Phosphorus fixing capacity of the Oxic Rhodustalf—alfisol soil in the Chotanagpur plateau region of Eastern India

doi:10.4236/as.2011.24062

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Vol.2, No.4, 487-490 (2011)

doi:10.4236/as.2011.24062

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: [email protected]

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

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)

100

150

200

300

400

500

600

750

2.5

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



yNxy







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:

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

P. Ghosal et al. / Agricultural Sciences 2 (2011) 487-490

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

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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