 5urface run0ff and er05~n and 1mpr0v- 1n9 5~1 pene~at10n 6y cr0p r00t5 (Van N00rdw~k et ~., 1991; 5an~n9a et ~., 1992; 5chr0th and 2ech,

* C0r~5p0n~n9 amh0~ F~. 0049~21 ~5224~

E15e~er 5dence 8.V. 55D10167-8809(95 ) 0 0 5 8 5 - 4

1995). 7hey may mke up nutf1em5 fr0m ~ e 5~1 5~u- f10n when n0 cr0p5 are pre5ent 0r thek r00t 5y5~m5 are n0t y ~ fuHy deve10ped, ~u5 redudn9 ~ac~n9 1055e5, a51n~cmed 6y ~wer nutr1ent ~ac~n9 under perenn1a1 ~an under annum cr0p5 (5eyfr1ed and Ra0, 1991; Kf1hn~ 1993). W1~ ~ r c0nt1nu0u5 mm0veL tree r00~ c0n~16u~ ~ ~ e 0r9a~c matter 5upp~ 0 f ~ e 5011 and ~ e mf1n~nance 0f ~ 0 ~ c f 1 acf1v1ff (Yam0ah et ~., 19866; 520tt et ~., 1991a). ARh0u9h the 1mp0~ tance 0f ~e5e pr0ce55e5 c e ~ n ~ depend5 0n 5pedf1c 51~ and mana9ement c0nd1t10n5, ~ey f0rm a c0n5~- eraNe part 0f ~ e ju5t1f1cat10n 0f a9r0f0re5try re5earch and e~enf10n.

~ ~ ~ h ~ 2 ~ h m ~ n / A 9 ~ ~ 0 ~ ~ d ~v~nment ~ ~ 995) 8 ~ 1 ~

7he d15advant~e 0f ~t1ve Vee r00~ ~ ~0pNn9 5y5~m~ h0weve~ 15 p~ent1N c0mpet1t10n w1th the cr0p5. 5evern w ~ r 5 h ~ e 5~e55ed the ~m11ar1~ 0f r00t ~5~6uf10n 1n the 5011 pr0f11e 6~ween tree5 and annuN cr0p~ ~Ncat1n9 a c 0 ~ ~ 0vef1~Nn9 0f the 5011 re50urce5 they u5e (J0n550n ~ N., 1988; DhyaN et N., 1990; RuN9wa ~ N., 1992). Y1e1d ~ 0 n ~ 5 0f annuN cr0p5 t0 ~ e ~duct10n ~ ~ee r00t c0mpet1t10n 6y r00t ~enc~n9 ~ r 0 ~ 6arr1er5 ~ a ~ 0 ~ 5 ~ y a~0- c1at10n5 have 6een ~ p ~ d (Nn9h ~ N., 1989; 0n9 et N., 1991; Ra0 et N., 1991; 5 c ~ h et N., 1995). 7 0 ~ t h ~ w1th 5h0~ c 0 m p ~ 0 n ~ r 1 ~ , m ~ c0m- ~ 1 0 n ~ r w ~ ~ d n u ~ 15 0ften ~1d ~0n5161e f0r 065erv~ y1e1d dep~5510n5 ~ the t ree~r0p 1nterface 0f a 9 0 ~ 5 ~ y ~50cNt10n5 (LN, 1991; 520~ ~ N., 19916; 5Na2~ et N., 1993).

70 ~01d ~ 9 ~ 1 n t ~ t 1 0 ~ ~ ~ 9 r 0 f 0 r ~ y ~5- ~m5, V ~ ~eNe5 ~0Md 6e 1dent1f1ed wh~h ~ 0 v ~ e the ~ 5 1 r ~ N~f10n5 ~ tree r00t5 1n the f1e1d ~ m1m 1mum c0mpet1t10n c 0 ~ F0r th1~ 1n~rm~0n ~ 0 u t the ~5tr16ut10n and dynam1c5 ~ tree r00t5 under ~fferent 51~e and m a n a ~ m e m c0nd1t10n5, the1r ~mpet1t10n w1th ~ffer¢nt cr0p5 ~ d the1r effec~5 0n 5011 ~ 1 1 t y 15

m4u1r~. Y0un9 (1989) ~ 9 9 ~ d th~ ~ m ~ u N ~ 6em ef1c1a1 effec~ 0f r00~ c0Md c0mpen5ate ~ r ~mpet1- f10n, and ~ c h 15 needed~.

7he ~ e n t ~ ~ m p ~ e 5 the effec~ ~ 1hr~ tree ~ec1e5 0n ma1~ ~ N1ey ~0pNn9 .7he effec~ ~ hed9e m~ch 0n cr0p y1e1d5 and ~11~ nu~ent ~v~5 w ~ ~v~f19a~d. R 0 ~ effe~5 w~e ~uNed 6y the 1n~N1at10n 0f r00t 6arr1er5 1n ~6p10t5. 6~d~nt5 0f ma1~ ~eN5 a5 a ~nct10n 0f hed9e ~ a n c ~ w1th and w1th0~ r0~ 6arr1er5, w~e m e ~ u ~ d ~ ~ d ~ t0 d ~ -

m1ne the ex~n510n 0f hed9e r00t effe~5, t0 5e1ect ~ee 5pec~5 cf 10w c0mpet1t1vene55 f0r the 5tudy 51te and t0 4uant1fy the 1nf1uence 0f a11ey w1dth 0n cr0p y1e~5.

~ 5 m d y ~ a n d m e ~ 0 ~

2.1. ~ n ~ d ~

7he tr1N wa5 c0nduc~d ne~ Ka2a60ua ~ the 5u6- hum~ 5avanna 0f cen~N 7090 ( 1 ~ E , 8°26•N, appr0x1mate1y 300 m a60ve 5ea ~ v d ) . Mean annuN r~nfa11 6~ween 1980 and 1992 wa5 1165 mm, w1th a u~m0d~ ra1ny ~ 0 n ~0m Apr11 m 0~06e~ 1n the expef1memN y e ~ 1992 the ra1nfa11 wa5 rdat1ve~ N9h w1th 1259 mm. 7he 5mdy 5~e wa5 5Ruated 0n a very 9ent1e 510pe ( appr0x1mate~ 1%) wRh 50~hw~d ~ d ~ nat10n. 7he 50115 were ~1mh~ and Fe~1c Acf15~5 acc0r~n9 m F A 0 / U n e ~ 0 (1990). 5011 fert11Ry w ~ 10w (7a6~ 1). 7he ~amy-5andy t0p5011 w ~ v ~ y ~ w 1n m~1 C and N. 7he ava11a6~ P c0n~m5 we~ rda- t1ve~ N9h ~ the ~p5N1, 6 ~ very 10w ~ ~ e 5u65N1 (01~n and 50mmer5, 1982). 7he 2n ~veN we~ 6e~w ~ e cf1t1cN vNue f0r ma1~e (0.8 m9 k9 -1) (C0und1 0n 5N1 7e5t1n9 and ~an t A n ~ y ~ 1980). 7he 5and~ c1ayey 5u65N1 h0r120n wa5 0ften h~dened and wa5 p ~ 5 e ~ at deNh5 vary~9 6~ween a60ut 20 and 0ver 100 cm w1th1n the ~ea 0f th15 exper1ment.

2.2. 7r1a1 de519n

7he f1e1d exper1ment c0n515ted 0f three ~ee 5pec1e5 and a c0n~01 w1th0ut ~ee5 a5 the f0ur ma1n p10t trea6

7 ~ 1 ~ ~ a ~ m a ~ 1 p r 0 ~ ~ ~ ~ r ~ ~ d ~ ~ a ( ~ ~ d )

DeNh 7e~u~ 8~k pH ~ N~ P (cm) d~5 den5~y (H20) (m99 -~) (m99 -1) (~9k9 -1)

(9Cm -3)

85 (% ECEC) (m9k9 -~)

0-19 L5 1.53 6.49 7.5 0.49 44.8 3.74 19-56 L5 1.77 6.08 4.1 0.31 0.4 2.62 56-87 5L 1.95 6.35 0.3 0.31 0 2.35 87-106 5C 1.37 5.70 ND 0.32 0 1.66

106 + 5C 1.83 5.69 ND 0.37 0 3.04

2.89 0.65 1.84 053 1.33 0~8 059 050 1.07 1.44

0~6 96 0~9 94 0.10 95 0.07 70 0.13 87

0.33 0.16 0.14 0.16 0.30

~ h ~ e ~ 5 (cm01¢ ~-1 ). E~C, e ~ c ~ ~ c ~ ( ~ ~ 1); 85, 6~e ~ ; ND, ~ ~rm1ned. L5,1~my 5~d; 5~ 5 ~ ~am; 5C, ~ndy d~.

~ ~ h ~ 2 ~ h ~ 1 ~ r 1 c u ~ Ec0~tem5 ~ d ~ n t ~ (19~ 8~1~ 91

men~. 7he ~ee 5pec1e5 wem 611r1cM~5ep~m (Jac4.) 5~ud., Ca111andra ca~thyr5u5 Me155n. and 5enna 51a- mea (Lam.) 1rw~ • 8arne6y (5yn. C a ~ 5~mea Lam.). 7he n0~N-f1~n9 5enna w ~ kn0wn ~ 6e wd1 adap~d t0 ~ e ~n9 dry 5ea50n and the 5 h ~ w 5andy 5~15. 7he N-f1~n9 5pede5 611r1c1d1a and C a ~ n d r a were tr1ed a5 ~ rna f1ve5 t0 Leucaena ~uc0cepha~ wh~h had ~ven un5at15facmry re5d~ ~ 50me e~11er exper1men~. 7he m~n ~ 0 ~ were arran9ed ~ a ran- d0m~ed c0mp1ete ~0ck de5~n w1th f0ur m ~ a t 1 0 n ~ 7he ~2e 0f ~ e m~n ~ 5 , e1~er t~e ~ 5 0r c0n~01, w ~ 24 m × 12.8 m. Each ~ee ~ c 0 n ~ e d tw0 hed9e5 0f 24 m 1en~h at 6.4 m ~5~nce. 7he hed9e5 we~ 0f1en~d E-W, and ~ e ~ a n c e 6~ween ~ e t~e5 w1~1n the hed9~ w ~ 0.25 m. 7he hed9e5 were e5~6- f15hed 1n June 1990. 6 ~ a wa5 ~ a ~ e ~ wh11e 5enna and Ca111andra were 50wn d~ect~. M ~ n 9 tree5 we~ ~ p e m e ~ y ~ a c e d dur1n9 1990 and 1991. 1n May 1991 ~1 hed9e5 were pruned ~ 50 cm, and 1n Ju1y 1991 the 611r1c1d1a hed9e5 we~ a9~n pruned t0 50 cm, wh1~ ~ e 0~er tw0 5pec~5 5h0wed ~0wer ~ 9 r 0 w ~ and were 0n1y cut 6ack 1~era11y t0 av~d 5ha~n9 0f ~ e ~0p5.

7he hed9e prun~95 were a p ~ d a5 m~ch 0n ~ e f1e~ 5~1p5. ~5tead 0f a p ~ n 9 h ~ f 0f ~ e prun~95 0f a hed9e 0n e1th~ ~de 0f ~ hed9~ ~ e pru~n95 ~0m 0ne hed9e we~ d15tr16u~d 0n the ~ y 6~ween ~ e tw0 hed9e5 w1th~ a ~0t, and th05e ~0m ~ e 5ec0nd hed9e were ~5tr16med 0n a 6and 0f ~m11~ w1•h 0n the ~ h ~ ~de 0f th15 hed9e (~9 . 1 ). 7hu5, every ~0 t

c 0 n 5 ~ d 0f tw0 m 9 ~ 1 y mu~hed f1dd 5tr1p5, 0f wh1ch 0ne wa511m1ted 0n 60~ 51de5 6y hed9e5 ( ~ d a11ey•), wh11e the ~ h ~ 0ne ( •0pen ~ y ~ ) w ~ 11m1~d 0n 0~y 0ne ~de 6y a hed9e and 0n ~ e 0 ~ ~de 6y a ~0pped 6and 0f 8 m w1•h, wh~h 5erved a5 a 6uffer 5tr1p 6~ween tw0 adjacem ~m5. 7h15 de5~n ~ w e d u5 t0 te5t ~ e effe~5 0f ~ e hed9e5 0n ~ e cr0p5 under n0rm~ ~1ey ~0p~n9 c0n~f10n5 1n ~ e d05ed ~ y 5 , and ~ 4uant1~ 9rad1en~ ~ ~0p y1e1d w1~ ~cma5~9 d15tance t0 ~ e hed9e5 ~ ~ e 0pen a11ey5. A 6uffer 591p 0f ~ v ~ m ~ 5 w ~ ~0und ~ e wh~e ~1~ ~ e a wa5 ~50 ~0pped.

7he effect 0f ~ e 9ee r0~5 0n the cr0p5 wa5 ~5~d 6y ~v1d1n9 each m~n ~ 1m0 tw0 5u6~0t5 0f 12 m 1en~h and ~p~at1n9 ~ e r00t1n9 20ne 0f ~ e hed9e5 and ~ e cr0p5 0 f ~ e 0pen ~ y 1n 0ne mnd0m~ ch0~n 5u6p10t per m~n ~ (F19. 1). 7he ~p~at10n 0f ~ e r00t1n9 20ne5 w ~ acc0m~hhed 6y ~ 9 ~ n 9 a U-5haped tmnch ~0n9 ~ e hed9e t0 75 cm d e ~ u n ~ a c0nf1m u0u5~ h~dened 5u65011 h0r120n wa5 enc0un~md 1n a 10wer de~h. A 0.8 mm PVC 5heet wa5 ~aced 1n the trench at 40 cm fr0m ~ e hed9e. 7he 9enche5 wem ref1Hed w1~ 5u65011 f01~wed 6y ~p5~1 6~ween $ e PVC 5heet and the hed9e, ~em6y re5t0r~9 the 0r1~na1 5~1 h0r120n5 ~ f ~ ~ p055161e and ~af1n9 ~ e cr0pped 5~1 u n ~ m d . 7he 6a~1er5 wem ~ d 1n 0 c ~ 6 ~ 1990 when ~ee r00t5 had n0t yet c~0~2ed ~ e f1e1d 5tr1p5 6ey0nd the ~enche5.

7hu5, each m~n ~ c0nta1ned ~ree 5u6p10t5 (~9 . 1 ): tw0 0pen ~1ey ~0t5 w1~ and w1~0ut r0~ 6arr1er~

~ hed9e 1 C105ed e11ey

5u6p10t ~ 6

~ . . . . . . . . 2 . . . . . . . . . ~1~22~~.~~h ~ ~ ~ 2 4 - - - 7 . . . . . . . . ~ . . . . . . . ~ 7 ~ - - ~ . . . . . . ~ - - ~ . . . . . . . . . . ~ - -

1 0 p e n 011ey 0 p e n 011ey 8

5u6p10t 5u6p10t ~

. . . . . . . . . . . . . . . . . . . . . . . . .

f 24 m

~$. ~. ~ e ~ e[ a ~ ~ w~h ~e ~ e ~ 0 ~ 5 ~ ~ X • 2.~ ~ , c 0 ~ t~ee 5u6~et5 ~ 8 ~ X ~ ~ ~ . ~ e ~ c 0 ~ 5 twe hed9e5, a de5ed ~ 6~weeu the ~ d ~ 5 ~ d ~ e ~ ~1e~ 6e~ew ~ 2. ~ e ~ 1 ~ ~ ~ d ~ • ~e ~ e d ~ ~ c h ~ t ~ d 0 5 ~ ~ , a~d t ~ prun1n950f hed9e 2 ~ the 0~n ~ . ~ e ~ c0~5ted ~ ~ ~0c~, each ~0ck ~ 9 c0m~5ed ~ ~ur m~n p~5.

~ ~ ~ h ~ 2 ~hma~ 1 ~ u ~ ~ 0 ~ ~ d ~ n ~ m ~ (1995)8~1~

and 0ne d05ed ~1ey N0t. 7he ~0pped 5urface wa5 8 m × 5 . 6 m (5even cr0p r0w5) ~ r the 5 u 6 ~ 5 w1th hed9e5 and 8 m × 6 . 4 m ( d 9 ~ c ~ p r0w5) ~ r me 5u6~0t5 0f the c 0 n ~ . 70 av~d ~tefac~ due ~ m 0 ~ 1f1ed deve10pme~ 0f me un11a~ra11y c0nf1ned hed9e m ~ 5y51em~ ~ e ~c5ed a11ey ~ w ~ ~way5 51tua~d ~ ~ p ~ t cf me c ~ d ~ y w~ch w ~ 6mdend 6y hed9e5 w1~0ut r00t 6 a ~ 70 av~d effec~ 0f 510pe ~ exp051t10n 0n y1e1d 9rad1enk 1n me 0pen ~ y ~ ~ e wen 5~ua~d 0n me n 0 r ~ n , up~0pe 5~e 0f me hed9e 1n tw0 ~0ck5 and 0n me 50mh~n, d0wn~0pe 51de 0f me hed9e 1n tw0 ~ h ~ ~0ck5.

7he exper1me~ wa5 0~y de5truct1ve1y ~mp1ed 2 ye~5 a~er the end 0f ~ e v1~, when ~ 0 k 0f a11 ~ee 5p~c1~ had p ~ d 6d0w me 6arr~r and ~0wn 1m0 the ~ y 5 . A c c ~ n 9 t0 th15 and ~m11~ 065ervat10n5 fr0m ~ h ~ exp~1mem5 (5~9h et ~., 1989), ~ mu~ 6e ~5umed ~ m ~ exc~5~n w ~ ~ n a d y 1 n c 0 m ~ e dur1n9 me exper1mem, and cr0p y ~ 1ncn~e5 due ~ me 6a~1~ ~ e m1~mum ~ t 1m m ~ ~ r ~ee ~0~ c0m- pet1t10n. 7he ~ m a t 1 v e 5 ~ e 9 y 0f npea te~y Vench- 1n9 ~ee ~ 5 ~ the 1nt~face ~5~ad 0f me p~manem 6 a ~ r w ~ av~ded, 6ecau~ me nutr1ent n ~ e ff0m cut 0ff ~ee r00k w0~d have 6een 1~dy ~ 1ead t0 an 0ven5t1mat10n ef ~ e r 0 ~ c0mpet1t10n ( 5 c ~ h ~ ~., 1995).

2.3. Cr0p5

7he ~te wa5 ~0pped w~h ~0undnuk 1n 1990 and w1~ 50ya 6ean5 ~ 1991.7he5e 5erved a5 c0ver cr0p5 un~ ~H ~m~15hme~ 0f me hed9~, and n0 m e ~ menk were c0nduc~d 0n 6em.

0n 21 and 22 May 1992, ~ad1t10na1 5~1 t111a9e wa5 carr~d 0ut 6y hand-h0e (•da6a•), ~ r m ~ 9 r1d9e5 0f a60m 30-40 cm h~9~ , 80 cm ap~t, p~a11d ~ ~ e hed9e5.7he f1r~ r1d9e wa5 80 cm ~0m ~ e hed9e. 0n 22-24 May, a11 hed9e5 were pruned t0 50 cm h ~ 9 ~ and ~ 0 m ~ 5 a p ~ d t0 the r1d9e5 a5 mu~h. 7he 610- m~5 w ~ wd9he~ me ~ ~ 6~nch ~f10 d ~ m ~ e d 0n 12 ~ a ~ 5 p ~ ~ , and me d ~ w e ~ 0f 1eave5 and 6ranche5 w ~ de~rm1ned 6y d ~ 9 5u6~mp1e5 ~ 7 ~ C unt11 c0n5tant w d 9 ~ . 7he5e were n t~ned ~ r nmf1e~ anMy~5.

0n 26 May, m~2e 0fthe v~1ety P02a R1ca w ~ 50wn 1n me mu~hed r1d9~ ~ 80 cm × 40 cm, tw0 ~ n 5 p ~ ~H, after an ~ n ~ v e ra1nfa11. M15~n9 ~ant5 wen n ~ a c e d cn 5 June. 0n 1 and 2 J~y, me hed9e5 w~e

pruned a9~n and me ~ 0 m ~ 5 a p ~ d ~ m~ch 6etween the m~2e r0w5. Weed1n9 w ~ carr1ed 0ut 6y hand h0e, and n0 ~ 1 h 2 ~ w ~ a p ~ d f0r ea~er de~cf10n 0f p05~ve and ne9at1ve effec~ 0f me hed9e5 0n me cr0p5. At 511k1n9 5~9e, the c06 ~ave5 0f ~ e m~2e ~ a n k w e n taken ~ me f1r~, 5ec0nd, f0u~h and 5even~ r0w5 ~0m me hed9e ~0m ~1 5u6~0t5 0f me 0pen a11ey5. 7he ~ a v ~ wen wa5hed 1n tap water and dr1ed m 70°C ~ c0n~am w~9~. 7he m~2e w ~ h~ve5~d 0n 26 5ep~m6e~ P1ant num6er and 9ra1n d ~ we19~ (105°C) w~e de~rm1ned per r0w 1n e~ch 5 u 6 ~ .

2.~ R00t d1~6u~0n

7he ~5~16ut10n 0f ~ee r00k ~ the ~1ey5 wa5 5tud1ed 1n the 5enna N0t5 6~ween 27 June and 6 Au9u5t. 50H c0n5 were ~ken ~ me 0pen ~ y ~ 5 w1~0m 6arr1~ w1~ a 5~1 c0nr 0f 8 cm d1ameter. 7he ~ m ~ e 5 w~e taken ~0m 0-10 cm de~h 6~ween me r1d9e5 ~ ~ tance5 0f0A, 1.2, 2.8 and 3.6 m ~0m me hed9e. 5am- p~5 ~0m the r1d9e5 w0~d have c0nta1ned ~9her p~p0rt~n5 0f dead ~ee r00~. 7hree c0~5 ~0m the 5ame ~ and ~5~nce were m1xed a~er cutt1n9 10n9 r00~ 1m0 ~ece5 0f a ~ w c e n f 1 m e ~ ~n9~ , and a 5u65amp1e 0f 100-400 9 wa5 wa5hed 0ver a 0.5 mm 5~ve ~ r ~ ex~act10n, tak1n9 1~9~ 5 u 6 5 a m ~ ~ r h19her d1~ance~ 7he m~h0d ha5 6een de5cr16ed 6y 5chr0~h and K016e (1994). 5ennar00t5were5ep~ated ~0m 0ther r00k and ~ 9 a ~ c de6r15 under × 10 ma9- n~cat10n, when nece55ary, w1~0m d15t1n9~5h1n911ve and dead ~ 5 . R 0 ~ ~ n ~ h w ~ m e ~ u n d after 7en- nant (1975), and r00t ma55 wa5 0 ~ n e d af1~ ~y1n9 at 70°C ~ r 48 h. A11 r00t w~9~5 were c0nverted t0 45% C m c0~e~ ~ r adher1n9 5011 p~t1c1e5.7he 5011 w ~ c0~em w ~ m e ~ e d 6y d ~ 9 5 u 6 ~ m N ~ m 105°C t0 c0n9ant w~9N, and mtN ma55 and v~ume cf ~ e 5011 ~ m N e and m~5 0f ~ e 5u6~mNe ~ r mm e x ~ t 1 0 n wen u5ed t0 c0nve~ r00t 1en~h 1nm cm c m - 3 0f 5011 and r0~ ma551nt0 k9 ha - 1 d m - ~. N~a11y 1t wa5 1~ended t0 c0nduct r00t ~ud~5 0n N1 hed9e 5pe~e~ 6ut 1nten51ve pre11m1nary ~ u ~ nveNed ~ 6~r1c1d1a and C a ~ n d ~ f1ne r00k c0Md n0t 6e d15- t1n9~5hed ~0m weed and mN2e r00~ wRh 5uff1c~m prec1510n. 5enna r00k wen ea51~ ~ent1f1ed 6y ~ r Nack cN~ , 6ut n0 v15u~ 0r mechan~N ~1~r1a c0uN 6e ~ta6115hed f0r ~ 5 t 1 n 9 ~ 1 n 9 11ve and dead r00~.

~ 5 c h ~ 2 Lehmann/A9r1cu1ture, Ec05y5~m5 andEn~nment54 (199~ 89-1~

7a~e 2 An~y~5 ~ v a r 1 ~ t~1e ~ r ma1~ ~ d d d~a

93

50u~e ~ v a r 1 ~ d.~ F F (5%) F (1%)

5 u ~ 6 ~ 5 223 5 u 6 ~ 5 31

M~n ~ 5 (MP) 15 8~ck5 (81) 3 5pec~5 (5p) 3 0.726 3.86 6.99 MP e~0r 9

R0~ 6 ~ ( ~ ) 1 3.157 4.75 9.33 5p × R8 3 2.389 3A9 5.95 5 u 6 ~ e ~ 12

~ (D) 6 3.157* 2.66 4.01 ~ c 18 D×5p 18 2.585** 1.79 2.28 E ~ d 54 D × R8 6 1 ~38 2.66 4.01 E ~ e 18 D× 5p× R8 18 2.070* 1.79 2.28 E ~ f 54

*P< ff05; **P<ff01.

2.~ P~nt ana~5~

1n ~e 9r0und m~2e and hed9e 5am~e5, N wa5 me~- u~d 9 ~ h r 0 m ~ 0 9 r a p h ~ w1~ a CN-an~y2e~ F0r Me 0M~ d e m e ~ 5u65am~e5 w~e dr~a5hed ~ 560°C f0r 14 h and Me a5h ~ v e d 1n 10% HC1. P wa5 me~ured p h ~ 0 m ~ f 1 c ~ w1~ the m~y6denum Mue m~h0~ and cat10n5 6y at0m1c a650rpt10n 5pec- ~0me9y. A c0mp0f1~ 5am~e 0f 5enna r00~ 0f each 0f Me ~ame~r c ~ e 5 0-0.5 mm and ff5-2 mm w ~ an~y2ed f0r C, N and 5 w1~ an E~ment~ An~y2~ and ~ r 0M~ nutr1en~ w1th Me 5ame me~0d5 a5 the ~ h ~ Nam 5am~e5.

2.~ 5mt15~ca1 a n a ~ 5

7he dma w~e an~y2ed 6y an~y515 0f v~1ance ~1- 10wed 6y F-~5t. 1n ca5e 0f 5~n~cam F-~5~ at P < 0.05, t ~ m e ~ mean5 wem c0mp~ed 6y ~a5t ~ ~f1cant ~f fe~nce te5t5. 7he re5d~ ~0m ~e d05ed and Me 0pen ~ y 5 were an~y2ed ~ p ~ d y . F0r Me c105ed ~ y ~ Me d~19n w ~ a ~nd0m12ed c0m~e~ M0ck de5~n w1M ~ v ~ u ~ r0w5 a5 5p11~610ck ~ct0r (L1~e and H1115, 1978). F0r ~ e 0pen ~ y 5 , ~e de~9n w ~ a ~nd0m~ed c 0 m ~ e M0ck de519n w1th Me m ~ 6~r1~ ~ 5 p 1 ~ ~ 0 r ~nd ~ d u ~ r0w5 ~ 5p11~ Mcck fac~r (7a6~ 2). ~ add~0~ an AN0VA w ~

c0mpu~d 5eparate1y f0r every hed9e 5pe~e5 f0r the 0pen M1ey y1e1d5, wh~h M10wed t0 ~ f0r 1n~racf10n5 6~ween r00t 6arr~r and hed9e d1~ance f0r every 5pe- c~5.

• R ~ and ~ u ~ n

~1. P m ~ ~ ~

De5p1~ ~mp0r~y ~ 6 a c k 5ympmm5 0f Ca111andra 6ranche5 ~ Me end 0f Me d ~ 5ea50n 0f 1991/1992 a5 de5cr16ed 6y Nat10n~ R e ~ c h C0un~1 (NRC, 1983), ~1 0f Me te5~d ~ee 5pec1e5 ~emed t0 t01era~ ~e d1ff1cu1t 51~ c0n~f10n~ ~M0u9h the pr0duct1~ff 0f 611r1~d1a and Ca~ndra w ~ 10w (7aMe 3). CaH~n- dra 15 t e~ adapted m m0~ hum1d d1mme5 (NRC, 1983; Pa~a1tan ~ ~., 1993). Dur1n9 1992, 5enna wa5 much m0~ pr0duct1ve than the 0~er 5pec1e5 (7a6~ 3), m ~n ~ 6ecau5e ~ c0nt1nued ~ 9r0w rap1d1y dur1n9 the dry 5ea50n. 7he ~9r0wM 0f 611~d1a a~er ~e prun1n9 1n Ju~ 1991, h0weve~ wa5 very 510w, 5u9- 9e5t1n9 that t~5 5pec~5 5h0~d n0t 6e pruned f0r at 1ea5t 2 m0~h5 6 e ~ Me 0n~t 0f ~e dry 5ea50n at M15 51te. 7he nmr1em ~an5~r 1n the Ca~ndra prun1n95 w ~ 10w~ Man 1n the 611r1c1d1a pru~n95 6ecau5e 0f a 10w~ pe~ema9e cf 1eave5 1n Me ~0m~5. A~0, Me

~ ~ ~ h ~ 2 ~ h m ~ n / ~ u ~ ~ 0 ~ ~ d ~ v ~ n m e n t ~ (1995) 8~101

7 ~ 3 MM~ ~ d ~ N e m ~ c ~ ~ r u ~ ~ c m ~ ~ (5N ~ m- ~ ~ e ) w ~ ~ 0 pmN~5 ~ M ~ ~ d Jdy 1~2

Hed9e 70tN Le~ mdch N P K Ca M9 Fe Mn 5 p e ~ m~ch

(k9ha -1) (k9ha ~) (k9ha -~) (k9ha-•) (k9ha ~) (k9ha -~) (k9ha -~) (9ha ~) (9ha -~)

2n Cu

(9ha -~) (9ha -~)

6~c1d1a 1683 903 41.1 2.6 13.1 11.8 4.8 175 57 14 26 Ca111andra 1890 527 26.5 1~ 5.9 7.2 2A 112 62 23 23 5enna 4092 1809 42.2 3.0 17.0 41.6 5.2 257 122 39 61

L5D5% 1265 356 13.1 n~ 4.8 9.5 1.5 73 35 12 17

~ m ~ n0t ~9mf1~m ~ P<0~5 .

c0ncenUat10n5 0f N, P, K and M9 we~ N9he~ 1n the 611r1c1d1a N0ma55, wNch N50 5h0wed the m05t rap1d nutr1em re1ea5e fr0m dec0mp05h9 ~ave5 and r00t5 (Lehmann m N., 1995). 5enna c0mpen5a~d ~w nuU1- ent c0ncen~at10n51n the N0m~5 6y N9h N0m~5 Fr~ ducf10n.

~2. Ma12e y1e1d5 1n the c105ed a1~y5

De5p1~ Nv0~Ne ra1nfa11, the m~2e y1e1d5 ~e~ ~w 6ecau~ 0f the 10w ~rt11hy 0f the ~ and the a6~nce 0f m ~ N ~11~at10n dur1n9 the pa5t 3 year5. C 0 n ~ ef1n9 ~e wh01e ~ area 1ndu~n9 the 12.5% 0f the 5urface th~ wa5 0ccu~ed 6y the hed9e5, the c 0 n ~ 9ave the ~9he~ y1dd ( 1.42 9 ha- ~ ), and the Ca~an- dm p10t5 9ave the ~we~ y1e1d ( 1.03 9 ha- a ) ; 611r1- c1d1a (1.20 9 ha -~) and 5enna (1.19 9 ha ~) were 1 ~ m e ~ e . 7he ~f fe~nc~ w~e n~ 5~f1ca~.

7he ~w y1e~ ~ the Ca~and~ ~0t5 w~ a ~5dt 0f ~ d depr~0n5 ~ the ~ee-cr0p 1nterfac~ wh~h ~d n0t 0ccur 1n the pr0x1m1ff 0f the 0th~ hed9e 5pec~5 (~9. 2). ~ 5 t 1 n 9 ~ , the y1e1d5 0f the r0w5 next t0 the 611r1c1d1a and 5enna hed9e5 were even ~19ht1y ~9h~ than th05e 0f the f01~w1n9 ~w5. 1n the cen~N part 0f the N~y5, the y ~ 5 p~ r0w w~e 51mHar ~ a11 hed9e tre~men~ and ~ the c0ntr01.7he y1e1d reduct10n 1n the f1r5t r0w5 0f the Ca~andra ~ 5 wa5 part1y a re5u~ 0f reduced p1a~ num6~5 (~9 .2) , 6ut m ~ y 0f reduced y1e1d5 p~ p1an~ N0 reduct10n 1n ~ a ~ num- 6er5 wa5 065erved 1n the pr0~m1ty 0f ~e 0th~ hed9e 5pec~5.7~5 may ~ c ~ e an N1d0path~ effe~ 0f Ca~ ~and~ 0n m~2e 9~m1nat10n, p0~1~y thr0u9h ex~ac~ 0f 1eave5 0r ~ 5 , wh~h have part1cu1ar1y h19h p0~phen~ c0n~m5 (Lehmann et N., 1995), 0r an 1 n c ~ e d a c t 1 ~ 0f ~ed p~d~0r5 near the C a ~ n d ~ hed9e5. A11e10p~c effect5 0n 9erm1nat10n and ~0wth

0f her6ace0u5 p1an~ have 6een dem0n5~a~d w1th ~af and r00t ex~ac~ 0f 5evern a9r0f0re5~y 5pec1e5 (5ure5h and V1naya RN, 1987; Chaturved1 and Jh~ 1992; Hau5eC 1993) and may 6e a w1de5pread phe- n0men0m 1ncrea5ed p1ant 10~e5 due t0 5eed predat0~ 11ke m1ce and 61rd5 h1d1n9 under perenn1N p1ant5 have N50 repe~ed1y 6een 065erved 1n a9r0f0re5~y 5y5~m5 (LN, 1989; 5chr0tN 1994; 5chr0th et N., 1995).

7he 10wer per-hectare yMd5 1n the ~ee p10t5 c0m- pared w1th the c0n~01 (5ee a60ve) 5h0w5 that N~y cr0pp1n9 w1th 6A0-m-w~e a11ey5 wa5 a9r0n0m~N~ n0t advan~9e0u5 1n the th1xd year after the e~a61Nh- ment 0f the hed9e5. 7here wa5 n0 ~ndency f0r yMd 1ncrea5e51n the N~y5 0fany 0fthe hed9e 5pec~5 wh1ch c0dd have c0mpen5a~d f0r the 5urface 0ccup1ed 6y the hed9e5, wh1~ the mN2e y1e1d5 were depre55ed 1n the pr0~m1~ 0f the Ca111andra hed9e5.

~ Effea ~ d 9 e ~ t a n ~ ~ ~ ~ ~ ~ ~en ~ w1~0ut ~0t 6ar~er

1n N~y cr0pp1n9 w1th ~n9~ hed9e~ the 610ma55 0f the hed9e pru~n95 per un1t 0f cr0pped 5urface decrea5e5 w1th 1ncrea51n9 a11ey w~th. H0weveL the u5e 0f pa1red 0r mu1t1p1e hed9e5 a110w5 the a11ey w1dth t0 6e ~crea5ed w1th0ut chan91n9 the prun1n9 610ma55 per u~t are~ thu5 reduc1n9 the d~ect 1nf1uence 0f the hed9e5 0n the cr0p5. F19. 3 5h0w5 h0w far th15 5 ~ e 9 y w0dd have 6een u5efu1 f0r the three 1nve5t19a~d tree 5pec~5. 7he 0pen N~y5 ~ th15 tr1M appr0x1ma~ the 51tuat10n 1n N1ey5 w1th 14 m~2e r0w5 ( 11.2 m w~th 0f cr0pped area) 6etween p~red hed9e5.

7he re5u1~ fr0m ~e 0pen N1ey5 were c0n515tent w1th th05e f0m the d05ed N~y ~0t5 (F19. 2). A pr0- n0unced y1dd depre5510n ~ the ~ee-cr0p 1nterface wa5 065erved 1n the Ca~1andra, 6ut n0t 611r1c1d~ and

~ ~ h ~ 2 ~ h m a ~ 1 A 9 ~ u ~ ~ 0 5 y 5 ~ ~ d ~ r 0 n m e m ~ (1995) 8 ~ 1 ~ 95

7

.•

.E

0

•

1 •

6EdcN~ 5ep1um 2,0

1,5

1.0

0.5

•

1

..... C0ntr01 (y1e1d and p1ant num6er)

0.0 ~ 1 ~ ~ ~ ~ ~

0.0 0.8 1.6 2.4 3.2 2.4 1.6 0.8 0 0

D15tance fr0m the hed9e [ m ]

40 ;

30 R

20 ~

7

E .~

.E

•

1 •

C a ~ n d r 0 c a 1 ~ r 5 u 5 2.0

1.5

1.0

0.5

•

0.0 1 1 1 1 1 1 1

0.0 0.8 1.6 2.4 3.2 2.4 1.6 0.8 0.0

D15tance fr0m the hed9e [ m ]

- 4 0 ;

0

3 0 ~

8

-20 ~

7

.~

•

.5

•

1 •

5enna 51ame0 2.0

1.5

1.0

0.5

1

t

0.0 ~ ~ ~ ~ ~ ~ ~ 0.0 0.8 1.6 2.4 3.2 2.4 1.6 0.8 0.0

D ~ 0 n ~ fr0m the hed9e [ m ]

- 4 0 : :

0

• 30 ~

• ~ 0

H9.2. MM2e ~ d d 5 (mean5 and 5E) and p1ant num6er per ~ w ~ the d05ed MM~. 7he c0ntr01 y1e1d d0e5 n0t take the 1~9er cr0pped 5urface c0mp~ed w1~ the hed9e tremmen~ 1nt0 acc0unL

96 ~ ~hr0~ 2 ~hma~ 1 A 9 ~ u ~ E ~ 5 ~ m 5 ~ d ~ n m e m ~ (19~) 8~101

2.5

1.5

.~ ~ 1.0 6 .~ 5 0.~

0.0 0.0

6f1dc~ 5ep1um

~ - - ~ untrenched 0 - - 0 : ~ ~ + : : ~ . + ~ . , trenched [

0 1

0.8 1.6 2.4 3.2 4.0 4.8 5.6 D15tance fr0m the hed9e [ m ]

40

3 0 ~

9 2 0

6 .4

2.5

2.0

1.5

1.0

0.5

0.0 0.0

C~f1andra ca10th~5u5 1 1 1 1 1 1 1

1

A"

0.8 1.6 2.4 5.2 4.0 4.8 5.6 D15tunce fr0m the hed9e [ m ]

40

3 0 ~

9 2 0

6 .4

2.5

~ 2.0 2

1.5

~ 0.5 0

0.0 0.0

5enn6 51amea

......... •

1

0.8 1.6 2.4 32 4.0 4.8 5.6 D15t0nce fr0m the h e d 9 e [ m ]

4 0

3 0 ~

3

2 0 6 .4

F19.3. M~2e y1dd5 (~rc1e5, mean5 and 5E) and p1ant num6eR (tr1an91e5) per r0w 1n the 0pen M1ey~ 7he p1a5t1c 5heet f0r r00t 5eparat10n wa5 1n~ 1e d at 0 4 m d1~ance fr0m the hed9e5. F0r hed9e d15tance5 0f 4 m and m0re, 0n1y avera9e y1dd5 0f 5u6p10t5 w1th and w1th0ut r00t 6arr1er are 5h0wm 7he c0n~01 y1dd d0e5 n0t take the 1ar9er cr0pped 5urface c0mpared w1th the hed9e treatmen~ 1nt0 acc0unt.

~ ~ h ~ £ ~ h m ~ n 1 A 9 ~ u ~ ~05y5tem5 ~ d Env1r0nment ~ (1995) 8 ~ 1 ~ 97

7 ~ 4 Nutf1em c0ncen~af10m ~ t ~ d ~ m a ~ ~ mM~ e ~ ~ m ~ , taken fr0m r0w54 ~ d 7 ~ ~e 0 ~ n ~ 5 ( m e ~ 0f 5 ~ 0 t 5 ~ ~ d ~ th0m r ~ t 6arr1er). ~ r ~ c M ~ 5 ~ 5~ ~

5pede5 N P K Ca M9 2n Cu Mn (m99 -1) (m99 -~) (m99 - t ) (m99 -~) (m99 - t ) (m9k9 -~) (m9k9 -~) (m9k9 -1)

6~r1c1d1a 14A 1.40 18.9 2.94 1.86 11 12 26 Ca111andra 12A 1.28 17.5 2.40 1.75 10 11 24 5enna 12.3 1.43 16.8 2.69 1.61 10 12 24 C0n~01 11.7 1.33 17.0 2.65 1.61 10 1 • 21

5enna ~0~ w1~0ut r0~ 6arr~L whem ~e y~M5 a9Mn ~ c ~ e d ~ h t 1 y 1n ~e f1r5t r0w next t0 the hed9~. 7he cv~M1 5pec~5 effe~ cn mM~e y1e1d5 w~ n0t M~ n1f1canL 6ut the 1n~ract10n 6~ween 5pec~5 and ~ tance wa5 ~9h~ 5~n~cam (7a61e 2), ref1ect1n9 a • ffer1n9 ~acf10n 0f mM2e y1e1d5 m 1ncrea51n9 d15tance fr0m ~e hed9e5. 1n ~e Ca111andra ~ 5 , ~ c ~ 9 MMy wM~ w0u~ have pr09re551ve~ reduced ~e ne~ at1ve M~fface effecU, 6ut ~e 9r0w~ c0nd1t10n5 0f mM2e w~e never 6e~er ~an ~ the 50M cr0p#n9 c0n- 9~. ~ ~e 5enra ~ mM2e y1e1d5 Fer r0w ~emed m 6e 1ndependem 0f hed9e d15tance and ~m119 m ~05e 0f ~e c0n901, 50 ~ a c0mpen5at10n f0r ~e ~duced 5ur~ce w~ e4uM~ n~ p05~M~ 6~c1d1a w ~ ~e 0n1y hed9e 5pec~5 that 1ncm~ed mM2e ~eM5 p~ r0w ~ c0mp~150n m ~e c0n9M, ~u5 5h0w1n9 a p~enf1M ~r the 1mpr0vemem 0f pev~ea ~e1d5 1n w1de a11ey5. H0weveL ffca1cu1ated f0r the wh01e 5urface 0f~e 0pen MMy5 Mdu~n9 ~e 5urface 0ccu#ed 6y ~e hed9e5, ~e y ~ 5 we~ Mm05t ~m11~ ~ 611r1c1d1a and c0nU~ #~5 w1~ 1.51 9 and 1.48 9 ha -~, ~5pect1ve~. A1~0u9h ~e MMy ~0p~n9 5y5~m wa5 ~u5 n0t yet advama9e0u~ F19. 3 5u99e~5 ~at, m a #ven am0unt 0f hed9e pmn~95 per un1t cr0pped 5urface, ~e pr0~ a6111~ 0f a c h ~ n 9 n~ ~ d d 1 n c ~ 1n a11ey ~0pp~9 ~ e ~ e d w1~ MMy w1dth m t~5 M~.

7he ~ffef1n9 y ~ effe~ 0f ~e hed9e5 w~ ~ M~t part1y due m ~e nutr1em5 1n ~e m~ch. F011~ anMy~5 0f mM2e 5h0wed def1c~m Mvd5 0f N, P and 2n, and K wa5 at the •0wer end 0f ~e 5uff1c~ncy ran9e (J0ne5 et M., 1990) (7a6M 4). N-def1dency wa5 M50 rec0~ ~2ed 6y Maf cM~at10n. 7he c0ncen9at10n5 0f m0~ nutr1em5 ~ mM2e 1eave5 were h19he~ ~ ~e 6 ~ c M ~ #0t5, a1th0u9h ~e d1fference5 were 0n~ 5~n~ca~ ~ ~e 6% and 7% Mvd5, ~5pect1vdy, ~ r N and K. 7he Ca~ndra ~0m~5 had added ~9~f1cant1y M55 nutr1- en~ t0 the cr0pped 5011 than the 0~er 5pec1e5 (7aMe

3). A 6etter m5p0n~ cf mM~ m 611r1cM~ c0mp~ed w1~ Ca~ndra mdch ha5 M50 6een ~und 6y 6 m ~ v 1d9e (1992). 7he m0~ ~v~aMe effect 0f 611r1c1d1a c0mp~ed w1~ 5enna 0n the mM2e may 6e ex~Mned 6y ~e 5~w~ nuMem re1ea~ fr0m ~e 5enna M0m~5 (Lehmann ~ M., 1995), w~ch may have ~duced ~e u~ake ~ ~e nu~en~ 6y ~e ~0p.

~ ~ Effe~ 0f r0~ 6ar~e~ 0n ma~e ~e1d5

MM2e ~dd5 ~ ~e c0n9M tremmenL whe~ r0d 6 a r r ~ wen M50 ~5ta1M~ 9ave n0 ~ca t10n ~m ~e ~ t 1 c 5hed had an 1nf1uence 0n the mM2e when ~MMd 6etween tw0 mM2e r0w5 ~5~ad 0f a mM2e r0w and a hed9e (dam n0t 5h0wn). L~M 1nf1uence 0f d~#n9 M0ne ha5 M50 6een f0und 6y W111ey and Reddy ( 1981 ) 1n a 51m11~ expef1menL

7he y1eM ~5p0n5e 0f mM2e ~ ~e r0d 6arr1er ~ ~ d 6~ween ~eatmen~, ~ ~f1ec~d 6y a ~9~f1cam three-way M~ract10n 6~ween the p ~ n c e 0f r00t 6arr1er~ hed9e ~5mnce and 9ee 5pec~5 (7a6M 2). M the Ca~ndra ~0t5, ~e ~ d d dep~5~0n m the ~ v ~ce w~ e~m1nmed 6y ~e r0~ 6arr1er fr0m ~e ~c0nd mw 0n, ~5u1t1n9 ~ a ~9~f1cam ~ract10n 0f 6arr1er treatment and ~ a n c e (P<~05) . WhHe the y1e1d d e p ~ n 1n ~e f1~t 10w ff0m ~e hed9e w~ part1y due t0 a ~duct10n 0f p1am num6er5, ~e 6arr~r effect wa5 e n f 1 ~ due t0 ~ffef1n9 ~dd5 per ~am. 7h15 5h0w5 ~m the Ca111andra hed9e5 exe~ed a 519n1f1cant r00t c0mpedf10n 0n the mM2e un~ a60ut 2.5 m d15- mnce ff0m ~e ~ee5, and ~m ~e 6arr1er wa5 5~1 effec- t1ve ~ ~du~n9 th15 2 ye~5 a~er ~e~ M~a11at10n. Y1dd ~ c ~ due ~ r00t ~p~at10n have M50 6een ~p0~ed ~0m a550c1ad0n5 w1~ Leucaena ~uc0ce- pha~ (5~9h ~ M., 1989; 0n9 ~ M., 1991; Ra0 et M., 1991 ). At 1.6 m hed9e ~5~nce, wh~e ~e 6arr1er effe~ wa5 ~e m05t ~ n ~ , ~e c0ncen9af10n5 0f m0~ nutf1-

98 ~ 5 c h ~ 2 ~ h~1A9~cu~ Ec0~5te~ and Env1r0nmem ~ ~ 995 ) 8~101

7 ~ 5 N u ~ t ~ n ~ m ~ ~ the d ~ maRer ~ mM~ ~ Mave5 m ~ L t ~ e n ~ m ~ ~ d mw ~ ~ 0 ~ n ~ey5 ~ ~ ~111andra p10t5. F0r 5 ~ M ~ 5 ~ 5 ~ e text

5u6p10t N P K Ca M9 2n Cu Mn

(m99 -~) (m99 -~) (m99 -~) (m99 -~) (m99 -~) (m9k9 -1) (m9k9 -~) (m9k9 -1)

W1th 6arr1er 13.3 1.21 18.1 2.65 192 11 11 24 N0 6arder 12.2 1.50 17.1 2.32 133 8 8 19

en~ ~ the mM2e Mave5 were ~9her 1n the 5u6~0t5 w1th than w1th0ut r00t 6arr~r (7a61e 5), 5u99e5t1n9 thm r00t c0mpet1t10n wa5 part1y f0r nu~1en~. H0weveL 0w1n9 t0 c0n5M~a6M var1a6111ty the ~fference wa5 0~y 519n1f1cant m the 5% 1evd f0r 2n and Cu (P < ~06 ~r K). A reduct10n 0f f011ar 2n Mvd5 0f mM2e under ~9h tree c0mpet1t10n ha5 ear1~r 6een rep0~ed fr0m th~ ~te (5chr0th ~ M., 1995).

1n the 6 ~ c M ~ and 5enna ~ mM2e y1e1d5 were reduced rather than 1ncrea5ed 6y the r00t 6arr1er, wh1ch ~0v0ked a marked y1e1d depre5510n m the hterface, h the f1r5t cr0p r0w fr0m the hed9~, the reduct10n wa5 ~9~f1cam m P < ~01 ~ the ca5e 0f 5enna (L5D ~ ) . 7~5 5u99e~5 that a m~0r effe~ 0f the 6arr~r5 wa5 t0 11mff the r00t1n9 vdume 0f the mM2e 6y exdud1n9 k5 r00t5 ff0m the 5M1 6eneath the hed9e5. 7he 1n~u~0n 0f mM2e r00t5 ~t0 the 5011 under 6 ~ v ~ a r06u5~ hed9er0w5 ha5 6een rep0~ed (Hu~ey et M., 1994). A 51mftar ex~anat10n wa5 9Nen 6y W1~ey and Reddy (1981) f0r 90wth reducd0n5 and pMe Maf cd0r 0f m~et when 1t5 r00t1n9 20ne wa5 5eparated ff0m that 0f 1ntercr0pped 9r0undnut5. FM1ar nu~1em Mvd5 0f mM2e were n0t ~9n~cam~ reduced 6y the r0~ 6ar- 6er5 (data n~ 5h0wn), 6m water uptake may have 6een affected. 7he 9~ater r00f1n9 vdume 0f the mM2e at the ~ r ~ c e may ex~Mn why h the 5 u 6 ~ 5 w1th0m 6arr~r the y1e1d 0f the cr0p r0w ne~ t0 the 611~c1d1a and 5enna hed9e5 ~nded m 6e 5119hf1y M9her than thm 0f ~e adjacem r0w (F195.2 and 3).

7w0 year5 after th0r 1n5ta11at10n, the r00t 6arr1er5 were certa1~y M~ eff1c~m ~ exch~n9 ~ee r0~5 ff0m the a11ey5 than 1n exc1ud1n9 mM2e r00t5 ~0m the 5011

6e10w ~e hed9e5. 7h15 may part1y exp1Mn the y1e1d depre5~0n5 ~ ~e 1nterface ~ the 6 ~ c 1 d ~ and 5enna 5u6p10~ w1th r00t 6arr1er. Further fact0r5 may have 6een 50me 5had1n9 dur1n9 the f1nM ~a9e5 0f mM2e devd0pment 1n the 611r1c1d1a (and Ca~ndra) p10t5, p00r 9erm~at10n and 1ncrea5ed 5eed predat10n a5 ~d1- cated 6y the ~duced p1ant num6e~ 1n the 5ame ~em- ment5 (F19. 3), and pre5uma61y an 1ncrea5ed pe~enta9e 0f re50wn p1an~ wh1ch 9ave 10wer ~ d 5 per p1ant. 1n the 5u6p10t5 w1th0ut 6arr1eL the5e ne9at1ve 1nf1uence5 0f the tree5 were apparent1y ent1re~ c0m- pen5med 6y the ~crea5ed r00t1n9 v01ume 0f the mM2e at the 1nterface, 50 th~ y1e1d depre~10n5 ~d n0t 0ccur (F195.2 and 3). 7he Ca111andra hed9e5, h0wever, were apparent1y t00 c0mpet1t1ve, 50 thm the mM2e c0u1d n0t pr0f1t fr0m the ~crea5ed r00t1n9 v~ume m the 1nter- face.

A m0re 5pecu1at1ve rea50n f0r the y1e1d d e p r e ~ n 0f the ma~e ~ the 611r1c1d~ and 5enna 5u6p10t5 w1th r00t 6arr1er ~ th~ the ~ee r00t5 may have had a fav0v a6M effect 0n the cr0p 6y 1mpr0f1n9 5011 phy~cM, chem1c~ and 6 1 ~ 0 9 ~ pr0pe~5 0f the 50ft, 0r thr0u9h nutr1ent reMa5e ~0m hed9e r00t5 k111ed dur1n9 5011 f1Ha9e (7a61e 6), and thm the5e were reduced m 1ea5t ~mp0rar1~ 6y the r00t 6 a r r ~ Yam0ah et M. (1986a) rep0~ed 1ncrea5ed mM2e y1e1d5 near Leu- caena hed9e5 h unfe~1112ed M1ey cr0pp1n9 p10t5 w1th pru~n95 rem0ved and exp1Mned th15 w1th Htterfa11, 6ut Y0un9 (1989) 5u99e5~d fav0ra6M r00t effect5 a5 an ad~f10nM exp~nat10n. 1n fe~1~2ed p10t5 th15 wa5 0uv w~9hed 6y 9ee c0mpet1t10n. 0ur 50ft5 were hherenf1y nutr1ent p00r and unfe~1112e~ and the mu1ch pr0duc-

7 ~ M 6 Macr0nu~ent5 (k9 ha- 1 d m - ~) c0nta1n~ h ~ e 5en~ r00t5 5~wn ~ F19. 4 ~ 06tMn~ 6y 11ne~ 1nterp01at10n ~ the r00t m~5 ~ t w ~ n the p01nt5 ~ me~uremem fr0m 0.4 m 3.2 m ~ d muMp11caf10n w1th nu~ent c 0 n ~ n ~ 0 n 5

N 5 P K Ca M9

5.6 0.6 0.4 2.3 4.9 1.0

~ ~ h ~ 2 ~hmann1A9r1cu1tu~ E c 0 ~ a n d ~ v 1 r 0 n m e n t ~ (1995) 89-101 99

7

7

5enna r00t m055 1209 7

~ 1 ~ ~ t 0 0 0 t •

800• [ ~ k 0--00--00-20-05mmmm

0 40 0 - - - - 0•8 1 61 241 3 ~

D15tanCe ~0m ~e h~9e [ m ]

E 0 E

5enn0 r00t 1en9th

~ 1 4

3

2

1

0 0

w~ •

~ " ~ - ~ L ~ c ~

1 . . . . . . ~ - - - ~ • • ~ - - ~ . . . . ~

40 0~ 16 24 5 2 40 D8t05ce fr941 tne neccc [ ~" ]

F19. 4. R00t ma55 and r00t 1en9th den51ty 0f5enna 51amea 1n 0-10 cm 5011 depth 6etween the r1d9e5 a5 a funct10n 0fthe d1~ance fr0m the hed9e5 1n the 0pen a11ey5 (f1ve + dead r00t5; mean5 and 5E).

f10n 0f ~ e hed9e5 wa5 ~w. ~ 5eem511ke~ ~ ~51t1ve e ~ c ~ 0f ~ee r00t5 0n cr0p 9r0wth are m05t e ~ de~c~d under c0nd1t10n5 ~ p00r 5~1 ~ 1 1 ~ ~ c0m- N n ~ 0 n wkh 10w ex~rn~ 1nput5.

~ e ~ w m ~ d e n ~ ~ ~ c M ~ 5 ~ m and c0n- 5e4uem~ 10w r00t c0mpet1t10n w1~ cr0p5 ha5 repeat- e~y 6een 065erved (8uddma~ 1990; 5 c ~ h and 2ech, 1995), ~ 0 u 9 h the ~ read1~ ~0wth h~1t 0f • 15 5pec1e5 ~v0r5 c0m~t1t10n ~ r 119ht. ~nna 5~mea, h0weve~ ~ n0~t10u5 ~ r k5 ~ n 5 e and c 0 m p ~ e r0~ 5y5~m when 9r0wn ~ a ~ee (V0n M ~ d ~ , 1986; 5 c ~ 0 ~ ~ ~., 1995), and 5en~ r00t5 were ~und up t0 a d15tance 0f 3~ m ~0m ~e hed9e5 ( ~ 9 . 4 ) . H0w- eve~ the r00t 5y~em 0f r e 9 ~ y pruned hed~5 0f ~nna 5~mea 5eem5 ~ ~ ~55 c0m~t1t1ve ~an th~ 0f ~ee5 0f ~ 5 ~ e c ~ , pr06a~y 6ecau5e 0f th~r ~wer ~0m~5 and c 0 n 5 ~ u e ~ y nu~ent and w~er c0n- 5um~0n. ~ d d ~ p r e ~ 0 n 5 0f r1ce and m~2e 1n ~ y ~0p~n9 w~h 5en~ 5~mea have 6een rep0r~d 6y Dan50 and M0r9an (1993~6), 6ut the ~ de~9n ~d n0t ~10w d 1 ~ r e ~ 0 n 6~ween ~ 0 ~ and r0~ c0m- p ~ n .

7he h19h c0mpet1t1vene55 ~ t h e Ca111andra r0~ 5y5- tem may have 6een due t0 ~9h nu~ent and w~er c0n5um~0n, a5 the C a ~ r a hed9e5 re9rew ~90~ 0u~y a ~ r ~ e 3~y p r u n ~ 6m ~ 1 0 p a ~ e~c t5 mu5t ~50 6e c0n5~ered 1n ~ r e 5m~e5. A1~0u9h ~e r00t den~y 0f Ca1~ndra c0uM n ~ 6e 4 u a ~ e d (5ee M ~ h 0 ~ ) , 1t 5eemed t0 6e 4 ~ e den5e. ~ c h u m and Kan9 (1989) 065erved n0 y ~ d ~ p r e ~ 0 n 0f m~2e a~acem t0 ~ n d r a hed9e~ w ~ ~ d d reduct10n5 ~ c0w~ a were m ~ 6 ~ e d t0 5had1n9. ~15 ~ wa5

carr1ed 0ut 0n a much m0re fert1~ ~ ~an 0ur exper- 1me~, 50 ~ nu~1e~5 and water may have 6een ~55 9r0wth-11m1t1n•

• C0ndu~0n5

Numer0u5 a60ve- and 6d0w-9r0und pr0ce55e5 may 0ccur f1mu1tane0u51y at the Wee-cr0p 1nterface, fr0m m0d1f1cat10n51n m1cr0cf1mate and pe~ act1v1ty t0 rec1p- r0c~ r00t c0mpet1t10~ chan9e51n 5011 fe~111ty and ~1e- 10path~ 1nteract10n5. 7he 5um 0f the5e effect5 determ1ne5 whether cr0p 9r0wth at the ~ee-cr0p 1nte~ face 15 depre55ed, n0t affected 0r even 1mpr0ved. 8ecau5e 0f the c0mp1ex1ty 0f the5e pr0ce55e5 and the 1nc0mp1etene55 0f r00t 5eparat10n 6y mechan~a1 6ar- t1er5 (51n9h et a1., 1989; 5chr0th and 2ech, 1995), the5e are hard1y 5u1ted t0 4uant1fy r00t c0mpet1t10n exact1y, 6ut may 91ve 4u~1tat1ve 1nf0rmat10n a60ut the re1at1ve c0mpet1t1vene55 0f d1fferent tree r00t 5y5tem5. Fr0m the re5u~5 0f th15 expet1ment 1t 15 c1ear that the r00t 5y5tem 0f Ca~1andra wa5 marked1y m0re c0m- pet1t1ve than th05e 0f 611r1c1d1a and 5enna, re5u1t1n91n y~1d depre5f10n5 at the Wee-cr0p 1nterfac~ wh~h c0u1d 6e reduced 6y r00t 6arr1er~ 1n the a550dat10n w1th CaH1andra, 6ut n0t the 0ther tw0 ~ee 5pec1e5.7h15 make5 Ca111andra m0re 5u1ted f0r fa110w 1mpr0vement than f0r tree--cr0p a550c1at10n5 at th15 51te. P055161e rea50n5 f0r th15 c0mpet1t1vene55 1ndude h19h r00t 1en9th den51ty, h19h nu~1ent and water uptake rate5, ~1e10path~ effec~ 0r p055161y even the pr0m0t10n 0f r00t d15ea5e5. M0re re5earch 5h0u1d 6e c0nducted 0n

100 ~ 5¢hm~ 2 ~ h m a n n 1 A 9 r 1 c u ~ Ec05y5te~ and Env1~ment ~ ~ 89-1~

• e ~ent1f1cat10n 0f ~05e ch~ac~f15f1c5 wh~h deter- m1ne ~e n a effe~ 0f a tme r00t 5y5~m 0n a550c1ated cr0p5 under ~ f f e ~ m mana9ement c0nd~0n5 1n a9r0- f0re5try.

7h15 w0rk 91ve5 ~50 50me ~ c m ~ n ~at ~e pr0~ 1m1~ 0f tree ~ 5y~em5 can ~ c m ~ e ~0p ~ d d 5 . 7 ~ 5 wa5 pr06aNy due t0 an 1 n c ~ e d v~ume 0f ~e ~0p r00t1n9 20ne at the tree-cr0p ~terfac~ 6ut ~ v ~ a 6 ~ effec~ 0f tree r0~5 0n 5011 ~111ty ~50 ~em p0~161e. 7he 4 u e ~ n 0f w h e ~ 0r n0t a cr0p can pr0f1t ~0m ~ v ~ a ~ e effect5 0f ne~h60r1n9 tree5 depend5 0n the c0mpet1t1vene55 0f the tree5, and pr06a61y 0n 50H c0n- d1t10n5.

1n ad~f10n t0 Wee 5pec~5 5decf10~ ~e ch~ce 0f ~ y w~th 1nf1uence5 f1n~ ~0p y1e1d5 6y determ1~n9 • e pe~en~9e 0f the ~0pped 5ur~ce ~at 151nf1uenced 6y ~ r ~ c e effect5.7he ~ 5 d ~ p m ~ e d 5u99e~ ~ 0n ~e 51te 0f th15 5~dy, w1de ~1ey5 6~ween mdf1~e hed9e5 w0~d 6e p ~ e t0 narr0w ~1ey5 6etween

~n~e hed9~.

A c ~ 0 ~ 9 m ~

7he au~0r5 ~ank ~ e pr0ject Devd0ppement 1nt~ 9r6 de 1a R6~0n C e n ~ e du 7090 0f ~e Dem~he 6~e11~haf1 f0r 7echn15che 2u~mmen~6e1t ( 6 7 2 ) ~ r f1nanc~9 ~15 ~ c h w0rk, and ~e D1~ct10n R6~0n~e du D6vd0ppement R ~ ~ 50k0d6 ~ r pe~ m155~n t0 w0~ ~ the re5e~ch ~at10n at K~a60ua and ~ r the 9 e n ~ 0 ~ and u n c 0 m ~ a ~ d 5upp0~. N. P0~y and ~5 ~am ~0m the ~5e~ch 5tat10n at K~a60ua c0n~6u~d ~ ~155~dy w1~ ~ d r c0mm1tted w~k and en9a9ed ~5cu5~0n5. D. K0~e and D~ P. D r e c ~ d 9ave ve~ v~ua~e t e c h n ~ 5upp0~. 7he f1~t au~0r 151nde6ted t0 7. K1tt ~ r ~5 h0~1t~1ty and ~5 ~ m ~ 1n t~5 expe~menL

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