Two field experiment were conducted in Tegzerte, Siwa Research Station; Desert Research Center during winter seasons of 2003 and 2004 to study the effect of phosphorus fertilization levels (0, 15.5, 31.0 and 46.5 kg/fed.), nitrogen fertilization levels (0, 80.0, 100.0 and 120.0 kg/fed.) and wheat grain rates (70.0, 80.0 and 90.0 kg/fed.) on weed control and relationship to wheat production. The experimental design was a split split-plot design with four replicates in both seasons, where the phosphorus fertilization treatments occupied the main plots, nitrogen fertilization treatments were arranged in the sup main plots and grain rates treatments in the sub-sub main ones, respectively. Weeds interference treatments were broad leaf weeds, grassy weeds and total annual weed.
Results showed that increasing phosphorus and nitrogen fertilization levels and wheat grain rates led to decrease significantly broad leaf weeds (Chenopodium album, Malva parviflora, Cichorium pumpilum, Beta vulgaris, Convolvulus arvensis, Melilotus indicus and Medicago polymorpha), grassy weeds (Zygophyllum album, Phragmites australis, Setaria viridis and Echinochloa colonum), while wheat biological, grain and straw yield were increased significantly as a results of applied the treatments.
Higher observation of biological, grain and straw yield were taken from the interaction between the three main factors, especially with (31.0 p kg./fed. & 100.0 N kg./fed. and 90.0 kg. wheat grains /fed. ), which led to 6.0, 2.4 and 3.6 ton. /fed., respectively compared to other treatments