The researchers studied how different amounts of potassium affected the growth of four types of sweet potatoes. They found that adding 300 kg/hm2 of potassium increased the growth of one type of sweet potato but decreased the growth of two others. The type of sweet potato that grew the best with potassium was SU11. This means that SU11 is the best choice for soil with enough potassium, while NZ1 and SU14 are better for soil that lacks potassium.