Sweet potato belongs to underground root crops, and the demand for potassium fertilizer is relatively large. Fertilizer is the basis of increasing production and income of sweet potato. It should be noted that "fertilizer is the treasure of crops, and you can't live without it." A flower in a crop depends entirely on fertilizer. Irrational use of chemical fertilizers, yield is a problem. There is not enough fertilizer, and the income is discounted. "Every mu of sweet potato field can be applied with 50 ~ 100 kg of double-chelated and double-patented high-potassium compound fertilizer with the ratio of nitrogen, phosphorus and potassium of 17: 14: 20. Sweet potatoes don't need much nitrogen fertilizer. With more nitrogen fertilizer, sweet potato seedlings grow longer and do not bear sweet potatoes. In case of rainy weather and heavy rainfall, sweet potato fruit will soften and rot, and raw chicken manure, pig manure, duck manure and various animal manure cannot be used without harmless treatment, otherwise the potato pieces will soften and rot. Nitrate nitrogen fertilizer will make potato chips crack and rough skin, which will affect the commodity value and cannot be applied. It is best to apply 100 ~ 200 kg biological commercial organic fertilizer with active bacteria of meat protein and plant ash organic fertilizer. Plant ash is a fertilizer with high potassium oxide content, which is needed by all underground root crops. These fertilizers are used as base fertilizers or as furrow fertilizers when ridging. Planting sweet potatoes requires ridging. Planar planting is not conducive to the expansion of sweet potato roots.
(2) Potassium fertilizer application technology
Sweet potato is a potassium-loving crop. Among the three elements of fertilizer, the demand for potassium is the largest, followed by nitrogen and phosphorus. The content ratio of nitrogen, phosphorus and potassium in sweet potato root tuber is generally 2∶ 1∶3. Therefore, if potassium deficiency occurs in the early stage of sweet potato growth, internodes will appear, petioles will become shorter, leaves will become smaller, and veins in the late stage of potassium deficiency will be seriously green and gradually die, which will have a great impact on yield. Therefore, scientific application of potassium fertilizer is an important measure for high and stable yield of sweet potato. Applying enough potassium fertilizer as base fertilizer is the basis of high yield of sweet potato. It is also a high-quality organic fertilizer. Because of the poor water and fertilizer conservation ability of sandy soil, semi-mature organic fertilizer should be used as base fertilizer; Clay should be applied with decomposed organic fertilizer. Combined with ploughing and ridging, plant ash 100 ~ 150 kg or 3500 ~ 5000 kg of high-quality farmyard manure containing more potassium should be applied in layers. When applying plant ash, be careful not to mix it with ammonium nitrogen fertilizer or human feces to avoid nitrogen volatilization loss. In addition, sweet potato is a chlorine-free crop and potassium chloride should not be applied. Potatoes soaked in potassium can improve the survival rate and promote early development. The specific method is as follows: 0.5 kg of potassium sulfate and 25 kg of water are fully stirred to prepare a potassium solution with a concentration of 2%, and the cut sweet potato vine seedlings are soaked in the potassium solution, and the top leaves are exposed to the water. After general soaking 1 hour, take it out and dry it a little before planting. About 40 days after sowing, potassium sulfate 10 kg per mu was used to cut holes at the base of potato seedlings 7 ~ 10 cm, and then covered with soil to promote the formation and expansion of tuberous roots. When the potato vines grow to about 1 m, in the morning when there is no wind or dew, about 50 kilograms of plant ash can be directly sprinkled on the leaves per mu, which can prevent the potato vines from growing white and promote the swelling of potato pieces. During the potato expansion period, if the soil is wet and rainy and the vine leaves turn to Huang Shi, plant ash can be applied more.