The use of plastic film to cover the cultivation of vegetables in greenhouses artificially creates conditions for warming and heat preservation, avoiding the catastrophic climate, accelerates the process of fertility, and makes vegetables ripe and productive. However, due to the accelerated production cycle of vegetables, the amount of fertilizer required is larger than that of open vegetables, and the amount of fertilizer is generally higher than 50%.
With the increase in the amount of fertilizer applied to shed vegetables, there are often problems in the process of fertilization, especially in winter and early spring, some problems are more obvious. First, the amount of fertilizer applied is too large, so that the concentration of soil solution increases, the reverse osmosis phenomenon occurs in vegetables, and the roots and lags appear; the second is the application of chemical fertilizers, especially nitrogen and phosphate fertilizers, resulting in imbalance of vegetable nutrition ratio; When urea and ammonium bicarbonate are applied, it is difficult to convert the fertilizer to the nitrate state, the vegetable is forced to absorb a large amount of ammonium nitrogen, and the ammonium poisoning hazard occurs; the fourth is the shallow application or application of urea and ammonium bicarbonate, which also causes the ammonia to volatilize. Intoxication of vegetable stems and leaves.
In order to improve the fertilization level of shed vegetables in the winter and early spring growth stages, the following four points should be noted in the technical aspects.
First, regulate the base fertilizer topdressing. In order to prevent the amount of one-time fertilizer from being too large, the base fertilizer should be applied and the fertilizer should be applied at the right time. Generally, the proportion of base fertilizer should account for 60% of the total fertilizer application, and the phosphate fertilizer can be increased to 70% due to slow decomposition. The fertilizer for nitrogen and potassium should be 40%. High-quality farm compost and manure should not exceed 5000 kg per mu. High-quality organic compound fertilizer is generally 75 kg per mu, and should not exceed 100 kg.
Second, increase the application of organic fertilizer. Organic fertilizer can not only improve the soil, improve the ability of retaining fertilizer and water retention, but also make the fertilizer release steadily, and also adjust the pH of the balanced soil. In addition to the application of fertilizers produced by farmers, it is also strongly recommended to apply bio-organic fertilizers and refined active organic fertilizers such as Huimanfeng and Diledan. This kind of organic compound fertilizer can supply a large amount of elemental fertilizer, a variety of trace elements, supplement the organic matter to improve the soil, inhibit the damage of some pests and diseases in the soil, and avoid the fertilizer damage caused by concentrated soil fertilization.
Third, the shallow topdressing is prohibited. Due to the good degree of airtightness in greenhouse vegetables, shallow fertilization or spreading of fertilizers can easily cause the fertilizer to volatilize, which not only reduces fertilizer efficiency but also causes ammonia hazard. When topdressing, one must apply or apply a depth of 5-6 cm. Second, keep a distance of 8-10 cm from the root of the vegetable.
Fourth, suitable temperature to apply nitrogen fertilizer. Nitrogen fertilizers, especially urea and ammonium bicarbonate, are easily absorbed by vegetables only when converted to nitrate nitrogen. The external cause of temperature is temperature. When the temperature in the shed is lower than 15 °C, nitrifying bacteria and activities will be inhibited. Therefore, the topdressing nitrogen fertilizer should be selected around noon on a sunny day, too early or too late will reduce the effect of topdressing due to low temperature. It is recommended to use a 0.5-1.0% concentration of urea solution to fertilize the root when it is above 15 °C.
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