Maize Yield and the Associated Weeds as Affected by Plant Population Density and Weed Control Treatments

Two field experiments were carried out in the Farm of Agricultural Research and the Experimental Center of Faculty of Agriculture at Moshtohor, (Toukh Directorate, Qalyubia Governorate) Benha Univ. Egypt, during 2017 and 2018 seasons to investigate the effect of five plant population densities, i.e. 18, 21, 24, 27 and 30 thousand maize plants/feddan (fed) {one fed = 4200 m²} and five weed control treatments, i.e.pendimethalin 682.5 g a.i./fed (stomp extra 45.5 % CS),acetochlor840 g a.i./fed (harness 84 % EC), nicosulfuron24 g a.i./fed (active 6 % SC), hand hoeingtwice and the unweeded check (the control) on yield, some of its components and associated weeds in maize (single cross hybrid 2036 for MisrHytech Seed Int.). Increasing plant population density from 18 to 30 thousand maize plants/fed reduced weed biomass at 50 days after sowing as well as significantly increased mean values of silking date, leaf area index at 80 days after sowing, plant height, ear height, No. of barren plants/fed, No. of ears/fed and stover yield/fed in both seasons. On the other hand, mean values of area of topmost ear leaf at 80 days after sowing, leaf area/plant at 80 days after sowing, stem diameter, No. of plants carried two ears/fed, ear length, No. of kernels/ear, weight of kernels/ear, shelling %, 100-kernel weight and harvest index were significantly decreased in the two seasons.Maize planted at 24000 plants/fed produced the highest mean values of grain and biological yields/fed in both seasons. Weed control by hand hoeing twice or using nicosulfuron herbicide surpassed the other weed control treatments in depressing mean values of fresh and dry weights of broad-leaved, grassy and total annual weeds at 50 days after sowing maize, as well as gave the best mean values of all maize traits without significant difference between them. Maize planted at 30000 plants/fed under mechanical weed control (hand hoeing twice) or using nicosulfuron herbicide gave the lowest mean values of all weed measurements at 50 days after sowing as well as gave the greatest mean values of leaf area index, plant height, ear height, No. of ears/fed and stover yield/fed in both seasons. The greatest mean values of area of topmost ear leaf, leaf area/plant, No. of kernels/ear, weight of kernels/ear and 100-kernel weight were obtained from planting 18000 maize plants/fed with hand hoeing twice. Maize planted at 24000 plants/fed and hand hoeing twice produced the greatest mean values of biological yield/fed in both seasons. The maximummean values of grain yield/fed were obtained by maize planted at 24000 and 21000 plants/fed and hand hoeing twice the first and second seasons, respectively.Planting maize by 21000 plants/fed with hand hoeing twice gave the highest mean values of nitrogen uptake/fed and protein yield/fed in both seasons.