الفهرس Only 14 pages are availabe for public view
 |  | from | 96 |  |  |
| | | from | 96 | | |
Abstract
1. INTRODUCTION
Rice, (Oryza sativa, L.), is one of the major cereal field crops, preferred by a large group of the Egyptian population in comparison to the other carbohydrate rich foods. The total planted area with rice in Egypt is about 1.543 million feddan. The total production of rice has increased from about 2.40 million tons in 1984 -1987 to 6.38 million tons in 2004, (Anonymous 2004). It is noteworthy to mention that the increase in rice production is mainly due to the increase in production per unit area. The national average grain yield of rice increased from 2.40 tons/fed in 1984-1987 to 4.155 tons/fed in 2004 season (Anonymous 2004). Such average (9.97 t /ha.) was the highest and ranked the first compared to the world average (3.97 t /ha.), due to presence of newly released highly productive local rice varieties, ideal weather, rich soil, abundant water, a relatively pest free environment and above all, our hard working farming community make this possible. Accordingly, Egypt has become self-sufficient in rice production for many years and, hence, the increased amount of surplus (one million tons) was exported during 2004 season.
One of the major problems we face today in Egypt is the steadily increasing population growth rate over a period of 50 years; the growth rate has gone up from 1.8 to 2.7 %. At the present rate, we add every year about 1.35 million people to an already oversized population. Egypt must continue to increase rice production and in less favorable economic circumstances than in the past, until populations are stabilized. The rice belt is restricted to the northern half of the Delta, soils of the Northern Delta include large areas with various levels of salinity. Salinity problems in Egypt affect one-third of the irrigated lands (2 million acres) and consequently, productivity is affected. In the costal areas of Egypt, salinity occurs because of direct inundation by salt water or by the upward or lateral movement of saline ground water.
Overcoming salinity problems would require the use of various strategies, such as reclamation, good drainage, water control and soil amendments. In the early stages of soil reclamation, rice is planted as reclaimed crop to help leach and lower their salt content. In spite of the fact that Egypt has a high average of rice grain yield, the need to raise the productivity per unit area in the newly reclaimed soils is a matter of importance and challenge. Great opportunities exist for increased rice production through increased application rate and improved management of nitrogen fertilizers and through an integrated agronomic practices management.
Hill spacings plays an essential role in rice production. The optimum plant density has to be well designated to obtain high yield. The low tillering capacity gave low number of panicles/m2, while the high tillering capacity caused competition and more shading consequently low yield of paddy.
Increasing nitrogen efficiency through the use of optimum nitrogen fertilizer level is one of the most important factors that limit productivity of rice. Because nitrogen is one of the basic plant nutrients, it considers one of the major constituents of protein, lipids and nucleic acid molecules. Nitrogen deficient lead to growth delay, less branches and growth of small, fine and yellow color leaves. Also, optimum number of seedlings/hill is also important factor to produce reasonable grain yield and better grain quality.
This investigation aimed to:
1- Determine the effect of either plant spacings or number of seedlings/hill with different nitrogen fertilizer levels on agronomic, root, shoot, yield, yield components and some grain quality characters of rice.