Detailed Explanation of High-Efficiency Cultivation Techniques for Potatoes with Three-Layer Film Mulching

In early spring in the Lunan region, potatoes are cultivated with three-layer film mulching - a large arch shed with small arch sheds inside and plastic film covering the cultivation ridges. The harvest period is around late April, about 40 days earlier than open-field potatoes reaching market, with a price of up to 4 yuan per kilogram; generally, 667 sq m yields 2000-2500 kg of tubers, with an income of 8000-10000 yuan. The main cultivation techniques are introduced as follows:

1. Select good varieties

For three-layer film mulched potatoes, early-maturing varieties with a short dormancy period, early tuber formation and resistance to rot should be selected, such as Luyin No. 1, Jinshu No. 8 and Zaodabai, etc.

2. Land preparation and fertilization

Potatoes thrive in loose, fertile, well-aerated slightly acidic to neutral soil with a pH of around 6; they are prone to scab in alkaline soil. Potato roots are mainly distributed in the top 33 cm of soil, so deep plowing should be carried out appropriately. After deep plowing and leveling combined with the application of organic fertilizer, the medium arch shed should then be built. Since potatoes have a high nutrient demand and a short growth period, basal fertilizer should be applied heavily. In three-layer film mulching cultivation of potatoes, all required fertilizer is generally applied fully during plowing and sowing, and no additional topdressing is generally done during the growth period. For every 667 sq m, more than 3000 kg of high-quality decomposed farmyard manure should be applied; where farmyard manure is insufficient, the amount of cake fertilizer should be appropriately increased. Generally, about 50 kg of cake fertilizer can be applied per 667 sq m. Small quantities of well-decomposed high-quality manure, cake fertilizer and chemical fertilizer can be applied between the two seed potatoes in the furrow when opening furrows for sowing. Among chemical fertilizers, 10-15 kg of urea, 30 kg of potassium sulfate or 150 kg of plant ash, and 10 kg of diammonium phosphate can be applied per 667 sq m. To control underground pests, 2 kg of 5% phoxim granules per 667 sq m can be mixed into the farmyard manure and cake fertilizer, and 0.75 kg of 5% phoxim granules mixed with fine soil can be scattered in the sowing furrow.

3. Treating seed potatoes

1. Warming and sunning the seeds. Before sprouting the seed potatoes, it is best to first warm and sun them. Place whole seed potatoes in a sunny cold frame, a warm room or a winter-warm greenhouse at around 20°C, or lay them out in a single layer to sun for 5-6 days.

2. Cutting seed potatoes into pieces. This is best done 1-2 days before sprouting so the wounds can fully heal. When cutting, cut the seed potato lengthwise from the top downward into several pieces, each with 1-2 buds; after cutting, air-dry for 4-8 hours. The cut pieces should ideally weigh about 25 g each. If a diseased seed potato is cut, immediately disinfect the knife with alcohol or strong liquor, or soak the knife in 3% carbolic acid water for 5-10 minutes. Avoid letting the seed pieces come into contact with oily substances.

If a healthy, disease-free small whole potato of about 50 g is selected as seed, since the whole potato has strong vitality, apical dominance and concentrated nutrients, and reduces the chance of wound-borne disease infection, it has a fairly obvious yield-increasing effect.

3. Disinfection treatment of seed potatoes. There are two commonly used methods: first, warm water soaking - pre-soak the seed potatoes in warm water at 40-50°C for 1 minute, then place them in water at 60°C for 5 minutes; second, soak in 200-fold dilution of 40% formaldehyde for 5 minutes, remove and cover tightly with plastic sheeting for 2 hours. Through seed potato disinfection treatment, good preventive effects are achieved against scab, powdery scab, early blight, late blight, ring rot, etc.

4. Soaking seeds with gibberellin (920). Since three-layer film mulched potatoes are sown early, gibberellin should be used for seed soaking to break dormancy and promote germination. Cut seed potatoes can be soaked in 1-2×10-6 gibberellin solution for 8-10 minutes, and whole potatoes should be soaked in 5-10×10-6 gibberellin for 1-2 hours. When preparing the gibberellin solution, first dissolve the gibberellin with a small amount of alcohol or strong liquor, then add water to the required concentration. When using gibberellin to promote sprouting, do not arbitrarily increase the concentration, otherwise the sprouts will be thin and weak, which is unfavorable for growth.

4. Seed soaking and sprout promotion

After soaking the seeds in gibberellin solution, sprout promotion can be carried out. Sprout promotion can be done about 25 days before sowing. It can be carried out in a hotbed, a cellar or at the base of the gable wall inside a winter-warm greenhouse. During sprout promotion, alternate one layer of wet sand and one layer of seed potatoes, stacking 4-5 layers in total, cover the top layer tightly with wet sand, and then cover with woven "snake skin" bags, which both preserve moisture and block dripping water inside the greenhouse. Keep the sprouting bed at 15-20°C. When sprouts reach 1-2 cm, they can be sown. 5-7 days before sowing, the sprouted seeds can be placed under diffused light (maintaining a low temperature of 10-15°C) to air and dry, making the sprouts green and thick.

5. Building the medium shed

The medium arch shed can generally be built to the standard of 1.8 m top height and 6 m width, and should be built after the land is fully plowed and leveled and before sowing; the length is generally 60-80 m.

6. Timely sowing

The sowing time is 5-7 days before "Start of Spring". Before sowing, first plan the positions of the small arch sheds; a 6 m wide medium arch shed contains 2 small arch sheds each 2.3 m wide. Leave a 40 cm walkway between the two small arch sheds, and leave 50 cm low-temperature zones on both sides where straw mats can be placed during the day. After planning the small arch sheds, sowing can begin. Sowing adopts a single ridge with double rows. When setting out the lines for the border rows, first leave 50 cm outside the small arch shed, and also leave 35-40 cm inside the small arch shed. Therefore, the border rows should be 85-90 cm from the edge of the medium arch shed, then open small furrows in sequence at a row spacing of 45-47 cm for small rows and 63-65 cm for large rows, pour "horse-running water" (a quick flow of water), then sow in the furrows at a plant spacing of about 25 cm; high-quality organic fertilizer (such as cake fertilizer) and chemical fertilizer can be applied between the two seed potatoes. Then take soil from the large rows to cover the seeds; the border rows must also take soil from outside the border rows. The soil covering thickness is about 10 cm. After covering with soil, the ridge height is about 20 cm, the ridge width is 80-85 cm, the furrow width is 25-30 cm, and a small furrow about 10 cm wide and 10 cm deep is left in the middle of the ridge; after slight compaction, lay plastic film 100-110 cm wide. A 6 m wide medium arch shed can form 4 large ridges and plant 8 rows of potatoes. The seeding rate per 667 sq m is generally 100-150 kg. If whole potatoes of about 50 g are all selected, the seeding rate per 667 sq m is 200-250 kg.

7. Covering with small arch sheds

After sowing, promptly cover with small arch sheds 2.3 m wide and 1.2-1.4 m high according to the positions planned for the small arch sheds before sowing. Each small arch shed exactly covers 2 large ridges and 4 rows of potatoes.

8. Post-sowing management

1. Management during the emergence period. During the emergence period, the daily average temperature of the 10 cm soil layer is generally required to reach 10-15°C; after sprout promotion, seedlings generally emerge in about 20 days after sowing. During this period, because the air temperature is relatively low, the main focus should be on heat preservation and raising soil temperature; during the day, the film of the small arch shed should be opened to facilitate ventilation and raise soil temperature, and before 5 p.m. straw mats should be promptly covered on the small arch shed for insulation. When potato sprouts push through the soil and emerge, promptly cut a "cross" in the film to release the seedlings.

2. Management during the seedling stage. From emergence to the formation of one leaf sequence (rosette stage), generally about half a month. During this period, all stolons are formed and their tips begin to swell. Because the air temperature is relatively low, the main focus is on preserving moisture, keeping warm and raising soil temperature; generally no watering is done, and the suitable field water-holding capacity is 50%-60%. If it is indeed dry, "horse-running water" can be poured in the small furrows; if too wet, it is unfavorable for raising soil temperature. During the day, open the film of the small arch shed to keep the air temperature at 20-25°C; when the air temperature exceeds 25°C, open the medium shed film for ventilation and cooling; before the sun sets in the afternoon, promptly cover the small arch shed with straw mats so that the nighttime temperature is not lower than 8°C.

3. Management during the plant-growing stage. From the rosette stage to budding is the plant-growing stage, requiring 20-30 days. During this period, attention should be paid to ventilation and cooling, not exceeding 25°C during the day, and insulation at night; in the later part of the plant-growing stage, fertilizer and water should be controlled to facilitate the transition from plant growth to tuber formation and to control excessive vine vigor.

4. Management during the tuber-forming stage. ① Water management. During the tuber-forming stage, growth is dominated by cell expansion, requiring sufficient and uniform soil moisture supply, with soil moisture reaching 80%-85% of field water-holding capacity. The flowering stage is especially sensitive to water; water shortage during this period can reduce yield by about 50%; after budding, promptly remove flower buds to reduce nutrient consumption, and irrigate once heavily; where basal fertilizer was insufficient, a small amount of phosphorus and potassium fertilizer can be applied with irrigation; in the late tuber-forming stage, after flowering and fruiting end, watering should be reduced and stopped; if soil moisture is too high, the tuber skin easily cracks, respiration is impeded, scab is likely to occur, storage tolerance is poor, and yield and quality are affected. ② Temperature management. Throughout the tuber-forming period, special attention should be paid to ventilation and temperature regulation. As the air temperature rises, ventilation time should be increased on sunny days, keeping the daytime below 23°C, the first half of the night at around 15°C, and the second half of the night at around 12°C, appropriately widening the day-night temperature difference. If soil moisture is too high, the plastic film can be lifted to facilitate ventilation and moisture dissipation.

9. Pest and disease control

1. Common potato diseases include early blight, late blight, scab, powdery scab and ring rot. ① Early blight mainly damages leaves; leaf lesions are dark brown, round, nearly round, polygonal or irregular, with concentric rings. ② Late blight mainly attacks leaves, mostly starting from leaf tips or leaf margins with yellow-brown water-soaked spots surrounded by a yellow-green halo; when humidity is high, the lesions expand rapidly and a ring of white mold forms at the edges; when dry, no white mold is seen, but the lesions do not easily rupture. ③ Scab: small brown spots first appear on the tuber surface, and after expanding they form brown round or irregular large patches with a rough surface; later the center is slightly sunken or raised into scab-like hard patches. The lesions are limited to the skin and do not penetrate deep into the tuber. ④ Powdery scab mainly damages tubers and roots. When tubers are infected, pinhead-sized brown spots first appear on the epidermis, later forming "blister spots" 3-5 mm in diameter. After the "blister spots" rupture, they sink into a crater-like shape, and the tissue beneath the skin releases a large amount of dark brown powdery material. When roots are infected, bean-sized solitary or clustered tumor-like growths appear on one side of the root. ⑤ Ring rot: infected aboveground parts show either blight spots or wilting. When tubers are affected, cutting them open reveals the vascular bundles turning milky yellow and dark brown, with ring-shaped or arc-shaped necrosis in the cortex, hence the name ring rot. Even if diseased seed potatoes can sprout and emerge, they will form diseased plants; the vascular bundles of the root stem turn brown, and sometimes white bacterial pus oozes from the diseased vines.

Control methods: Selecting disease-free seed potatoes and the aforementioned seed potato disinfection are the most effective preventive methods; at the same time, apply more organic fertilizer, use formula fertilization, and especially increase potassium fertilizer to enhance disease resistance. During the growth period, promptly remove diseased plants at the early stage of disease, and spray 1:1:200 Bordeaux mixture or 500-fold 64% Sandofan wettable powder, which can control both early blight and late blight. For early blight alone, 400-fold 40% captan wettable powder can be used; for late blight, 1000-fold 69% Anke Manganese Zinc wettable powder can be used. For scab, powdery scab and ring rot, apart from selecting disease-free seed potatoes and disinfecting seed potatoes, there is no good chemical control during the growth period. To control ring rot, when cutting seed potatoes for sowing, disinfect the knife with 75% alcohol; when sowing, soak the seed potatoes in 500-fold 50% thiophanate-methyl wettable powder or 800-fold 70% thiophanate-methyl.

2. The main pests harming potatoes are ladybugs, aphids, etc. To control ladybugs, 1000-fold 80% dichlorvos, 3000-4000-fold Kung Fu, or 3000-fold 20% fenvalerate can be used alternately, applying once every 7-10 days for 2-3 consecutive applications. To control aphids, 20 g of 5% Yadasao per 667 sq m can be mixed with 50 kg of water and sprayed evenly; areas where aphids are concentrated should be sprayed more heavily.

10. Timely harvesting. When potatoes mature, the stems and leaves turn pale yellow, the basal leaves wither and fall, the stolons shrink and dry, and the tuber skin lignifies and no longer expands. Harvesting should be done on a sunny day when the soil is dry, avoiding damage to the tubers.