What are the key points for autumn field management of carrots?

Carrot (Daucus carota), also known as ganxun, is a biennial herbaceous plant of the genus Daucus in the Apiaceae family. Its fleshy root is eaten as a vegetable. It originated in southwestern Asia, with Afghanistan as the earliest center of evolution, and has a cultivation history of more than 2,000 years.

Morphological characteristics of carrot The carrot has a taproot system, with the main roots distributed within a 20-90 cm soil layer and reaching 180-250 cm deep. The upper part of the taproot, including a small portion of the hypocotyl, thickens to form a fleshy root that extends below the soil surface, with four rows of slender lateral roots growing on it. The fleshy root shape may be round, oblate, conical, cylindrical, etc. Root color may be purple-red, orange-red, pink, yellow, white, or green. It is mainly composed of secondary phloem, with a small xylem called the core. The exterior of the taproot is smooth. The leaves are clustered on a shortened stem and are tripinnate compound leaves. The petioles are slender, the leaves are dark green, the leaf area is small, and the leaf surface is densely covered with fine hairs. After the fleshy root is stored over winter, it bolts and flowers. The main bolt appears first, followed by lateral branches. Each flowering branch is composed of many small umbels forming a large compound umbel. A single plant often has more than a thousand small flowers. The flowering period is about one month. The flowers are complete, white or pale yellow, and insect-pollinated. The fruit is a schizocarp that splits into 2 at maturity, generally mistakenly called a seed. It is oval, leathery, and densely covered with bristles on the longitudinal ribs. The embryo is very small and often poorly developed or absent, with poor emergence ability, and the germination rate is as low as about 70%. A biennial herb, 15-120 cm tall. The stem is solitary, with white coarse stiff hairs throughout. The basal leaves are membranous, oblong, bipinnate to tripinnate, with the final segments linear or lanceolate, generally 5-15 mm long and 0.5-4 mm wide, with sharp tips and small mucros, smooth or with rough stiff hairs; the petiole is 3-12 cm long; the cauline leaves are nearly sessile, with leaf sheaths, and the final segments are small or slender. Compound umbels, the peduncle 10-55 cm long, with rough stiff hairs; the involucre has many bracts, leaf-like, pinnately divided, rarely undivided, the segments linear, 3-30 mm long; the rays are numerous, 2-7.5 cm long, and the outer rays curve inward when fruiting; the involucel bracts are 5-7, linear, undivided or 2-3-lobed, with membranous margins and cilia; the flowers are usually white, sometimes tinged with pale red; the pedicels are unequal in length, 3-10 mm long. The fruit is round-ovate, 3-4 mm long and 2 mm wide, with white bristles on the ribs. The flowering period is from early May to mid-July. Autumn is a critical period for carrot growth, and strengthening field management is crucial.

1. Sowing: Carrot is one of the main autumn vegetables. It is sown around the Beginning of Autumn, usually by broadcasting. Generally, the seeding rate for bare seeds is 1.5 jin per mu, and for hairy seeds it is 2-3 jin per mu. After sowing, rake the bed surface and press it firmly with the feet.

2. Thinning and hoeing weeds: Thin for the first time when there are 1-2 true leaves, with a plant spacing of 3 cm. Then hoe shallowly to remove weeds and preserve soil moisture, promoting seedling growth. The second thinning is at 3-4 true leaves, and final thinning is at 4-5 leaves. For small and medium varieties, the plant spacing is 10 cm; for large varieties, the plant spacing is 13-15 cm, and a second cultivation is carried out.

3. Irrigation and fertilization: In the seedling stage, promote first and then control. After the "root-setting stage," when the root head of the fleshy root is about as thick as a finger, it is the period of fastest fleshy root growth. Water should be applied in time to keep the soil constantly moist, and watering should be stopped half a month before harvest. Carrots are generally topdressed 2 times. The first topdressing is carried out 20-25 days after emergence, when there are 3-4 true leaves, generally applying about 15 jin of urea, 18 jin of superphosphate, and 5 jin of potassium chloride per mu; the second topdressing should be carried out at final thinning 40-50 days after emergence, generally applying 20-25 jin of urea, 8 jin of superphosphate, and 8 jin of potassium chloride per mu.

First, thin in time and strengthen cultivation and weed control. Throughout the whole growth period, carrots need to be thinned twice. The first thinning is at 1-2 true leaves, then hoe shallowly to remove weeds and preserve soil moisture, promoting seedling growth. The second thinning is at 3-4 true leaves, and it is best to use this to final-thin. For small and medium varieties, the plant spacing is 10 cm; for large varieties, the plant spacing is 13-15 cm, and cultivation is carried out. Reasonable close planting is one of the important measures for high carrot yields. If the density is too high, plants easily shade each other, photosynthesis weakens, and especially the lower leaves tend to senesce early, ultimately leading to reduced yield.

Second, scientifically manage fertilizer and water. Water must not be lacking at the emergence stage, and the soil should be kept moist. Too dry or too wet is unfavorable for seed germination and emergence. During the growth period, topdressing should be applied 2-3 times. The first topdressing is carried out at the carrot soil-breaking stage, combined with watering, applying 1000 kg of decomposed human manure or 20 kg of urea per mu. After 20 days, apply the second or third fertilizer, each time applying 15-20 kg of urea, and appropriately adding a small amount of potassium fertilizer. When entering the period of vigorous leaf growth, water should be appropriately controlled to prevent excessive growth.

Third, harvest in good time. The carrot growth period is generally 100-130 days. In the central-southern Hebei region, harvesting in late October to early November is suitable. Too early will affect yield, and too late makes them prone to freezing and unsuitable for storage.