Key Points of High-Yield Cultivation Techniques for Autumn-Planted Potatoes

I. Seed Potato Selection

For autumn-planted potatoes, first, choose varieties with strong stress resistance, especially those resistant to high temperatures; second, choose varieties with a short dormancy period (dormancy period of 30-40 days); third, choose early-maturing and extremely early-maturing varieties that form tubers early, such as Dongnong 303, Favorita, Zhongshu No. 1, etc. They can all be harvested 60 days after emergence, and some can be harvested 45 days after emergence.

For autumn-planted potatoes, it is best to plant small whole seed potatoes, each weighing about 25 grams. If large potatoes are used as seed potatoes, they should be cut into pieces and sprouted before germination.

II. Seed Potato Treatment

1. Cutting. Autumn potato cutting should be carried out under cool conditions to avoid seed rot. 7-10 days before sowing, select single potatoes that are free from disease and damage and weigh 70-80 grams as seed potatoes, use a sharp knife to cut vertically downward along the apical bud into 3-4 pieces, each piece must have 1-2 bud eyes, and the cut surface should be close to the bud eyes. The cutting knife must be disinfected to prevent the spread of pathogens. When cutting potatoes, if diseased potatoes with brown vascular bundles are found, they should be removed. As you cut, wash off the starch slurry seeping from the cut surface with cool water (preferably well water) to promote wound healing and prevent piece rot.

2. Soaking seeds. Soaking with gibberellin (920) can break the dormancy period and promote germination. The method is: use whole potato soaking or cut-piece soaking. For whole potato soaking, soak with 10-20 ppm gibberellin for 30 minutes; for cut-piece soaking, soak with 0.5-2 ppm gibberellin for 5-10 minutes. Before soaking, wash the starch at the cut surface clean with clear water; after soaking, remove the cut pieces and place them in a cool place to air-dry for 4-8 hours. Do not expose them to direct sunlight to avoid seed rot. The gibberellin solution can be reused for soaking 4-5 times. Note that the gibberellin dose should not be too large to prevent excessive vegetative growth after sowing.

3. Sprouting. Choose a ventilated, cool, empty room that does not receive direct sunlight, or build a shade shed outdoors under tree shade for the sprouting bed. Spread clean wet sand on the ground (moderately wet, so that it forms a ball when squeezed tightly by hand and breaks apart when the hand is released), about 10 cm thick, with a bed width of 1 m. During sprouting, the potato pieces can be arranged close together on the sprouting bed, with the bud eyes facing up. First arrange a layer closely at the bottom without overlapping, then cover with a 3 cm thick layer of wet fine soil or yellow sand. Then arrange one layer of potato pieces and one layer of fine soil or sand, arranging up to three layers in this way, and finally press the bed surface firm. Cover the top with rice straw or plastic film to keep warm, maintain the bed temperature at 25-28°C, and keep the humidity such that the surface soil is not too dry. If the bed sand soil is too dry, sprinkle a small amount of cool water with a watering can to maintain moisture, and sprouts will emerge after 4-6 days. For whole potato sprouting, the potato pieces do not need to be covered with sand soil; simply cover the potato pieces with a layer of wet straw bag. When the sprouts grow to 0.5-1 cm, they can be taken out for sowing. If the weather is bad, place them under scattered light for 2-3 days to make the sprouts green and sturdy, then sow them in the field.

III. Sowing Methods

1. Timely sowing. Autumn potato sowing occurs in early autumn. If sown too early, the temperature is too high and the potatoes are prone to rot; if sown too late, the growth period is shortened, which affects yield. Generally, when the average daily temperature drops below 25°C, sowing is relatively safe. Generally, August 25 to September 10 is the suitable sowing period. Early-maturing varieties such as Favorita and Zaodabai can be sown in mid-September, and extremely early-maturing varieties such as Zhongshu No. 1 can have their sowing period postponed to the end of September. In mountainous areas where the temperature is lower, sowing can be appropriately earlier, so that the early growth stage catches up with the already cooler October, the plants grow vigorously, and the later stage of tuber formation in the lower-temperature November just suits the growth characteristics of potatoes, thus forming more tubers and achieving high yield.

2. Cooling and protecting seedlings. At sowing time, the surface soil temperature of the bed is often above 35°C during the day, which is not suitable for seedling growth; if drought occurs during land preparation, it is advisable to irrigate 2-3 days before sowing. After the soil is thoroughly wet and loosened, plow and prepare the land and make beds to keep the soil moist. Choose cloudy and rainy days or early morning and evening to open furrows and sow. When sowing autumn potatoes, the bud eyes should face downward, and the sowing depth should be kept at 10-15 cm; too shallow is unfavorable for emergence. After sowing, cover the bed surface with melon vines, green grass, rice straw, etc., which can provide shade and cooling, prevent drought and preserve moisture, and prevent erosion by sudden rain and soil crusting. In this way, seedlings emerge quickly and uniformly, ensuring full and strong seedlings.

3. Reasonable close planting. Autumn potatoes grow quickly and form tubers early. The aboveground plants do not grow as vigorously as spring potatoes and are not prone to excessive growth, so the sowing density should be appropriately increased. Proper close planting can not only make full use of light and soil fertility and increase yield, but also promote more stems and leaves. A thicker soil covering layer can cool and moisturize the field soil, which is beneficial to growth and improves seed quality. The row spacing for autumn potatoes is generally 35-40 cm, and the plant spacing is 18-22 cm, with 7000-9000 hills planted per mu. Lean land can be planted more densely than fertile fields.

IV. Field Management

1. Water and fertilizer management. Autumn potato sowing occurs in a high-temperature and dry season. If there is no rain after sowing, irrigate once every 3-5 days to lower the soil temperature and promote early and good emergence. After the seedlings emerge, if the weather continues to be dry, still irrigate frequently with a small amount of water to keep the soil moist and promote stem and leaf growth. Entering the tuber formation stage, the climate gradually becomes cooler, the stems and leaves close the rows, and plant transpiration and ground evaporation are small; keeping the soil moist is sufficient, and do not irrigate unless the furrows dry. If continuous rainy weather occurs, do a good job of drainage.

Autumn temperatures gradually decline and sunshine shortens, which is unfavorable for stem and leaf growth. Therefore, after full emergence, promptly topdress fertilizer to promote plant growth. Apply 15 kg of ammonium sulfate and 5 kg of urea per mu. Strive to have the aboveground stems and leaves of autumn potatoes close the rows in early to mid-October. According to measurements, 0.5 g of spring potato stems and leaves produces only 0.5 kg of tubers, while 0.5 g of autumn potato stems and leaves can produce 1 kg of tubers. Therefore, in autumn potato management, measures to promote stem and leaf growth are very important for increasing yield.

2. Cultivation and earthing up. In order to meet the needs of autumn tuber development, timely cultivation and earthing up should be done to maintain low soil temperature and moisture. Throughout the entire growth period of autumn potatoes, cultivation and earthing up are generally done 2-3 times: the first earthing up after emergence, 3 cm thick; after 10-15 days, stolons begin to grow, and the second earthing up is about 6 cm thick; after another 10-15 days, the third earthing up. Each time earthing up, combine it with cultivation and topdressing to increase soil aeration, promote stolon formation at each node, increase the tuber-bearing layer, and raise yield.

3. Spraying potassium dihydrogen phosphate. Spraying 0.3%-0.35% potassium dihydrogen phosphate at the full flowering stage of potatoes can increase yield by 15%-20%. It is best to spray twice in succession, the first time at the full flowering stage, and again after 7-10 days, using 50 kg of 0.35% potassium dihydrogen phosphate solution per mu each time.

V. Pest and Disease Control

1. Pest control. There are many pests that harm potatoes. Generally, pests that harm solanaceous vegetables can all harm potatoes. The main ones are the 28-spotted ladybird beetle, cutworms, white grubs, etc. Among these pests, the most serious are aphids and white grubs. In the early stage of aphid occurrence, spray with 2.5% deltamethrin diluted 2500 times with water, and the effect is relatively good.

To prevent white grubs, dissolve 500 g of 90% crystalline trichlorfon in water and spray it onto 35 kg of fine soil, then apply it into the planting holes or seed furrows at sowing time; this amount can be used for one mu of field.

2. Disease control. The main diseases harming potatoes are late blight, bacterial wilt, ring rot, and viral diseases. For viral diseases, ring rot, and bacterial wilt, these are generally overcome by selecting disease-resistant varieties, producing virus-free seed potatoes, and implementing reasonable crop rotation, avoiding continuous cropping with solanaceous vegetables.

Late blight is the most widespread disease in China and the most serious disease harming potatoes. In the early stage of the disease, spray with 400-500 times diluted carbendazim and mancozeb solutions, used alternately, once every 7-10 days, for a total of 2-3 times, which has a relatively good control effect.