Shed vegetable winter spring å’‹ fertilization

Producing vegetables in the shed, artificially creating conditions for warming and warming, avoiding disastrous weather and making vegetables ripe and productive. However, the shed greenhouse has a large amount of fertilizer, is tightly closed, and has weak light. The nitrate reductase activity in vegetables is low, and it is easy to accumulate nitrate. Therefore, in order to reduce the nitrate content in shed vegetables, the following problems should be noted when fertilizing in winter and spring.

First, increase the application of organic fertilizer

It is best to apply organic fertilizer with a high content of cellulose, which can greatly enhance the nutrient buffering capacity of the soil, prevent salt accumulation and delay the process of soil salinization, but the organic fertilizer must be decomposed to prevent the transmission of pathogens and eggs to vegetables. In addition, if the organic fertilizer is re-cooked in the greenhouse, ammonia will be produced and the "burn" seedlings will be produced.

Second, the application of nitrate nitrogen fertilizer is prohibited

The nitrate nitrogen fertilizer includes ammonium nitrate, potassium nitrate and a compound fertilizer containing nitrate nitrogen. The application of these fertilizers tends to accumulate nitrates in vegetables. In addition, it is not suitable to apply a chlorine-containing chemical fertilizer such as potassium chloride or ammonium chloride in the greenhouse. This is because chloride ions can reduce the starch and sugar content in vegetables, reduce the quality of vegetables, and when the chloride ion content in the soil is too high, it is easy to make the soil calcium deficient and compact. Fertilizers such as magnesium sulfate and ammonium sulfate are also not suitable for large-scale application in the shed, because the application of these fertilizers into the soil will decompose sulfate ions, which will not be absorbed by vegetables, and will endanger the growth of vegetables when it accumulates too much. It is forbidden to apply ammonium bicarbonate. Because ammonium bicarbonate is volatile, a large amount of ammonia gas causes ammonia damage to greenhouse vegetables.

Third, control the amount of nitrogen fertilizer application

The application of nitrogen fertilizer in greenhouse vegetables is conducive to the growth of vegetables, but not excessive. Generally, 10-12 kg of pure nitrogen per mu is suitable. Nitrogen fertilizer should be applied in combination with phosphorus and potassium fertilizer, or ternary compound fertilizer should be applied, and soil should be covered in time after application. It is best to use the fertilizer intubation or combined with the drip irrigation under the membrane to apply roots to reduce the loss. However, the top dressing should be stopped 20 days before the harvest. Because of the good degree of airtightness, the greenhouse can easily fertilize the fertilizer by spreading or shallow fertilization, which not only reduces the fertilizer efficiency but also easily causes the ammonia gas hazard. When applying fertilizer, it is necessary to apply a hole or a strip, and the depth should be 5-6 cm.

Fourth, the implementation of formula fertilization

The period when the different vegetable varieties require the most fertilizer is also different. For example, 30-52 days after transplanting, the pepper is 30-60 days after transplanting, and the cucumber is about 75 days after transplanting. In addition, each vegetable has a suitable ratio of nitrogen, phosphorus and potassium three elements, such as 1:0.67:1.83 for cucumber, 1:0.38:1.75 for tomato, and 1:0.38:1 for sweet pepper. . Although the demand for trace elements in vegetables is extremely small, it is indispensable. The concentration and standard should be mastered when using micro-fertilizer foliar spray. For example, ferrous sulfate is 0.1-0.3%, zinc sulfate is 0.05-0.2%, borax is 0.3-0.5%, and copper sulfate is 0.02-0.04%. Note that leafy vegetables are best not to foliar spray, so as not to increase nitrate content. Generally, vegetables require a large amount of nitrogen and potassium, and require less phosphorus. It is not advisable to apply more diammonium phosphate. Potassium is required before and after flowering, and gradually decreases afterwards.