1, temperature: carrot is a semi-cold-resistant crop, and its cold resistance and heat resistance are stronger than radish, so it is safe to cultivate it in the open field in our city for the winter. Carrot seeds can germinate at 4 ~ 6℃, but the optimum germination temperature is 20 ~ 25℃. Suitable growth temperature: daytime 18 ~ 23℃, nighttime 15 ~ 18℃. Growth is blocked above 25℃ and stagnated below 3℃.
2. Nutrients: In the whole growth and development process, potassium is absorbed the most, followed by nitrogen and calcium. The absorption ratio of N∶P∶K∶Ca∶Mg is100 ∶ 40 ~ 50 ∶150 ~ 250 ∶ 50 ~ 70 ∶ 7 ~10, so we should pay attention to the rational use of potassium fertilizer in carrot fertilization technology. Calcium magnesium phosphate should be selected as the phosphate fertilizer.
3. Soil: Carrots have similar requirements for soil conditions as radishes, and sandy loam with rich organic matter, deep soil layer and pH value of 5 ~ 8 is the best.
4. Moisture: The root system of carrot is developed, the leaves belong to 3-4 pinnate compound leaves, the leaf area is small, the water loss is less, and it is more drought-tolerant; When the soil is too wet, tumors and fibrous roots are easy to grow on the surface of tuberous roots, and the number of root cracks increases; However, excessive drying affects the yield and the texture of fleshy roots becomes hard; Generally, 60% of the maximum water capacity in the field is appropriate (kneading into strips by hand is extrusion dispersion).
Second, high-yield cultivation techniques of carrots in spring
(1) variety selection
At present, the varieties suitable for planting in spring and meeting the requirements of export processing are: New Kuroda Five-inch Ginseng, Li Hongwu-inch Ginseng, Hongyi and Xiawu-inch Ginseng.
(2), land selection and land preparation
1. site selection requirements: considering the quality requirements, we should choose a good environment and pollution-free area for development; In recent years, the soil with high pesticide residues, such as carbofuran, is no longer suitable for the production of export processed carrots. Judging from the characteristics and growth conditions of carrot, it belongs to root vegetables, and the size and quality of fleshy roots are closely related to soil texture. Therefore, we should choose to plant on silty loam or sandy loam with high terrain, good drainage, deep soil layer, brittle texture and high organic matter content. For example, when planting in cohesive soil, the amount of farm manure should be increased, or a certain amount of chaff ash should be applied during ploughing. In addition, ridging cultivation is also an effective measure to prevent soil from being wet and sticky, which can significantly improve yield and quality.
2. Soil preparation and fertilization: The yield of "New Black Field Five-inch Ginseng" is high, and the fleshy root is more than 20 cm long. Therefore, the ploughing depth should be controlled at 25~30 cm, and it is best to plough deeply with animal power before winter. Before sowing, combine applying base fertilizer and ploughing again; The dosage of base fertilizer is: 3000 ~ 4000 kg of decomposed farm manure per mu, 50 kg of potassium sulfate compound fertilizer, 50 kg of calcium magnesium phosphate fertilizer and 25 kg of potassium sulfate. It is required to be evenly buried in the soil layer below 6 cm from the topsoil. The frame width is 1 10~ 130 cm, and the frame height is 30 cm, which is slightly turtle-backed.
For plots with poor drainage and heavy soil, ridge farming can be carried out. Ridge farming has the following advantages: when it rains, it is beneficial to drain water and reduce humidity, and avoid waterlogging; Increasing soil permeability can make carrots with high quality and high yield and reduce root cracking. The key points of its cultivation are: first, plough the whole layer according to the depth of 25~30 cm, and then make flat-topped ridges according to the height of 15 ~ 20 cm, and the width of ridges and ditches is 20 cm. 2 rows of seeds with a ridge top width of 30 cm and 3 rows of seeds with a ridge top width of 40 cm. Basic fertilizers such as organic fertilizer should be buried under the ridge. After ridging, according to the row spacing of 15 cm, a sowing ditch with a depth of 2 cm was opened at the top of the ridge.