J. Basic. Appl. Sci. Res., 5(12)102-108, 2015
© 2015, TextRoad Publication
ISSN 2090-4304
Journal of Basic and Applied
Scientific Research
www.textroad.com
Effect of Agrosol Treatment and Phosphorus Levels on Pea Plants
(Pisum Sativum L.)
Hala Kandil
Plant Nutrition Dep., National Research Centre, El-Bhoosest., Dokki, Giza, Egypt
Received: August 28, 2015
Accepted: November 1, 2015
ABSTRACT
Two field experiments were conducted to evaluate the effects of phosphorus level and Agrosol treatment on pea
(Pisum sativum L.) yield quantity and quality, under drip irrigation system, during 2012 and 2013 seasons.
Experiments were carried out in the Research and Production Station, National Research Centre, El-Nobaria
Site, Beheara Governorate, Delta Egypt. Phosphorus fertilizer was applied at rates of 0, 40, 80 and 120 kgP2O5
ha-1before planted and Agrosol at three levels (0, 2, 4 and 6 mg L-1) as foliar spray. Plants were sprayed two
times with Agrosol in intervals of 30 and 45 days from sowing.
The obtained results could be summarized in the following:
Growth and yield parameters were significantly increased by increasing phosphorus levels. Dry weight, weight
of 100 seeds and yield were significantly increased by increasing of Agrosol levels. The combination between
phosphorus at 80 kg P2O5 ha-1 and Agrosol at rate 6 mg L-1 gave the highest growth and production as well as
minerals composition (N, P, K, Fe, Mn, Zn and Cu) and protein content compared to other treatments. Agrosol
fertilizer decreased soil pH and increased the availability of phosphors and micronutrients.
KEY WORDS: Phosphorus, Agrosol, pea plant, micronutrients, macronutrients.
INTRODUCTION
Pea (Pisum sativum L.) is one of the most important vegetable crops grown in Egypt. Its growth as well as
of other legumes was found to be affected by both phosphorous and humic acid application (Hala Kandil, 2014).
Pea plant has many nutritional values such as high content of protein, carbohydrates, phosphorus, iron, calcium
and vitamins A and B (Watt and Merrill, 1963 and Hassan, 1997). Increasing the production of peas green pods
and dry seeds with high quality is considered an important aim and this aim could be achieved through using
phosphor and foliar application of Agrosol fertilizers.
Phosphorus is one of the most important elements significantly affecting plant growth and metabolism. The
crop production on more than 30% of the world arable land is limited by P availability (Tesfaye et al., 2007).
Phosphorus may be a critical constraint of legumes under low nutrient environments because there is a
substantial need for P in the N2 fixation process (Tsvetkova and Georgiev, 2007). The high requirement for P in
legumes is consistent with the involvement of P in the high rates of energy transfer that must take place in the
nodule. In addition, phosphorus has an enhancing impact on plant growth and biological yield through its
importance as energy storage and transferee necessary for metabolic processes (Nassar and Ismail, 1999).
Sharma (2002) reported that one of the advantages of feeding the plants with phosphorus is to create deeper and
more abundant roots. Phosphorus causes early ripening in pants, decreasing grain moisture, improving crop
quality and is the most sensitive nutrient to soil pH (Malakooti, 2000). It also raised the efficiency of plants to
photosynthesis, enhances the activity of rhizobia and increases the number of branches and pod /plants,
consequently produces a greater total yield of pea (Omar et al., 1990).
Phosphorus is necessary for protoplasm formation, yielding capacity and considerably influenced by the
quantity of plant available nitrogen. Phosphorus is also essential to the reproductive parts of corn plant as well as
inflorescence, grain formation and ripening. Many investigators have reported the response of maize plants to
phosphorus application. Salem (2000), Badr et al. (2003) and Ibrahim and Hala Kandil (2007) found that
increasing phosphorus from 15.5 to 22.75 or 30 kg P2O5 fed-1 induced favourable effect on plant height, ear
length and grain yield.
Agrosol (the new fertilizer technology, 2007) was developed to enable and promote healthy plant growth.
Plants are supplied from the outside with foil and soil fertilizers, providing for missing nutrients. As water
becomes scarce and groundwater tables recede, supplying the plants with sufficient amounts of water is
becoming increasingly difficult. As a consequence, artificial irrigation needs to be applied. These two factors
(supply of nutrients and water from alternative sources) have been common knowledge for quite some time.
However, what is still largely unknown (especially in open land cultivation) is CO2 fertilization. Plants need a
certain CO2 balance to achieve ideal growth. The optimum level for photosynthesis is a CO2 content between 0.1
*Corresponding Author: Hala Kandil, Plant Nutrition Dep., National Research Centre, El-Bhoosest.,Dokki, Giza, Egypt
102
Kandil, 2015
and 1.0% by volume. Air has a CO2 content of only 0.03 % by volume. Therefore, plants are operating way
below their full potential. Agrosol is mixed with water and is applied onto the leaves surface via a fine spray
mist. Since the discharge of CO2 takes place inside the leaf, this CO2 production does not generate a burden for
the environment.
Agrosol fertilizer has increase the yield, increased quality of the produce, increased resistance to stress by both
dry and wet stress, reduced water requirement, healthier and more vigorous plant, stronger and heavily branched
root system, optimization of the pH value of the plant better use of available fertilizer and increased chlorophyll
intensity higher level of photosynthetic activity of canola (Harker and Hartman, 2013).
The present study was aim to evaluate the effect of different level of phosphorus and Agrosol on pea (Pisum
sativum L.) yield quantity and quality.
MATERIALS AND METHODS
Soil analysis:Physical and chemical properties of El-Nobaria Soil were determined and particle size distributions along with
soil moisture were determined as described by Blackmore (1972). Soil pH, EC, cations and anions, organic
matter, CaCO3, total nitrogen and available P, K, Fe, Mn, Zn, Cu were run according to Black et al., (1982).
Some physical and chemical properties of El-Nobaria soil are shown in Table (1).
Table (1): Some physical and chemical properties of the used soil.
Particle size distribution %
Soil moisture constant %
Sand
Silt
Clay
Texture
Saturation
68.7
24.5
6.8
SL
32.0
19.2
pHa
ECb dSm-1
CaCO3 %
OMc %
Chemical
7.8
1.8
3.07
0.16
Soluble cations (meq/l)
Soluble anions (meq/l)
Ca++
Mg++
K+
Na+
CO3=
HCO33.00
2.00
0.32
2.09
0.00
1.41
Total
Available
Available micronutrients
N
P
K
Fe
Mn
mg/100 g soil
ppm
15.0
9.4
16.0
7.8
3.3
a: Soil pH was measured in 1:2.5 soil-water suspension, b: EC was measured as dSm-1 in soil paste, S L: sandy loam
c: organic matter.FC: Field Capacity, WP: Wilting point, AW: Available Water.
Soil property
Physical
Experimental works:Two field experiments were conducted at the agricultural experimental station at National Research Centre,
in El-Nobaria, Behera Governorate, Delta Egypt to study the effect of different levels of both P (0, 40, 80 and
120 Kg P2O5 ha-1) and at levels (0, 2, 4 and 6 mg L-1) as foliar spray on growth and yield of pea (Pisum sativum
L.) plant under drip irrigation. Experiment was laid out in randomized complete block design, which consisted of
four replications, and plots area 21 m2 (4.2 X 5.0 m). Each plots contents of six row and space between plant 50
cm. Phosphorus treatments in the form of mono super phosphate were added during soil preparation. Foliar
application of Agrosol was added at 30 and 45 days after sowing.
Samples of pea plants from every treatment in four replicates were taken 75 days after sowing and all
growth parameters such as plant height, number of leaves per plant, number of branches per plant, fresh weight
and dry weight were recorded. At harvest time, all yield parameters such as pod length, number of seeds per pod,
weight of 100 seed, pod yield per plant and seeds yield per plant were recorded also.
Macronutrients (N, P and K) as well as micronutrients (Fe, Mn, Zn, Cu, along with Mo) were determined
according to the method described by Cottenie et al., (1982). All data were subjected to statistical analysis
according to procedure outlined by Snedecor and Cochran, (1982).
RESULTS and DISCUSSION
The results in Table (3) show that the response of pea growth to different levels of P2O5 and Agrosol levels.
All P2O5 levels (0, 40, 80 and 120 Kg P2O5 ha-1) promote growth parameters such as Plant height (Cm), No. of
leaves plant-1, No. of branches plant-1, No. of pod plant-1 and dry weight (g plant-1) of pea plants significantly
compared to control.
The growth parameters were increased by increasing P2O5 levels. Similar results were reported by Ibrahim
and Hala Kandil (2007) found that increasing phosphorus rate induced favourable effect on plant height, ear
length and grain yield of corn. Also Data revealed that the application of Agosol increasing all growth parameter
under different level of P2O5. This result is accordance with Harker and Hartman, (2013), who found that foliar
application of Agrosol was promote healthy plant growth of canola.
103
J. Basic. Appl. Sci. Res., 5(12)102-108, 2015
The highest significantly levels of growth parameters of pea plants i.e plant height (31.3), no. of leaves
plant-1 (13.9), no. of branches plant-1 (1.74), no. of pod plant-1 (16.32) and dry weights plant-1 (24.96) were
obtained when 80 Kg P2O5 ha-1 and Agrosol at 6 (mg L-1) used. These results are harmony with those by Abdal
Salam and Al-Shebani (2010) who found that phosphorus application enhanced all growth and yield parameters
for mungbean. Also, Agrosol (the new fertilizer technology, 2007) was increase plant growth from 10%- 15%.
Table (2): Effect of phosphorus level and Agrosol on growth parameters of pea plant.
Treatments P
(Kg P2O5 ha-1)
0
40
80
120
Mean
LSD at 5 %
Agrosol ( mg L-1)
0
22.4
25.8
26.5
27.3
25.5
0.37
0
40
80
120
Mean
LSD at 5 %
10.8
11.5
11.9
12.0
11.6
0.17
0
40
80
120
Mean
LSD at 5 %
1.05
1.13
1.34
1.51
1.26
0.07
0
40
80
120
Mean
LSD at 5 %
11.61
12.33
13.90
14.11
12.99
0.28
0
40
80
120
Mean
LSD at 5 %
18.32
19.65
21.43
21.71
20.28
0.39
2
LSD at 5 %
4
6
Plant height (Cm)
24.6
25.1
28.4
29.2
29.2
29.7
30.3
30.4
28.1
28.6
0.34
0.39
25.8
29.7
30.5
31.3
29.3
0.42
23.9
28.3
29.0
29.8
0.33
0.41
0.22
0.35
12.4
13.2
13.7
13.9
13.3
0.21
11.8
12.6
13.0
13.2
0.19
0.21
0.15
0.23
1.21
1.29
1.54
1.74
1.45
0.09
1.15
1.23
1.47
1.65
0.07
0.09
0.09
0.06
13.34
14.13
15.99
16.22
14.92
0.30
12.67
13.44
15.19
15.40
0.32
0.29
0.34
0.22
21.05
22.54
24.61
24.96
23.29
0.44
20.00
21.43
23.39
23.71
0.45
0.34
0.33
0.42
No. of leaves plant-1
11.8
12.1
12.7
12.9
12.9
13.3
13.2
13.5
12.7
13.0
0.22
0.19
No. of branches plant-1
1.15
1.18
1.24
1.27
1.47
1.51
1.66
1.69
1.38
1.41
0.08
0.09
No. of pod plant-1
12.76
12.98
13.51
13.78
15.29
15.57
15.50
15.78
14.27
14.53
0.36
0.34
Dry weight g plant-1
20.13
20.48
21.56
21.95
23.54
23.97
23.86
24.30
22.27
22.68
0.44
0.32
Mean
Results in Table (3) indicate that foliar application of Agrosol enhanced all yield parameter under
different levels of P2O5 i.e pod length, no. of seeds plod-1, weight of 100 seeds, pod yield plant-1 and seed yield
ha-1. These results are agree with obtained by Hala Kandil et al., (2013) reported that the highest number of pods
per plant and length of pod were produced when 150 Kg fed-1 P in two common bean varieties.
Data also clearly indicated that the highest values of pod yield was obtained by 80 Kg P2O5 ha-1 and Agrosol at 6
(mg L-1) used. Result also showed that the relative calculate values as percentage from control. This treatment
increased the yield %26.19. Similar result were obtained by Getachew Agegnehu (2009) who found that
application of phosphate fertilizer at the rates of 10, 20 and 30 kg P ha-1 increased mean grain yields of field pea
by 36, 67 and 57%, respectively compared to the control.
104
Kandil, 2015
Table (3): Effect of phosphorus level and Agrosol on yield parameters of pea plant.
Treatments P
(Kg P2O5 ha-1)
Agrosol ( mg L-1)
0
2
0
40
80
120
Mean
LSD at 5 %
5.3
5.9
6.6
6.8
6.2
0.22
0
40
80
120
Mean
LSD at 5 %
5.9
6.2
6.6
6.8
6.4
0.18
0
40
80
120
Mean
LSD at 5 %
18.21
19.17
20.11
20.45
19.49
0.22
0
40
80
120
Mean
LSD at 5 %
44.64
45.32
48.53
48.98
46.87
0.85
0
40
80
120
Mean
LSD at 5 %
2.008
2.039
2.138
2.204
2.097
0.044
4
6
Pod length(Cm)
5.8
5.9
6.1
6.5
6.6
6.8
7.2
7.4
7.5
7.4
7.6
7.8
6.8
6.9
7.1
0.17
0.19
0.20
No. of seeds pod-1
6.5
6.6
6.7
6.8
6.9
7.1
7.2
7.4
7.6
7.4
7.6
7.8
7.0
7.1
7.3
0.21
0.22
0.17
Weight of 100 seeds (g)
20.00
20.43
20.92
21.08
21.53
22.00
22.19
22.60
23.10
22.50
22.90
23.83
21.44
21.87
22.46
0.28
0.33
0.42
Pod yield g plant-1
49.11
49.95
50.11
49.85
50.76
52.00
53.38
54.35
55.81
53.88
55.05
56.33
51.56
52.53
53.56
0.79
0.75
0.81
Seed yield ha-1
2.212
2.252
2.311
2.290
2.320
2.354
2.360
2.384
2.412
2.421
2.431
2.453
2.321
2.347
2.383
0.053
0.056
0.048
Mean
LSD at 5
%
5.8
6.5
7.2
7.4
0.18
0.21
0.22
0.19
6.4
6.8
7.2
7.4
0.22
0.19
0.19
0.21
19.89
20.95
22.00
22.42
0.37
0.42
0.29
0.33
48.45
49.48
53.02
53.56
0.76
0.82
0.73
0.69
2.196
2.251
2.324
2.377
0.043
0.052
0.039
0.042
Table (4): Effect of phosphorus level and Agrosol on macronutrient in pea seeds.
Treatments P
(Kg P2O5 ha-1)
Agrosol ( mg L-1)
0
2
0
40
80
120
Mean
LSD at 5 %
3.09
3.87
4.16
4.79
3.98
0.38
N (%)
3.77
4.42
4.98
5.31
4.62
0.32
0
40
80
120
Mean
LSD at 5 %
0.13
0.19
0.21
0.23
0.19
0.01
0.16
0.21
0.23
0.25
0.21
0.02
0
40
80
120
Mean
LSD at 5 %
0.89
0.92
0.95
0.97
0.93
0.02
0.98
1.03
1.06
1.08
1.04
0.02
105
4
3.96
4.89
5.54
5.97
5.09
0.25
P (%)
0.18
0.22
0.24
0.28
0.23
0.01
K (%)
1.01
1.05
1.08
1.14
1.07
0.03
LSD at
5%
6
Mean
4.26
5.38
6.14
6.79
5.64
0.33
3.77
4.64
5.21
5.72
0.22
0.36
0.28
0.33
0.21
0.24
0.26
0.32
0.26
0.01
0.17
0.22
0.24
0.27
0.02
0.02
0.01
0.02
1.07
1.09
1.12
1.19
1.12
0.02
1.01
1.02
1.05
1.10
0.02
0.03
0.03
0.02
J. Basic. Appl. Sci. Res., 5(12)102-108, 2015
The importance of N element, beside its importance in protein formation, is an integral part of chlorophyll.
It is known that P plays a role in energy storage and transfer within the plant. Also it’s well known that P
accelerates flowering, increases flowering capacity, as well as percentage of yield. As well it is known that K
plays an important role in many vital processes such as enzyme activation, osmotic regulation, production of
high (ATP) energy and plant translocation of sugars (Eissa, 1996).
Results presented in Table (4) showed that all P2O5 levels significant increased the content of N, P and K as
compared with control. The highest values of N (6.79%), P (0.32%) and K (1.19) contents in pea seeds were
obtained by using 80 Kg P2O5 ha-1 and Agrosol at 6 (mg L-1). These results are harmony with obtained by Hala
Kandil (2014) she reported that all macronutrient content in pea seeds increasing with increasing the phosphorus
levels. Also, Agrosol (the new fertilizer technology, 2007) increased nutrients content in plant by the way
enhance the utilization of nutrients available in the soil.
Fig (1): Effect of phosphorus level and Agrosol on protein percentage in pea seeds.
Data in Fig. (1) Clearly indicated that the foliar application of Agrosol resulted in the highest values of
protein percentage were obtained by using at 6 (mg L-1) with 120 Kg P2O5 ha-1. Result also showed that the
relative calculate values as percentage from control. This treatment increased the seed content of proteins
%41.18. The minimum protein contents in control treatments. Togay (2002) reported that protein ratio in the
lentil grain increasing with increased phosphorus applications.
Micronutrients (Fe, Mn, Zn and Cu) have favourable effects on plant growth due to their effects on the vital
processes in plants, such as oxidation, reduction, electron transport in photo system II, enzyme systems,
chlorophyll synthesis and auxin metabolism.
Data in Table (5) show the effect of P levels and Agrosol application on the micronutrients (Fe, Mn, Zn and Cu)
in pea seeds. Result reveal that increasing the P levels significant increased micronutrients in the absence or
presence of Agrosol fertilizer. These results are in full agreement with data obtained by Hala Kandil (2014).
Also, Mesut (2010) pointed that phosphorus applications increased N, P, K, Ca, Mg, S, Mn and Cu contents of
shoot of pepper seedling. Agrosol (the new fertilizer technology, 2007) increased roots grow deeper, finer, and
wider. This helps the plant to better extract nutrients from the soil and utilize them for a healthier growth and
increased nutrient content in plant.
106
Kandil, 2015
Table (5): Effect of phosphorus level and Agrosol on micronutrient in pea seeds.
Treatments P
(Kg P2O5 ha-1)
Agrosol ( mg L-1)
0
0
40
80
120
Mean
LSD at 5 %
39.13
40.15
43.16
49.18
42.91
0.78
0
40
80
120
Mean
LSD at 5 %
21.21
22.34
23.36
25.38
23.07
0.83
0
40
80
120
Mean
LSD at 5 %
8.33
9.35
11.36
13.40
10.61
0.76
0
40
80
120
Mean
LSD at 5 %
20.34
21.43
22.46
24.51
22.19
0.68
2
Fe (ppm)
43.04
44.21
46.48
51.97
46.43
0.86
Mn (ppm)
23.33
23.47
24.50
26.58
24.47
0.87
Zn (ppm)
9.57
10.92
12.76
14.33
11.90
0.79
Cu (ppm)
21.65
22.47
23.95
25.57
23.39
0.73
LSD at 5
%
4
6
Mean
43.83
46.95
48.03
54.56
48.34
0.90
44.98
48.12
50.44
56.96
50.13
0.84
42.75
44.86
47.03
53.17
0.88
0.97
0.83
0.91
25.46
26.32
28.63
32.14
28.14
0.89
27.55
29.17
34.56
34.75
31.51
0.82
24.39
25.33
27.76
29.71
0.75
0.79
0.73
0.77
10.24
11.93
13.55
15.82
12.89
0.82
12.34
14.22
16.42
18.11
15.27
0.79
10.12
11.61
13.52
15.42
0.77
0.84
0.80
0.79
23.14
25.86
26.71
27.15
25.72
0.78
25.17
26.94
27.19
29.21
27.13
0.69
22.58
24.18
25.08
26.61
0.73
0.59
0.67
0.77
CONCLUSION
Foliar application of Agrosol at 6 mg L-1 with 80 Kg P2O5 ha-1 significantly increased all growth and yield
parameters. Maximum N, P, K, Fe, Mn, Zn and Cu concentration and protein percentage were obtained at 6 mg
L-1 with 120 Kg P2O5 ha-1 in pea seeds.
REFERENCES
Abdalsalam, A.A. and Y.A. Al-Shebani (2010). Effect of various nitrogen and phosphorus fertilization levels on
growth, yield and yield attributes of local mungbean (Vigna radiata ( L.) R. Wilczek) in Yemen. Egypt.
J. of Appl. Sci., 25 (2A): 57-71.
Agrosol (2007).The new fertilizer technology.www.agrosolution.eu.
Badr, M.M., S.A.A. Bassal and E.M. Ibrahim, (2003). Effect of preceding winter crops, nitrogen and
phosphorous fertilizer levels on growth and yield of maize (zea mays L.). J. Agric. Sci. Mansoura Univ.,
28(9): 6591-6601.
Black, C.A., Evans, D.D., Ensminger, L.E., White, G.L. & Clarck, F.E. (1982). Methods of Soil Analysis Part 2.
Agron. Inc. Madison. Wisc.
Blackmore, L.C. (1972). Methods for chemical analysis of Soil. Newzealand Soil Durean, P. A2 1, Rep. No. 10.
Cottenie, A., M. Verloo, L. Kiekens, G. Velgh and R. Camerlynk (1982). Chemical Analysis of Plants and Soils.
P 44-45. State Univ. Ghent, Belgium, 63.
Eissa, N.M. (1996). Studies on sustainable agriculture for some vegetable crops using animal manure. M.Sc.
Thesis Institute of Environmental Studies and Research, Ain Shams Univ., Cairo, Egypt.
Getachew Agegnehu (2009). Phosphate fertilizer and weed control effects on growth and yield of field pea on
Nitisols of Highland Ethiopia. SINET: Ethiop. J. Sci., 32(2): 1-8.
Hala Kandil (2014). Response of pea plants (Pisum sativum L.) to phosphorus levels and humic acid levels.
International Conference of Agricultural Engineering - AgEng 6-10 July 2014 Zurich, P0136.
107
J. Basic. Appl. Sci. Res., 5(12)102-108, 2015
Hala Kandil; Nadia Gad and M. T. Abdelhamid (2013). Effects of Different Rates of Phosphorus and
Molybdenum Application on Two Varieties Common Bean of (Phaseolus vulgaris L.). Journal of
Agriculture and Food Technology, 3(3)8-16.
Harker N. and M. Hartman (2013).Ultimate Canola Challenge. www. farming smarter.Com.
Hassan, A.A., (1997). Vegetable fruits. Al-Dar Al-Arabia Publications and distribution, Cairo, Egypt, pp: 241.
Ibrahim S.A.; and Hala Kandil (2007). Growth, yield and chemical constituents of corn (Zea maize L.) as
affected by nitrogen and phosphors fertilization under different irrigation intervals. J. Apllied Sci.
Research, Pakistan 3(10): 1112-1120.
Malakooti, M.J. (2000). Sustainable Agriculture and Yield Increment by Optimum Fertilizer Utilization in Iran.
2nd edition. Agricultural Extension Publications, Iran.
Mesut K. Cimrin, Önder Türkmen, Metin Turan and Burcu Tuncer (2010). Phosphorus and humic acid
application alleviate salinity stress of pepper seedling. African Journal of Biotechnology Vol. 9(36), pp.
5845-5851.
Nassar, K.E. and K.M. Ismail (1999). Effect of ascorbic acid and phosphorus application on lupin yield (Lupinus
termis L.) grown on sandy soil. Egypt J. of Appl. Sci., 14 (10): 357-368.
Omar, N.M.; A.M. Shaheen and M.O. Bakry (1990). The residual effect of sulphur and phosphorus ation on the
growth yield of pea (Pisum sativum L.) plants. Egypt J. Agron. 15 (1-2):87.
Salem, M.A., 2000. Response of maize (zea mays L.) growth and yield to chemical and biofertilization. Zagazig,
J. Agric. Res. 27(4): 845-858.
Sharma, A.K. (2002). Bio-fertilizers for sustainable agriculture. Agrobios Indian publications.
Snedecor, G. W. and W. G. Cochran (1982). Statistical methods. 7th Edition Iowa State Univ. Press. Ames.
Iowa, USA.
Tesfaye, M.; J. Liu; D.L. Allan; and C.P. Vance (2007). Genomic and genetic control of phosphate stress in
legumes. Plant Physiol., 144, 594- 603.
Togay, Y. (2002). The effect of different Zinc and phosphorus levels on the yield and yield components in lentil
(Lens culinaris Medic). PhD Thesis, Yuzuncu Yil University Van, Turkey.
Tsvetkova, G.E. and G.I. Georgiev (2007). Changes in phosphate fractions extracted from different organs of
phosphorus starved nitrogen fixing pea plants. J. Plant Nutr., 30, 2129-2140.
Watt, B.K. and A.L. Merrill, (1963). Composition of foods .U.S. Department of Agriculture, Agricultural
Research Service, USDA .Hand Book. 8: 190.
108