Key Technical Points for Pollution-Free, High-Yield Potato Cultivation

In recent years, with the adjustment of the agricultural planting structure and the development of high-yield, high-quality, high-efficiency agriculture, the potato planting area in our city has continued to increase. For this reason, the author and researchers from the Laiwu City Institute of Agricultural Sciences conducted research on pollution-free, high-yield, high-efficiency model cultivation techniques for potatoes, summarized pollution-free spring planting and autumn delayed cultivation techniques for potatoes, and successfully achieved a bumper harvest in pollution-free spring planting and autumn delayed cultivation of potatoes. The yield and efficiency increases were significant. The main techniques are summarized as follows.

1. Overview of the experimental site

Fengcheng Subdistrict, Laiwu City, Shandong Province, is an important pollution-free potato production base in central Shandong. The average annual temperature is 12.5°C, the average January temperature is -2.8°C, the annual precipitation is 760mm, the frost-free period is 203d, the average annual effective accumulated temperature is 4264.5°C, and the average annual sunshine hours are 2629.2h. The soil is loam with a deep soil layer, organic matter 7.3mg/kg, total nitrogen 6.5mg/kg, total phosphorus 4.5mg/kg, alkaline hydrolyzable nitrogen 49mg/kg, available phosphorus 4.8mg/kg, available potassium 136mg/kg, soil pH 6.5-7.0, and good drainage. Over three years of trials, the general yield for spring planting was 2000-2500kg/667 sq m, with high yields reaching 3500kg/667 sq m. The average yield for autumn planting was 2285kg/667 sq m, with a high selling price and good returns.

2. Main production techniques

2.1 Selection of improved varieties: Select virus-free varieties with high quality, high yield, and disease resistance, such as Luyin No. 1, Jinyin No. 8, Holland 15, Dongnong 303, Zhongshu No. 2, Taishan No. 1, Kexin No. 1, etc. Seed potatoes should be free of pests and diseases, rot, and damage.

2.2 Land preparation and fertilization: The production site should be clean and sanitary, far from areas polluted by "industrial three wastes," and should have a deep soil layer, convenient irrigation and drainage, and loose, fertile soil. Sandy loam soil is ideal, and the previous crop should not be solanaceous fruit vegetables or root and tuber vegetables. Fifteen days before sowing, apply 5000kg/667 sq m of high-quality decomposed organic fertilizer or 1000-1500kg of decomposed chicken manure and 100-150kg of potassium sulfate ternary compound fertilizer (N15%, P15%, K15%), applied in two batches: half broadcast before plowing, and half applied in bands beside the sowing furrow or in holes within the sowing furrow at sowing. To increase the supply of potassium in the soil, add 10% potassium sulfate fertilizer to the compound fertilizer. Deep plow and harrow finely twice to achieve a level ground surface.

2.3 Seed potato treatment: For spring planting, use the cut-seed potato sprouting method. Select seed potatoes free of disease and frost damage 10-15 days before sowing and cut them into pieces, each piece retaining at least 1-2 eyes, and place them in a dark, moist place to sprout. When sprouts reach 0.5-1.0cm, spread them out to air-dry the sprouts, and air-dry for 2-3 days before sowing. For sprouting autumn-planted potatoes, because seed potatoes from spring plastic tunnels are harvested too late or because spring open-field seed potatoes have not completely broken dormancy by autumn planting time, to prevent late emergence and weak plant vigor, soak whole tubers in 5-10mg/kg gibberellin aqueous solution, or cut pieces in 0.5-1mg/kg gibberellin aqueous solution, for 5-10 minutes before sprouting. After soaking, cool slightly, then pile to sprout. Sprouting can be done by the direct piling method or the sand-layer method. For direct piling, after soaking, cool the seed potatoes slightly and pile them directly in a ventilated, shaded, rain-sheltered place, about 30kg per pile, then cover with straw mats to retain moisture. Check the piles after 7-10 days; when sprouts reach 2-3cm, open the piles, remove the seed potatoes, and let the sprouts green and harden for 1-2 days before sowing. The sand-layer method uses one layer of wet sand and one layer of seed potatoes, generally 2-3cm each; other methods are the same as direct piling. During the sprouting and seedling stages of autumn-planted potatoes, the high-temperature and high-humidity climate makes diseases such as late blight and early blight prone to occur and spread, causing rotting of autumn-delayed potato beds and uneven field emergence. To prevent disease and ensure full and uniform stands, seed potato treatment must be done well. Soak seed potatoes in 500-600 times dilution of 64% Sandofan or 50% carbendazim for 15-20 minutes; alternatively, after sowing, spray the sowing furrow with the above solution or mix the chemical with soil at 1:40 and apply 5kg per 667 sq m in the sowing furrow.

2.4 Sowing dates: For spring planting, choose late February to early March. When the temperature stabilizes at 5-7°C and the soil temperature at 10cm depth reaches 7-8°C, this is the suitable period for spring potato sowing. Using plastic film mulching cultivation can increase soil temperature by 3-5°C and generally allows sowing about 10d earlier. In central Shandong, plastic film mulching cultivation is generally used from late February to early March. For autumn planting, sowing from "Start of Autumn" to "End of Heat" (August 5-15) is more suitable.

2.5 Sowing techniques: On deeply plowed and leveled plots, use wide and narrow row sowing. When sowing, the wide row spacing is 50cm, the narrow row spacing is 30-40cm, and the plant spacing is 25-30cm. For spring planting, 4000-5000 plants per 667 sq m; for autumn planting, 5000-6000 plants per 667 sq m is suitable. In principle, early-maturing varieties should be denser and late-maturing varieties sparser; fertile land should be sparser and poor land denser; early sowing should be sparser and late sowing denser; when the delay period is long and the crop is mainly for table potatoes, it should be sparser, and when the delay period is short and the crop is mainly for seed potatoes, it should be denser. Use furrow sowing; water first, then place the seed potatoes in the furrow with sprouts facing up. To control underground pests, apply 250ml of 50% phoxim per mu mixed with 10-15kg of fine soil, then cover with soil. Between two plants, apply 70kg of ternary compound fertilizer and 50kg of ammonium bicarbonate per hole. After covering with soil, earth up to form ridges 10-15cm high, then spray 150ml of 50% acetochlor emulsifiable concentrate per 667 sq m mixed with 40-50kg of water evenly to control weeds, and finally cover with plastic film. The film should be pressed down well to achieve weed control, moisture conservation, warming, and yield increase. For autumn planting, first, avoid rainy days; second, sow shallowly, with sowing depth within 5cm, to prevent rotting of seeds and sprouts from too-deep sowing combined with autumn waterlogging or rainy days; third, after sowing, cover the ground with corn stalks or shade netting to lower soil temperature and reduce soil moisture evaporation.

2.6 Field management

2.6.1 Timely film breaking and seedling inspection and replanting: For spring-planted potatoes, when young leaves are flat and open, cut the plastic film to release the seedlings, and cover the holes with fine soil. For autumn-planted potatoes, inspect seedlings promptly after sowing. For plots with severe seed potato rot and more than 50% missing plants, reselect seed potatoes, prepare the land, and sow again. For plots with fewer missing plants, replant with large green-leafed sprouts, directly digging holes and transplanting, or select vigorous seedlings from the field and pull them from the base of the seed piece for transplanting.

2.6.2 Timely hoeing and earthing up to maintain ridges: Generally, after watering and after rain, hoe promptly to loosen the soil. At the same time, after potato emergence, earth up and maintain ridges multiple times. In the later growth stage, timely earth up around exposed tubers and soil cracks to prevent tubers from turning green.

2.6.3 Fertilizer and water management: Before emergence of spring-planted potatoes, focus on raising temperature and conserving moisture, and keep the soil moist; generally do not water, but if the soil is dry, water appropriately. From full emergence to the rosette stage, focus on conserving moisture and promoting growth, and strive to topdress early, water early, and cultivate early. Topdressing should mainly use quick-acting nitrogen fertilizer, with pure nitrogen applied at 2.5-5kg per 667 sq m. From rosette stage to flowering, focus on moisture conservation; if the soil is dry, water promptly, and generally do not topdress. Before and during the early tuber bulking stage, keep the soil moist; in the late tuber bulking stage, reduce soil moisture to benefit later storage. If base fertilizer is insufficient, spray 0.2-0.3% monopotassium phosphate twice in the middle and late growth stages to prevent premature senescence. At the bud and flowering stages, for fields showing excessive vegetative growth, spray 20-25g of 15% paclobutrazol per 667 sq m mixed with 40-50kg of water to prevent lodging. To increase yield, spray tuber swelling agents at the beginning of tuber bulking to promote tuber expansion.

2.6.4 Autumn delayed plastic tunnel covering and management techniques: Use bamboo strips or small bamboo poles as arches. Generally, bamboo strips 4cm long are used, arching over 4 rows of potatoes. Small bamboo poles can be joined end to end at the smaller ends, with no need for support posts. The tunnel should be completed before October 20, that is, before the arrival of early frost, and tunnel materials should be prepared in advance. Cover the tunnel film when daytime temperatures fall below 15°C and nighttime temperatures fall below 7°C. In our city, early frost generally arrives after October 20, so cover the tunnel promptly according to weather changes. Maintain 20-25°C inside the tunnel during the day and 10-15°C at night. Regardless of the weather, ventilate during the day. When outside daytime temperatures are above 20°C and nighttime temperatures are above 10°C, remove the film all day. When daytime temperatures are above 15°C and nighttime temperatures are 7°C, ventilate all day. When outside daytime temperatures are below 15°C and nighttime temperatures are below 7°C, ventilate appropriately by opening the vents gradually from small to large during the day, then from large to small, to avoid frost damage. If humidity inside the tunnel is too high, ventilate promptly to remove moisture. On frost-free sunny days, ventilate early.

2.6.5 Timely control of pests and diseases: Control of viral diseases: strengthen field management and prevent high temperature and drought. In the early stage of disease, spray 500 times dilution of 20% Virus A or 1000 times dilution of 1.5% Zhibingling emulsifiable concentrate.