This study was conducted to examine the effect of five organic and mineral nitrogen fertilizer levels (F1 = 0, F2 = 17.5 kg organic nitrogen (ON) + 17.5 kg mineral nitrogen (MN), F3 = 35 kg MN, F4 = 35 kg ON + 35 kg MN and F5 = 70 kg MN / fed) on the growth characters, yield, its component and some chemical properties of three bread wheat cultivars (Sids 12, Gemmeiza 11 and Giza 168).

Two field experiments were conducted on the Agricultural Research and Experiment Center, Faculty of Agriculture Moshtohor, Benha University, Toukh Directorate, Kalubia Governorate, Egypt,during the two successive summer seasons of 2014 and 2015 tostudy the effect of four nitrogen fertilizer treatments, i.e. 40, 70, 100 and 130 kg N/fed. and foliar spray by five micronutrient treatments, i.e. Non-fertilized, Zn, Mn, Fe and Zn + Mn + Feon the growth traits, yield, its component and some chemical properties of maize(white single cross hybrid 2031). The experimental design was split plot design in four replications. The obvious results of this investigation can be summarized as follows: All traits of maize under study (plant height, No. of green leaves/plant and leaf area index at 100 days from planting, No. of ears/fed., ear length, ear weight, weight of kernels/ear, 100kernel weight, kernels shelling %, biological yield/fed., grain yield/fed., stover yield/fed., harvest index %, kernels nitrogen uptake/fed., kernels protein yield/fed., leaf and kernel nitrogen contents, zinc, manganese and iron contents of maize leaves in the two seasons.) showed significantly increased by increasing nitrogen fertilizer rates, except, mid tasseling and silking dates significantly decreased with increasing nitrogenrates in the both seasons. Application of 130 kg N /fed significantly gave the maximum values of above traits. Results revealed that micronutrient foliar spray using Zn + Mn + Fe treatment was the most effective treatment forprevious growth, yield and its components traits of maize in the two seasons. Meanwhile, maize plants which foliar spray by singly Zn, Mn and Fe treatments significantly gave the highest values of leaf zinc content, leaf manganese content and leaf iron content, respectively in 2014 and 2015 seasons. The interaction between nitrogen fertilizer by 130 kg N/fed.and foliar spray by mixed Zn + Mn + Fe treatment significantly gave the greatest values ofmaize traits, i.e. plant height, No. of green leaves/plant and leaf area index at 100 days from planting, No. of kernels/ear, ear weight, weight of kernels/ear, biological yield/fed., grain yield/fed, kernels nitrogen uptake/fed.and kernels protein yield/fed.in the both seasons. It could be summarized that fertilization of maize field by 130 kg N/fed.and foliar spray by mixed of Zn + Mn + Fe to maximized grain yield/feddan.

Tow field experiments were carried out during the two successive summer seasons of 2010 and 2011 at the Agric. Res. and Exp. Center of Fac. Of Agric. Moshtohor to study the effect of five plant population densities (20, 22, 24, 26 and 28 thousand maize plants per fed.) and seven periods for weed control (un-weeded control (1), weed control at 20 (2), 20+35 (3), 20+35+50 (4), 20+35+50+65 (5), 20+35+ 65+80 (6) and 20+35+80+95 days after sowing (7)) on growth, yield and its components of maize, associated weeds as well as the net economic return of maize. The obvious results of this investigation can be summarized as follows: Increasing plant population density from 20 to 28 thousand plants /fed. significantly decreased total number and fresh weight of removed weeds in the first season, total fresh and dry weights of weeds at harvest, number of green leaves / plant, leaf area / plant, stem diameter, ear length, number of grains / ear, ear weight, shelling %, 100-grain weight and grain yield / plant in both seasons. On the other hand, plant height, leaf area index, number of ears /fed., Stover yield, nitrogen uptake and protein yield / fed. were significantly increased. Generally, the greatest grain and biological yields / fed. were results from maize planting by 26000 plants/ fed. This was true in the two growing seasons. Un-weeded check significantly decreased all these characters except total fresh and dry weights of weeds at harvest compared with weed removal even once after maize emergence. The maximum grain and biological yields/ fed. were produced from planting maize under weed control at 20, 35, 50 and 65 days after sowing. The critical period of weed control (CPWC) in maize crop based on 5% acceptable yield loss was 20-35 days after sowing. The highest values of leaf area index and stover yield / fed. were recorded from planting maize at the highest density under weed control by treatment 5. While, the lowest plant density under the same weed control gave the maximum values for No. of green leaves / plant, leaf area / plant, ear length, No. of grains /ear, 100-grain weight, ear weight and grain yield / plant in the two growing seasons. Meanwhile, the greatest maize grain and biological yields / fed. were resulted from maize planting by 26000 plants / fed. under the same weed control (weed control at 20 +35 + 50 + 65 days after sowing). The best treatment was that planting 24000 maize plants / fed. under weed control by either treatment 5 or 6 in the first season and planting 26000 maize plants /fed. with weed control by treatments 5 in the second season, where the net farm return valued 1945.2 and 2981.0 L.E. / fed. in the first and second seasons respectively.