The study aimed to find the best way to fertilize virus-free potatoes in Bijie City, Guizhou Province. By testing different fertilization ratios on a potato variety called Xuanshu3, researchers discovered the optimal amounts of nitrogen, phosphorus, and potassium for different soil fertility levels. They found that medium fertility soil needed specific amounts of each nutrient, while low fertility soil required different ratios. High fertility soil didn't need extra nitrogen, but did benefit from additional phosphorus and potassium. Overall, the study provided useful guidance for farmers to maximize potato yields in the field.