Vol.2, No.4, 487-490 (2011)
doi:10.4236/as.2011.24062
C
opyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/AS/
Agricultural Scienc es
Phosphorus fixing capacity of the Oxic Rhodustalf—
alfisol soil in the Chotanagpur plateau region of
Eastern India
Prabir Ghosal1*, Trishit Chakraborty2, Pabitra Banik3
1Agricultural and Ecological Research Unit, Indian Statistical Institute, Kolkata, India; *Corresponding Author:
2Department of ASEPAN, Palli Siksha Bhavana, Sriniketan, Visva Bharati, Bolpur, India;
3Agricultural and Ecological Research Unit, Indian Statistical Institute, Kolkata, India.
Received 4 September 2011; revised 12 October 2011; accepted 30 October 2011.
ABSTRACT
The P-fixing capacity of a soil governs the P-nu-
trition of crop plants. P-nutrition of the crop
plant is more a soil problem and a higher dose
of phosphatic fertilizer is necessary for soils
having high P-fixing capacity. The phenomenon
of P-fixation and the great variation in the P-
fixing capacity of different soils has thus im-
portant bearing on crop response to P-appli-
cation. The eastern plateau region of India with
acid lateritic soil is chronically deficient in av-
ailable phosphorus resulting in very low pro-
ductivity. An experiment was thus carried out to
estimate the P-fixing capacity of soil collected
from two depths, 0 - 20 cm and 20 - 50 cm, from
the Agricultural experimental farm of Indian
Statistical Institute, situated at Giridih, Jhark-
hand, in the eastern India. The soil was acidic in
reaction (pH-5.4) with presence of Fe (1.60%)
and Al (17.2%). The P-fixing capacity of the soil
was estimated to be 59.60% and 64.94% for the
surface and the subsurface soil respectively
showing lower P-fixing capacity of the surface
soil as compared to the subsurface soil which
may be due to presence of more organic matter
in the surface soil as organic molecules re-
leased on decomposition of org anic matter c o m -
plexes with Fe and Al in the soil thereby block-
ing the P-fixing sites in the soil.
Keywords: P-Fixing Capacity; P-Nutrition;
P-Fixation
1. INTRODUCTION
Phosphorus (P) is an essential element for plant growth
and productivity, and lack of available P in soils can se-
verely affect crop yields [1]. Plants extract P from the
soil solution in the form of orthophosphate ion (24
HPO

or 4 HPO

) and there is strong competition between
plants and soil minerals for these forms of P, particularly
in the highly weathered soils of the tropics, most of
which contain large amounts of iron oxides, aluminum
oxides, or amorphous alumino-silicate clays. These soil
minerals “fix” P firmly through a process known as
sorption, making the P virtually unavailable for plant
uptake [2].
The P-fixing capacity of a soil is influenced by a
number of factors, such as pH, CaCO3, sesquioxides,
moisture and clay contents [3]. When phosphatic fertil-
izers are added to a soil, a series of chemical reactions
take place between the soil constituents and soluble
phosphorus, rendering the added phosphorus relatively
less available. The soil factors contributed to 80 to 83
per cent of the variations in the amounts of P fixed at
various levels of added P and also of the maximum P
fixation capacity [4]. Thus, it is now well understood
that P-nutrition of the crop plants is more a soil problem
and a higher dose of phosphatic fertilizers are thus nec-
essary for soils having high P-fixing capacity. It has been
reported th at about 10% to 30% of add ed phosphorus, is
utilized by the crop and the rest is accumulated in the
soil in one form or anoth er thereby en riching th e reserve
phosphorus pool of the soil. An increase in the Relative
Agronomic Efficiency of less water-soluble P sources on
high soil P adsorption capacity has also been reported [5].
Thus, the phenomenon of P-fixation and the great varia-
tion in P-fixing capacity of different soils has important
bearing on crop re sponse to phosphorus application.
The eastern plateau region of India is chronically low
in productivity of food grains [6]. One of the reasons for
this is attributed to very low phosphate availab ility o f the
soil (20 - 25 kg P2O5/ha) due to its acidic reaction and
presence of large amount of hydroxides of iron and alu-

P. Ghosal et al. / Agricultural Sciences 2 (2011) 487- 490
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488
minum [7].
With this background, an experiment was carried out
in the laboratory of the Agricultural and Ecological Re-
search Unit of Indian Statistical Institute at Kolkata, on
soils collected from the Agricultural farm of Indian Sta-
tistical Institute situated at Giridih, Jharkhand in the
Chotanagpur plateau region of eastern India.
2. MATERIALS AND METHODS
The composite soil samples were collected from Ag-
ricultural experimental farm of Indian Statistical Institute
situated at Giridih, Jharkhand, from two depths, 0 - 20
cm and 20 - 50 cm. The soil samples were air dried,
ground and passed through 2 mm sieve. The physico-
chemical properties of the experimental soil are pre-
sented in Tables 1(a) and (b).
Treatment Details :
Concentrations of P
added as KH2PO4
(g/cc)
Soil
Taken
(g)
Effective concentration
on addition of 1 cc P
solution in 2.5 g of soil
(g/g)
Soil sampling
depth (cm)
0
50
100
150
200
300
400
500
600
750
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
0
20
40
60
80
120
160
200
240
300
0 - 20
20 - 50
3. METHODOLOGY
Two and a half gram (2.5 g) of air dried sieved soil
was taken for each treatment, for two soil depths (0 - 20
cm and 20 - 50 cm depth), in 100 cc conical flask. One
milliliter (1 ml) of different concentrations (0 g/cc, 50
g/cc, 100 g/cc, 150 g/cc, 200 g/cc, 300 g/cc, 400
g/cc, 500 g/cc, 600 g/cc and 750 g/cc) of soluble
phosphorus, in the form of potassium dihydrogen phos-
phate was carefully added to each flask as per treatment
so as to wet the soil uniformly. The conical flasks were
then plugged and incubated at room temperature (30˚C)
for 96 hours and available phosphate (P) was then esti-
mated by Olsen’s method [8]. The whole experiment
was carried out in three sets and the mean data have
been presented. According to Nad et al. (1975) the P-
fixation capacity of soil was worked out using the equa-
tion

2
2
x
yNxy
b
x
Nx




where, b represents the fraction of added P, which re-
mained available under the condition of the experiment.
Added P, released P and number of concentrations of P
added (10) are represented by x, y and N respectively.
The method is based on the relationship between avail-
able P (i.e. estimated P) and added P, which is virtually
linear and therefore the slope of the curve relating re-
leased P (y-axis) and added P (x-axis) was calculated out
by the standard equation mentioned above. The percent
of P-fixation of added P is thus given by

Phosphate fixation capacity %,P100100b
Table 1. (a) Physico chemical characteristics of the experimental soil; (b) Mechanical composition of the soil (in %).
(a)
Parameters Values
Physical characteristics:
Particle density (g/cc)
Bulk density (g/cc)
Water holding capacity (%)
Chemical characteristics:
pH
Organic Carbon (%)
Total Nitrogen (%)
Available Nitrogen (kg/ha)
Available P (kg/ha)
Available K (kg/ha)
Cation Exchange Capacity (me/100g)
Aluminium Oxide (%)
Iron Oxide (%)
2.49
1.33
23.1
5.4
0.52
0.059
135.0
5.6
89.5
10.19
17.2
1.60
(b)
Sand
Fine Coarse
Silt Clay Textural class
27.4 33.8 11.9 26.9 Sandy Clay Loam

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489489
4. RESULTS AND DIS CUSSION
The P-fixing capacity of a soil can be drawn from the
relationship of added phosphorus and extracted available
phosphorus on addition of graded quantum of phospho-
rus, after a time interval, in a particular soil. The data on
addition of graded amount of inorganic phosphorus (Ta-
ble 2) at both the soil depth indicated that the relation-
ship between available and added phosphorus was virtu-
ally linear (Figure 1). This was in accordance with the
findings of Nad et al. (1975). Thus the slope “b”, w hich
is the fraction of the added phosphorus remaining avail-
able under the conditions of the experiment, was calcu-
lated using the formula mentioned above and the values
were 0.404 and 0.351 for soils from 0 - 20 cm and 20 -
50 cm depths respectively. The percent fixation of phos-
phorus in the soil came out to 59.60% and 64.94% for
the surface and subsurface soil respectively. The P-fixing
values were close to that of the lateritic soil at Manga-
lore having pH 5.6. It may be noted that the subsurface
soil has higher P-fixing capacity than the surface soil.
This may be attributed to lower phosphorus content in
the subsurface as well as presence of more organic mat-
ter in the surface as co mpared to subsurface soil. Organic
matter on decomposition releases organic molecules,
which form complexes with Fe and Al ions thereby
blocking the sites which are mainly responsible for fixa-
tion of phosphorus [9-11]. This is supported by results of
another experiment [12] conducted in the same site
which showed that ad dition of organic manure markedly
increased the availability of phosphorus in the soil. This
increase in phosphorus availab ility in the soil was found
to be statistically significant over control treatment and
also over treatments with inorganic fertilizers.
Ta b le 2. Available P (g/g), on addition of graded amount of
inorganic phosphorus to the soil.
Available P (g/g)
Added P (g/g) 0 - 20 cm 20 - 50 cm
0 7.96 5.96
20 16.92 12.96
40 21.56 18.92
60 30.88 25.24
80 44.48 39.56
120 56.44 53.12
160 83.96 77.80
200 97.60 88.96
240 119.52 103.60
300 106.24 100.28
0
20
40
60
80
100
120
140
020 40 6080120160200240300
Added P (ug/g)
Extracted P (ug/g)
0 - 20 c m dept h20 - 50 c m dept h
Figure 1. Available P on addition of graded amount of inor-
ganic phosphorus in the soil collected from two depths.
Thus the soil of the eastern plateau area is character-
ized with low soil available phosphorus and as much as
60% of the applied P can get fixed in the soil. Under
such circumstance the P fixation capacity must be over-
come by application of fertilizer P at a higher rate or by
applying slow releasing P fertilizers as phosphate rocks
to have enough P left over for crops to increase produc-
tivity.
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