Key Technical Points for Early Spring Greenhouse Cultivation of Potatoes
???? Plot Selection, Fertilization and Land Preparation
1. Plot selection:
To achieve high quality and high yield of potatoes, it is very important to choose soil suitable for potato growth. The plot for planting potatoes should meet the following two basic conditions:
First, choose slightly acidic sandy loam or loam soil that is fertile, flat, convenient for irrigation and drainage, with deep soil layers and loose texture for cultivation.
Second, choose a plot where potatoes, tomatoes, peppers, eggplants and other Solanaceae crops have not been cultivated within three years, to reduce the occurrence of pests and diseases. The previous crop is best to be legumes, cruciferous plants, cereals and other crops. For example, using soybean, rapeseed, scallion or garlic as the previous crop can also effectively prevent the harm of bacterial bacterial wilt.
Third, plots where herbicides such as chlorimuron-ethyl, fomesafen, metsulfuron-methyl, chlorsulfuron, tribenuron-methyl or atrazine have been sprayed on the previous crop cannot be planted with potatoes within 1-3 years.
2. Land preparation and fertilization:
The amount of fertilizer applied has a great relationship with soil type and fertility. Generally, for medium-fertility soil, the total amount of fertilizer per mu is 35-50 loads of decomposed farmyard manure, (15-15-15) 45% potassium sulfate compound fertilizer 100-150 kg, and bio-organic fertilizer 100 kg. For greenhouse potato cultivation, the required fertilizer is generally spread in two applications: one as base fertilizer before plowing, and the other as seed fertilizer during sowing. Generally, no additional topdressing is applied during the growth period.
After the fertilizer is prepared, deep plowing of the land should be carried out before the Beginning of Winter. Before plowing, spread the farmyard manure all at once, and spread half of the per-mu amount of the ternary compound fertilizer and bio-organic fertilizer separately. Then plow deeply about 30 cm, so that the soil is frozen and weathered, reducing overwintering pests.
Greenhouse Construction and Film Covering
Early spring protected cultivation of potatoes mostly adopts a three-film cultivation method. Generally, ridges are made according to the width of the greenhouse (6 ridges, 8 ridges, 10 ridges) as one arched shed. Greenhouses include steel-frame greenhouses, bamboo-pole greenhouses and multi-span greenhouses. The greenhouse body is best oriented north-south and arranged east-west.
The greenhouse should be completed and covered with greenhouse film 15-20 days before potato sowing, to facilitate soil thawing and increase ground temperature.
Film covering: For the greenhouse film, anti-drip film with a thickness of 0.06-0.12 mm is mostly selected. Usually a three-piece film covering method is adopted. The junction between the top film and the skirt film should overlap by 20-30 cm, with the top film pressed on the outside of the skirt film. The part of the skirt film touching the ground should be sealed and pressed with soil. The film-pressing lines between two arches should be tightened and fixed. When covering the greenhouse film, choose windless weather to avoid wind, which is not conducive to covering the film or may tear the greenhouse film.
For the second film, it is best to choose polyethylene film with a thickness of about 0.03-0.04 mm, placed on the arch frame about 40 cm from the top film of the greenhouse. In this way, a "warm-shell inner" type "greenhouse within a greenhouse" is formed. When the second film is not in use, it can be fixed on one side of the arch frame with plastic rope.
? Seed Potato Selection and Treatment
1. Variety selection:
For early spring potatoes, early-maturing varieties with early tuber formation, fast tuber expansion, short dormancy period, high yield, good quality and disease resistance are generally selected. Such as Holland No. 7, Holland No. 15 and Holland No. 803, with companion planting varieties including Zaodabai, Zhongshu No. 3, Zhongshu No. 5, Youjin 885, etc. Virus-free seed potatoes must be certified, and it is absolutely forbidden to use commercial potatoes as seed potatoes for cultivation.
Generally, early spring potato seed potatoes have undergone long-term cellar storage, so their internal temperature is relatively low, physiological functions are inhibited, and the seed potatoes are in a dormant state. If they are taken out of the cellar and immediately sprouted and sown, seedlings often emerge slowly and unevenly, affecting yield. Therefore, seed potato treatment should be carried out before sowing to break dormancy and facilitate earlier seedling emergence.
2. Sunning seed potatoes
There are many methods of seed potato treatment, and sunning to awaken the potatoes is a relatively common method. Generally, 150 kg of seed potatoes are needed per mu. Choose a sunny day and place the selected seed potatoes in sunlight at a temperature of 12-15°C for pre-awakening, prompting the potatoes to break dormancy. During sunning, turn them once a day so that the seed potatoes are evenly exposed to light. During turning, remove mixed seed potatoes with abnormal tuber shapes, such as rotten potatoes, soft black-rot diseased potatoes, deformed potatoes, old potatoes, potatoes with necrotic buds, frost-damaged potatoes, etc. After sunning for 2-3 days, they can be cut according to tuber size for sprouting.
3. Sprouting of seed potatoes
Sprouting before sowing is an important measure for early spring potatoes to come to market earlier. It can not only promote early seedling emergence of potatoes, but also advance the potato growth period by 7-10 days, which is helpful to avoid high temperature and aphid damage. It is a key technique for spring seed potato production. The sprouting time is generally about 25 days before the local suitable sowing period for potatoes. Sprouting methods include cut-seed sprouting and whole-tuber sprouting. Cut-seed sprouting breaks the apical dominance of the seed potato (tuber), and after cutting, the buds on each piece receive similar nutrient conditions, so sprouting is fast and relatively uniform in size. At the same time, cutting is also a process of eliminating diseased potatoes. It not only enables young sprouts to root quickly, but also makes seedlings emerge early and uniformly, which is conducive to high yield, so it is widely used in production.
(1) Cutting: The time for cutting is preferably 1-2 days before sprouting. If too early, the cut pieces lose too much water or cause seed rot.
(2) Tool disinfection: For the cutting tools, one person needs to prepare two knives and use them alternately, and before cutting, place them in 75% alcohol or 0.5% potassium permanganate solution for disinfection.
(3) Cutting method: Because the yield of plants grown from tail buds of potatoes is very low, only one third of that from top buds or side buds. Therefore, when cutting for high-yield potato cultivation, the tail buds should be removed. Generally, seed potatoes below 50 g can be sown whole, only removing the tail buds; for seed potatoes of 50-100 g, after removing the tail buds, cut vertically into two halves; for seed potatoes of 100-150 g, first cut off one third from the tail, then split from the top bud, thus cutting into 3 pieces; for seed potatoes above 150 g, from the tail, according to the number of buds, cut the seed potato diagonally along the longitudinal direction according to the buds into several small three-dimensional triangular pieces. The cut should be close to the bud eye, which can stimulate early sprouting and facilitate early seedling emergence.
When one knife is used for cutting, the other knife should be soaked in disinfectant solution for disinfection, and the knife should be changed after cutting each seed potato. When cutting diseased or rotten potatoes, stop immediately, immerse the knife in the prepared disinfectant solution for a second disinfection, then switch to another knife to continue cutting, to prevent the spread of diseases during cutting.
The cut pieces should be uniform in size, generally 25-30 g each, and each piece should retain at least one healthy bud eye.
Spread the cut seed pieces in a sheltered, sunny place and dry the cut surfaces to promote wound healing. To avoid infection of the cut surfaces by pathogens, and at the same time prevent seedling-stage diseases and underground pest damage, it is best to dress the seeds with chemicals.