Five Key Points for Late-Stage Sweet Potato Management to Ensure a Bumper Harvest

After late August, summer sweet potatoes enter the critical period of tuber expansion. At this time, management should be strengthened. On one hand, the nutrients needed for tuber expansion should be met to the greatest extent possible; on the other hand, premature senescence of stems and leaves should be prevented, photosynthesis should be enhanced, and nutrient accumulation should be increased. Specific yield-boosting technical recommendations are as follows:

1. Pinching the growing tips

Pinching the growing tips can regulate the movement of nutrients and promote their transport to the storage roots. Pinching should be done twice in total. The first time, when the sweet potato vines grow to 30-40 cm long, pinch off the 1-2 cm tender tip; the second time, when the branches grow to about 30 cm again, pinch off the tender tips of the branches.

2. Pruning branches

For sweet potato fields with many branches and vigorous growth, scissors can be used to cut off 2-3 branches. This allows nutrients to flow back, giving the tubers more nutrients, while also improving light penetration between the sweet potato branches and vines and speeding up photosynthesis. However, pinching should not be done on poor, barren soil.

3. Increasing potassium fertilizer application

After the sweet potato vines close the rows in August, a potassium dihydrogen sulfate solution can be sprayed, that is, potassium dihydrogen sulfate mixed with water to make a 1-2% solution, spraying 50-70 kg per mu, once every 5-7 days, for 2-3 consecutive sprays. For fields with insufficient base fertilizer, thin stems and leaves, or nutrient deficiency in the later stage, use a mixture of 0.3% potassium dihydrogen phosphate solution plus 0.5% urea fertilizer liquid, spraying 50-70 kg per mu, once every 5-7 days, for 2-3 consecutive sprays.

4. Lifting the vines

For overly vigorous sweet potato fields, the method of lifting the vines can be used to prevent excessive rooting. If the sweet potatoes grow too vigorously after closing the rows, the vines can be gently lifted and then placed back in their original position. Vine lifting should be completed before the end of August, for a total of 2-3 times.

5. Applying crack fertilizer

The time for applying crack fertilizer is generally 70-80 days after planting, when the tubers enter the peak period of expansion and cracks appear on the bed surface. This should be determined specifically according to the growth of the summer sweet potatoes and the soil conditions. For fields with insufficient early-stage fertilizer, shallow and poor soil, and relatively poor plant growth, it can be applied earlier and more heavily; the topdressing amount can be 800-1000 kg of decomposed human and livestock manure water per mu, or 6-7 kg of urea mixed with 600 kg of water, applied along the cracks. If the early-stage fertilizer is sufficient and the plants are growing vigorously, less can be applied, or only soil-organic fertilizer and potassium fertilizer can be applied, without nitrogen fertilizer.