What are the key points of fertilization techniques for sweet potato cultivation?

Fertilization for sweet potato should adopt appropriate fertilization methods according to climate, soil characteristics and the growth conditions of the plant at each growth and development stage. The key points are as follows:

Base fertilizer is the main measure in sweet potato fertilization.             Base fertilizer should be mainly high-quality organic fertilizer. Sandy soil, with good permeability, a large day-night temperature difference and poor water and fertilizer retention capacity, is suitable for using semi-decomposed organic fertilizer as base fertilizer; clay soil is suitable for applying decomposed organic fertilizer. Part of the nitrogen fertilizer and all of the phosphorus and potassium fertilizers among chemical fertilizers can also be applied together with the base fertilizer.               Topdressing: if the amount of nitrogen applied in the base fertilizer is insufficient, topdressing should be carried out in stages, with the middle stage as the main one. The specific topdressing period should be flexibly controlled. If the soil is dry when transplanting the seedlings, the temperature is rather low, and the sweet potato seedlings are thin and weak, then seedling-promoting fertilizer can be applied early. During the branching and tuber-setting stage, if branching is relatively late, stem and leaf growth is not vigorous, and the leaves are small, plant-strengthening fertilizer should be applied early. If the plants grow normally, less or no fertilizer may be applied. When entering the stage of rapid tuber expansion, if the stems and leaves decline early, the leaf area index drops relatively quickly, and the defoliation rate increases, 1-2 applications of nitrogen fertilizer can be topdressed, with the amount determined according to climatic conditions and the condition of the seedlings. When the soil cracks and the tubers expand, if drought occurs, the stems and leaves turn yellow relatively early, and the number of yellow leaves increases, more human and livestock manure water should be applied. If the soil is moist and there is a lot of autumn rain, when the stems and leaves turn yellow, more plant ash can be used; if the weather is clear and rainless for a long time, it can be applied 1-2 more times, otherwise it should be reduced.