How should autumn sweet potatoes be managed to achieve high yields?
1. Select good varieties and strong seedlings. Choose early-maturing, high-quality, high-yielding “Su Shu No. 7”, “Su Shu No. 8”, “Yu Shu 303”, “Xu Shu 18”, “Yu Zi 263 (purple-fleshed sweet potato)” and other good varieties; select sturdy seedlings with pointed flat heads that have thick stems, dense nodes, moderate tenderness, rich sap, and are disease-free, non-degenerated, and free of adventitious roots; plant different varieties separately.
2. Apply heavy base fertilizer and plant densely on high ridges. In light loam or sandy loam fields, open the main ditch, surrounding ditch, and ridge ditches well, ensuring the ditch system is unobstructed, the ditch bottoms are flat and straight, and the ditches dry up after rain stops. Apply 25-30 kg per mu of high-efficiency compound fertilizer with an N-P-K ratio of 16-8-16 evenly, then level and form ridges. There are two ridge specifications: one is a ridge with a bottom width of 1.2 m, a height of 40 cm, and a surface width of 70 cm, planting 3 rows per ridge in staggered holes (walking-horse planting), with a hole spacing of 33 cm and 5,000 plants per mu; the other is a ridge with a bottom width of 1 m, a height of 33 cm, and a surface width of 60 cm, planting double rows per ridge in staggered holes, with a hole spacing of 33 cm giving 4,000 plants per mu, or a hole spacing of 30 cm giving 4,400 plants per mu. Also note that the density should correspond to the growth habits of the variety.
3. Plant early to seize the time. Early planting can extend the field growth period, increase photosynthetic potential, and improve yield and quality. Based on the actual conditions of our city, the most suitable planting period for autumn sweet potatoes is from late July to early August, and to ensure safe maturity, it must not be delayed until after the Start of Autumn. It should be noted that many farmers are accustomed to waiting for rain after preparing the land before planting, and some even plant as late as late August, wasting the excellent autumn sunlight, which is truly a pity!
4. Long-vine coil planting. On a sunny afternoon or cloudy day, select pointed sturdy seedlings that have not been aged by drought, with a seedling length of 30—40 cm and 8—10 expanded green leaves, preferably with 2—3 shoots of 5—10 cm at the base. When planting, first use a small “ash knife” or “ash trowel” to open a hole, then coil the sweet potato seedling into a ring shape, burying it 10—13 cm deep with 6—7 nodes, keeping the buried part flat, covering with soil so it is firm below and loose above, exposing all leaves and the seedling tip, and immediately apply human and livestock manure water thoroughly to stabilize the plant. If the soil is dry, first open the hole and pour water, then plant after it is absorbed; if there is high temperature and strong light, use rice straw to cover during the day and uncover at night for 2—3 days, or when planting, expose only the seedling tip and top three leaves, burying the remaining leaves in the soil to help ensure full seedling survival. The key points are: pointed long vines, coil planting with flat insertion, and burying leaves to stabilize the plant.
5. Careful field management.
First, topdressing to promote seedlings: 7—10 days after planting, cultivate the soil, and per mu apply 20—30 loads of human and livestock manure water mixed with 10—15 kg of ammonium bicarbonate or 5 kg of urea (preferably 7—10 kg of 40% high-efficiency compound fertilizer) into the holes; at the same time, apply 100—150 kg of plant ash per mu mixed with 25—30 kg of superphosphate between the holes, not inside the holes (if high-efficiency compound fertilizer was used as base fertilizer, only use human and livestock manure water to promote seedlings); when the vines and leaves close the rows, spray 0.5 kg of 21.8% zinc sulfate or 0.8 kg of compound zinc fertilizer per mu diluted in 50 kg of water on the leaves; in early October, spray 100 g of potassium dihydrogen phosphate and 150 g of urea per mu diluted in 50 kg of water on the leaves 2—3 times.
Second, pinch off the tips to promote branching: when the sweet potato seedlings survive, remove all seedling tips, which can shorten the vines, increase branching, increase green leaves, and improve plant shape, thereby facilitating more tuber formation. Note: do not turn the vines, and even more so do not “prune the branch vines”; for excessive growth, you can arrange the vines and lift them to cut off fibrous roots and control excessive growth.
Third, drain waterlogging and prevent waterlogging damage: always clear ditches and remove silt, repair the ridge surface, and ensure there is no standing water in the ridge ditches.
Fourth, harvest at the right time: dig and harvest sweet potatoes in early to mid-November, with the tubers used for seed, food, or feed; the vine tips used as vegetables; and the vines and leaves ensiled as feed. Note: harvesting too early or too late will reduce yield, quality, and storability. Those marketed as fresh sweet potatoes can be dug and harvested appropriately earlier.