What technical principles should be followed for soil testing and fertilizer application in celery?
Celery belongs to the Apiaceae family. There are three types: water celery, dry celery, and western celery. Their functions are similar, but dry celery is better for medicinal use. Dry celery has a stronger aroma and is called "medicinal celery". However, it is not the same species as cilantro. Celery is rich in protein, carbohydrates, carotene, B vitamins, calcium, phosphorus, iron, sodium, etc. At the same time, it has the effects of calming the liver and clearing heat, dispelling wind and promoting diuresis, relieving restlessness and reducing swelling, cooling blood and stopping bleeding, detoxifying and dispersing lung qi, strengthening the stomach and promoting blood circulation, clearing the intestines and relieving constipation, moistening the lungs and stopping cough, lowering blood pressure, and calming the mind. Regularly eating celery, especially celery leaves, is very beneficial for preventing high blood pressure, arteriosclerosis, etc., and has auxiliary therapeutic effects.
Fertilizer requirement: Celery has a high nutrient uptake during the peak vegetative growth period. During this period, the absorption of the five elements nitrogen, phosphorus, potassium, magnesium, and calcium accounts for more than 84% of the total absorption. Celery has the highest demand for nitrogen, followed by calcium and potassium, and the least for phosphorus and magnesium. Celery also has a large demand for boron. When soil is deficient in boron or absorption is inhibited by drought and low temperature, the leaf stalks are prone to transverse cracking, known as "stem break disease", which seriously affects yield and quality.
Fertilization: Under medium fertility levels, the fertilizer application rate for celery throughout the entire growth period per mu is 2500-3000 kg of farmyard manure (or 350-400 kg of commercial organic fertilizer), 13-16 kg of nitrogen fertilizer, 5-6 kg of phosphate fertilizer, and 6-9 kg of potassium fertilizer. Nitrogen and potassium fertilizers are divided into base fertilizer and three topdressings, with a fertilization ratio of 2:3:3:2. Phosphate fertilizer is all applied as base fertilizer. Chemical fertilizers and farmyard manure (or commercial organic fertilizer) are applied mixed together.
Base fertilizer: Apply 2500-3000 kg of farmyard manure or 350-400 kg of commercial organic fertilizer per mu, 4-5 kg of urea, 11-13 kg of diammonium phosphate, and 4-5 kg of potassium sulfate.
Topdressing: After seedling recovery, during the heart leaf growth period, apply 6-8 kg of urea and 3-4 kg of potassium sulfate per mu; in the early stage of vigorous growth, apply 8-11 kg of urea and 3-5 kg of potassium sulfate per mu; in the mid stage of vigorous growth, apply 6-8 kg of urea and 3-4 kg of potassium sulfate per mu.
Foliar topdressing: If heart rot is found, spray the leaves with 0.3%-0.5% calcium nitrate or calcium chloride. Foliar spraying of boron fertilizer can avoid stem cracking to a certain extent. Spray 40-75 kg of 0.2% borax or boric acid solution per mu each time. In protected cultivation, carbon dioxide gas fertilizer can be added. Pang Qiujuan