What are the correct fertilization methods for greenhouse vegetables?

Fertilizing is essential for vegetable growth. There are now a great many fertilizers: open-field fertilizers, greenhouse fertilizers, chemical fertilizers, organic fertilizers, farmyard manure, foliar fertilizers, with a wide variety of types. But fertilizer used in greenhouses must not be applied carelessly; apply it wrongly and the losses can be huge. So how do you fertilize vegetables correctly in a greenhouse?

Because protected vegetables grow in a favorable microclimate and develop well under artificial regulation, they can be produced all year round and yields are very high. Therefore, they consume large amounts of fertilizer, and the same vegetable has different nutrient requirements at different growth stages.

Owing to the microclimate conditions, fertilization differs from open-field practice and has the following characteristics:

1. Volatile chemical fertilizers are prohibited. Because greenhouses are well sealed and ventilation is minimal during winter cultivation, applying volatile chemical fertilizers produces toxic gases that harm both people and vegetables.

2. Unrotted organic fertilizer must not be applied. Unrotted organic fertilizer contains pathogens and insect eggs, and unrotted chicken manure also produces large amounts of ammonia gas, harming people and vegetables.

3. Apply more organic fertilizer. Organic fertilizer can increase soil vitality and also prevent salt accumulation. Apply less of chemical fertilizers such as potassium nitrate, potassium chloride and magnesium sulfate, which are easily adsorbed by the soil and form concentration obstacles.

Organic fertilizer has a relatively low mineral content and a slower fertilizer effect, but its nutrient content is complete, its fertilizer effect lasts a long time, and it does not easily cause salt accumulation in the soil. It is therefore the main type of fertilizer for greenhouse vegetables and is mostly used as a base fertilizer.

Chemical fertilizers have a relatively single mineral nutrient content, but a relatively large concentration, a fast nutrient release rate and a short fertilizer effect duration, and are used in smaller amounts in production. In greenhouse production, to reduce soil salt damage and nitrate accumulation pollution in vegetables, the amount of chemical fertilizer must be controlled even more; therefore, chemical fertilizers are mostly used as a top dressing.

In production, top dressing is mostly carried out 3~7 days before the key fertilizer-demand period of the vegetable. Fruit vegetables are mostly top-dressed in time after fruit set and before swelling, while leafy vegetables are mostly top-dressed during the vigorous leaf cluster growth period.

Soil nutrients vary greatly among different regions. Soils in southern regions are generally deficient in boron, soils in northern regions are generally deficient in nitrogen, and nitrogen deficiency is most severe in the northwest region. Trace element deficiencies are mostly addressed by foliar spraying.

As a vegetable grower, you must understand the land, understand fertilization methods, and know what crops your land is suitable for growing and what kind of fertilizer to apply. Only in this way can you manage the greenhouse well, plant crops suited to your own land, and let this land bring the greatest economic benefit.