The researchers studied how different plant densities and nitrogen fertilizer levels affect the growth and protein content of corn plants in competition with a weed called Amaranthus retroflexus. They found that using a certain corn cultivar (704) with a density of 80,000 plants per hectare and applying 400 kg of nitrogen per hectare resulted in the highest grain protein content. This combination also reduced the growth of the weed. So, for farmers in the Miandoab region, it is recommended to use this specific corn cultivar with the mentioned plant density and nitrogen level for better crop yield.