Coconut Research Institute Repository

Perera, L.

Russell, J.R.

Provan, J.

McNicol, J.W.

Powel, W.

Identification and characterization of microsatellites in coconut(Cocos nucifera L.) and analysis of coconut population in SriLanka

Madurapperuma, W.S.

Kumaragamage, D.

J. Soil Set Soc. Sri Lanka. Vol 11.1999 
Evaluation of AB-DTPA Extractant for the Estimation of Plant Available 
Macro and Micro Nutrients in Acidic and Neutral Soils 
W.S. Madurappe ruma 1 and D. Kumaragamage 1 
Institute of Fundamental Studies, Hantana, Kandy 
ABSTRACT 
Use of multi nutrient extractants to assess available nutrients in soils is economically 
advantageous in routine soil testing. Even though AB-DTPA extractant has been proved to be 
successful for alkaline soils, its potential as a multi nutrient extractantfor acidic soils has not 
been documented. This study examined the suitability of AB-DTPA extractant to determine plant 
available P, K, Na, Ca, Mg, Fe, Mn, Cu and Zn in acidic and neutral soils of Sri Lanka. Thirty 
one soils were collected from different locations, including alfisols, ultisols, entisols, and 
inceptisols. Available nutrient status of soils was analyzed by conventional methods as well as 
by AB-DTPA method. Conventional methods tested were; Olsen and Bray-1 methods for 
available P, neutral ammonium acetate extraction for exchangeable Ca, Na, K and Mg, and 
DTP A extraction for available Fe, Mn, Cu and Zn. Contents of nutrients in plants and plant 
uptake of nutrients were determined by conducting a pot experiment, using Guinea grass 
(Panicum maximum) as the indicator plant. Relationships between the amount of nutrients 
extracted by AB-DTPA method with those of conventional methods, and with plant nutrient 
concentration and uptake were analyzed using simple linear regression, for each nutrient 
separately. The amount ofP, K, Na,Ca, Mg, Fe, Mn, Cu and Zn extracted with AB-DTPA 
method showed highly significant correlation (p<0.001) with those extracted by conventional 
methods. The correlation between AB-DTPA extractable nutrient levels and plant uptake was 
highly significant for P (r= 0.85+**), K(r = 0.83***), Na (r = 0.86 ***), Mn (r - 0.75***), Zn 
(r -0.74***) and Cu (r = 0.75***). Comparatively weak, but a significant correlation was 
observed between AB-DTPA extractable Fe with plant uptake ofFe (r = 0.48*). However, Ca 
and Mg extracted by both AB-DTPA and ammonium acetate methods did not show a significant 
correlation with plant uptake, probably due to the relatively high level of Ca and Mg in the 
tested soils. It could be concluded that AB-DTPA method can be recommended as a suitable 
extraction for routine soil analysis for acidic and neutral soils of Sri Lanka. 
Key Words: Available nutrients, multi nutrient extractants, soil analysis 
Introduction 
A soil test provides an index of the plant 
available nutrients in soils. This, in turn, is 
used to provide the amount of supplemental 
nutrients needed. In addition, it helps to 
monitor the quantity of available nutrients 
present over time, which is useful in fertilizer 
management practices. Most biological 
methods of assessing nutrient status are 
laborious and time consuming, and are not 
suitable for the determination of soil nutrient 
status on routine basis. Therefore, much 
attention has been given for the use of 
Present Address : Coconut Research Institute, Bandirippuwa Estate, Lunuwila 
'Department of Soil Science, Faculty of Agriculture, University of Peradeniya, Peradeniya 
Madurapperuma and Kumaragamage; AB-DTPA extractant for the estimation of available nutrients in soils 
chemical methods to assess plant nutrient 
status. In routine laboratory analysis, use of 
multi nutrient extractants is more economical, 
because a range of nutrients can be 
simultaneously determined. 
Soltanpour and Schuwab (1977) 
introduced AB-DTPA extraction method (1M 
NIL.HCO3,0.005M DTPA, pH 7.6) as a new 
soil test for simultaneous extraction of N0 3 ", 
P, K, Zn, Cu, Fe and Mn from alkaline soils of 
Colorado State. Ammonium in this solution 
acts as a displacing agent for cations adsorbed 
onto clay minerals, and therefore is used for 
the extraction of exchangeable cations. 
Bicarbonate ion is used for the extraction of 
soil phosphorus while DTPA is used to extract 
micro nutrients. 
When practical aspects of soil tests are 
considered, multi nutrient extractants are 
useful in the sense of time, cost of analysis 
and material for routine analysis. When using 
the AB-DTPA extractant for SO soil samples, 
an estimated 6 hours can be saved due to the 
reduction in time spent on weighing, shaking, 
filtering and utensil washing (Soltanpour and 
Schuwab, 1977). 
In a preliminary study using Sri Lankan 
soils (Madurapperuma and Kumaragamage, 
199S), significant correlations were obtained 
between P extracted by AB-DTPA, Olsen and 
Bray 1 methods, and exchangeable cations 
extracted by AB-DTPA and standard 
ammonium acetate methods. However, the 
effectiveness of AB-DTPA extractant in 
assessing plant available nutrients is not 
documented for acidic soils, even though it 
has been proven successful for neutral and 
alkaline soils (Soltanpour and Schuwab, 
1977).This study examined the suitability of 
AB-DTPA extractant in determining available 
P, K, Na, Ca, Mg, Zn, Cu, Fe and Mn in 
acidic and neutral soils of Sri Lanka. 
Materials and Methods 
Soil samples were collected from different 
locations of Sri Lanka (Fig. 1), including 
different soil types, namely Reddish Brown 
Earth (Rhodustalfs), Non Calcic Brown 
(Haplustalfs), Reddish Brown Latosolic 
(Rhodudults), Immature Brown Loams 
(Ustropepts), Red Yellow Podsolic 
(Tropudults), Alluvial soils (Tropofluents), 
Red Yellow Latasols (Eutrustox) and 
Regosols (Quartzpsamments). Soils of the Ap 
horizon were collected from a depth varying 
from 1-15 cm. All samples were air dried, 
ground and passed through a 2 mm sieve for 
pot experiments and for laboratory analysis. 
Soil samples were analyzed for pH 
(Mclean,1982), organic matter content (Dalai, 
1979; Amato, 1983), texture (Bouycous, 
1926) and cation exchange capacity 
(Chapman, 196S). Most soils were acidic or 
neutral in reaction with pH values less than 
7.0. Only three soils exhibited pH values 
greater than 7.0 (Table 1). 
A pot experiment (3 kg soil per pot) was 
conducted using Guinea grass (Panicum 
maximum L.) as the indicator plant. Soil 
moisture was maintained approximately at 
70% field capacity throughout the experiment. 
Pots were arranged in a CRD design with 
three replicates. To obtain proper plant growth 
N was added at a rate of 0.262 g per pot (373 
N kg/ha) in the form of (NHJjSCv Because 
the amount of fertilizer added to a pot is 
minute, application was done by dissolving 
the fertilizer in de-ionized water. After 
application of N fertilizers, pots were kept at 
the green house for one week, maintaining the 
moisture status at 70% field capacity level. 
Five uniform rootstocks of Panicum maximum 
cuttings were planted in each pot. Pots were 
watered using de-ionized water twice a day 
throughout the experimental period. Two 
weeks after planting the weakest plant was 
removed and four plants per pot were left. 
30 
J. Soil Sci. Soc. Sri Lanka. Vol 11,1999 
Fig. 1. Locations of the sampling sites 
31 
Madurapperuma and Kumaragamage; AB-DTPA extractant for the estimation of available nutrients in soils 
Table 1. Important chemical and physical properties of soils used in the pot experiment. 
Location pH CEC OM Soil texture 
cmol(+)/kg (%) Sand% Silt% Clay% 
Girandurukotte 5.7 4.4 2.8 68.2 15.6 16.2 
Madugoga 5.7 18.1 9.3 75.5 11.6 12.9 
Mawathagama 5.6 6.1 1.5 48.7 29.7 21.6 
Kudagala 6.5 15.9 3.2 70.6 12.1 17.3 
Mahiyangana 6.3 12.2 2.3 80.1 10.5 9.4 
Nikawaratiya 6.4 9.8 1.3 81.1 10.1 8.8 
Anamaduwa 6.1 16.6 2.4 80.3 10.4 9.3 
Bangadeniya 7.6 11.1 2.0 79.1 11.3 9.6 
Bingiriya 6.7 7.1 1.0 48.9 32.4 18.6 
Hettipola 6.5 9.5 2.6 76.7 8.3 15.0 
Kuliyapitiya 6.2 5.0 1.1 72.5 15.6 11.9 
Giriulla 5.5 23.9 5.1 68.2 15.7 16.1 
Kegalle 4.8 17.7 2.8 46.6 13.1 40.1 
Wattegama 5.8 19.4 5.2 45.3 11.8 42.9 
Naula 6.2 15.1 3.3 42.6 22.9 34.5 
Elahera 6.3 23.2 3.0 6.4 68.0 25.6 
Maradankadawala 5.6 15.9 2.3 60.1 18.5 21.4 
Dadapihilla 6.8 27.8 3.2 79.5 12.6 7.9 
Maha Illuppallama 7.2 18.5 3.0 26.3 17.0 56.7 
Gampola 5.2 25.6 3.8 41.4 41.5 17.1 
Pussallawa 5.2 22.9 4.1 84.7 4.4 10.9 
Nuwara Eliya 3.8 49.3 10.1 36.1 28.7 34.2 
Hewahata 5.2 7.9 1.8 84.1 9.5 6.4 
Kalawana 4.5 17.8 2.8 79.1 12.7 8.2 
Kamburugamuwa 7.2 22.1 4.6 55.2 35.6 9.2 
Tangalle 5.1 4.7 1.7 93.1 2.1 4.8 
Ranna 6.5 22.9 2.9 36.8 13.6 49.6 
Kottegoda 6.2 17.0 1.9 65.1 10.3 24.6 
Ambilipitiya 6.7 19.7 2.8 67.2 6.2 26.6 
Galagedara 6.9 20.9 3.5 77.3 8.4 14.3 
Puttalum 6.5 24.5 0.2 89.1 4.1 6.8 
pH = 1:2.5 soil: H 2 0 ; CEC = Cation Exchange Capacity; OM=organic matter 
Harvesting was done at one-month interval 
on five occasions. Vegetative parts of each 
plant were cut about 4 cm above the soil 
surface. Each pot was treated with (NIL^SO, 
after each harvest, at the same rate as the 
initial application. Plant samples were washed 
thoroughly, oven dried, ground and analysed 
for nutrients according to the method of 
Chapman and Pratt (1961). 
Soil samples taken prior to treatment 
application were used for chemical analysis. 
Available P content was determined by 
extracting soils with 0.5M NaHC0 3 (Olsen et 
al, 1954) and 0.03 M NILF + 0.025 M HCI 
solution (Bray and Kurtz, 1945). 
Concentration of P in the extract was 
determined by molybdenum blue method 
(Murphy and Riley, 1962) using a UV / visible 
spectrophotometer. 
32 
J. Soil Sci. Soc. Sri Lanka. Vol II, 1999 
To determine the exchangeable Ca, Mg, K 
and Na, soil samples were extracted with 
neutral 1M ammonium acetate 
(Schollenberger and Simon, 1945). DTPA 
extracting solution (0.005 M DTPA, 0.01 M 
CaCl 2, 0.1M Triethanolamine) adjusted to a 
pH of 7.3 was used to extract cationic micro 
nutrients in soils (Lindsay and Norvell, 1978). 
Filtrates were analyzed for Ca, Mg, K, Na, Zn, 
Cu, Fe, and Mn using a Shimadzu AA-670 
Atomic Absorption Spectrophotometer. 
AB-DTPA solution was prepared by 
dissolving 1.97 g of DTPA in 800-ml distilled 
water to which 2 ml of 1:1 N H 4 O H was 
added. To the above solution, 79.06 g 
NH4HCO3 was added and stirred gently until 
complete dissolution. The pH in the solution 
was adjusted to 7.6 (Soltanpour and Schuwab, 
1977). Fresh solutions were prepared daily for 
analysis since ammonium bicarbonate is not 
stable for more than 24 hours. Ten g of soil 
was weighed into 250-ml polyethylene bottle, 
to which one tablespoonfUl of "C-Black" (free 
of P and other cations) and 20 ml of AB-
DTPA extractant were added, shaken for 30 
min and centrifuged. The solution was 
analyzed for P using the Murphy and Riley 
(1962) method. Exchangeable cations and 
micro nutrients were analyzed using the 
Atomic Absorption Spectrometer (Shimadzu 
AA-670). 
For each nutrient analyzed, simple linear 
regression analysis was carried out separately, 
to discern the relationships between the 
amount extracted by AB-DTPA method with 
that of conventional methods, as well as with 
plant nutrient concentration and plant uptake. 
Results and Discussion 
Phosphorus 
Highly significant correlations were 
obtained between AB-DTPA extractable P 
and Bray-1 P (r = 0.90*") and AB-DTPA 
extractable P and Olsen P (r = 0.71*"). 
Soltanpour and Schuwab (1977) have reported 
similar results for neutral and alkaline soils. 
All three methods of P extraction (Olsen, 
Bray-1, and AB-DTPA) showed highly 
significant correlation with plant P 
concentration and plant uptake (Table 2). In 
evaluating P availability no significant 
difference was observed between Bray-1, 
Olsen and AB-DTPA methods. However, 
when numerical values of the correlation 
coefficients were considered, Bray-1 gave the 
highest value compared with the other two 
methods. AB-DTPA extractable P showed a 
better correlation with plant P concentration 
than Olsen extractable P, indicating that the 
effectiveness of AB-DTPA method in 
evaluating phosphorus status of soils is equal 
or even better than the Olsen method. Critical 
level of AB-DTPA P calculated based on the 
established critical level of Olsen P and the 
regression equation between AB-DTPA and 
Olsen P (Fig. 2), was 1.16 mg k g 1 . 
Table 2. Relationships between P extracted by 
different methods with P concentration 
in plants and P uptake 
Method Correlation coefficients (r) 
P concentration P uptake 
Bray-1 P 0.827"* 0.856*" 
Olsen P 0.751*" 0.745'" 
AB-DTPA P 0.793*" 0.849*" 
Highly significant at p=0.001 
Exchangeable cations 
Highly significant correlations (Fig. 3) 
were observed between AB-DTPA extractable 
and ammonium acetate extractable values of 
K (r = 0.99*"), Na (r = 0.96*") and Mg (r = 
0.92"'). The correlation between AB-DTPA 
extractable and ammonium acetate extractable 
Ca was less, but still significant (r = 0.72"*). 
33 
Madwapperuma and Kwnaragamage; AB-DTPA extractant for the estimation of available nutrients in soils 
E 
a. 
o i 
CO 
< 
(a) y = 0.2316* 
r .= 0.71*" 
* ft 
* * 
* — 
* 
5 10 15 
Olsen P (mg kg"1) 
20 
10 
3 6 
& 
I 
CD 
< 
- (b) y = O.Wllx r = 0.90"« 
« 
* M 
J , 1 1 
10 20 30 40 
Bray P (mg kg"1) 
SO 
Fig. 2. Relationship between P extracted by 
conventional methods and AB-DTPA 
method (a) Olsen P (b) Bray P 
Extractable K and Na measured by 1 M 
ammonium acetate and AB-DTPA methods 
showed significant correlations with plant 
concentrations and plant uptake of K and Na, 
respectively (Table 3). However, extractable 
Mg and Ca evaluated by AB-DTPA and 1M 
Table 3. Relationships between Na, K, Ca and 
Mg extracted by different methods with 
plant concentrations and plant uptake 
Correlation coefficients (r) 
Plant concentration Plant uptake 
Element AB-
DTPA 
AA AB-
DTPA 
AA 
Na 
K 
Ca 
Mg 
0.808" 
0.857" 
0.165™ 
0.393™ 
0.815"* 
0.812"* 
0.364"* 
0.068" 
0.857" 
0.808" 
0.214"1 
0.134™ 
0.820*" 
0.812"* 
0.364" 
0.066" 
Highly significant at p = 0.001 
" Not significant 
AA- 1M ammonium acetate method 
ammonium acetate methods did not show 
good relationships with plant Mg or Ca 
concentrations, or plant uptake of Mg and Ca, 
probably due to the high level of Ca and Mg 
in tested soils. 
Critical levels for AB-DTPA method were 
calculated based on the established critical 
levels for ammonium acetate method (Landon, 
1984) and the regression equations between 
AB-DTPA and ammonium acetate extractable 
nutrients (Fig. 3). The calculated critical levels 
for K, Ca and Mg were 57.3, 15.6 and 30.2 
mg/kg, respectively. 
I too 
o 
S 
< 
g 100 
2 50 
y • 0.037BX 
• 
r = 0.T2-"* 
* * • 
* * 
. ' " is* 
• 
• -
 1 
400 
300 r a o.B2*~ 
200 
100 
0 
0 1000 2000 3000 0 300 600 900 1200 
Ammonium acatala extractable cation (mg kg"') 
Fig. 3. Relationship between K, Na and Mg 
extracted by ammonium acetate method 
and AB-DTPA method 
Micro nutrients 
Highly significant correlations were 
observed between AB-DTPA extractable and 
DTPA extractable Zn (r = 0.82***) Cu (r = 
0.91"*), Fe (r= 0.73***) and Mn (r = 0.78*"). 
Plant concentration and plant uptake data 
showed significant correlation with AB-DTPA 
extractable Zn, Cu, Fe and Mn (Table 4). 
However, DTPA extractable Fe and Mn did 
not show a significant relationship with plant 
34 
J. Soil Sci. Soc. Sri Lanka. Vol 11,1999 
uptake indicating that AB-DTPA method is 
y better than the conventional DTPA extraction 
L in assessing available Fe and Mn. 
Table 4: Relationships between Zn, Cu, Fe and 
Mn extracted by different methods with 
plant concentrations and plant uptake 
Correlation coefficients (r) 
Plant concentration Plant uptake 
Element AB-
DTPA 
AA AB-
DTPA 
AA 
Zn 0.895*" 0.703*" 0.736"* 0.467* 
Cu 0.851*" 0.748*" 0.748*" 0.540* 
Fe 0.706*** 0.547* 0.478* 0.283" 
Mn 0.809*** 0.589* 0.752*" 0.566* 
"* Highly significant at p =0.001 
Significant at p = 0.05 
™ Not significant 
Conclusions 
Based on the results of this experiment 
AB-DTPA method can be introduced as a 
multi nutrient extraction method in routine 
laboratory analysis for available P, Na, K, Zn, 
Cu, Fe and Mn. AB-DTPA method seems to 
be equally effective or better than Olsen 
method in extracting soil available P, whereas 
in extracting micro nutrients such as Fe, Mn, 
Cu and Zn, it proved to be better than DTPA 
extractant for the soils tested. AB-DTPA and 
1M ammonium acetate methods showed 
similar effectiveness in extracting 
exchangeable Na and K. Use of AB-DTPA 
method in routine analytical work will reduce 
the time and cost of analysis, since it requires 
only a single extraction to analyze many 
nutrients. Calculated critical levels for P, K, 
Ca and Mg were 1.16, 57.3, 15.6 and 30.2 
mg/kg, respectively. To use this method for 
fertilizer recommendation, critical levels 
should be validated, preferably under field 
conditions. 
References 
Amato, M. 1983. Determination of carbon "C 
and "C in plant and soil. Soil Biology and 
Biochemistry 15,5:611-612. 
Bouycous, G. L. 1926. Estimation of the colloidal 
material in soils. In: Black , C. A1965. 
Methods of soil analysis (Ed.), Part 1. 
American Society of Agronomy , Madison, 
Wisconsin, U.S.A. pp 545-566. 
Bray, R.H., and L.T. Kurtz. 1945. Determination 
of total organic and available forms of 
phosphorus in soils. Soil Sci. 59:39-45. 
Chapman, H. D. 1965. Cation exchange capacity. 
In: Black CA. 1965.. Methods of soil Analysis 
(Ed.) Part 2, American Society of Agronomy, 
Madison, Wisconsin, U.S.A. pp 891-901. 
Chapman, H.D. and P.F. Pratt. 1961. Methods of 
analysis for soils, plants and waters. Division 
of Agric. Sci., University of California, 
Riverside, U.S.A. pp 161-175. 
Dalai, R.C. 1979. Simple procedure for the 
determination of total carbon and its 
radioactivity in soils and plant materials. 
Analyst 104:151-154. 
Landon, J.R. 1984. Booker Tropical Soil manuel. 
A handbook of soil survey and agricultural 
land evaluation in the tropics and subtropics. 
Booker Agriculture International Limited, 
London, England. 
Lindsay, W.L., and W.A. Norvell. 1978. 
Development of a DTPA soil test for zinc, 
iron, manganese, and copper, Soil Sci. Soc. 
Am. J. 42:421-428. 
Madurapperuma, W.S., and D. Kumaragamage. 
1995. Use of a multi-ionic extractant to 
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acid soils of Sri Lanka. Trop. Agric. Res. 7: 
152-158. 
35 
Madurapperuma and Kumaragamage; AB-DTPA extractant for the estimation of available nutrients 
Mclean, E.0.1982. Soil pH and lime requirement. 
In: Black CA.1965. Methods of soil Analysis 
(Ed.) Part 2, American Society of Agronomy. 
Madison,.Wisconsin, USA. pp 199-224. 
Murphy, J., and J.P.Riley. 1962. A modified single 
solution method for the determination of 
phosphate in natural waters. Anal. Chem. 
Acta. 27:31-36. 
Olsen, S.R., C.V. Cole, F.S. Watanabe and L.A. 
Dean. 19S4. Estimation of available P in soils 
by extraction with Sodium Bicarbonate. U.S. 
Dept. Agric. Cir. 939. 
Schollenberger, C. J., and R.H. Simon. 1945. 
Determination of exchange capacity and 
Exchangeable bases in soil-ammonium acetate 
method. Soil Sci. Soc. Am. Proc. 25:274-
277. 
Soltanpour, P.N., and S.P. Schuwab. 1977. A 
new soil test for simultaneous extraction of 
macro and micro nutrients in alkaline soils. 
Comm. Soil. Sci. Plant Anal. 8:195-207. 
36 


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