Detailed explanation of pollution-free high-yield cultivation techniques for Jimsar white-skinned garlic

Garlic is a biennial herbaceous plant of the genus Allium in the Liliaceae family, semi-cold in nature, and prefers cool climatic conditions. Seedlings can withstand low temperatures of -10°C, the suitable temperature for sprouting is 16-20°C, and high temperatures above 30°C will force dormancy; the suitable temperature for garlic bulb growth is 12-25°C. Garlic is a shallow-rooted crop, with roots mainly concentrated in the 5-25 cm tillage layer, and a lateral spread diameter of about 30 cm. It grows best on sandy loam soil.

I. Natural conditions

The mountainous area of Jimsar County is the production base for Jimsar white-skinned garlic, located in the inversion temperature zone on the northern slope of the Tianshan Mountains, warm in winter and cool in summer, with a frost-free period of 120-140 days. It has excellent light conditions, humid air, an average July temperature of 17.8°C, a maximum temperature of 29°C, and annual precipitation of 230-240 mm. The base has large areas of irrigated chestnut-yellow soil, which is relatively loose in texture, rich in organic matter, and has good drainage, water retention and fertilizer retention performance, suitable for garlic growth. Within 3000 meters around the base there are no industrial or mining enterprises or other pollution sources, and it is far from highways and main roads with heavy traffic. It is sprinkler-irrigated with Tianshan snowmelt water, the farming and livestock structure is relatively reasonable, there is plenty of organic fertilizer, pesticide use is low and of short duration, and the soil is uncontaminated, enabling garlic production to meet the standards for pollution-free vegetables.

II. Pre-sowing preparation

1. Soil selection and crop rotation arrangement

Garlic has weak root absorption capacity and is suitable for planting in plots that are rich in organic matter, level, loose, fertile and convenient for irrigation. Soil that develops alkali return in spring is not suitable for planting garlic. Garlic should not be continuously cropped, nor should it be continuously cropped after chives, onions, Welsh onions and other crops; it should be rotated with a 2-3 year interval. Legumes, cucurbits, potatoes, Chinese cabbage types, root vegetables and solanaceous fruits can all serve as ideal preceding crops.

2. Fine cultivation, applying sufficient basal fertilizer, and light topdressing

After the preceding crop is harvested, carry out autumn plowing and winter irrigation, with a plowing depth of 20-30 cm. Before land preparation, apply 2500 kg of fully decomposed high-quality organic fertilizer, 50 kg of diammonium phosphate and 20 kg of potassium chloride per 667 sq m. Mix the fertilizer thoroughly with the tillage layer soil. Store sufficient bottom moisture water before winter, and in early spring carry out shallow plowing and fine harrowing to bring the land into a ready-to-sow state. Organic fertilizer must be composted through high-temperature piling for harmless treatment to kill pathogens and insect eggs in the manure, so as to prevent the odor released by undecomposed raw manure from attracting adult garlic maggots to lay eggs beside the plants, which after hatching enter the soil layer and damage the garlic.

3. Improving sowing quality

① Seed selection Select plants with pure variety, no pests or diseases, plump and round bulbs, consistent external color, similar number of cloves, and uniform size as seed garlic. During storage, seed garlic must never be subjected to freezing or heat. For garlic intended for export bases, seed cloves should preferably be large cloves or cloves larger than 4 grams, and the stem heel at the base of the clove should be removed to facilitate water absorption and rooting and sprouting after sowing. For soil with relatively high salinity and alkalinity, it is best not to peel off the garlic skin, in order to reduce saline-alkali damage.

② Seed soaking First method: Use 30% carbendazim wettable powder or 25% carbendazim aqueous solution, add water to make a 500-fold solution, soak the seed garlic for 24 hours, air-dry the moisture and sow immediately. 1 kg of medicinal solution soaks 1 kg of seed garlic. Second method: Before sowing, sun-dry the seed garlic for 2-3 days, then soak it in 40°C warm water for one day and night, changing the hot water 2-3 times during this period to maintain the water temperature; after removing, air-dry for 4-6 hours, then sow. Third method: Before sowing, soak the seed in 0.3% diammonium phosphate aqueous solution for 6 hours, and sow immediately after soaking. The above seed soaking methods can be selected as needed and need not all be used, but note: soaked seed garlic is only suitable for wet sowing, not dry sowing; in arid areas with poor irrigation conditions, seed soaking before sowing is not advisable. At sowing, apply 7-10 kg of diammonium phosphate as seed fertilizer per 667 sq m, scatter it into the furrow, cover with soil and compact.

③ Sowing period When the surface soil thaws and the daily average temperature steadily rises to 3-5°C, begin sowing, that is, around 5 days before and after Qingming as the suitable sowing period for garlic; sowing should be completed by April 20 at the latest.

④ Reasonable close planting The suitable density per 667 sq m is 20,000-30,000 plants, with a plant spacing of 8-11 cm and a row spacing of 20 cm, and the seed rate per 667 sq m should not exceed 30,000 cloves. Large-clove garlic should be sown sparsely, small-clove garlic densely; leaf-spreading varieties should be sown sparsely, leaf-upright compact varieties densely; fertile soil should be sown sparsely, poor soil densely.

⑤ Sowing method Mechanically open furrows, make a multi-row furrow opener, fix the row spacing, and sow by hand dibbling. When sowing, never pinch the top of the seed clove with your hand and press it hard into the soil, so as to avoid crushing and injuring the seed garlic. The sowing depth should preferably be 3-5 cm; large cloves are sown deep, small cloves shallow. Orientation of seed cloves: in addition to placing cloves according to the determined plant spacing, the dorsal-ventral line of the clove should be parallel to the row direction, and north-south row orientation should be used as far as possible. The cloves in each sowing row should be staggered in coordination with one another. After sowing, use the back of a rake to lightly rake along the furrow direction, level the furrow and cover with soil, and water promptly to promote rooting, compact the soil, and prevent garlic cloves from popping out.

III. Field management

1. Management during the germination period

Seedlings emerge 10-20 days after sowing; during this period the soil is generally required to be moist to promote rooting and sprouting. In principle, do not water or water less, and carry out more intertillage and weeding to keep the soil dry on the surface and moist below. However, when bottom moisture is insufficient and seedlings cannot emerge in time, a small watering can be given, followed by timely intertillage.

2. Management during the seedling period

The seedling period lasts 25-30 days. During this period, the soil temperature should be appropriately lowered to promote deeper root development and prevent excessive seedling growth. In the early stage, focus on intertillage to preserve moisture and delay the end of mother clove nutrient supply. In the later stage, increase fertilizer and water to promote seedling growth. When seedlings have 2-3 leaves, carry out the first intertillage and weeding, which should be deep intertillage, and after 4-5 days carry out one shallow intertillage. At the 4-5 leaf stage, the mother clove nutrient supply ends; combine watering and fertilizing to accelerate seedling growth. During this period, spray 1%-2% monopotassium phosphate on the leaves and apply 5-10 kg/667 sq m of diammonium phosphate as topdressing; if the soil is fertile, do not topdress.

3. Management during the differentiation period of bulb buds and flower buds

This period lasts about 10 days and is a key period in garlic growth, when growth speed accelerates and nutrient uptake increases. Keep the soil moist; if dry tips appear on the aboveground part, water promptly.

4. Management during the garlic scape elongation period

This period is when garlic has the greatest growth amount and also requires the most fertilizer and water. Water frequently, once every 5-6 days, to keep the soil moist; stop watering 3-5 days before harvesting scapes to avoid making the scapes too brittle. When the scape tail emerges, combine watering and fertilizing, spray 1%-2% monopotassium phosphate or microbial fertilizer on the leaves, and remove weeds promptly. The morphological standard for harvesting garlic scapes at the proper time: the top of the scape bends, the spathe begins to swell, the color changes from green to white, and 4-5 cm at the leaf sheath turns light yellow. When harvesting scapes, protect the functional leaves as much as possible, especially the top 1-2 leaves, which have the strongest physiological function at this time and have the greatest effect on bulb swelling. If they are broken off casually when harvesting scapes, bulb yield will be affected.

5. Management during the garlic bulb swelling period

This period is key to determining garlic bulb yield and marketability. The management goal is to prevent premature senescence, prolong the life of late-stage functional leaves and roots as much as possible, and promote bulb swelling. After harvesting scapes, water to promote bulb growth, replenish soil moisture, apply 20 kg of diammonium phosphate per 667 sq m as topdressing, and spray 50-60 kg of 2% monopotassium phosphate as foliar fertilizer, then spray again after 7 days. Stop watering 10 days before harvest, and prohibit watering and using urea before harvest, in order to improve garlic marketability and storage time.

IV. Harvest

1. Morphological characteristics of garlic bulbs at the proper harvest time

Most basal leaves of the plant have dried up, while 3-4 green leaves remain on the upper part; the leaf color is grayish green, leaf tips are dry, the pseudostem is soft, and the outer skin is dry, tough but not brittle. Generally, this morphology is reached 17-20 days after scape harvesting.

2. Harvest method

At harvest, to reduce damage to garlic bulbs, dig them up by hand. Arrange them in rows, trim off the fibrous roots, then lay the garlic leaves of the back row over the bulbs of the front row and dry them in place. After 2-3 days, braid them, then transport them back to a cool place to dry in the shade, so as to complete the after-ripening and drying process.

V. Pest and disease control

1. Garlic viral disease

Also called mosaic disease, mainly transmitted by aphids and thrips; virus-free garlic should be used as seed.

2. Purple blotch

Before sowing, soak seeds in 50-fold solution of 40% carbendazim suspension for 4 hours; at the early stage of disease, spray 600-fold solution of 50% thiophanate wettable powder, or 500-fold solution of 70% mancozeb wettable powder.

3. Rust disease

At the early stage of disease, evenly spray 1000-fold solution of 70% mancozeb wettable powder + 2000-fold solution of 15% triadimefon wettable powder; alternatively use 1600-fold solution of 16% triadimefon wettable powder, spraying once every 10 days for two consecutive sprays.

4. Garlic nematode disease

① Before sowing, first soak seed garlic in warm water for two hours, then place it in 50°C hot water for 11-20 minutes. ② Before sowing, soak seeds in 1000-fold solution of 90% trichlorfon crystals for 24 hours.

5. Garlic maggot control

① Use fully decomposed organic fertilizer, or during composting evenly spray 800-1000 fold 90% trichlorfon, then pile and compost. Carry out autumn plowing and winter irrigation; when pest damage is severe, evenly spray 90% trichlorfon crystals on plants and the ground. ② Drench roots with 2000-fold solution of 2.5% deltamethrin emulsifiable concentrate, or other pyrethroid pesticides, or 1000-fold solution of 40% phoxim emulsion. ③ Trap and kill with sugar-vinegar liquid. Mix sugar, vinegar, alcohol and water in a ratio of 3:3:1:10, add 1/10 part of 90% trichlorfon to make a mixed liquid, divide it into bowls, place 8-10 per 667 sq m, and add vinegar once every other day.

VI. Storage

Choose a ventilated and dry indoor space or build a shed outdoors in a high and dry area, set up hanging storage racks inside the shed, and hang fully dried garlic bulbs or garlic braids on the racks. During storage, keep the indoor temperature at 2-10°C; 2-5°C is safest, and garlic must never be subjected to freezing, heat or moisture.