Plastic Film Mulch Cultivation Techniques for Potatoes in Winter Fallow Fields

When cultivating potatoes in winter fallow fields, if the plastic film mulch cultivation method is adopted, the potatoes can be brought to market earlier, thereby achieving higher economic returns. The key cultivation techniques are as follows:

1. Soil selection

Choose slightly acidic light sandy soil that is loose, well-aerated and well-drained for cultivation. Clayey soil is heavy, poorly aerated and drains badly, which is unfavorable for tuber development and unsuitable for growing potatoes. When using harvested late rice paddies to grow spring potatoes, be sure to choose raised fields and second-bank fields with loose soil and good drainage. Potatoes are averse to continuous cropping; avoid previous crops from the Solanaceae family, flax, and other root and tuber crops.

2. Deep plowing and soil resting

Potato growth requires a tillage depth of 15-18 cm and loose soil. Deep plowing can improve the soil's water-holding and fertilizer-retention capacity, and is beneficial for root development and growth and tuber expansion. Deep plowing should generally reach 30 cm. After plowing, the soil should be fully rested to reduce soil moisture content, increase soil permeability, and make the solid, liquid and gas ratios of the soil more reasonable, which helps improve soil structure and raise soil temperature, satisfies the oxygen and temperature needed for seed potato development, and promotes early sprouting.

3. Land preparation and bed making

The main purpose of land preparation should be to facilitate rapid root growth and seedling emergence, so the soil must be finely prepared with suitable soil particle size and no large clods. Potato young roots have weak penetrating power; fine land preparation helps their growth and development, shortens emergence time, and minimizes seed potato rot caused by soil-borne diseases or other environmental factors. The Yangtze River basin has relatively abundant winter rainfall; to facilitate drainage, lower soil moisture and raise soil temperature, high-bed cultivation should be adopted. The bed width should be 1.6 m, bed height 0.25 m, and furrow width 0.4 m, with the bed surface slightly arched like a turtle shell and the furrows draining smoothly.

4. Applying sufficient base fertilizer

Potatoes are a high-yield crop, but high yields can only be achieved when nutrient needs are fully met. For early-maturing cultivation of spring potatoes in the Yangtze River basin, the growth period is short (60-70 days), so particular attention must be paid to applying sufficient base fertilizer. It is recommended to apply 1500 kg of farmyard manure or 75 kg of fermented cake fertilizer, 50 kg of potassium sulfate compound fertilizer, and 50 kg of calcium-magnesium-phosphate-potassium fertilizer per 1/15 hectare. The base fertilizer method is to open holes on the bed surface according to the potato sowing density, with holes 10-12 cm deep, and then apply the fertilizer into the holes.

5. Sowing time

The determination of the suitable sowing time for spring potatoes in the Yangtze River basin should take into account that the late frost has ended by the time of emergence, so as to avoid late frost damage at emergence. According to many years of meteorological data, the suitable sowing period is mid to late December.

6. Sowing density

In order to obtain a relatively high yield, the sowing density should be appropriately increased for early-maturing cultivation of spring potatoes. Open holes on the bed surface at a row spacing of 33 cm and a plant spacing of 40 cm, with holes 10-12 cm deep, 5 rows per bed, 5500 holes per 1/15 hectare, and a seed quantity of 150-200 kg.

7. Sowing and covering with soil

After opening holes and applying fertilizer, place the cut seed potatoes in the holes away from the fertilizer, with the cut side facing down and the eyes facing up. After sowing is completed, immediately level the soil on the bed surface to cover the seed potatoes, and smooth the bed surface.

8. Spraying herbicide

To prevent weeds from growing on the bed surface, before covering with film after sowing, a pre-emergence herbicide (Dual, Harness, etc.) should be used to prevent weed occurrence. Apply 100 ml of herbicide per 1/15 hectare, diluted with 50 kg of water, and spray evenly on the soil surface of the bed. In this way, the germination and growth of weed seeds on the soil surface can be suppressed throughout the growing season, effectively controlling weeds.

9. Covering with plastic film

Using plastic film cultivation for potatoes in winter and spring, on the one hand, helps raise soil temperature and promote earlier sprouting and emergence of seed potatoes; on the other hand, it prevents soil compaction and maintains a loose, breathable soil condition, which is beneficial for tuber development. According to trials, spring potatoes grown with plastic film mulch emerge 15 days earlier than those grown in open soil and increase yield by about 50%. Therefore, after spraying herbicide, the bed surface should be covered with plastic film. Both sides and ends of the bed should be sealed tightly with soil, and soil should be pressed on the bed surface at intervals to prevent the wind from damaging the film.

10. Breaking the film to guide seedlings and thin seedlings

About 1 month after sowing spring potatoes, the seedlings begin to emerge. When the seedlings push against the film, break the film at the seedling location to let the seedlings out. If there are many seedlings from the seed potatoes, consider thinning out some weak seedlings and keeping 1-2 strong seedlings, so as to avoid excessive seedling numbers, vigorous branching, many small tubers, a low rate of large tubers, and reduced marketability. After breaking the film to guide seedlings and thinning, press soil firmly around the seedling holes in the film to prevent air leakage, weed growth and rainwater entering the soil, which would affect the increase of soil temperature and soil permeability and be unfavorable for early and rapid plant growth and tuber expansion and development.

11. Plant regulation

If there is excessive nitrogen fertilizer in the soil, combined with continuous rainy weather and insufficient light, the plants are prone to excessive vegetative growth, with large amounts of nutrients transported to stems and leaves, resulting in only vine growth, no tuber formation, or delayed tuber formation. Therefore, some growth regulators must be used to regulate the growth of the aboveground and underground parts of potatoes, that is, to inhibit aboveground growth and promote underground tuber expansion. Commonly used growth regulators include paclobutrazol and uniconazole. The application method is foliar spraying, with a concentration of 100-150%. Spraying 0.2-0.3% potassium dihydrogen phosphate can also inhibit excessive vegetative growth, prevent premature senescence, and promote robust plants.

12. Timely harvest

Early-maturing cultivation of spring potatoes with plastic film mulch aims to bring fresh potatoes to market earlier. When tubers reach a certain size, they can be harvested successively for market. Early marketing means lower yield but good market price and relatively high output value; late marketing means lower market price but high yield, which will not affect output value. Therefore, each locality can grasp the harvest period according to market conditions. Generally, harvest for market can be done from late March to late April.