الفهرس 
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Abstract
The present study on biological nitrogen fixation was carried out in
two parts:
1- Effect of inoculation with Azospirillum in the presence of either
phosphate solubilizing bacteria or vesicular arbuscular mycorrhizae and
application of biogas manure or ammonium sulphate on sorghum
growth.
2- Selection of the most efficient species of Azolla in growth and nitrogen
fixation and study the response of rice plants to Azolla and! or urea
application, combined with different levels of phosphorus additions .
The first part:
The obtained results ill this experiment are summarized in the
following:
1- The microbial counts increased with the increasing of growth period of
sorghum plants. Ammonifying and nitrifying bacteria were the
highest in case ofbiogas manure + ammonium sulphate application
at a rate of 50 kg N/ fed. combined with mycorrhizal inoculation.
On the other hand, ammonifying and nitrifying bacteria were the
lowest in case of biogas manure + ammonium sulphate application at
a rate of 50 kg Nt fed. combined with phosphorus solubilizing
bacteria.
2- Azospirilla counts increased with the increasing of growth period.
Inoculation with Az. lipoferum in the presence of half dose of
inorganic N- fertilizer combined with mycorrhizal inoculation gave
the highest counts of Azospirilla. Whereas, Azospirilla counts
were the lowest in case of ammonium sulphate application only at a
rate of 100 kg N/fed. combined with phosphate solubilizing bacteria.
3- Total nitrogen in soil increased with the increasing of growth period
of sorghum to reach its maximum values at 60 days and decreased
thereafter. Ammoniacal and nitrate nitrogen concentrations in soil
showed the same trend of results except for the treatment of
ammonium sulphate at a rate of 100 kg NI fed. combined with either
mycorrhizal inoculation or phosphate solubilizing bacteria.
4- The rate of CO2 evolution in soil increased with the increasing of
growth period in all investigated treatments.
5- Mycorrhizal inoculation treatments gave higher values of total
nitrogen, ammoniacal and nitrate nitrogen and CO2 evolution than
phosphate solubilizing bacteria treatments.
6- Application of biogas manure at a rate of 100 kg N/fed. combined
with G. mosseae gave the highest values of total phosphorus in soil.
Whereas, the application of ammonium sulphate at a rate of ]00 kg
NI fed. combined with phosphate solubilizing bacteria gave the
lowest values of total phosphorus.
7- Application ofbiogas manure and ammonium sulphate (50 kg N/fed.
from each of them) combined with mycorrhizal inoculation gave the
highest values of available phosphorus. While, the lowest values of
available phosphorus resulted in the application of ammonium
sulphate at a rate of 100 kg N/fed. combined with phosphate
solubilizing bacteria.
8- The highest values of total potassium were in the treatments of biogas
manure (100 kg NI fed.) , Azospririllum inoculum + ammonium
sulphate (50 kg N/fed. ) and biogas manure (100 kg NI fed.)
combined with G. mosseae in all treatments at 30, 60 and 90 days,
respectively.
9- Application of biogas manure at a rate of 100 kg N/fed. combined
with mycorrhizal inoculation gave the highest values of soluble
potassium. While, the lowest values of soluble potassium were
resulted in Azospirillum inoculation + ammonium sulphate (50 kg
N/fed.) combined with phosphate solubilizing bacteria.
10- The treatments which included mycorrhizal inoculation gave higher
values of plant heights, leaves area! plant, fresh and dry weights of
root and shoot system I plant than parallel treatments which
included phosphate solubilizing bacteria.
11- The treatment of Azospirillum inoculum + ammonium sulphate (50 kg
N/fed.) combined with G. mosseae gave the highest values of total
nitrogen, phosphorus and potassium in shoots of sorghum plants.
Whereas, the lowest ones resulted from the application of
ammomum sulphate (100 kg N/ fed.), biogas manure + ammonium
sulphate (50 kg N/ fed.) from each of them and ammonium sulphate
at a rate of 100 kg N/ fed. combined with phosphate solubilizing
bacteria, respectively.
12- Crude protein was the highest in case of Azospirillum inoculum +
A.S. application (50 kg N/ fed.) combined with G. mosseae. While,
the lowest values of crude protein were obained from the application
of A.S. at a rate of 100 kg N/ fed. combined with PSB.
13- Regarding the chlorophylls pigments and carotenoids levels. it could
be concluded that the treatments included mycorrhizae fungus gave
higher values than parallel treatments which included phosphate
solubilizing bacteria.
The second part:
The obtained results in this part are summarized in the following:
1- Azollafilieuloides showed the accumulation of the greatest fresh and
dry yield of biomass compared with Azolla pinnata . The highest
yield of fresh and dry weights of biomass was obtained at the 21 st
day of incubation.
2- The highest biomass yield was recorded in case of Azolla spp.
grown in irrigation water compared with that grown in either
drainage or mixed water.
3- Azolla filiculoides gave higher percentages of total nitrogen than
Azolla pinnata under different types of water used and incubation
periods. Total nitrogen content % in both species of tested Azolla
was the highest at the 21 st day of incubation period.
4- Azolla filiculoides exerted higher N2 fixing capacity than A. pinnata,
and nitrogenase activity values were the greatest in case of Azolla
growing ill irrigation water followed by mixed water., and drainage
water.
5- Both species of Azolla gave the highest nitrogenase activity values at
the 21 st day of incubation period.
6- Ammoniacal nitrogen in the growth medium of Azolla increased with
the increasing of incubation period. On the contrary, nitrate
nitrogen decreased with the increasing of incubation period. The
same trend was observed in both Azolla filiculoides and A. pinnata
as well as when the two AzolIa species were grown in different
types of water.
7- Total microbial flora and phosphate solubilizing bacteria (PSB)
increased with the increasing of growth period of rice plants to
reach their maximal values at heading stage in all investigated
treatments.
8- Total microbial flora were the highest when Azolla was applied as a
green manure at a rate of 60 kg N/ fed. On the other hand, counts
of (PSB) were the highest in case of urea application at a rate of 60
kg N/ fed.
9- The lowest values of total microbial flora were observed when Azolla
was applied at a rate of 30,40 and 20 kg N/ fed. as a green manure
at tillering, heading and maturity stages, respectively. While, the
lowest counts of (PSB) were obtained with the application of Azolla
at a rate of 30, 30 and 20 kg N/fed. at tillering, heading and maturity
stages ,respectively. Population of total microbial flora and PSB
were the highest when Azolla was inoculated as a biofertilizer at a
rate of 100 gI m2 and 150 g/ m2 combined with 30 kg P20S/ fed. ,
respectively.
highest in case of Azolla application at a rate of 200 g! m2 combined
with 45 kg P20S/ fed.
15- Total nitrogen, phosphorus and potassium in soil were the highest
values with Azolla application as a green manure at a rate of 30,60
and 40 kg N/ fed. ,respectively. \Vhereas, the highest values of
total nitrogen, phosphorus and potassium were obtained from the
application of Azolla as a biofertilizer at a rate of 150 gI m2
, 200 gl
m2 and 200 g/ m2 combined WIth 30 kg P20S/ fed. , respectively.
16- Generally, the mean values of TN in soil after harvesting were higher
in the 1 st season than the 2 nd one. While, the mean values of TP
and TK were lower in the 1 st season than the 2 nd one.
17- The tallest plants were produced from the treatment in which Azolla
+ urea were applied at a rate of 30 kg N/ fed. Except the control,
the shortest plant heights were obtained from the application of
Azolla or urea at a rate of 60 kg N/ fed.
18- The highest values of fresh and dry weights of rice plants were
obtained when Azolla + urea were applied at a rate of 30 kg N/ fed.
from each of them. Except the control, the lowest values of fresh
and dry weights of rice plants were obtained from the application of
Azolla as a sole source of nitrogen at a rate of 60 kg N/fed.
19- The percentage of shoots contents of N, P and K was the highest at
tillering stage and this was true in all treatments as well as in both
seasons. Also, the application of 40 kg N/fed. as Azalia in the
presence of 20 kg Nt fed. as urea gave the highest percentage of
total nitrogen, phosphorus and potassium content. On the other hand,
the lowest percentage of N, P and K contents were obtained from
the application of urea only as a sole source of nitrogen at a rate of
60 kg N/fed.
20- Total nitrogen, crude protein, total phosphorus and potassium in
nee grains were the highest in case of utilization of 40 kg N/fed. as
AzoIla combined with 20 kg N/ fed. as urea in both seasons.
21- The highest levels of chlorophyll a, b and carotenoids resulted from
Azolla application at a rate of 40, 30 and 60 kg N/ fed. ,
respectively. Also, Azolla application at a rate of 40 kg N/fed.
combined with 20 kg N/ fed. as urea gave the highest values of total
carbohydrates in both seasons.
22- The highest grains yield/ fed. was obtained with using of 40 kg N/ fed.
as Azolla + 20 kg N/ fed. as urea while, the lowest value of grains
yield was observed in case of Azolla application at a rate of 20 kg
N/ fed. combined with 40 kg N/ fed. as urea.
23- The lowest straw yield! fed. was observed in case of Azolla
application at a rate of 40 kg N/ fed. combined with 20 kg NI fed. as
urea. The highest 1000- grain weight was obtained when Azolla
was applied at a rate of 40 kg NI fed. combined with 20 kg N/ fed.
as urea, whereas, the lowest 1000- grain weight was observed when
urea was only used at a rate of 60 kg N/fed.
24- Plant heights were nonsignificantly affected by different inoculum
rates of Azolla and phosphorus levels added and this was true in
both growing seasons.
25- Interaction effect between Azolla inoculum rates and phosphorus
levels was significant on the mean values of fresh and dry weights
of shoot system, the highest values of abovementioned parameters
were obtained from Azolla inoculum rate 150 g/ m2 combined with
30 kg P20:) fed.
26- Interaction effect between AzolIa inoculum rates and phosphorus
levels was significant on total nitrogen in rice plants. At tillering
stage, the highest values of total nitrogen content were obtained
from inoculation of AzolIa at a rate of 150 g! m2 combined with 15
kg P20S/ fed. While, the lowest values were obtained from Azolla
inoculation at a rate of 100 g/ m2 combined with 15 kg P20s! fed.
Generally, the mean values of total nitrogen content in the plants
were increased at tillering stage in all treatments and decreased
thereafter.
27- The percentage of phosphorus in rice plants was increased with the
increasing of phosphatic fertilizer level and this result was
observed at all growth stages of rice plants.
28- The highest values of P content inrice plants were observed when
Azolla inoculum was 150 g/ m2 combined with 30 kg P20S! fed. at
heading and maturity stages whereas, the lowest values of total
phosphorus content were obtained when Azolla inoculum was 150
g/ m2 and 100 g/ m2 combined with 15 kg P20S/ fed. at heading and
maturity stages, respectively.
29- The interaction effect between Azolla and phosphorus on total
potassium content of rice plants was significant. The highest
percentages of K were obtained from the treatments of 150 g Azolla!
mZ combined with 45 kg PzOs/ fed., 100 g Azolla + 15 kg PzOs/ fed.
and 100 g Azolla / m2 + 15 kg PzOs/ fed. at tillering, heading and
maturity stages, respectively.
30- Total nitrogen and potassium content in grams were significantly
affected by the interaction between Azolla and phosphorus while,
crude protein and total phosphorus were nonsignificantly affected.
The highest values of total nitrogen and potassium were obtained
when Azolla inoculum was 200 g/ ml combined with 30 kg P20S/
fed. Whereas, the lowest ones were when Azolla inoculum was
100 g/ mZ combined with 15 kg PlOS/ fed.
31- Chlorophyll a, b and carotenoids as well as total carbohydrates levels
of rice plants were differed by different inoculum rates of Azolla and
phosphorus levels. The highest values of chlorophyll a, band
carotenoids were obtained in the treatments of Azolla inoculum at a
rate of 150 gJ m2 combined with 45 kg P20S/ fed. and the same
trend of results was observed in both seasons. On the other hand,
the lowest values of chlorophyll a, band carotenoids were
observed In case of using Azolla inoculum at a rate of 100 gJ mZ
combined with 15 kg PzOs/ fed. and this was obvious in both
seasons.
32- The highest percentage of total carbohydrates of rice plants were
obtained in case of using Azolla inoculum at a rate of 150 gJ m2
combined with 45 kg PzOs/ fed. While, the lowest percentages
were obtained when Azolla inoculum rate was 100 g/ m2 combined
with 15 kg P20S! fed.
Generally, it could be concluded that the carbohydrates contents
were proportional to chlorophyll levels in various investigated
treatments since chlorophylls are responsible of photosynthesis and
consequently carbohydrates formation.
33- Grains and straw yields/ fed. as well as 1000- grains weight of rice
were significantly affected by different inoculum rates of Azolla
and phosphorus levels added in both growing seasons. The highest
values of grains and straw yields and 1000- grains weight were
obtained from the treatment of Azolla inoculation at a rate of 150 g/
m2 combined with 30 kg P20S/ fed. in both seasons, On the
contrary, grains and straw yields and 1000- grains weight were the
lowest in case of Azolla inoculation at a rate of 100 g/ m2 + 15 kg
P20S/ fed. , 100 g! m2 + 45 kg P20s/ fed. and 200 gJ m2 + 30 kg
P20s/ fed. , respectively. The same trend of results was observed in
both growing seasons.