الفهرس 
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Abstract
Biological nitrogen fixation ”BNF” is the natural environmentally safe process by which such major nutritional element is converted from its
gaseous state to a combined form in soil, firstly for the benefit of plants and subsequently of the other living organisms. Such process known as
”Diazotrophy”, is undertaken by a variety of soil microorganisms, i.e.,
bacteria, actinomycetes and cyanobacteria. Bacteria are the major group in
this concern, among them there are the chemo-organotrophic aerobic and
anaerobic, symbiotic, associative and free-living members.
In order to achieve appreciable benefits from the dinitrogen
fixation, it is practically recommended to inoculate the proper plants with
the responsible agents. Introduction of diazotrophs into agricultural soils is
performed via certain materials carrying the diazotrophic organisms known
as ”Bacterial carriers”. Efficiency of the N2-fixation process depends not
only on the fixer power, but also on the carrier type.
The present work was planned to compare among some materials
to ascertain their potentiality to serve as carries for dinitrogen fixing
bacteria, using specific culture media. Combinations among the diazotroph
carriers were then examined in greenhouse experiments, to declare their
contribution to plant growth traits.
The carriers used were: Standard (vermiculite 90% + peat 10%),
compost, biogas manure and filter mud (sugar industry residue). The
diazotroph inocula included the legume-symbiotic Bradyrhizobium and the
cereal-associative Azospirillum. The crops tested were the legume peanut
and the cereal maize. Pot experiments were performed using two types of
soil, i.e., sandy and calcareous.
The plant growth traits measured included the dry biomass yield
and NPK contents of roots and shoots of both crops, at 30 and 65 days from sowing. As well as, number of bacterial nodules formed on peanut plant
roots was counted.
The results gained were as follows:
I. The Laboratory Experiment
” Influence of Various Bacterial Carriers on Survival of Certain
Diazotrophs”
Data obtained revealed the following order of priority, among the
studied bacterial carriers, as to the preserve the viability of both inoculating
diazotrophs cultured on specific media, at succeeding intervals of storing
the inoculated carriers continued up to 90 days : compost > biogas manure
> standard > filter mud.
Prestrelization of the carrier materials suited the survival of the
inoculating N2-fixers along a storage period lasted for the 90 days.
II. The Greenhouse Experiments (detections were made at 60
and 120 days after planting): presterillized carriers inoculated with each
diazotroph, either fresh (7 days) or stored (for 2 months), were tested. Two
experiments were executed in order to study the effect of growth traits of
plants grown on potted sandy and calcareous soils. The treatments
inocluded : controls (without and with recommended doses of NPK mineral
fertilizers), standard carrier (100%) + mineral fertilizers, standard carrier
(50%) + each of the other materials (50%) + mineral fertilizers.
A. Bradyrhizobium/ Peanut crop
Peanut experiment included the following treatments:
1- Control uninoculated without N-fertilizer ”C0”.
2- Control uninoculated + recommended doses of N (40 kg N fed-1)
”C1”.
3- Inoculation with Bradyrhizobium (Vermiculite 90% + Peat 10 % ) +
20 kg N fed-1.
4- Inoculation with Bradyrhizobium (Vermiculite 50% + compost 50
%) + 20 kg N fed-1.
5- Inoculation with Bradyrhizobium (Vermiculite 50% + biogas
manure\50 %) + 20 kg N fed-1.
6- Inoculation with Bradyrhizobium (Vermiculite 50% + filter mud
manure 50 %) + 20 kg N fed-1.
The obtained results can be summarized as follows:
a) Action of soil type on the results generally:
The sandy soil excelled the calcareous one in all cases of the study,
due to the higher pH value and CaCO3 content of the later.
b) Role of bacterial inocula (carrier type and storage period) on:
1- Nodulation Status:
Root modules showed their highest numbers with the mixed carrier
containing biogas manure, which discerningly followed by those containing
compost, then the mixed filter mud and finally the 100% standard one.
Storing the inocula, as well as advancing the plant growth period decreased
the number of formed root nodules.
2- Plant growth traits (dry biomass yield of roots, shoots and pods
and their contents of NPK.
The assessed plant criteria showed progressive increases of their
values, as a result of materials accumulation as the growth had proceeded.
The carrier treatments showed an order of priority similar to that recorded
for nodule formation, as to affect the plant measures. Nutrient contents of
both plant roots and shoots responded proportionally with the changes in
the biomass yield, concerning the influence of carrier treatments, period of
the inoculated carrier storage and detection time. Nitrogen showed the
prime response to the undertaken treatments, comparing to phosphorus and
potassium, respectively, in order.
B. Azospirillum / Maize crop
Maize experiment included the following treatments:
1-Control uninoculated without N-fertilizer ”C0”.
2-Control uninoculated + recommended doses of N (90 kg N fed-1) ”C1”.
3-Inoculation with Azospirillun (Vermiculite 90% + Peat 10 %) + 60 kg N fed-1.
4-Inoculation with Azospirillun (Vermiculite 50% + compost 50 %) + 60 kg N fed-1.
5-Inoculation with Azospirillun (Vermiculite 50% + biogas manure 50 %) + 90
kg N fed-1.
6-Inoculation with Azospirillun (Vermiculite 50% + filter mud manure 50 %) +
60 kg N fed-1.
The obtained results can be summarized as follows:
There were no alterations in the result patterns of the various plant
traits detected for maize crop than those recorded by peanut crop,
concerning the action of the experimental treatments. Differences
appearing in the values of the biomass yields and nutrient contents, under
the same growth conditions and applied treatments, are actually referred to
the nature of each crop genetically and phenotypically.
Key words = Microbial carriers, dizotrophy, Bradyrhizobium,
Azospirillum, peanut, maize, plant growth, nutrient contents.