The study looked at how different amounts of nitrogen and potassium fertilizers affect the growth and yield of winter potatoes grown with black film covering. They found that increasing nitrogen fertilizer made the plants taller, while increasing potassium fertilizer made the main stem thicker. The best yield was achieved with a combination of 225 kg of nitrogen and 450 kg of potassium per hectare. Too much nitrogen or potassium decreased the yield, so it's important to find the right balance for optimal potato growth.