Managing residual and fixed phosphorus in soil

1. Syed Wali Jalalzai
ID. NO. PALB 2098

2. Managing residual
and fixed
phosphorus in soil
2
A single arbuscule
PSB

3. Outline of seminar
Introduction
Research papers
Summary

4. Phosphorus is an important natural resource which is
finite
It has great relevance to crop productivity in different parts of
the globe
Phosphate deficiency in soil is indeed widespread and has been
observed in several agricultural soil
Phosphorus application has almost invariably produced
comparatively richer harvests of grain and biomass, in
different soil types of each continent
Obviously, the inherent soil process that cause p fixation, as
well as relevant mechanisms to overcome such an enormous
soil fertility problem is felt strongly by agriculturists
Agricultural production needs to increase
which is related to increased use of inorganic
inputs such as phosphorus

5. Importance of
Phosphorus to Plants
important in cell division and
development of new tissue
Phosphorus is also associated
with complex energy
transformations in plants
Adding phosphorus to soil
low in available phosphorus
promotes root growth and
winter hardiness, stimulates
tillering, and often hastens
maturity
Phosphorus is a component of
complex nucleic acid structure
of plants, which regulates
protein synthesis

6. In soils P may exist in many different forms. In practical terms, however, P in
soils can be thought of existing in 3 "pools":
Forms of Phosphorus in Soils
Residual P: When the amount of fertilizer P added to soil exceeds removal by
cropping the fertilizer P residues gradually increase, with corresponding rise
in P concentration in the soil solution
Also
• Very small and will usually contain only a
fraction of P per acre.
Solution P pool
• P on the solid phase which is relatively
easily released to the soil solutionActive P pool
• Made of inorganic phosphate compounds that are
very insoluble and organic compounds that are
resistant to mineralization by microorganisms in the
soil
Fixed P pool

7. P dynamics in the soil/rhizosphere plant continuum.
Jainbo Shen et al. 2011

8. Fate of Phosphorus
Tisdale et al. 1993

9. P fractions
P fractions in soil
Inorganic
Saliod P:
Al P
Ca P
Fe P
Occluded P
Organic: (50%).
Inositol
phosphate 10-
50%
Phospholipids
1-5%
Nucleic
acids0.2-2.5%
Responsible for P fixation and P
build up

10. Factors influencing P build up
Factors
influenci
ng P
build up
Nature
and
amount of
soil
minerals
Soil pH
P fixation
Fertilizer P
manageme
nt
Organic
matter
Reaction
time and
temperatu
re
Anion
effects
Cation
effects
Let me explain
2
3
4
5
6
7
8
1

11. 1) Soil pH
Lowell et al 2009

12. Figure. Relationship between P adsorbed by soil and P in solution
Lowell et al 2009
2) Soil p adsorption and release

13. P build up - consequences
 Phosphorus buildup is caused by use of inorganic fertilizer
which undergo fixation reaction in soil
 Buildup of phosphorus in croplands can cause poor plant
growth and thus low productivity
 Excessive soil phosphorus reduces the plant’s ability to take
up required micronutrients, particularly iron and zinc, even when
soil tests show there are adequate amounts of those nutrients in
the soil
High soil phosphorus levels threaten streams, rivers, lakes and
oceans due to possible pollution of the water bodies

14. Management of fixed and residual P
Acidifying and Liming
Application of Biofertilizers
Agronomic practices: Deep plowing,, P holiday and
others
Plant breeding and Genetics: To develop cultivars
that will grow well by using native or built up P
Root geometry change
Acidic rhizosphere
Managing Organic acids in soil

15. 1. Root modification (Proteoid roots)
Proteoid roots
produced by white
lupin with (A) and
without (B) phosphate.
There is an enormous
increase in the root
surface area helping to
forage more p

16. P uptake by cluster roots
The ability of the cluster roots of white lupin to excrete
organic acid is associated with several physiological
mechanisms (Neumann and Martinoia, 2002)

17. H release by white lupin roots during a 3-week
cultivation period

18. WHEAT TOMATO CHICKPEA WHITE LUPIN
| + P - P | +P -P | + P - P | + P - P - P |
non-proteoid proteoid
Carboxylate concentration [µmol g-1
FW]
| 1.18 5.38 | 8.48 12.03 | 8.50 17.11 | 8.70 15.98 28.12 |
PEP-carboxylase activity [nmol NADH min-1
mg protein-1
]
| 426 703 | 90 375 | 144 302 | 120 210 330 |
P deficiency-induced changes in PEP carboxylase activity as
related to organic acid accumulation in the root tissue
I. Citrate synthase enzyme involved in synthesis of citrate
II. Is also synthesized in higher quantities
III. The excess citrate is released into the rhizosphere, which
solubilizes bound P
PEP: phosphoenolpyruvate

19. A. Low molecular weight, non amino organic acid anions such as citrate,
malate, oxalate, fumarate, and malonate
B. Organic acid concentrations in the cytosol are relatively stable whereas,
in the vacuole vary in response to nutrient availability and metabolic
activity
C. Exudation is usually localized to specific regions of the root system
Organic acids in soil
Regulation of
cellular pH
and osmotic
potential
Maintenance of
elecro neutrality
during excess
nutrient cation
uptake
Involved in
assimilation of
nutrients
Supply of
energy to
symbiotic
bacteria(malate,
malonate,
oxalate)
Functions of organic acids in soil

20. 1. Minimizing reaction of P fertilizer with unfavorable soil components
2. Modifying soil chemical environment to suit better P acquisition by plant
3. Selecting proper P source and timing of its application

21. RESEARCH PAPERS

22. Evaluation of residual and
cumulative phosphorus effects in
contrasted Moroccan calcareous
soils
Amrani et al. 1999
1st paper

23. To evaluate the residual and cumulative P effects on crop growth and P uptake in
contrasting calcareous soils from the arid and semiarid zones of Morocco
Objective

24. Materials and methods
Thirteen calcareous soils were collected from three regions of arid and semi-arid
zones of Morocco. The soils were air dried, crushed and sieved through a 2-mm
screen
Available P was extracted by 0.5 M NaHCO3 solution and analyzed by the ascorbic acid
method
Five kg of each soil was placed in polyethylene plastic
pots. Three successive crops were grown as follows
Greenhouse experiment
Third crop: WheatFirst crop: Wheat Second crop: Corn

25. First crop: Wheat
Supplemental fertilization added to each pot consisted of:
1) 100 mg N kg-1 from NH4NO3, one half at sowing and the other at
tillering
2) 50 mg K kg-1 from K2SO4
3) 3.5 mg Zn kg-1 from ZnSO4.7H2O
4) 8 mg Fe kg-1 from Fe - Chelate (10%)
5) 4.5 mg Cu kg-1 from CuSO4.5H2O
6) 8 mg kg-1 from MgSO4.7H2O
Fertilizer P solutions were prepared using reagent grade monocalcium phosphate
and mixed with soil at rates :
a. 0, 3.4, 6.7 and 13.4 mg P kg-1 soil
b. Four replications
c. Nineteen wheat seeds (cv. Merchouch) were placed at a depth
of 2 to 3 cm in each pot
d. Thinned to 9 plants, 12 days after sowing
Pots were watered regularly (every 3 days) with enough deionized water to
bring them to 90% of field capacity
The greenhouse was maintained at 24 ◦C day and 15 ◦C at night

26. Soil Soil type Clay Silt Sand pH
water
CEC
cmol(+)/k
g
Organic
matter
%
Lime
(CaCO3)
%
Olsen-P
mg kg-1
MBC
——-%———
1 Palexerolic
Chromoxerets
56 20 23 7.9 56 1.6 7 3 364
2 Vertic Calcixerollic 42 8 48 8.1 39 2.3 1 8 131
3 Calcic Argixerolls 51 28 22 8.2 50 1.9 15 10 363
4 Typic Chromoxererts 48 8 39 7.9 39 2.2 6 6 184
5 Typic Rendolls 56 14 27 7.7 26 4.6 4 7 332
6 Xerochrepts 47 23 27 8.0 28 1.6 21 8 351
7 Xerochrepts 49 9 39 8.0 28 2.3 37 23 367
8 Argiustolls 26 8 64 7.7 10 2.8 1 14 99
9 Typic Rendolls 28 15 67 8.2 27 3.7 14 8 101
10 Aridic SG of Ustolls 27 7 66 8.1 13 2.5 1 9 102
11 Chromoxererts 45 10 43 7.6 43 1.4 1 9 174
12 Xerochrepts &
Ustochrepts
53 8 37 7.5 28 2.6 1 26 404
13 Arguistolls 10 2 87 7.9 1 0.6 1 9 35
Table 1: Selected physical and chemical characteristics of surface (0–20 cm)
soils used in study
MBC = maximum buffering capacity

27. The greenhouse experiments were conducted as completely randomized
factorial designs with:
a) Two factors for the first crop (wheat)
b) Two factors for the second crop (corn)
c) Three factors for the third crop (wheat)
An analysis of variance and fitted model were performed on measured and
calculated variables using the SAS package (SAS Institute, 1985)

28. Result and discussion
Variable Source DF Crops
Wheat Corn Wheat
(1st crop) (2nd crop) (3rd crop)
Direct P RP CP RP
—————————-P—————————-
Grain yield Soils 12 0.01 – 0.01 0.01
P rates 3 0.01 – 0.01 0.01
Soils×P rates 35 0.01 – 0.01 0.01
Dry-matter Soils 12 0.01 0.01 0.01 0.03
P rates 3 0.01 0.01 0.01 0.01
Soils×P rates 35 0.01 0.01 0.13 0.01
Total Puptake Soils 12 0.01 0.01 0.01 0.01
P rates 3 0.01 0.01 0.01 0.01
Soils×P rates 35 0.01 0.01 0.02 0.04
Table 2: Analysis of variance of the direct, cumulative, and residual effect of P on
succeeding crops grown under greenhouse conditions
- only corn dry matter was harvested. P is probability. RP=residual P. CP=cumulative P

31. Fig. Relative grain yield of wheat as a function of initial NaHCO3 – P mg kg -1

32. i. The effect of residual P on succeeding crops was evident in this study
ii. The response of both corn (second crop) and wheat (third crop) to previously
applied P supported the observation that much of the P applied to a crop as
fertilizer may not be used by that crop
iii.Response of corn to residual P was significant for soils with initial NaHCO3 – P
test level less than 9 mg kg-1 and no response above 14mg kg-1
Conclusion

33. Crop yields and phosphorus fertilizer
transformations after 25 years of
applications to a subtropical soil under
groundnut-based cropping systems
Research Paper - 2
Aulakh et al 2003
Objective
To determine the status of different soil P pools in long term
fertilized soils
To assess and make use of accumulated fertilizer P for sustainable
crop production and environmental safety

34. A field study was conducted for 25 consecutive years (1975/1976–
1999/2000) on a semiarid, irrigated.
Material and Methods
Location: Tolewal sandy loam soil (Typic Ustochrepts) at Punjab
Agricultural University Research Farm, Ludhiana, India.
Temperature 6- 20Cο
in January and
27-41Cο
in June
Annual rainfall 600 – 1200mm
pH 8.7
EC 0.21 dSm-1
OC 3.8g kg-1
Olsen P 11.6 kg ha-1
 The experimental design was a completely randomized block (CRBD)
 12 treatments (four P rates x three P frequencies) were randomized within
three blocks

35. Table 1 : Groundnut based cropping sequences, crop cultivars (cv.), and rates
and frequencies of fertilizer P followed during 25 years (1975–2000)

36. Results and Discussion

37. Table 2: Pod yield of groundnut from plots receiving different rates and frequencies
of fertilizer P in three groundnut based cropping sequences
a LSD005: rate = 130; year = 250; frequency, rate x frequency, year x frequency, year x rate, and year x rate x frequency =
nonsignificant. b LSD0.05: year = 200; rate, frequency, rate x frequency, year x frequency, year x rate, and year x rate x
frequency = nonsignificant. c LSD005: rate = 300; year = 380; rate x frequency, year x frequency, year x rate, and year x rate
x frequency = nonsignificant.

38. Table 3: Grain yield of winter-grown wheat and seed yield of mustard and rapeseed crops from
plots receiving different rates and frequencies of fertilizer P in the groundnut-based cropping
sequences
a LSD0 05: rate = 350, frequency = 220, year = 210, rate x frequency = 335; year x frequency, year x rate, and year x rate x
frequency = non-significant. bLSD0.05: rate = 67, frequency = 49, year =110, rate x frequency = 110; year x frequency, year
x rate, and year x rate x frequency = non-significant. c LSD0 05: rate = 140, frequency = 120, year = 210, rate x frequency =
210; year x frequency, year x rate, and year x rate x frequency = non-significant.

39. Table 4: Transformations of residual fertilizer P in different P fractions
in soils after 25 years of fertilizer P applications in groundnut-based
cropping systems (values are means of three fertilizer P rates)a
Pi: inorganic P; Po: organic P

40. Number of experimental years
Cont….

41. Fig. . Dynamics of Olsen-P in soil during 25 years in no-P control and with
fertilizer P applications to summer-grown groundnut, winter crop and both crops
each year. P1 P2, and P3 refer to 30, 60 and 90kgP2O5 ha-1 applied in groundnut-
wheat; 20, 40 and 60 kg P2O5 ha-1 in groundnut-mustard; 20, 30 and 40kgP2O5 ha-1
in groundnut-rapeseed sequence, respectively.

42. Conclusion:
i. P-build up to a high fertility range would increase plant available P,
albeit at a diminishing rate, continuous high application rates of
fertilizer P may also result in P induced micronutrient deficiencies.
ii. Results indicated a marked difference in P fraction changes between
fertilized and non fertilized control plots.
iii. The conversion of fertilizer P to non labile P forms is significantly
enhanced by increasing rates and frequency of applied P.

43. Research Paper - 3

44. To evaluate both the initial year’s response to P fertilization of corn in south
eastern Turkey as well as its residual effect over a number of years.
Objective
Material and methods
Field location
1. Multiple years field corn experiments as a second rotation crop were conducted at
the Research Station of Cukurova University in Adana, Turkey.
2. The soil was a loamy, smectitic and calcareous
3. Selected physical and chemical properties of soil that might influence P use and
crop growth were:
• pH 7.6 (1:5 soil:water),
• organic matter content (0.74%),
• High CaCO3 (29%),
• cation exchange capacity (29 Cmol kg-1)
• Marginal levels of plant available P, i.e., 10 mg kg-1 NaHCO3- extractable P
(Olsen).

45. Corn genotype (Hybrid XL72AA) was planted manually in late June to early July,
based on the weather conditions of that specific year
Treatments:
In the first year (1998), the main plots were fertilized with 0,33, 66 and 99 kg
P ha- (as triple superphosphate) prior to the experiment in order to establish a
range of soil test values for the following years.
During the second and following years, the main plots were divided into
subplots, each receiving 0, 9, 18, 27 and 36 kg P ha-1
The first year experiment was arranged in a randomized complete block
design, and then became a split-plot design having:
a) 0, 33, 66 and 99 kg P ha-1 rates as main plots
b) 0, 9, 18, 27 and 36 kg P ha-1 rates as subplots
c) Four replications in 1999, 2000, 2001 and 2002

46. RESULTS AND DISCUSSION
Table 1. Initial (main plot) and currently applied (sub plot) fertilizer P in relation to
yield and increment.

47. Table 2. Initial (main plot) and currently applied (sub plot) fertilizer P in relation to grain P
uptake, total plant P uptake and P recovery.

48. Main plots P rates kg P ha Relative yield
1999 2000 2001 2002
0 119 121 128 135
33 123 124 106 132
66 126 124 107 133
99 112 126 106 136
Average 120 124 112 134
Table 3. Relative corn yield to currently applied P for
4 years after the initial P applicationa.
a Mean response of the 9,18,27,36 kg P ha a -1 rates relative to the control
for each initial level of P.

49. Figure . Extractable P status in 2002 after 5 years of P fertilization. Initial main-
plots received 0, 33, 66 and 99 kg P ha-1 in 1998 and sub-plots 0, 9, 18, 27, 36
kg P ha-1 annually from 1999-2002

50. CONCLUSION
i. Residual P from fertilizer application does accumulate rapidly for the
benefit of succeeding crop
ii. The phenomenon occurs in calcareous Mediterranean soils which ‘‘fix’’
applied P fertilizer
iii.Based on research in the Mediterranean region, and data from that
study was, the fertilization value of P fertilizer residues can easily
assessed and monitored by soil testing

51. Rescheduling of phosphorus application to FCV tobacco grown
on Phosphorus build up soils of KLS(Karnataka light soil)
region
Vasuki et al. (2002)
objective
To ascertain the effect of reducing the level as well as omitting the application
of P on yield and quality of FCV tobacco
4th Paper

52. Material and Methods
1. Location: Agricultural Research Station Navile, Shimoga. In
plot where tobacco continuously grown.
2. Available P was very high (130 kg P2O5 ha)
3. Design was RBD.
4. Long term field trial on P application was conducted with
reduced level of P 30 and 60kg h in combination of with
different schedules of application
1. Every year
2. Once in two year
3. Once in three year

53. Results and Discussion
S/No treatments Nicotine (%) Reducing sugar(%)
X L X L
1 No P2O5 1.63 1.70 15.2 14.9
2 30 kg P2O5 (E. yr.) 1..63 1.85 16.1 15.6
3 30 kg P2O5 ( once in 2 E. yr.) 1.68 1.83 16.5 14.1
4 30 kg P2O5 ( once in 3 E. yr.) 1.67 1.73 16.4 15.3
5 60 kg P2O5 (E. yr.) 1.66 1.81 15.2 15.1
6 60 kg P2O5 ( once in 2 E. yr.) 1.59 1.77 15.6 15.2
7 60 kg P2O5 ( once in 3 E. yr.) 1.61 1.74 16.5 15.2
S.Em. +/- 0.10 0.08 0.68 1.17
C.D. 0.05 Ns Ns Ns Ns
CV.% 11.4 9.7 13.6 15.8
Table 1: Nicotine and reducing sugar levels of FCV tobacco as influenced by P
application (Average of six year)
FCV: Flue Cured Virginia

54. Table 2: depletion of available P at the end of sixth year
S/No treatments P2O5 kg ha-1 Extent of
depletion
kg ha-1
% of
depletion1994 initial 1999
1 No P2O5 171.6 97.5 74.3 43
2 30 kg P2O5 (E. yr.) 194.0 131.0 63.0 32
3 30 kg P2O5 ( once in 2 E. yr.) 195.9 139.0 56.8 29
4 30 kg P2O5 ( once in 3 E. yr.) 170.4 117.8 52.5 31
5 60 kg P2O5 (E. yr.) 192.8 142.0 51.0 26
6 60 kg P2O5 ( once in 2 E. yr.) 187.1 139.0 48.0 25
7 60 kg P2O5 ( once in 3 E. yr.) 194.1 141.0 53.5 27
S.Em. +/- 11.6 9.3 11.2
C.D. 0.05 Ns 27.5 Ns
CV.% 9.6 24.3 39

55. S/No treatments Av. Yield kg ha-1 B: C ratio*
1 No P2O5 1102 1:18.36
2 30 kg P2O5 (E. yr.) 1075 1:14.8.
3 30 kg P2O5 ( once in 2 E. yr.) 1107 1:16.42
4 30 kg P2O5 ( once in 3 E. yr.) 1134 1:17.31
5 60 kg P2O5 (E. yr.) 1162 1:13.71
* Input – output costs arrived based on the returns of corresponding years and input
multiplied by the costs of respective years.
Table 3: Economic performance of rescheduling of P to FCV tobacco.

56. Conclusion
The depletion of available soil P in long run in plots where
no P applied and with a view to sustain the P supply to the
crop at the optimum level over the years, it is advisable to
go for 30kg ha application once in three years

57. Organic acids exuded from roots in phosphorus uptake
and aluminum tolerance of plants in acid soils
Hocking 2001
objective
I. To understand how organic acid exudation from roots benefits
the P nutrition of plants.
II. To determine the role of organic acid in mobilizing fixed P
for plant nutrition
5th paper

58. Fig 1: Outline of the main processes affecting P availability in the rhizosphere and P supply to plant roots.
Root take up inorganic P (Pi) from the soil solution. Which is replenished by Pi from the solid phase and by
hydrolysis of organic P (Po) from the soil solution and solid phase. Root exudates particularly organic acids
increase rates of solubilization, desorption. and mineralization either directly or indirectly via the activity of
microorganisms. Mycorrhizal fungi increase the absorbing area of the root system and the volume of soil
exploited.

59. Table 1: Organic acids exuded from roots of selected crop species grown under P stress
Plant
species
Growth
conditions
Organic aced exuded from roots (whole root
system; μ mol g-1 dry wt h-1
References
citric Malic Malonic Others
White
lupine
P-deficient
solution
11000 8000 - Traces of aconitic,
fumaric ,oxalic and
succinic
Johnson et al.
1996
Rice Low - P soil 2300 - - Traces of oxalic,
malic, lactic and
fumaric
Kirk et al. 1999
Maize P-deficient
soil
1300 6000 - Jones and Darrah
1995
Alfalfa P-deficient
sand
650 279 Succinic Lipton et al. 1987
Pigeon
pea
P-deficient
solution
2.3 trace 752 Oxalic, Picidic and
tartaric
Otani el al. 1996
Chick
pea
P-deficient
solution
209 74 41 aconitic, fumaric and
succinic
Ohwaki and Hirata
1992

60. Fig 2: Effect of adding various amounts of citrate to an Oxisol on the quantities
of P subsequently extracted. Levels of 50 to 100 μ mol citrate g-1 soil are similar
to those found in rhizospheric soil of white lupine proteoid roots. Note: citrate
increase the extraction of both fixed soil P and recently added P.

61. Fig. 4: defferences in the capacity of crop species to access poorly availabe soil P as assessed
by a 32P isotope dilution (L- value) techinque. The L- value is a measure of the total quantity
of palnt avaible P: the higher the value . The greater the plant access to soil P. the plants were
grown in pot culture for 30 days in a P-fixing Oxisol high in total P but low n available P.
histograms with the same letter do not differ at p=0.05.

62. I. Based on current consumption of P fertilizer. It is estimated that world
reserves of rock phosphates will be exhausted within the next 60-90 years.
II. Currently many developing countries in the tropics have to contend with
very low soil P reserves and soils fixing high P
III. Consequently there is increasing pressure to manage the use of P fertilizer in
food and livestock production systems in acid soil to minimize actual and
potential adverse environmental effects caused by P
Conclusion:

63. Objective:
To investigate the effects of PSB and AMF
and their interactions on, biological properties
and inorganic phosphorus fractions of
different soil types and crop
Research Paper - 6

64. Materials and Methods:
Soils: Four soil samples (0-10 cm), low in phosphorus, were used for the pot
experiments (Table 1). Subsamples were used to determine chemical properties and
soil texture.
Experimental Design: The experimental treatments were arranged in split plot
factorial based on a complete randomized block design including:
1) Four soil types (clay, clay loam, loam and sandy loam)
2) Three phosphorus fertilizer levels (0, 20 and 40 mg kg_1P)
3) Four levels of phosphate solubilizing microorganisms (PSM)
A. Mixture of three phosphate solubilizing bacteria (PSM) including:
Azotobacter chrocooccum strain 5, Pseudomonas fluorescens 187 and
Pseudomonas fluorescens 36,
B. Mixture of arbuscular mycorrizal fungi (AMF) including: Glomus mossea and
Glomus intraradices,
C. Mixture of PSB and AMF
D. Control
E. The experiment was replicated thrice
F. Total numbers of plots were 144.

65. Table 1: Some physical and chemical properties of soils

66. Soil type Ca10-P O-P Fe-P Al-P Ca8-P Ca2-P Total P
Clay 432 22 20 18 152 7.6 952
Clay loam 392 16 17 19 142 4.9 822
Loam 401 17 16 10 130 6.2 789
Sandy loam 255 11 14 15 113 4.6 510
Table 2: The concentration of inorganic phosphorus fraction (mg kg -1) of
different soil types

67. Variable df Shoot dry
weight
Root dry
weight
Plant
height
Spike
length
Grain
spike
number
Grain
yield
Colon
percent
Spore
number
PSB
number
Replication ® 2 0.8 0.3 2.7 19.8 5.2 0.4 5.3 10.8 1.1×109
Soil type (S) 3 5.3** 0.1 25.7 21.4 5.1 0.5 51.5 429.3** 7.4×109**
Phosphorus
fertilizer (P)
2 7.8** 0.3 0.9 18.9 10.9 0.1 7671.0** 1300.5*
* 10.0×109**
S × P 6 0.2 0.2 21.4 19.6 7.3 0.1 136.0 26.4 1.2×109
Biological
fertilizer (B)
3 14.7** 0.7** 1.0 21.7 45.2** 16.9** 9089.0** 662.3** 3.4×1010**
S× B 9 1.3* 0.2 23.0 21.1 7.3 1.6** 27.7 97.9** 8.1×108
P× B 6 0.9 0.4 14.0 21.7 9.1 3.6** 2245.0** 429.4** 3.9×108
S× P ×B 18 1.1 0.1 24.2 20.9 2.9 0.5 12.8 15.4 8.1×108
Error 93 0.6 0.1 18.6 0.4 17.8 0.6 94.9 17.8 8.2×108
CV - 20.4 19.4 8.0 9.3 23.6 8.9 47.7 23.6 32.3
*Significant at P < 0.05, ** Significant at P < 0.01
Table 3: Analysis of variance of measured parameters of crop performance and
biological properties

68. Table 4: Mean comparisons of the main effects on Wheat growth properties.

69. Fig. 1: Interaction effects Soil kind and Biological fertilizer on shoot dry weight (a), grain
yield (b), colonization(c) and ∆P-Olsen (d). (PSB: phosphate solubilizing bacteria, AMF:
arbuscular mycorrhizal fungi)

70. Fig. 2: Interaction effects of Soil kinds and phosphorus level (P0=0, P20=20 and
P40=40 mg kg 1P) on ∆Ca2-P percentage (PSB: phosphate solubilizing bacteria, AMF:
arbuscular mycorrhizal fungi)

71. a. Application of biological fertilizers reduced%∆Ca2-P and% ∆Ca8-P
and increased% ∆ P-Olsen.
b. AMF no effect on% ∆P-Olsen and PSB number whereas increased
colonization percentage and spore number
c. Application phosphorus fertilizer increased% ∆Ca2-P and% ∆Ca8-P and
no effect on% ∆P-Olsen whereas reduced colonization percentage,
spore and PSB number
d. The present study demonstrated the benefits of arbuscular mycorrhizal
fungi (AMF) and phosphate solubilizing bacteria (PSB) for enhancing
the growth of wheat
CONCLUSION

72. Summary
I. Temporally fixed P also called residual P becomes available with
time but at slow rate.
II. The availability of residual P in the soil is related to the rate of P
application and quantity of P taken by plant.
III. Residual P is governed by soil characteristics which include soil
physicochemical and biological properties.
IV. AMF no effect on % ∆P-Olsen and PSB number whereas
increased colonization percentage and spore number
V. Based on current consumption of P fertilizer. It is estimated that
world reserves of rock phosphates will be exhausted within the
next 60-90 years.

73. STRATEGIESFORIMPROVINGP EFFICIENCYIN THESOIL/RHIZOSPHERE-PLANTCONTINUUM
The effective strategies for P management may involve a series of multiple level
approaches in association with soil, rhizosphere, and plant processes.
P input into farmland can be optimized based on the balance of inputs/outputs
of P.
Soil based P management requires a long-term management strategy to
maintain the soil available P supply at an appropriate level through monitoring soil
P fertility because of the relative stability of P within soils.

74. Some soil and rhizosphere microorganisms such as AMF and plant growth
promoting rhizobacteria also contribute to plant P acquisition (Richardson et al.,
2009).
successful P management can be achieved by breeding crop cultivars or
genotypes more efficient for P acquisition and use.
I. wheat (Triticum aestivum) variety Xiaoyan54 that secreted more carboxylates
(e.g. malate and citrate) into the rhizosphere than P-inefficient genotypes (Li et
al., 1995).
II. soybean (Glycine max) ‘BX10’ with superior root traits that enable better
adaptation to low P soils
In addition, the ability to use insoluble P compounds in soils can be enhanced
by engineering crops to exude more phytase, which results from over expression of
a fungal phytase gene (George et al., 2005b).
The integration of genetically improved P efficient crops with advanced P
management in the soil plant system is important for improving nutrient use efficiency
and sustainable crop production.