Two field experiments were conducted at El-Serw Agricultural Research Station, Damietta Governorate, during 2008/2009 and 2009/2010 seasons, to study the effect of farmyard manure (0, 10, 20 and 30 m 3 /fad), plant densities (33600, 42000 and 56000 plant/fad), four biofertilizer treatments (without treated, inoculation seeds with Cerialine, Netrobine at 450 g/fad and 90 kg N/fad as a mineral fertilizer)and their interactions on growth and yield of sugar beet. The obtained results indicated that farmyard manure had a significant effect on average values of root fresh weight, sucrose %, purity % and yields of top, root and sugar/fad in both seasons. Increasing farmyard manure rate up to 30 m 3 /fad significantly increased root fresh weight, top yield/fad, root yield/fad as well as sugar yield/fad but, decreased sucrose % and purity % as compared to control (without added farmyard manure) in both seasons. Plant density significantly affected all studied traits in both seasons. The highest plant density 56000 plant/fad gave the highest values of sucrose %, purity %, top yield /fad, root yield /fad and sugar yield/fad, but it gave the lowest root fresh weight. On the contrary, the heaviest root was recorded with the lowest plant density 33600 plant/fad as compared with other studied plant densities in 2008/2009 and 2009/2010 seasons. Results indicated that fertilization treatments had a significant effect on all studied characters in both seasons. Applying nitrogen as a mineral fertilizer at a rate of 90 kg N/fad gave the highest values of root fresh weight, top yield/fad, root yield/fad and sugar yield/fad as compared with all other fertilization treatment, in 2008/2009 and 2009/2010 seasons. In this connection, cerialine biofertilizer followed the mineral nitrogen of the mentioned previously traits. The interaction between farmyard manure rates and plant densities, the interaction between farmyard manure rates and biofertilization treatments and the interaction between plant densities and biofertilization treatments were significantly affected all studied traits in both seasons. The interaction effect among farmyard manure, plant density and fertilization treatments was significant on all studied characters in both seasons. Plants received 30 m 3 /fad farmyard manure at the highest plant density 56000 plant/fad and fertilized by 90 kg N/fad gave the highest top yield/fad 33.65 and 39.28 tons, root yield/fad 40.76 and 39.20 tons as well as sugar yield/fad 7.11 and 6.75 tons compared to all other this interaction treatments in 2008/2009 and 2009/2010 seasons, respectively. Generally, it could be recommended that applied farmyard manure at the rate of 30 m 3 /fad for sugar beet plants sown at plant density of 56000 plant/fad, and fertilized by 90 kg N/fad gave the highest root and sugar yield/fad at North Delta,

These experiments were performed in Agronomy Department, Faculty of Agriculture, Al-Azhar University, during 2008/2009 and 2009/2010 seasons to investigate the allelopathic potential effect of five weed species viz. Chenopodium album, L. (W1), Euphorbia peplus, L. (W2), Melilotus indica, (L.) All. (W3), Avena fatua, L. (W4) and Phalaris minor, Retz. (W5) on germination and seedling development of wheat (Triticum aestivum, L. local var. Sakha 94). So,two experiments were carried out, the first (in laboratory) to study the effect of weed parts (root and shoot) water extract at different concentration (0,10, 20 and 30%). The second experiment (in wirehouse) to study the effect of previous weed shoot residues at different concentration (0,1, 2 and 3% (w/w)). Results of the first experiment indicated that the differences between weed species for all studied traits were significant in the means of two seasons. All extracted of Chenopodium album, L. and Melilotus indica, (L.) All. significantly inhibited germination %, germination rate, root length, shoot length, root and shoot dry weights compared with other weed species. The differences between weed parts extracted were significant for all studied traits in the means of two seasons. Shoot extraction significantly inhibited all studied traits. Also, results indicated that the differences between extract concentrations were significant for all studied attributed in the means of the two seasons. Application 30% concentration significantly decreased grain germination and seedling growth of wheat. All the interactions between weed species, weed parts and concentration extracted were significant, except germination rate in the means of two seasons. Melilotus indica, (L.) All. × the shoot extract × 30% concentration increased effective allelopathic on all studied attributes under experiment conditions. Results of the second experiment indicated that the effects of weed residues species and concentrations on seedling growth of wheat were significant in means of two seasons. The interactions between different species and 3% concentration were significant for all studied traits. Avena fatua, L. and 3% concentration significantly inhibited most studied traits in means of two seasons.