Technology of topdressing for high yield of sweet potato

The root system of sweet potato is deep and wide, the stem vine can take root on the ground, and the fertilizer absorption is very strong. A certain amount of yield can also be obtained on poor soil. This often leads to the misunderstanding that sweet potatoes do not need to be fertilized. The practice shows that sweet potato is a crop with strong fertilizer demand, and the yield increasing effect of fertilization is in the following order: nitrogen, phosphorus and potassium is greater than nitrogen and potassium, nitrogen and phosphorus is greater than nitrogen, which shows that potassium fertilizer has the greatest effect on the yield of sweet potato, followed by nitrogen and phosphorus. However, the functions of the three elements of nitrogen, phosphorus and potassium are different and irreplaceable. The topdressing of sweet potato should be determined according to soil fertility, the amount of base fertilizer, different growth periods and growth conditions of sweet potato. If the amount of nitrogen application of base fertilizer is insufficient, or phosphorus and potassium fertilizer is also insufficient, in the spring and summer potato area of North China, the growth period of spring and summer potato is short, and nitrogen fertilizer should be applied mainly in the early stage, while in the autumn and winter potato area in the south, topdressing should be applied many times in stages, but mainly in the middle stage. And should be divided into: 1, raising seedling fertilizer. This is an effective fertilization technique to preserve seedlings, promote early development and accelerate the growth of potato seedlings. Generally speaking, the fertilizer can be applied after the survival of the seedlings, and the general plots are mainly to apply small seedlings and weak seedlings, so that the small seedlings can catch up with the big seedlings and grow neatly. Topdressing standard nitrogen fertilizer 2--3kg or mature human feces and urine 250kg per mu can irrigate trees with water or immediately after topdressing by opening holes next to the ridge. 2. Fertile tuber from strong plants. This is a fertilization method used in the stage of branching and fruiting and before the long-term growth of stems and leaves. Its purpose is to promote the growth of stems and leaves and the formation of potato tubers. Therefore, the masses call it "strong plant fat" and "tuber fertilizer". The high-yielding fields in spring and summer potato areas of North China are generally dominated by phosphorus and potassium, supplemented by nitrogen (which is different from field crops, which tend to apply nitrogen fertilizer instead of phosphorus and potassium fertilizer). In the plots with better water and fertilizer conditions, topdressing too early or too much will also cause excessive growth in the middle stage, hinder the transport of nutrients to the roots, but will delay the formation of potatoes. Therefore, in the fertile land, it is better to apply nitrogen fertilizer after the tuber has been formed for 40 days. However, the fertilizer effect can not be achieved in time even if it is too late. The growth period of sweet potato in southern summer potato region is long, and regular drought often occurs in July and August. In the case of early planting, there are two peak periods of tuber hypertrophy in the growing period. The fertiliser for tuber setting of strong plants can be properly advanced, and it is better to topdressing potato seedlings for 30 days after transplanting. According to the study, under dry conditions, fertilizer should be topdressing 20 days after transplanting, and under suitable conditions, Rain Water should be topdressing at 30 Murray 40 days after transplanting. Generally, standard nitrogen fertilizer 10kg or mature human feces and urine 800kg can be applied per mu. 3. Promote potato fertilizer and long potato fertilizer. Edge fertilizer, generally about 45 days after planting, the aboveground part has been thrown under the ridge, the potato block has been basically shaped, on one side of the ridge, use a plow to break 1 big 3, and then apply fertilizer. Ridge-breaking fertilization not only improves the aeration of the soil, but also facilitates the expansion of potato lumps. Crack fertilizer, sweet potato in the late growth stage, potato pieces are long, in the ridge back cracks, the fertilizer applied is crack fertilizer, white dew fertilizer, or long potato fertilizer. Generally using human feces, urine water or chemical fertilizer water per mu with 500--750kg, pouring from the cracks, in the case of insufficient base fertilizer, there is a good yield-increasing effect. However, topdressing should be applied about two months before harvest, too late is easy to cause potato leaves withered, potato pieces do not gain weight and other consequences. Extra-root fertilizer, in the later stage of sweet potato growth, the root absorptive capacity is weakened, so extra-root topdressing can be used to make up for the lack of nutrition. This method has a quick effect and a good effect. 0.5% urea dilute solution, 2% Mel 3% superphosphate solution and 0.2% potassium dihydrogen phosphate solution are sprayed outside the root. Apply in the evening, spray every 7 days, a total of 2 Murray 3 times, each mu spray 75--100kg solution, generally can increase production by about 10%.