T 

ABSTRACT 

t h i s sUiiJy was conduc t ed u i t h t h e inn In aim of f i n d i n g o u t the e f f e c t s 

of phosphorus q u a n t i t y and I n t e n s i t y r e l a t i o n s h i p s on P a v a i l a b i l i t y of 

s o i l s . f o r t h i s p u r p o s e , four s o i l s ( t h r e e U l t i s a l - t and one A K i s o l ) 

u n r e c o l l e c t e d from d i f f e r e n t l o c a t i o n s of S r i Lanka f namely t P ln ta le , 

Hapnlnnn t Ambeuela and flaha I I luppnl Lama , Tn a s s e s s P a v a i l a b i l i t y 

of t h e s e s o i l s n n o t e s p e r i m e n t u a s conduc tnd u s i n g rye n r a s s ( Lol ium 

mul Iii l o r ium L . ) a s t h e i n d i c a t o r p l a n t . Phosphorus u a s added t o a l l 

: : o i l s a t the r a t e of 20 mq 100 g ' ' s o i l s , and t h e P s t a t u s u a s e v a l u a t e d 
f 

u s i n g q u a n t i t y t I n t e n s i t y and b u f f e r c a p a c i t y p a r a m e t e r s . O l s e n - P f 

CAL-P and flray 2-P v a l u e s i , n r e t a k e n a s q u a n t i t y measu remen t s • w h i l e 

the c o n c e n t r a t i o n s i n a s o i l s u s p e n s i o n of 0 .1 W KC1 ( s o i l : s o l u t l o n 

= 1:1Q ) s e r v e d a s t h e i n t e n s i t y measurement . To o b t a i n I n f o r m a t i o n 

on P b u f f e r c a p a c i t y a s o r p t i o n s t u d y UIJS conduc t ed by eoui l l b r a t l n q 

s o i l s a t i n c r e a s i n g c o n c e n t r a t i o n s of P in a medium of 0 . 1 PI KC1 , The 

amount of P so rbed ( x ) s e r v e d a s the Q u a n t i t y f a c t o r w h i l e e q u i l i b r i u m 

P c o n c e n t r a t i o n ( c ) r e p r e s e n t e d t h e i n t e n s i t y f a c t o r . Us ing t h e s e 

s u r p t i o n d a t a , s o r p t i o n i s o t h e r m s were p l o t t e d a c c o r d i n g t o d i f f e r e n t -

ma thema t i ca l models r and b u f f e r c a p a c i t i e s and n t h e r s o r p t i o n i n d i c e s 

were c a l c u l a t e d . In a d d i t i o n , P r e p l e n i s h i n g speed uas c a l c u l a t e d by a 

c o n t i n u o u s e x t r a c t i o n method . To e v e i u a t n P u p t a k e r t h r e e c u t s of 

rye g r a s s u c r e t aken u i t h i n a pe ri. od of 72 days and the cumuia t i v e P 

u p t a k e uns c a l c u l a t e d . To o b t a i n a d d i t i o n a l i n f o r m a t i o n on P u p t a k e 

a s e e d l i n g e x p e r i m e n t u i t h mr ( B i o p s i c a j u n c e a I . ) uas c o n d u c t e d 

a c c o r d i n g t o the Neubauer t u u m i o u e . The P t r e a t m e n t s u e r e i d e n t i c a l 

t o the P l e v e l s of t h e s o r p t i o n s tudy . S e e d l i n g s u e r e h a r v e s t e d a f t e r 

two weeks and the P u p t a k e was c a l c u l a t e d . 



II 

In the pot. expe r imen t the cumula t i ve P up tak e shourcd a s i g n i f i c a n t 
*# 

l i n e a r r e l a t i o n s h i p w i th P q u a n t i t y meaaurrd ns Cllgen-P ( r = 0 . 6 8 ) , 
» #» •» 

CAI.-P ( i = 0 . n s ) and Bray 2-P ( r = 0 . 7 " ) , ns u e l l a s w i t h i n t e n s i t y 

( r»n.6!) ) v a l u e s . The m u l t i p l e r e g r e s s i o n a n a l y s e s showed t h a t the 

i n c o r p o r a t i o n of b u f f e r c a p a c i t y c a l c u l a t e d a c c o r d i n g to mas t m a t h e ­

m a t i c s J mode 19 improved the P u p t a k e rt;5 n Ii .msM p u i f) 1 s e n - P , b u t 

t h i s uas n o t the c a s e for CAL-P , Bray 2-P and P i n t e n s i t y . Phosphorus 

r e p l e n i s h i n g speed e s t i m a t e d by thn con t i no OUR OX t r a c t i on me thod d id 

n o t si unj H can t ly improve any P s ta ?,us rnrnsur<:men t -/i th P op t ake . 

In tha s e e d l i n g n x p e r i m e n t . P u p t a k e e x h i b i t e d a s i g n i f i c a n t l y 

bet r e l a t i o n s h i p wi th the i n t e n s i t y v a l u e r ( r = n.BD ) than u.M.h 

q u a n t i t y v a l u n s ( r = 0 . 4 3 ) . This shnus t h a t f o r r e l a t i v e l y s h o r t 

vecje ta t i on p° r i uds P ava i labi.l i ty i s more riwpt-jnden t. on P in t ens i 

than P riunnti t.y . Uhen b u f f e r c a p a c i t y c o n c e p t was f p p l i e d os in the 

c a s e of pot e x p e r i m e n t , the r e l a t i o n s h i p a r P u p t a k e u i t h r iunnt i ty 

va Lues improved , bu t no t u i th in t e n s i ty va l u e s . However , mu I t i o l e 

r e l i n k s ) on p r iua t inns i n d i c a t e d t h a t at nona) q u a n t i t y l e v e l s . i n c r e a s i n g 

P huf f e r caoac i ty deer eased P un tai' n . I h i s a in i n shows the impor t ance 

o f i n t ens i ty va 1 ue uhen P a va i l a b i I i ty for a ve ry s h o r t c e r i od i s 

<;r;r>cj rned , i nee the in ten s i ty a t the s.i'iu; t t i ty 1 n ve I d e c r e a s e s 

ui th the i nc rn/ia inn hu f f r»r canac i ty .