Plastic Mulch Cultivation Techniques for Winter-Planted Potatoes, A Planting Guide for the Nanyang Basin

Potato is a crop used both as food and as a vegetable, and winter-planted potato is currently one of the more ideal winter crops. Spring potato production in the Nanyang Basin suffers few disasters and can guarantee supply during the early-summer vegetable off-season, with relatively high economic returns. In recent years the cultivated area has grown larger and larger, and in some places potato has become the main cash crop for local farmers. The winter-planted potato cultivation techniques for the Nanyang Basin are described below.

1. Choose good varieties. After full emergence, the effective growth period of winter-planted plastic-mulched potato in the Nanyang Basin is about 90 days, so seed potatoes should be selected from excellent varieties that are suitable for local growth, table-use, virus-free and high-yielding, such as "Dabaihua". Choose tubers with sunken eyes, no disease spots, no insect holes and no wounds. Each 667 sq m (1 mu) requires 150-200 kg of seed.

2. Site selection and land preparation. Spring in the Nanyang Basin is dry with little rain, so choose a plot with convenient drainage and irrigation, a deep plow layer, medium or higher fertility, and no potato or other Solanaceous crops grown in the past 3 years. After the previous crop is harvested, plow the land deeply to 20-25 cm. In early December, apply 20 kg of urea, 25 kg of superphosphate and 20 kg of potassium sulfate per 667 sq m, then shallow-plow, harrow until broken up, harrow level and form ridges. The ridge width is 110 cm, the ridge surface width is 80 cm, the furrow width is 30 cm, and the furrow depth is 25 cm.

3. Sowing. The suitable sowing period for winter-planted plastic-mulched potato in the Nanyang Basin is from late December to early January. Before sowing, cut the seed potatoes into pieces according to tuber size, generally to 20-30 g per piece. Cut lengthwise so that every piece carries an eye. After cutting, spray the seed pieces with a 0.2% solution of carbendazim or chlorothalonil (100 g of the chemical in 50 kg of water) to disinfect them; spraying until moist is enough. Plant two rows per ridge in holes, with a row spacing of 40 cm and a hole spacing of 20 cm, arranged in a staggered pattern, at a density of 6000 plants per 667 sq m. With each hole, apply 30 kg of a three-element compound fertilizer containing 15% each of nitrogen, phosphorus and potassium plus 100 kg of plant ash per 667 sq m, mix well with the soil in the hole, and then drop in the seed. Sow at a depth of 6-8 cm; after sowing, water thoroughly, cover with soil, seal with herbicide and then cover tightly with plastic film.

4. Field management. (1) Help seedlings emerge through the film. In late February and early March, once the seedlings have emerged, promptly break the film to help the seedlings out. Specific method: poke a small hole in the plastic film directly above the seedling, carefully take the seedling out, then seal the plastic film at the base of the seedling firmly with soil. (2) Watering and drainage. Potato growth is generally best when the relative soil water content is kept at 60%-80%. Winter-planted plastic-mulched potato in the Nanyang Basin generally needs watering 4 times in the middle and late stages, once each at full emergence, the rosette stage, the bud stage and the tuber-setting stage. When watering, the ridge surface should be evenly and thoroughly penetrated. During the tuber-setting stage, avoid flood irrigation to prevent tuber rot. Stop watering 1 week before harvest. In low-lying land and places where water collects in the furrows, drain promptly. (3) Intertillage and earthing up. After the potatoes emerge, promptly weed and loosen the soil in the furrows and protect the integrity of the ridge surface and the plastic film. Remove the film in the late branching stage and earth up in combination with intertillage. When removing the film and earthing up, take care not to damage the functional leaves. (4) Control excessive growth. If soil fertility is high and humidity is great, and the plants show a tendency toward excessive growth with long internodes, large leaves and markedly tender, weak branches and leaves, spray 0.005%-0.01% paclobutrazol in the middle branching stage and at the bud stage; this can both inhibit plant growth and promote tuber enlargement. (5) Pest and disease control. In the middle and late stages, promptly control the 28-spotted ladybird and trap and kill underground pests. For fields prone to late blight, use Bordeaux mixture at 1:2:200 (copper sulfate:lime:water) for early control at the initial stage of the disease, and strengthen field inspection; pull out diseased plants immediately to prevent the disease from spreading. Chemical control: spray with mancozeb at 1000 times or 75% chlorothalonil at 600-800 times.

5. Harvest. Winter-planted plastic-mulched potato in the Nanyang Basin should be harvested promptly in the late tuber-bulking stage. Harvest on a sunny day when the soil is dry. Harvesting in mid-May can increase income by 0.2-0.3 yuan per kg. Finish harvesting by the end of May at the latest, so as not to affect summer harvest and summer sowing.