Coriander prefers cold climate to high temperature, and stops growing when the temperature exceeds 30℃. So, how can we grow coriander well in summer?
1, variety selection. Choose varieties with heat resistance, late bolting and fast growth, such as Beijing coriander and North China big leaf.
2. Soil preparation and fertilization. Choose a plot with fertile soil, good water and fertilizer conservation performance, good water irrigation and waterlogging drainage, and good permeability, which has not been planted with coriander for more than 5 years, and must not be replanted. Every 667 square meters (1 mu), 4000 kilograms of decomposed farm manure and cake fertilizer 100 kilograms were applied. The residues of previous crops should be removed to reduce the occurrence of pests and diseases. Deep ploughing and fine harrow should be used to make the border, and the width of the border should be 1- 1.5 meters and the length should be 8- 10 meters.
3. Soak seeds to accelerate germination. The sowing date of planting coriander in summer is not strict. Generally, it is sown in May-June and harvested 40-50 days after sowing. Before sowing, seeds should be soaked to accelerate germination, which can ensure the emergence of seedlings evenly and quickly. Method of accelerating germination: Soak the seeds in clear water for 24-30 hours, take them out and spread them on wet and pollution-free sacks with a thickness of 2-3 cm, and cover them with wet sacks. When the temperature is 20-25℃, stir 1-2 times a day to keep the seeds with certain moisture, and sprout and sow after 3-4 days.
4. broadcast seedlings. It is better to sow coriander in summer. After sowing, seedlings can cover the border, reduce water evaporation and reduce the temperature between the surfaces. The sowing method is "sow two beds first and leave one bed". Place the mulch soil on the two sides of the reserved border, then fill it with water, sow it evenly after water infiltration, cover the soil with 2 cm after sowing, and then sow the left empty border in the same way as sowing first. The amount of seeds used per mu is about 2 kg. After all the broadcasts, conduct a suppression to preserve soil moisture. If the weather is dry and the soil humidity is low, it will affect the emergence of seedlings, and it can be watered once with small water.
5. Field management. When the height of the seedlings is 4-5cm, the seedlings should be thinned and weeded, and the spacing between the seedlings should be 2-4cm. After thinning seedlings, combine irrigation to chase thin manure water once. When the seedling height is 7-8 cm, the first fertilization should be applied. At this time, the amount of fertilization should be large, and 20-30 kg of ammonium sulfate should be applied topdressing per mu. Keep the soil moist, water it every 4-5 days, and take shade to cool down. In summer, coriander can be harvested in batches in combination with thinning seedlings.