الفهرس 
Effect of N-sourcesOnly 14 pages are availabe for public view
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Abstract
Wheat (Triticum aestivum L.) is one of the most important cereal crops
grown in the world. It is used as a staple food grain for urban and rural societies.
Despite the significant increase in production, it is not enough to meet the needs
of the consumer, which led to increased reliance on import from foreign markets
to fill the food gap and thus, led to the formation of a significant burden on the
balance of payments and the exposure of food security of Egypt to many risks.
Therefore, increasing the productivity of wheat is one of the main goals of the
Egyptian agricultural policy. This can be achieved through horizontal expansion
of the cultivation of newly reclaimed land and vertical expansion through the
use of best agricultural transactions, including the foliar application of organic
compounds as Ascorbic acid, Gibberellic acid, humate potassium, bio-fertilizer
and organic manure.
Maintaining soil fertility and the use of plant nutrients in sufficient and
balanced amounts is one of the key factors in increasing crop yield (Diacono et
al., 2013). Nitrogen (N) is the most important nutrient supplied to most non–
legume crops, including wheat. The most important role of nitrogen in plants is
its presence in the structure of the protein and nucleic acids, which are the most
important building and information substances of every cell. In addition,
nitrogen is also found in chlorophyll that enables the plant to transfer energy
from sunlight by photosynthesis. Thus, nitrogen supply to the plant will
influence the amount of protein, amino acids, protoplasm, and chlorophyll
formed. Moreover, it influences the cell size, leaf area, and photosynthetic
activity (Diacono et al., 2013 and Piccinin et al., 2013). Therefore, adequate
supply of nitrogen is necessary to achieve high yield potential in crops, nitrogen
fertilizer is known to affect the number of tiller m 2 , the number of grains /spike,
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spike length and weight, 1000 grain weight and grain yield of wheat (Kandil et
al., 2011 and Campuzano et al., 2012).
Organic materials have different effects on modifications of the physical
and chemical properties of soils as well as the influence of their nutrition status
and soil fertility. Incorporation of plant residues sustains organic matter in the
soil, enhances the biological activity, and improves soil physical properties
(Kumar and Goh, 2000 and Palm et al., 2001). Also, compost is a rich source
of organic matter which plays an important role in sustaining soil fertility and
hence in sustainable agricultural production. In addition to being a source of
plant nutrients, it improves the physicochemical and biological properties of the
soil. As a result of these improvements, the soil: (i) becomes more resistant to
stresses such as drought, diseases, and toxicity; (ii) helps the crop in improved
uptake of plant nutrients; and (iii) possesses an active nutrient cycling capacity
because of vigorous microbial activity.
Bio-fertilizers are considered as a promising alternative approach for
wheat and other crop species production. These bio-fertilizers are mainly based
on beneficial microorganisms in a viable state applied to seed or soil aiming to
increase soil fertility and plant growth by increasing the number and biological
activity of desired microorganisms in the rhizosphere. As soil is a complex
system which can be affected by several factors. Improving such beneficial
microbial communities in the soil is an important factor in the biogeochemical
cycling of both inorganic and organic nutrients, specifically, in the rhizosphere
zone which can increase the availability of nutrients to plants and also improve
the soil quality. The plant growth-promoting rhizobacteria (PGPR) was used for
the first time at the end of the 1970s in many key ecosystem processes, such as
bio-fertilizers and bio-pesticides. Recent studies have reported that the bio-
fertilizers can promote plant growth through nitrogen fixation, phytohormone,
phosphate (P), and potassium solubilization (Namvar et al., 2012 and Rana et
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al., 2012). Azotobacter sp. and Azospirillum sp. are used as bio-fertilizers in the
cultivation of many agricultural crops. The estimated contribution of these free-
living N fixing prokaryotes to the N input of soil ranges from 0–60 kg/ha per
year (Vessey, 2003). Existence of microbial communities like Azotobacter sp.
and Azospirillum sp. in the rhizosphere promotes the growth of the plant through
the cycling and availability of nutrients, increasing the health of roots during the
growth stage by competing with root pathogens and increasing the absorption of
nutrients and water (Zorita and Canigia, 2009 and Daneshmand et al., 2012).
Kandil et al., (2011) studied the effects of inoculation with Azotobacter sp. and
Azospirillum sp. on wheat and observed that inoculated wheat plants gave higher
plant height, spike per unit of area, grains per spike, grain weight, biological
yield, grain yield, and straw yield compared to non-inoculated cultivars. Some
of the investigations have suggested that integrated nutrient management
strategies involving inoculation of seeds with Azotobacter sp. and Azospirillum
sp. in combination with chemical fertilizers result in improving both growth and
yield of crops, i. e. wheat (Saini et al., 2004 and Piccinin et al., 2013).
Recently, great attention has been focused on the possibility of using
natural and safe substances in order to improve plant growth. In this concern,
antioxidants have synergistic effects on growth, yield, and yield quality of many
plant species. These compounds have beneficial effects on catching the free
radicals or the active oxygen that producing during photosynthesis and
respiration processes (Ali et al., 2006). Leaving these free radicals without
chelating or catching leads to lipids oxidation and the loss of plasma membrane
permeability and the death of cells within plant tissues. Antioxidants have also
an auxinic action. One of the most familiar antioxidants is ascorbic acid (vitamin
C) which is synthesized in higher plants and affects plant growth and
development. Ascorbic acid plays an important role in plant growth such as
regulation of cell division, photosynthesis, flowering, cell wall expansion, and
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other developmental processes (Davey et al., 2000 and Barth et al., 2006).
Ascorbic acid is found in the cytosol, chloroplasts, vacuoles, and mitochondria
of plant cells. It has a great effect on physiological processes such as cell
division, plant growth, and the biosynthesis of the cell wall, metabolites, and
phytohormones. Moreover ascorbic acid plays a vital role in the renovation of
chloroplast and mitochondrion membranes (Barth et al., 2004; Pavet et al.,
2005 and Barth et al., 2006). These results are in conformity with those
acquired by Gamal El-Din (2005), who reported that foliar application of
ascorbic acid increased plant growth of wheat plants. The effect of ascorbic acid
on plant growth may be due to the fundamental role of ascorbic acid in many
metabolic and physiological processes. Ascorbic acid acts as an important
cofactor in the biosynthesis of many plant hormones such as gibberellin and
abscisic acids (De Tullio & Arrigoni, 2003). Also, ascorbic acid is considered
as one of no enzymatic antioxidants caused an increment in growth characters of
wheat plants, compared with untreated plants (Abd El-Al, 2009).Humic (HA)
acids as a foliar spray to plant as a vital part of their fertilizer program. Humic
substances are a vital soil component because they constitute a stable fraction of
carbon and improve water holding capacity, pH buffering, and thermal
insulation (McDonnell et al., 2001). Humic substances have also, a positive
effect on plant growth through their importance of optimum mineral supply,
independent of nutrition (Yildirim, 2007). Stimulation plant growth through
increased cell division as well as optimized uptake of nutrients and water,
besides, humic acid stimulated the soil microorganisms (Chen et al., 2004).
Humic acid plays a prominent role in various physiological and biochemical
processes related to environmental stresses. Humic acid has ecological
importance, as they intervene in the regulation of a large number of chemical
and biological processes that occur in the natural ecosystems (Chen et al.,
2004). Asik et al., (2009) reported that the lowest doses of both soil and foliar
application of humic substances increased the nutrient uptake of wheat.
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Furthermore, El-Hefny (2010) reported significant increases in plant height, the
number of branches, fresh weight, leaf area/plant, total pods yield, N, P, K
uptake as well as protein and carbohydrate contents in cowpea seeds with
increasing the rate of humic acid application from 1, 3, 4.5 up to 6 kg/fad.
Ghorbani et al., (2010) reported that foliar spray with humic acid has
remarkable effects on vegetative growth of the plant and increases
photosynthetic activity and leaf area index of corn. The objectives of
experimentation were to assess the effect of replacing part of chemical N
fertilizers through organic, bio and foliar application of organic stimulants on
growth, productivity, nutrient uptake and quality of wheat plants (Triticum
aestivum L.) cv. Sakha 93 and secondly for improving the biological properties
of these soils