الفهرس 
RhizosphereOnly 14 pages are availabe for public view
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Abstract
This study has been carried out to isolate N2- fixing Azotobacter
strains from leafy vegetables plants rhizosphere i.e. spinach (Spinacia
oleracea) and corchorus (Corchorus olitorius). Isolates were
characterized and identified biochemically and genetically. They were
evaluated to recognize the impacts of most effective Azotobacter strains
to be used as bio-fertilizers in sand soil, for improving spinach and
corchorus vegetables production and nutritional values. The obtained
results could be summarized as following:
Part І: Microbiology results
1- Two rhizosphere soil samples collected from Mashtol region,
Belbeas, Sharqiya Governorate, Egypt, with spinach and
corchorus standing crops used for nitrogen fixers Azotobacter
spp. isolation.
2- The Azotobacter like colony morphology was selected,
exanimated, and purified.
3- The most effective four strains in atmospheric N2-fixation,
phytohormones like substances production i.e. auxin,
gibberellin and cytokinin, and the siderophores production
ability were selected as bio-fertilizers.
4- Based on the 16s rRNA gene sequences identification, the
isolates nomenclature as A. chroococcum strain S11 (Az.
Msp7), Az. chroococcum AtP (Az. Msp8), Azotobacter sp.
ART001 (Az. Msp13), and Az. chroococcum AcN1 (Az.
Msp18).Part ІІ: Pot experiment
Most effective four strains used as biofertilizers in a pot
experiment at Soil and Water Research Department, Nuclear Research
Center, Atomic Energy Authority, Abou Zaabal, Egypt. Spinach and
corchorus plants were grown in the net house for about two months.
Different parameters of spinach and corchorus plants were recorded, as
well as evaluation of nitrogen mineral fertilizers utilization by using 15N
tracer technique. All of the nitrogen derived from fertilizers percentage
(%Ndff), nitrogen derived from air percentage (%Ndfa), and nitrogen
derived from compost percentage (%Ndfc) for both leafy vegetable crops
were determined using the emission spectrometer (NOI-6PC). The
obtained results could be summarized as following:
Experiment І: spinach (Spinacia oleracea)
1) The spinach leafs reflected the highest total chlorophyll
concentration 2.77 mg/ml achieved by application of 25% mineral
fertilizer + 75% compost + strain Azoto AtP.
2) The superior spinach whole plant fresh weight 53.02 g pot-1, whole
dry weight 6.7 g pot-1 and leaf dry weight 5.93 g pot-1 were gained
with 75% mineral fertilizer + 25% compost application in the
presence of strain S11.
3) The spinach plants moisture percentage wasn’t significantly different
between all treatments and strains.
4) Optimum nitrogen uptake by spinach shoot was 77.17 mg N pot-1
resulted from application of 75% mineral fertilizer + 25% compost
treatment + strain S11. While the root-N uptake was 7.37 mg N pot-1
with strain ART001 and treatment 50% mineral fertilizer and 50%
compost.
5) The 15N tracer technique results clarified that nitrogen derived from
air was the dominant N source in spinach plants when inoculated
with strain S11 and strain ART001 (33.9, and 33.5 mg pot-1,
respectively), followed by nitrogen derived from fertilizer (Ndff) (15.4, and 12.5 mg pot-1, respectively), then the N derived from
compost (Ndfc) (11.2, and 10.7 mg pot-1, respectively) came to the
next. In somehow, both strains Azoto AtP and Azoto AcN1 showed
little difference where the second source of nitrogen was the
compost. The main N source was Ndfa (29.8, and 27.5 mg pot-1,
respectively), followed by Ndfc (14.6, and 8.7 mg pot-1,
respectively), then Ndff (12.2, and 8.4 mg pot-1 respectively).
6) Nitrate uptake by shoot was high 293.871 mg NO3 pot-1 as affected
by combined treatment 75% mineral fertilizer + 25% compost in the
presence of strain S11. It is known that the decrease of nitrate
uptake into spinach shoot is more important than increasing. So, the
minimum value of 46.75 mg NO3 pot-1 was obtained when plant
treated with 100% compost in presence of strain Azoto AtP.
7) The highest phosphorus uptake of spinach’s shoot was 129.992 mg
P pot-1 with fertilization treatment 75% mineral fertilizer + 25%
compost plus strain S11. Furthermore, the spinach’s root phosphorus
uptake showed the highest value 12.853 mg P pot-1 with application
of 50% mineral fertilizer + 50% compost combined with strain
ART001.
8) High value of potassium uptake by spinach’s shoot 15.494 mg K
pot-1 was achieved by fertilization treatment 75% mineral fertilizer +
25% compost combined with strain S11. Furthermore, the spinach’s
root potassium uptake showed the highest value 1.574 mg K pot-1
with the application of 75% mineral fertilizer + 25% compost
combined with strain S11.
9) Shoot total carbohydrates percentage of 3.42% was induced with
combined treatment 25% mineral fertilizer + 75% compost plus
strain Azoto AcN1.
10) The shoot oxalate contents showed the lowest value 0.55 mg/ml
when plant treated with 100% compost plus strain S11, and strain
Azoto AtP; application 75% mineral fertilizer + 25% Compost +
strain Azoto AtP; application 50% mineral fertilizer + 50% Compost, and 25% mineral fertilizer + 75% compost, when both
treatments combined with strain ART001.
11) Increase of Vitamin C content 7.02 g /100g in spinach’s shoot was
detected with the treatment 100% mineral fertilization combined
with strain Azoto AtP.
12) The maximum Vitamin B1 (Thiamine) content 0.465 g/100g of
spinach’s shoot induced by the fertilization rate 75% mineral
fertilizer + 25% compost, combined with strain Azoto AtP.
13) The superior vitamin B2 (riboflavin) content 2.396 g/100g plant in
spinach’s shoot was achieved by strain Azoto AtP combined with
50% mineral fertilizer + 50% compost.
Experiment ІІ: corchorus (Corchorus olitorius)
1) The corchorus leafs reflected the highest total chlorophyll
concentration 35.67 SPAD when 25% mineral fertilizer + 75%
compost in the presence of strain S11, was applied.
2) The highest corchorus whole plant fresh weight 75.1 g pot-1 was
obtained by 75% mineral fertilizer + 25% compost treatment plus
strain ART001. While whole dry weight 18.1 g pot-1 and leaf dry
weight 7.3 g pot-1 both were with 100% mineral fertilizer treatment
plus the same strain.
3) The corchorus plants moisture percentage showed no significant
difference with both 100% compost, and 75% mineral fertilizer +
25% compost when both treatments combined with strain ART001.
4) The corchorus leaf optimum nitrogen uptake was 59.2 mg N pot-1 and
the upper corchorus’s stem nitrogen uptake 24.4 mg N pot-1 were
resulted with 100% mineral fertilizer plus strain S11. Came to the
next, corchorus’s root nitrogen uptake was 42.3 mg N pot-1 induced
by addition of 50% mineral fertilizer + 50% compost plus strain S11.
5) The 15N tracer technique gave the chance to distinguish the N uptake
from the different nitrogen sources, which clarified that the highest N
source in corchorus plants when they were treated with strain S11,strain Azoto AtP, strain ART001, and strain Azoto AcN1 was Ndfa
(34.5, 31.1, 33.8 and 32.1 mg pot-1, respectively), followed by Ndfc
(30.1, 28.3, 33.2 and 19.8 mg pot-1, respectively), then Ndff (24.6,
26.1, 15.1 and 10.3 mg pot-1, respectively).
6) The total carbohydrates percentage (4.08%) in corchorus leafs was
obtained with the fertilization treatment of 50% mineral fertilizer +
50% compost + strain Azoto AtP. Also, the corchorus’s stem total
carbohydrate percentage (1.79%) was detected with the application
of 25% mineral fertilizer mixed with 75% compost combined in the
presence of strain ART001. Came to the next, the value of
corchorus’s root total carbohydrate percentage (2.25%) induced with
75% mineral fertilizer + 25% compost combined with strain Azoto
AcN1.
7) It appears that the optimum phosphorus uptake by corchorus’s leaf
(51.7 mg P pot-1). Furthermore, high corchorus’s stem phosphorus
uptake 41.2 mg P pot-1 was detected with the application of 100%
mineral fertilizer + strain ART001. Corchorus’s root phosphorus
uptake 55.8 mg P pot-1 was resulted with Azoto AtP combined with
100% mineral fertilizer.
8) High potassium uptake of corchorus’s leaf was 1.66, and 1.65 mg K
pot-1 was detected with the application of 100% mineral fertilizer +
strain S11, and ART001, respectively. So, the corchorus’s stem
potassium uptake value was 1.49 mg K pot-1 induced by the
application of 100% mineral + strain ART001. The corchorus’s root
potassium uptake recorded 1.51 mg K pot-1 was achieved with strain
S11 combined with 100% compost.
9) The superior vitamin C content 7.06 g/100g plant corchorus was
found with the 75% mineral fertilizer + 25% compost treatment plus
strain ART001. Also, high vitamin C 5.46 g/100g stem was gained
with strain Azoto AtP, and strain Azoto AcN1 when combined with
100% compost fertilization, and strain ART001 combined with 100%
mineral fertilizer. While in the roots, the highest vitamin C value recorded 2.36 g/100g was gained when strain Azoto AcN1 plus 75%
mineral + 25% compost was applied.
10) Vitamin B1 (Thiamine) showed the highest content 2.95 g/100g in
corchorus’s leaf with application of 100% compost in the presence of
strain Azoto AcN1. Otherwise, the corchorus’s stem vitamin B1
showed high concentration 3.5 g/100g with fertilizer applied at 100%
mineral fertilizer combined with strain S11. The corchorus’s root
vitamin B1 showed a value about 3.52 g/100g when Azoto AcN1
strain combined with 50% mineral fertilizer + 50% compost.
11) The superior value of vitamin B2 (riboflavin) 1.08 g/100g in
corchorus’s leaf was obtained with the application of 100% compost
plus strain Azoto AcN1. As well as, the corchorus’s stem vitamin B2
showed high concentration 1.84 g/100g with 100% compost
combined with strain S11. The corchorus’s root vitamin B2 reflected
a value of 1.917 g/100g with Azoto AcN1 combined with 25%
mineral fertilizer + 75% compost.not clear such as the previous strains, upon the mineral and nutritional
values contents in spinach’s shoot.
Also, spinach results indicated that to enhance the NPK content
and nutritional value of consumed shoot of spinach plants, only 75% of
recommended mineral fertilizer level in agriculture report (250 kg
Ammonium sulfate/ Fed.) combined with Strain S11, and Azoto AtP is
enough since it has the same effect as 100% mineral fertilization rate. In
the other turn, if the aim is to produce spinach plants with minimum
levels of both nitrate and oxalate, only the organic fertilizers combined
with same recommended strains could be used.
from the corchorus experiment, results showed that application of
Strain S11 as biofertilizer which had superior production for cytokinin
and siderophore with complete mineral fertilizer rate (100 kg Ammonium
sulfate/ Fed.) enhanced leafs NK uptake. While the 25% of recommended
mineral fertilizer + 75% compost from recommended dose enhanced the
total chlorophyll.
As well as, Azoto AtP strain which had highest nitrogen fixation
ability, and the highest production of siderophores enhanced the plant
moisture content and total carbohydrate percentage when combined with
50% mineral fertilizer + 50% compost treatment.
On another hand, the role of strain ART001 which had the highest
indole acetic acid production, affected by the fertilization treatment. With
complete mineral fertilizer rate (100 kg Ammonium sulfate/ Fed.)
enhanced plant dry, leafs dry weight, and P uptake. While with the 75%
of recommended mineral fertilizer + 25% compost from recommended
dose enhanced the fresh weight, plant moisture, and vitamin C, and B1
content.
Finally, used Azoto AcN1 strain as biofertilizer which had upper
gibberellin production ability, enhanced the corchorus’s leafs vitamin
content (Vit. B1, and B2) with complete compost dose (15 – 20 m3 fed.-1)
as the only source of fertilizers.Therefore, corchorus results indicated that to enhance the NPK
content and nutritional value of consumed leafs of corchorus plant, only
75% of recommended mineral fertilizer level in agriculture report (100 kg
Ammonium sulfate/ Fed.) combined with ART001 is enough since it has
the same effect as 100% mineral fertilization rate.