In recent years, along with the needs of foreign trade export and processing, China's anti-season spring sowing carrot area has been increasing. However, due to improper selection of spring planting varieties and uncomfortable cultivation techniques, it often leads to large-area convulsions and a large number of deformed roots. Bring a lot of economic losses. The author summarizes the cultivation experience in recent years, and describes the causes of spring sowing of carrot twitches and the reasons for the increase in deformities and preventive measures.

I. Causes of convulsions and prevention

Carrots are chloroplast vernalization long-day crops, according to different varieties of low temperature sensitivity in different, can be divided into easily deflated varieties, more resistant to blister varieties and resistant varieties. The easy-to-tethered varieties can undergo flower bud differentiation when they have 4 to 5 true leaves or even 2 to 3 true leaves at the seedling stage, and then flower and bud under long-term sunshine conditions in May and June. According to research by Japanese scholars, the "Kuroda Five-inch" type seedlings encounter the risk of convulsions at low temperatures below 10°C for more than 360 hours. The lower the temperature, the longer the duration of low temperature, the higher the convulsive rate, up to 90 %the above.

According to the author's understanding, spring sowing varieties in most regions in China are still selected for the Japanese autumn sowing variety "New Black Five-inch" or the Kuroda five-inch series. These varieties are all easily convulsed varieties, so to avoid losses, the spring sowing needs to select varieties that are insensitive to low temperature and resist seizures.

Second, the causes and prevention of deformity

The malformed roots of carrots often have bifurcations, cracked roots, bends, knobs, green shoulders, long hair roots, and color variations. The formation of carrot fleshy root requires good soil conditions, cultivation techniques and climatic conditions. If the cultivation layer is too shallow, the soil is rough and there are stones, or the application of organic fertilizer is not decomposed, easily lead to bifurcation, bending; soil viscosity is not easy to breathe, easy to produce nodules, fibrous roots; uneven water supply during growth, dry Humidification can easily lead to the increase of cracking roots; the plough layer is too shallow, and the root enlargement phase does not pay attention to soil, and the root enlargement phase is prone to high temperatures in July and August, resulting in the accumulation of carotenoids, lycopene, and color variation. White or yellow.

Therefore, in order to obtain high quality and high yield of spring sowing carrots, sandy soil with loose soil and fertile soil should be selected. The depth of the tillage layer should not be less than 25cm. The base fertilizer should be applied with decomposed organic fertilizer, and the water supply should be even during the growth period and be in the fleshy quality. In the early days of root enlargement, pay attention to earth. The suitable temperature for carrot root expansion is 18-25°C, so the spring planting in the northern part of North China is generally conducted from late March to April 10. The southern and central parts of North China should be completed from mid-March to early April. The region needs to select a suitable sowing date based on the local temperature.

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