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Abstract
I. INTRODUCTION
Maize is one of the most important strategy cereal crops in Egypt. The total production of maize in 2003 season reached about 5.76 million tons resulted from an area of 1.66 million feddans (feddan=4200m2). Most of that area is planted by high yielding hybrids. Maize productivity increased from 10.8 ard./fed-1 (ardab=140kg) in 1980 to 24.80 ard./fed-1in 2003. This increase in productivity has been realized as a result of different factors such as release of high yielding hybrids, fertilizers and plant densities.
The increase of grain yield of maize could be achieved by the development of maize could be achieved by the development of high yielding varieties suited to different environmental conditions, better soil management and use of improved form techniques.
The growth, Yield and yield components of corn were studied by many others. In this respect Kennedy and Tchan (1992), Gouda et al (1993), Tantaway (1994); Aly et al. (1996) and Soliman et al. (1999) showed that raising nitrogen fertilization levels considerably increased grain yield and most of its components but the use of intensive and untraditional rates of mineral fertilizers increase the costs of agricultural production. It is well known that nitrogen plays an important role in different growth processes in maize plant but most of mineral fertilizer elements are either fixed in soil or leached to pollute the environment (Salem 2000). The considerable variation in the response of ear population density to N among seasons and sites might be the consequence of variation in the timing of N application and availability in relation to crop demand.
Maize grain yield can be increased by raising plant population (Larson and Hanwey 1977). But this relationship is parabolic. At low populations, yield is limited by the number of plants, while at high population, Yield is limited by the number of barren plants intrarow spacing and competition for water as well as light and nutrients determine optimum plant densities for each grow environment (Karten and Comp 1985). The aim of the present investigation was to study effect of varieties nitrogen fertilization and plant density and their interactions on growth attributes, yield and yield components as well as grain yield of maize.