S.L.J Tea Sci. 69(1 & 2), 5-19,2004, Printed in Sri Lanka
(Reproduced from the Proceedings of the First Symposium on Plantation Crop Research published
in July 8-9, 2004)
Boundary-Line Approach in Specifying Nutrient
Diagnosis Ranges for Vegetatively Propagated Tea in
Sri Lanka
2
*G P Gunaratne, ' L S K Hettiarachchi and A N Jayakody
'Soils a n d P l a n t N u t r i t i o n D i v i s i o n , T e a R e s e a r c h I n s t i t u t e o f S r i L a n k a , T a l a w a k e l l e ,
Sri Lanka
d e p a r t m e n t o f S o i l Science, F a c u l t y o f A g r i c u l t u r e , U n i v e r s i t y o f P e r a d e n i y a ,
Peradeniya, Sri Lanka
ABSTRACT
A relatively new approach, the 'boundary line' approach, for objectively assessing
cause-and-effect relationships in biology, was made to a systematically-collected
set o f data, representing climates, soils, ownerships and management practices,
from the present distribution o f vegetatively-propagated tea plantations in the
corporate sector o f Sri Lanka. This was primarily to investigate whether this
technique could be used to study tea nutrition and determine nutrient sufficiency
or deficiency, and to investigate whether diagnosis ranges for vegetativelypropagated tea could be upgraded with a view to using leaf analysis as an effective
diagnostic tool.
Accordingly, nutrient diagnosis ranges were arrived at f o r nitrogen ( N ) ,
phosphorus ( P ) , potassium ( K ) , sulphur (S) and magnesium ( M g ) , and rated as
'optimum', 'deficient', 'low' and 'excess'. The optimum nutrient ranges are 2.78 3.39, 0.12 - 0.15, 0.91 - 1.24, 0.23 - 0.37, and 0.13 - 0.22, respectively. A n
attempt was also made to compare the diagnosis ranges with those ranges currently
in use in Sri Lanka, and other tea-growing countries. I t is apparent that the
'optimum' leaf-nutrient ranges for tea in Sri Lanka had been fixed using a limited
set o f information, representing a limited number o f areas. Hence, the nutrient
diagnosis ranges established using the boundary line approach, can be used to
improve the utility o f plant testing in tea when more precise interpretation and/
or more narrow ranges o f critical values are warranted.
K e y w o r d s : b o u n d r y l i n e a p p r o a c h , nutrients c r i t i c a l values
5
INTRODUCTION
T e a i n S r i L a n k a is p l a n t e d f r o m a l m o s t m e a n sea l e v e l t o a r o u n d 2 2 0 0 m e t r e s a b o v e
m e a n sea l e v e l , i n t h e w e t a n d i n t e r m e d i a t e zones o f the country. O f t h e t e a e x t e n t ,
a p p r o x i m a t e l y 4 6 % a r e u n d e r o l d s e e d l i n g w h i l e t h e rest is v e g e t a t i v e l y p r o p a g a t e d
( V P ) t e a w i t h h i g h y i e l d p o t e n t i a l . T h e t e a lands are classified as h i g h - ( a b o v e 1 2 0 0 m ) ,
medium- (between 600-1200 m ) and l o w - grown (below 6 0 0 m ) , depending o n the
e l e v a t i o n o f t h e green leaf-processing f a c t o r i e s . T h i s classification o r i g i n a t e d i n t h e
e a r l y d a y s o f t e a p r o d u c t i o n , a n d is p r i m a r i l y t o h e l p c o n s u m e r s t o r e c o g n i z e t h e
characteristics o f m a d e tea a v a i l a b l e f o r sale.
T h e soils present i n the t e a - g r o w i n g areas f a l l into three large groups, n a m e l y R e d Y e l l o w
Podzolic ( R Y P ) , Reddish B r o w n Latasolic ( R B L ) and Immature B r o w n L o a m ( I B L )
( M o o r m a n a n d P a n a b o k k e , 1 9 6 1 ) . A c c o r d i n g t o the U S D A s o i l t a x o n o m i c c l a s s i f i c a t i o n
( A n o n . , 1 9 7 5 ) , t h e R Y P a n d R B L groups a r e regarded as a n order U l t i s o l w h i l e I B L is
r e g a r d e d as I n c e p t i s o l .
Besides these large groups, the soils o f the w e t z o n e have been p r o v i s i o n a l l y characterized
and classified into series levels, using b o t h t h e U S D A and F A O / U N E S C O systems ( M a p a
et a l . , 1 9 9 9 ) . A c c o r d i n g l y , 13 m a i n series h a v e b e e n r e c o g n i z e d f r o m the f o l l o w i n g t e a g r o w i n g areas: M a t t a k e l l e , M a s k e l i y a , N u w a r a E l i y a , Kandy, U k u w e l l a , A k u r a n a ,
M a l a b o d a , Pallegoda, Weddagala, and Dodangoda, Ragala, Badulla and Mahawalatenne.
A n n u a l r a i n f a l l , m e a n temperature a n d t h e d u r a t i o n o f m e a n a n n u a l sunshine v a r y w i d e l y
w i t h i n t h e t e a - g r o w i n g areas i n S r i L a n k a . T h e c l i m a t i c conditions, together w i t h t h e
soil p r o p e r t i e s at a g i v e n l o c a t i o n , d e t e r m i n e t h e l a n d use a n d m a n a g e m e n t r e q u i r e m e n t s .
F o l l o w i n g this criterion, the areas w i t h s i m i l a r c l i m a t i c and soil conditions w e r e i d e n t i f i e d
a n d d e m a r c a t e d as a g r o - e c o l o g i c a l regions ( A E R ) ( P a n a b o k k e a n d K a n n a n g a r a , 1 9 7 5 ) .
A c c o r d i n g l y , 12 A E R s h a v e b e e n i d e n t i f i e d w i t h i n t h e t e a - g r o w i n g areas ( s e e F i g . 1).
H o w e v e r , t h e rate o f g r o w t h , a n d i n t u r n t h e p r o d u c t i o n o f harvestable shoots f r o m a
g i v e n site, p r i m a r i l y depend o n t h e interactive r o l e o f c l i m a t e , soil a n d p l a n t factors,
t o g e t h e r w i t h a host o f m a n a g e m e n t practices.
G e n e r a l l y , t h e r e is a basic relationship b e t w e e n the concentration o f a p l a n t n u t r i e n t a n d
t h e g r o w t h r a t e , o r y i e l d , o f the p l a n t ( D o w a n d R o b e r t s , 1 9 8 2 ; M e n g e l a n d K i r k b y ,
1 9 8 7 ) . O v e r t h e range o f this r e l a t i o n s h i p , t h e critical nutrient range o f c o n c e n t r a t i o n
( C N R ) o r sufficiency range is a n a r r o w r a n g e , a b o v e w h i c h , w i t h a reasonable c o n f i d e n c e ,
t h e p l a n t is a m p l y supplied, and b e l o w w h i c h t h e plant is d e f i c i e n t ( D o w a n d R o b e r t s ,
1 9 8 2 ) . Plant-tissue analyses p r o v i d e a satisfactory basis f o r d e t e r m i n a t i o n o f t h e r e l a t i v e
p r o p o r t i o n o f nutrients present i n plants a n d / o r a v a i l a b l e i n soils. I n S r i L a n k a , t h e m o t h e r
leaf, i n w h o s e a x i l a p l u c k a b l e shoot has d e v e l o p e d , has b e e n s h o w n t o b e t h e m o s t
6
Agaro-Ecological Region Boundary
suitable f o r m o s t p l a n t nutrient analyses, and also f o r the diagnosis o f m o s t nutrient
deficiencies a n d excesses ( H a s s e l o , 1 9 6 5 ; W i c k r e m a s i n g h e a n d K r i s h n a p i l l a i , 1 9 8 6 ) .
H o w e v e r , f o r f o l i a r analysis the first and/or t h i r d l e a f o f t h e p l u c k a b l e shoot f r o m the
bud is s a m p l e d in East A f r i c a ( T o l h u r s t , 1 9 7 2 ; W i l l s o n , 1 9 7 4 ) , w h i l e the u p p e r m o s t
mature l e a f is s a m p l e d in K e n y a ( O t h i e n o , 1 9 8 8 ) .
L e a f analysis is b e i n g increasingly used as a diagnostic t o o l f o r p e r e n n i a l crops. T h e
concentration o f nutrients i n the plant tissue reflects w h a t the plant has o b t a i n e d f r o m
the s o i l , i n r e l a t i o n t o its g r o w t h up to the t i m e o f s a m p l i n g . I t is based o n the p r i n c i p l e
that the nutrient levels reflect f e r t i l i t y factors a f f e c t i n g the g r o w t h o f the plant.
L e a f - n u t r i e n t c r i t e r i a c a n also be d e v e l o p e d f r o m the relationship b e t w e e n plant-nutrient
concentration a n d plant p e r f o r m a n c e , o r y i e l d , in f e r t i l i z e r treatments. H o w e v e r , several
years are o f t e n r e q u i r e d b e f o r e crops respond t o a d d e d fertilizer, and m a n y years o f f i e l d
data, collected o v e r a range o f c o n d i t i o n s , are required to d e v e l o p critical concentrations
o r ranges. A p a r t f r o m the t i m e d u r a t i o n , in t h e case o f v e g e t a t i v e l y - p r o p a g a t e d tea in Sri
L a n k a , there exist variations a m o n g the cultivars or clones o w i n g to clonal characteristics,
and w i d e variations in soil a n d c l i m a t i c conditions.
7
A r e l a t i v e l y n e w a p p r o a c h to t h e study o f c r o p p r o d u c t i v i t y has b e e n d e v e l o p e d , i n w h i c h
the p e r f o r m a n c e o f the best i n the s a m p l e e x a m i n e d is t a k e n as a standard against w h i c h
t o j u d g e the r e m a i n d e r ( W e b b , 1 9 7 2 ) . T h i s is o n t h e a s s u m p t i o n that there exist reasons
other t h a n c h a n c e , w h i c h accounts f o r the i n f e r i o r p e r f o r m a n c e o f part o f t h e p o p u l a t i o n .
A s a n e x a m p l e , w h e n t h e points i n r e l a t i o n t o nutrient status and c r o p y i e l d , o r r e l a t i v e
y i e l d , are p l o t t e d i n a scatter d i a g r a m , there is a l w a y s a l i n e o n t h e u p p e r e d g e o f the d a t a
range. I t represents t h e highest y i e l d s observed o v e r the range o f nutrient values m e a s u r e d ,
a n d is called t h e 'boundary line'. T h e boundary line also describes the response t o v a r i a t i o n
i n the test parameter, w h e r e a l l the other factors d o n o t l i m i t crop y i e l d ( L a r k , 1 9 9 7 ;
S c h n u g et a l . , 1 9 9 6 ; W e b b , 1 9 7 2 ) .
W a l w o r t h et a l . ( 1 9 8 6 ) a n d E v a n y l o a n d S u m n e r ( 1 9 8 7 ) o p i n e d that it is possible t o use
t h e b o u n d a r y - l i n e a p p r o a c h t o q u i c k l y d e r i v e s u f f i c i e n c y ranges f o r nutrients a n d o t h e r
parameters. S u r v e y i n g tissue c o m p o s i t i o n i n h i g h l y p r o d u c t i v e fields has b e e n r e c o g n i z e d
as a t o o l i n establishing s u f f i c i e n c y nutrient ranges ( P o o v a r o d o m a n d C h a t u p o t e , 2 0 0 2 ) .
S e v e r a l researchers h a v e e f f e c t i v e l y used this t e c h n i q u e f o r v a r i o u s crops ( H a n e k l a u s e
a n d S c h n u g , 1 9 9 4 ; K h i a r i et a l . , 2 0 0 1 ; P o o v a r o d o m a n d C h a t u p o t e , 2 0 0 2 ; S u l l i v a n et a l . ,
1 9 9 6 ; W a l w o r t h a n d K i l b y , 2 0 0 2 ; Z h e n m i n et a l . , 1 9 9 9 ) .
O p t i m u m o r c r i t i c a l n u t r i e n t levels, or n o r m s , or standards, a n d e v e n ranges, h a v e b e e n
established i n tissues f r o m survey databases using this t e c h n i q u e : f o r S i n o i l s e e d r a p e
g r o w n in N o r t h e r n G e r m a n y ( H a n e k l a u s e and S c h n u g , 1 9 9 4 ) , f o r P i n potatoes g r o w n i n
Q u e b e c ( a c r i t i c a l n u t r i e n t diagnostic i n d e x , K h i a r i et a l . , 2 0 0 1 ) , a n d f o r N , P, K , C a , M g
and Z n in d u r i a n g r o w n i n eastern T h a i l a n d ( P o o v a r o d o m and C h a t u p o t e , 2 0 0 2 ) . H o w e v e r ,
h a r d l y a n y i n f o r m a t i o n w a s f o u n d o n the a p p l i c a t i o n o f this t e c h n i q u e f o r crops g r o w n
in Sri Lanka.
T h e o b j e c t i v e o f this study w a s t o f i n d out w h e t h e r n u t r i e n t sufficiency, o r diagnosis
ranges, f o r v e g e t a t i v e l y - p r o p a g a t e d t e a c o u l d be established using a large b o d y o f s u r v e y
data, c o l l e c t e d f r o m t h e e n t i r e t e a - g r o w i n g area i n t h e country.
MATERIALS AND
METHODS
Survey methodology
A n i s l a n d - w i d e s u r v e y w a s c a r r i e d o u t d u r i n g J u l y 2 0 0 1 - M a r c h 2 0 0 3 t o collect d e t a i l e d
i n f o r m a t i o n from V P t e a fields i n 2 0 0 corporate-sector estates, o u t o f a total o f a b o u t
4 0 0 , representing d i f f e r e n t c l i m a t e factors, s o i l , o w n e r s h i p , a n d p l a n t a t i o n m a n a g e m e n t
practices. H i g h - y i e l d i n g f i e l d s , not m o r e t h a n 10 to I S years after first c a n o p y p r u n i n g ,
w e r e chosen. I n g e n e r a l , n o nutrient d e f i c i e n c y s y m p t o m s w e r e observed i n t h e c h o s e n
8
fields. The survey was primarily to identify the factors affecting responses to applied
fertilisers, with special emphasis on potash and sulphur.
A multi-stage sampling method was used to select the estates, as shown in Fig. 2. Detailed
information, on field management practices, bush characteristics, pest and disease records,
yield data, and climate and site characteristics, was collected from a selected VP tea
field on each estate.
STAGE1
(Rainfall zone)
1'
STAGE2
(Elevational category)
Up
Mid
STAGE3
(AER)
WUl
WU2
| Low
WU3
STAGE4
(Tea Planting District)
STAGE5
(Plantations company)
Maskeliya
Agarapatna
STAGE6
(Estate)
9 Estates
4 Estates
Fig 2 . Multistage sampling scheme for the Islandwide survey
9
Sampling procedure
T h e first m a t u r e leaf, f r o m w h o s e a x i l t h e p l u c k a b l e shoot emerges, w a s s a m p l e d f o r
l e a f - n u t r i e n t analysis. T h e s a m p l e d leaves w e r e d r i e d o v e r n i g h t a t 8 0 ° C , a n d g r o u n d i n
a leaf-grinding mill.
Leaf nutrient analysis
A g r o u n d l e a f s a m p l e ( 0 . 2 g ) w a s placed i n a d i g e s t i o n t u b e , a n d ashed i n a m u f f l e
f u r n a c e o v e r n i g h t a t 4 8 0 ° C . T h e ash content was dissolved i n 0.5 m l o f digestion m i x t u r e
( H C 1 : H N 0 : H 0 i n t h e p r o p o r t i o n 1:1:2), a n d d r i e d a g a i n o v e r a h o t plate.
3
2
Ten m l o f 0.05 M H C 1 solution w a s added t o the dried ash, and m i x e d w e l l . Suitable
a l i q u o t s w e r e used t o d e t e r m i n e K a n d M g u s i n g a f l a m e p h o t o m e t e r , a n d a t o m i c
absorption spectrophotometer, respectively. Phosphorus w a s determined b y t h e
v a n d a m o l y b d a t e m e t h o d ( J a c k s o n , 1 9 5 8 ) , a n d sulphate b y t h e B a C l m e t h o d ( B u t t e r s
2
a n d C h e n e r y , 1 9 5 9 ) , u s i n g a n U V / v i s i b l e spectrophotometer. T h e nitrogen content w a s
determined b y the Kjeldhal method (Bremner and M a l v a n e y , 1982).
Statistical analysis
T h e y i e l d d a t a c o l l e c t e d a n d leaf-nutrient concentrations estimated w e r e t a b u l a t e d , a n d
the highest y i e l d s o b s e r v e d o v e r t h e range o f nutrient concentrations (the b o u n d a r y - l i n e
points) w e r e selected f o r p l o t t i n g scatter diagrams. M o d e l s (linear, reciprocal, l o g a r i t h m i c ,
e x p o n e n t i a l a n d p o l y n o m i a l ) w e r e fitted using t h e Statistical A n a l y s i s S y s t e m ( S A S ) ,
v e r s i o n 6 ( A n o n . , 1 9 9 5 a ) a n d M i c r o s o f t E x c e l ( A n o n . , 2 0 0 0 ) packages. T h e c o e f f i c i e n t
2
o f d e t e r m i n a t i o n ( R ) w a s used t o select t h e best-fitted m o d e l .
U s i n g the m a t h e m a t i c a l equation o f the best-fitted boundary l i n e , y i e l d ranges representing
l o w , d e f i c i e n t a n d o p t i m u m w e r e e s t i m a t e d as < 6 0 % , 6 0 - 9 0 % , a n d 9 0 - 1 0 0 % ,
respectively. E x c e s s i v e nutrient ranges, w h i c h p r e s u m a b l y cause d e c l i n e i n y i e l d , w e r e
t a k e n t o b e t h e c o n c e n t r a t i o n b e y o n d t h e m a x i m u m p o i n t o f the s u f f i c i e n c y range.
RESULTS AND DISCUSSION
2
T h e coefficients o f d e t e r m i n a t i o n (the R v a l u e s ) , w h i c h is a n indicator o f t h e degree o f
v a r i a t i o n i n a d a t a set ( t h e 'goodness'), a n d e x p l a i n e d b y t h e regression m o d e l s o n t h e
highest y i e l d s o v e r t h e r a n g e o f l e a f nutrient c o n c e n t r a t i o n , a r e g i v e n i n T a b l e 1 , a l o n g
2
w i t h their respective p r o b a b i l i t y values. T h e R values, e x p l a i n e d b y the regression m o d e l s
fitted c o n v e n t i o n a l l y t o select the best regression o n y i e l d o v e r the nutrient ranges, a r e
also g i v e n , a l o n g w i t h t h e i r respective p r o b a b i l i t y v a l u e s , i n T a b l e 2 .
10
T h e best-fitted m o d e l s f o r the highest y i e l d observed o v e r the n i t r o g e n ( N ) , phosphorus
( P ) , potassium ( K ) , m a g n e s i u m ( M g ) a n d sulphur ( S ) ranges, w h i c h are i n f a c t the bestfitted b o u n d a r y lines, are s h o w n in F i g s . 3 t o 7 , a l o n g w i t h their respective distributions
o f t o t a l s a m p l e populations, as scatter d i a g r a m s .
2
T h e R values have been s i g n i f i c a n t l y i m p r o v e d , f o l l o w i n g the e l i m i n a t i o n o f i n f e r i o r
p e r f o r m a n c e s b y a part o f the p o p u l a t i o n ( c o m p a r e values g i v e n i n T a b l e s 1 and 2 ) .
2
B a s e d o n the R values o f m o d e l s tested f o r d e t e r m i n i n g best-fitted b o u n d a r y lines, and
t h e i r P v a l u e s , it w a s f o u n d that t h e p o l y n o m i a l m o d e l s s a t i s f a c t o r i l y d e s c r i b e t h e
variations in diverse s a m p l e p o p u l a t i o n s a c c o u n t i n g f o r 18 t o 4 7 % ( T a b l e 1). T h i s is
p a r t i c u l a r l y so, as the goodness o f f i t (the. R
2
v a l u e ) p r i m a r i l y indicates t h e possible
c a u s e - a n d - e f f e c t relationship e x i s t i n g b e t w e e n t w o variables, despite t h e p o o r level o f
significance f o r a g i v e n m o d e l o f regression as P values indicate the degree o f p r o b a b i l i t y
f o r r e p e t i t i o n . I n fact, the degree o f v a r i a t i o n accounted f o r in the case o f K w a s 2 5 % ,
w h i c h w a s e v e n higher t h a n f o r S , a l t h o u g h their P values w e r e 0 . 4 2 9 1 a n d 0 . 0 4 3 1 ,
r e s p e c t i v e l y ( T a b l e 1).
T a b l e 1 . Coefficient of determination for different m o d e l s fitted to select t h e best boundaryline regression on t h e h i g h e s t yields o v e r t h e nutrient r a n g e s .
M o d e l ; [Yield = f (plant nutrient concentration)]
Linear
P
K
S
Mg
Logarithmic
Exponential
Polynomial
2
Co-efficient o f d e t e r m i n a t i o n ( R )
Nutrient
N
Reciprocal
0.138
(0.1421)
0.039
(0.5003)
0.082
(0.4547)
0.107
(0.0591)
0.237
(0.0185)
0.226
(0.0536)
0.002
(0.8808)
0.031
(0.6513)
0.050
(0.2033)
0.082
(0.1859)
0.183
(0.0867)
0.014
(0.6829)
0.056
(0.5416)
0.079
(0.1075)
0.154
(0.0645)
0.031
(0.4994)
0.044
(0.4742)
0.110
(0.3824)
0.117
(0.477)
0.257
(0.0135)
* Probability v a l u e s (or level o f significance) a r e given in p a r e n t h e s i s
11
0.474
(0.0112)
0.340
(0.0661)
0.246
(0.4291)
0.184
(0.0431)
0.311
(0.0023)
T a b l e 2 . Coefficient of d e t e r m i n a t i o n for different m o d e l s fitted conventionally to s e l e c t
t h e b e s t r e g r e s s i o n o n t h e yields o v e r t h e nutrient r a n g e s .
M o d e l ; [Yield = f (plant nutrient c o n c e n t r a t i o n ) ]
Linear
Reciprocal
Logarithmic
Exponential
Polynomial
2
Nutrient
Co-efficient of d e t e r m i n a t i o n ( R )
0.004
(0.50f6)
0.190
(0.0001)
0.024
(0.0947)
0.078
(0.0022)
0.003
(0.5640)
N
P
K
S
Mg
0.008
(0.3355)
0.143
(0.0001)
0.026
(0.0828)
0.067
(0.0049)
0.002
(0.6379)
0.006
(0.4114)
0.169
(0.0001)
0.025
(0.0869)
0.074
(0.0021)
0.002
(0.6038)
0.001
(0.8177)
0.193
(0.0001)
0.022
(0.1102)
0.079
(0.0022)
0.003
(0.5512)
0.002
(0.6010)
0.205
(0.0001)
0.023
(0.1065)
0.079
(0.0021)
0.003
(0.5212)
* Probability v a l u e s (or level of significance) a r e g i v e n in p a r e n t h e s i s
N u t r i e n t diagnosis ranges f o r t h e V P t e a distribution w e r e established f o r t h e first t i m e
f r o m a single data set s y s t e m a t i c a l l y collected, using t h e best-fitted p o l y n o m i a l b o u n d a r y
l i n e e q u a t i o n w i t h respect to s t a n d a r d i z e d y i e l d categories, as d e f i n e d a n d g i v e n i n T a b l e
3 . A n a t t e m p t w a s also m a d e t o c o m p a r e t h e diagnosis ranges w i t h t h e r a n g e o r ranges
c u r r e n t l y in use b o t h in S r i L a n k a ( T a b l e 3 ) , and in other t e a g r o w i n g countries ( T a b l e
4 ) , w i t h a v i e w t o u p g r a d i n g l e a f - n u t r i e n t standards.
2
Yield = - 7 8 7 * N + 5275*N - 6113
4000-1
A - Boundary line
O - Other
^ 3000 H
x:
J 2000 -J
1000 -
i
o
>
—i—
2.0
2.5
0°
— i —
—i
3.0
i—
3.5
4.0
Leaf N Concentration (%)
—i
4.5
Fig 3. The best fitted boundary line for N concentration and yield.
12
Yield = -159032'F* + 4 9 5 8 0 * P - 1 0 3 4
A - Boundary line
O - Other
4000
^•3000
IB
•5
11000
0.08
0.12
0.16
0.20
0.24
Leaf P Concentration (%)
F i g 4. T h e best fitted boundary line for P concentration and yield.
Yield = -2615*K? + 6555*K - 1 0 2 8
A - Boundary line
O - Other
4000-1
-£3000
CO
.22000
£
1000
o o
0.8
o
i
1
i
1.2
1.6
2.0
Leaf K Concentration (%)
Fig 5 . T h e best fitted boundary line for K concentration and yield.
8
Yield = - 1 1 5 5 4 * S + 8 7 5 7 * S + 1 0 1 7
4000
A - Boundary line
O -Other
A
A
A
A
0 A
A
Oo
O
020
A A
A
1
I
I
1
I
0.30
0.40
0.50
0.60
0.70
Leaf S Concentration (%)
Fig 6 . T h e best fitted boundary line for S concentration and yield.
13
2
Yield = - 2 9 2 6 0 * M g + 130S4*Mg + 1 2 1 4
• - Boundary line
O - Other
4000
3000
JZ
! » 2000
$
1000
0.10
0.20
0.30
0.50
0.40
Leaf M g Concentration (%)
Fig 7. The best fitted boundary line for M g concentration and yield.
T a b l e 3. A c o m p a r i s o n b e t w e e n t h e ' o p t i m u m ' nutrient r a n g e s currently in u s e in Sri
L a n k a , a n d nutrient diagnosis r a n g e s obtained f r o m the boundary-line technique.
P l a n t nutrient (%)
Nitrogen
Phosphorus
Potassium
Sulphur
Magnesium
Nutrient d i a g n o s i s r a n g e s o b t a i n e d f r o m b o u n d a r y line t e c h n i q u e
Low
< 2.19
< 0.56
<0.08
<0.04
0.56-0.91
0.08-0.23
0.04-0.13
<0.07
Deficient
2.19-2.78
0.07-
Optimum
2.78-
0.12-0.15
0.91-1.24
0.23-0.37
0.13-0.22
0.15 >
1.24 >
0.37 >
0.22 >
Excess
3.39
3.39 >
0.12
N u t r i e n t r a n g e s currently in u s e *
3.00-4.00
0.2-0.30
1.50-2.00
0.20-
0.30
0.20 >
Anon, (1995b)*
Source: Anon. (1995b)*
I n spite o f the heterogeneous nature o f seedling tea a n d v a r i a t i o n s a m o n g the cultivars
o w i n g t o v a r i e t a l characteristics, a n d the w i d e variations in soil a n d c l i m a t i c c o n d i t i o n s ,
a range f o r each nutrient supposedly ' o p t i m u m ' ( T a b l e 3 ) h a v e b e e n a r r i v e d at.
T h e s e ranges appear t o h a v e b e e n d e v e l o p e d f r o m a large b o d y o f d a t a o n g r o w t h and
y i e l d responses to nutrient status u n d e r d i f f e r e n t e x p e r i m e n t a l c o n d i t i o n s o v e r a l o n g
p e r i o d o f t i m e , a l o n g w i t h the a n a l y t i c a l data generated o n s o i l - a n d leaf- samples a n d
submitted b y plantations f o r the last t w o t o three decades ( J a y m a n a n d S i v a s u b r a m a n i u m ,
14
T a b l e 4 . Critical levels of nutrients in t h e u p p e r m o s t m a t u r e a n d third leaf of the pluckable
shoot, e s t a b l i s h e d by K e n y a a n d E a s t Africa respectively
P l a n t nutrient (%)
Nitrogen
Phosphorus
Potassium
Sulphur
Magnesium
Critical levels of nutrients in t h e u p p e r m o s t m a t u r e leaf *
Deficient
<3.0
< 0.15
< 1.20
Borderline
3.0-3.5
0.15-0.17
1.20-1.50
Adequate
3.5 >
0.17 >
1.50 >
-
< 0.10
-
Critical levels of nutrients in t h e third leaf o f a shoot **
Deficient
3.00
0.35
1.60
-
0.05
Subnormal
4.00
0.40
2.00
0.05
0.10
Normal
5.00
0.50
3.00
0.50
0.30
S o u r c e s ; O w u o r a n d W a n y o k a ( 1 9 8 3 ) * ; a n d B o n h e u r e a n d Willson ( 1 9 9 2 ) '
1980; Pethiyagoda and Krishnapillai, 1 9 7 0 ; Sivasubramanium and Jayman, 1 9 7 6 ;
W e t t a s i n g h e a n d W a t s o n , 1 9 8 0 ) . C o n t r a r y t o the o p t i m u m N a n d K ranges g i v e n , results
f r o m a recent t r i a l , o v e r a five-year p r u n i n g c y c l e , s h o w e d that the s u f f i c i e n c y range f o r
l e a f N v a r i e d f r o m 3 t o 3 . 5 % , a n d f o r l e a f K f r o m 1.25 t o 1 . 5 % ( H e t t i a r a c h c h i et a l . ,
2003).
T h e m a x i m u m concentrations o f the best-fitted p o l y n o m i a l b o u n d a r y lines, as s h o w n in
F i g s . 3 to 5, w e r e 3 . 3 9 , 0 . 1 5 a n d 1.24 % w h i l e the o p t i m u m ranges w e r e 2 . 7 8 - 3 . 3 9 , 0 . 1 2
- 0 . 1 5 and 0 . 9 1 - 1.24, f o r N , P and K , respectively. T h e s e ranges are l o w e r t h a n the
o p t i m u m ranges c u r r e n t l y used in Sri L a n k a , e x c e p t f o r S and M g ( A n o n . , 1 9 9 5 b ) . •
A study w a s carried o u t b y P e t h i y a g o d a and K r i s h n a p i l l a i ( 1 9 7 0 ) o n the m i n e r a l nutrition
o f t e a b y i n d u c i n g m a j o r n u t r i e n t deficiencies in sand culture. T h e y d i d this b y e x c l u d i n g
f r o m the supplied solution a single nutrient at a t i m e , and w e r e able to establish the l e a f
N , P, K , C a and M g concentrations associated w i t h d e f i c i e n c y s y m p t o m s . R e c o v e r y to
n o r m a l c y f o l l o w e d restoration o f nutrient supply.
T h e results o f nutrient analyses o f s o i l - and leaf-samples f r o m the first-ever designed 3
3
N P K factorial trial o n l o w j a t seedling tea, t a k e n in c o n j u n c t i o n w i t h the c o r r e s p o n d i n g
y i e l d s f o l l o w i n g l o n g - t e r m f e r t i l i z a t i o n , s h o w e d that l e a f K reached a m a x i m u m v a l u e
o f a p p r o x i m a t e l y 1 . 8 % w h e n t h e w a t e r - s o l u b l e soil K content w a s around 12 p p m , w i t h
1
the y i e l d response at 8 4 k g K j O ha"' y r ( S i v a s u b r a m a n i u m and J a y m a n , 1 9 7 6 ) . S i m i l a r l y ,
P reached a p p r o x i m a t e l y 0 . 2 4 % w h e n the b o r a x - e x t r a c t a b l e soil P w a s a r o u n d 2 0 p p m ,
1
w i t h the y i e l d response at 3 3 k g P 0 ha" y r ' ( J a y m a n and S i v a s u b r a m a n i u m , 1 9 8 0 ) . It
2
5
15
appears that these values m a y also h a v e b e e n t a k e n into consideration w h e n the o p t i m u m
n u t r i e n t ranges c u r r e n t l y in use w e r e a r r i v e d at, in spite o f o b v i o u s differences b e t w e e n
seedling and V P tea.
W e t t a s i n g h e a n d W a t s o n ( 1 9 8 0 ) studied t h e effect o f three levels o f N , P, K a n d M g o n
l e a f - n u t r i e n t c o m p o s i t i o n , using l o n g - t e r m fertiliser trials w i t h V P teas g r o w n i n l o w
c o u n t r y c o n d i t i o n s . T h e y f o u n d that increasing t h e rate o f N fertiliser resulted i n a n
increase i n l e a f - N c o n c e n t r a t i o n . A l t h o u g h t h e l e a f - N c o n c e n t r a t i o n increased w i t h
increasing l e v e l s o f N fertiliser at each l o c a t i o n , the relationship w a s n o t q u i t e clear
w h e n t h e d a t a w e r e p o o l e d , i n d i c a t i n g the possible i n f l u e n c e o f other factors such as
c l i m a t e , soil t y p e a n d c l o n e , o n the l e a f - N content. T h e authors o p i n e d that there appeared
t o b e a f i n e b a l a n c e b e t w e e n N , K a n d M g , b u t f e l t it w a s p r e m a t u r e t o a t t e m p t t o d e f i n e
critical v a l u e s f o r t h e v a r i o u s nutrients f r o m these results.
L a t e l y , a p o t t r i a l c a r r i e d o u t t o test the a g r o n o m i c effectiveness o f increasing rates o f P
using E p p a w a l a r o c k phosphate a n d T r i p l e super phosphate o n assessing the g r o w t h o f
8 - m o n t h o l d t e a plants f r o m T R I 3 0 7 2 i n a n U l t i s o l o v e r a p e r i o d o f 10 m o n t h s s h o w e d
that the P c o n c e n t r a t i o n o f the first m a t u r e l e a f c o r r e s p o n d i n g t o 9 5 % o f the m a x i m u m
dry matter yield was approximately 0 . 1 8 % (Zoysa, 2 0 0 0 ) .
N o a t t e m p t w a s m a d e t o c o m p a r e t h e diagnosis ranges a r r i v e d at f r o m t h e m o t h e r leaf,
w i t h the c r i t i c a l levels o f nutrients in the t h i r d l e a f o f the shoot ( B o n h e u r e a n d W i l l s o n ,
1 9 9 2 ) , as the c o n c e n t r a t i o n o f N , P a n d K i n the f o l i a g e decreases s i g n i f i c a n t l y w i t h l e a f
m a t u r i t y ( H e t t i a r a c h c h i et a l . , 1 9 9 7 ) . A l s o , there exist significant d i f f e r e n c e s b e t w e e n
the c r i t i c a l levels o f nutrients in the u p p e r m o s t m a t u r e l e a f w h e n c o m p a r e d t o diagnosis
ranges in t h e m o t h e r leaf, a l t h o u g h t h e y appeared t o be quite similar.
I n g e n e r a l , soil properties are related t o c l i m a t e , parent m a t e r i a l , l a n d r e l i e f a n d changes
in use pattern. A s the soils w e r e also c o l l e c t e d s i m u l t a n e o u s l y w i t h l e a f samples f r o m
each f i e l d i n this survey, a n attempt w i l l b e m a d e t o correlate a l l t h e p l a n t - a v a i l a b l e soil
n u t r i e n t levels w i t h l e a f - n u t r i e n t concentrations, and y i e l d data, i n d u e course f o r a
subsequent p u b l i c a t i o n .
I t is e v i d e n t t h a t t h e b o u n d a r y - l i n e a p p r o a c h c a n be used t o upgrade n u t r i e n t - d e f i c i e n c y
diagnosis in t e a plantations. It is w o r t h w h i l e c o n s i d e r i n g the nutrient diagnosis ranges
established f o r V P teas f o r i m p l e m e n t a t i o n .
«-»
A n o t h e r a d v a n t a g e o f this t e c h n i q u e is the i d e n t i f i c a t i o n o f incipient n u t r i e n t - d e f i c i e n c y
p r i o r t o .the presentation o f s y m p t o m s , a n d t h e possibility o f e a r l y c o r r e c t i o n o f such
16
deficiencies t o p r e v e n t a deleterious effect o n t h e o p t i m u m rate o f g r o w t h i n V P t e a
plants.
CONCLUSION
It is a p p a r e n t that t h e so-called o p t i m u m l e a f - n u t r i e n t ranges f o r t e a i n S r i L a n k a h a v e
been d e v e l o p e d w i t h l i m i t e d i n f o r m a t i o n f r o m o n l y c e r t a i n areas. I t is n o w necessary t o
revise t h e standards, a n d t h e nutrient diagnosis ranges, established using the b o u n d a r y line a p p r o a c h , c a n b e used t o i m p r o v e t h e u t i l i t y o f plant-testing i n tea, w h e n a m o r e
precise interpretation a n d n a r r o w e r ranges o f c r i t i c a l values a r e w a r r a n t e d .
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19