الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
Barley (Hordeum vulgare L.) in the world`s fourth most important cereal crop after wheat, maize and rice (FAO report, 1985).
Barley is one of the main cereals of the belt of Meditrranean agriculture and is a founder crop of old world food production and one of the earliest domesticated crop (Harlan and Zohary, 1966).
Barley is the most cereal crop grown along the North- Western Coast of Egypt under rainfed conditions It is grown on large scale in the rainfed areas Libya. In Libya, the most part of barely production area is located in Coastal Stripe under semi- dry conditions and irrigated by annual rains.
Also, it grow in the newly reclaimed lands and old ones. Barley has been recognized as an adapted crop to adverse conditions as heat, salinity, drought and poor soils. It could survive and grow satisfactory under such conditions than several other crops.
The major use of barley is for animal feeding and soft drink industry. However, there is an interest in using it as human food in regions where other cereals do not grow well due to latitude, low rainfall or soil salinity. In additions to grain uses, the straw is used for animal bedding and immature barley plants are harvested for grazing hay or silage. In Egypt and Libya, barley faces severe competion, in old valley with other Winter crops i. e. Wheat, sugar beet , legumes and clover etc.
FAO (2001) reported that the average of barley production in world was 2.3 (ton / hectar) for the year 1985, and it was 2.6 (ton / hectar) in 2001. This quantity was achieved by 79 million hectars in 2001.
On the other hand in Egypt the cultivated area was 56000 hectar in 1985 and 31000 hectars in 2001, giving an average of 2.7 ton / hectar and 3 ton / hectar, respectively. In Libya the area of barley is about 24000 hectars giving the total production of about 262000 ton (LAM 2002).
Good soil fertility management ensures adequate nutrient availability to plants and increased yield. Fertilization is one of the most important limited factors in barley production. Traditional agriculture system are based on the use of chemical fertilizers to promote growth and provide essential nutrients to plant in available from which leads to improve productivity. One of the major essential elements for growth of plants is nitrogen. Nitrogen is required in large quantities for plants to grow, since it is the basic constituent of proteins, and nucleic acids. Nitrogen is provided in the form of chemical fertilizer. Such chemical fertilizers dose a health hazard, soil and water pollution problems beside making the cost of production high. In such a situation the use of biofertilizers with chemical fertilizer may be effective for further increase in barley yield.
Biofertilizers N2- fixing bacteria and fungus (Arbuscular mycorrhizal) and contribute to nitrogen requirements and the capability to mobilize phosphate, for barley plants. Therefore the importance of the present study was justified according to following reasons.
1. Rainfed barley develops normally without nitrogen fertilizer, so, it is assumed that barley could satisfy part of its N- requirements by N2- fixing organisms, naturally, present in the soils (Fayez 1989).
2. A- Mycorrhizae fungi develop a hyphal network that serves as a fundamental link between the soil, the nutrient reservoir, and the plant. The hyphal network is more efficient for uptake of nutrient than root hairs (Dorneless et al. 2001).
3. Limitation of N- fertilizer technology, Pollution, losses of N- fertilizers. The destructive effects of dinitrification products on ozone, application costs and production difficulties (Zaid, 1992).
4. Using mixtures of microorganisms is a promoting trend for increasing efficiency of N2 – fixing bacteria (Belimov et al 1995).
5. A- Mycorrhizae have the capability to mobilize phosphate, micronutrients and to promote root development and therefore enhance nutrient uptake (Marschner, 1995).
Therefore, the objectives of this research are to determine the effects of the following factors on barley production:
- Effect of barley cultivars.
- Effect of biofertilizers.
- Effects of N- levels.