Vegetables are hi calcium crops. People tend to pay attention to the application of nitrogen, phosphorus, and potassium fertilizers when planting, but they do not pay attention to the application of calcium fertilizers. With the emergence of a large number of facility cultivation, soil calcium deficiency is more likely to occur in greenhouses.
According to experiments, when producing greenhouse vegetables, rational use of calcium fertilizer can generally increase production by 10% to 20%. The application of calcium fertilizer to vegetables can increase the calcium content of the plant, maintain the appearance of bright color for a long time, and obviously improve the appearance quality and intrinsic quality. In addition, calcium deficiency is an important cause of illness and rot in many vegetables.
There are many reasons for the crop's calcium deficiency: the low content of available calcium in the soil can not meet the requirement of vegetables for calcium; the high salt content in the soil inhibits the absorption of moisture and calcium by the root system, especially in the strong red soil and yellow soil In loam soil, the absorption of calcium by vegetable roots is severely affected; the concentration of soil solution is too high, or there is a large amount of ammonium nitrogen, which impedes the absorption of calcium in vegetable roots; the soil in shallow layers, especially the sandy soil, has poor water retention and fertility. The loss of calcium is large; in the case of large-scale application of nitrogen fertilizer, excessive nitrogen fertilizer will reduce the effectiveness of soil calcium. With the slow movement of calcium in the plants, the nutritional problems of calcium deficiency in vegetables have become a prominent issue in cultivation.
In general young vegetables, young leaves and young tissues and fruits are very susceptible to calcium deficiency. The symptoms are as follows: the newly emerged parts of plants, such as apical buds and root hairs, become stagnant and atrophic; the new leaves adhere and often do not expand normally. Edge, incomplete; plants dwarf soft, internode shortening; fruit prone to depression, dark brown necrosis; growth point necrosis when severe calcium deficiency.
The use of calcium supplements for vegetables requires a reasonable selection of calcium fertilizers. Different calcium fertilizers have different properties. The pH value of the soil in the greenhouse is mostly 6.5 to 7.5. Alkaline substances or neutral fertilizers such as slaked lime, calcium nitrate, etc. should be used instead of acidic or physiological acidic substances. Ordinary phosphate fertilizers such as superphosphate, calcium magnesium phosphate, and heavy superphosphate are all important calcium sources. In addition, bone powder, plant and wood ash all contain a certain amount of calcium, which is also a non-negligible source of calcium. It is recommended to use calcium-containing trace nutrient water-soluble fertilizer (not less than 120g/L for calcium, not less than 20g/L for magnesium, not less than 50g/L for zinc, not less than 3g for boron, etc.) L)) Calcium is supplemented with other trace elements at the same time. Attention should be paid to the use of fertilizers with low EC (salt concentration) to make crops safer.
The second is to determine the appropriate period of fertilization. After the vegetables enter the prosperous period, the soil calcium nutrition began to decrease, while the calcium in the leaves began to decrease. At this time, the application of calcium fertilizer is the best period. Therefore, in the production of calcium deficiency in the early stage to prevent the growth of vegetables, basic application can be adopted. In greenhouses planted for many years, generally, 2000-3000 kg of decomposed organic fertilizer is applied to Mushi, and then superphosphate is added to 30-45 kg.
The third is targeted selection of fertilization methods. For heavier exposed or greenhouse vegetables, the method of replanting the basal fertilizer is used, ie 100 kg of wood ash per acre or 50 kg of hydrated lime is used to regulate the pH of the soil. The specific approach is to spread the organic fertilizer with hydrated lime or ash, evenly applied to the surface of the ground and plowed into the ground. For growing vegetables, especially after entering the vigorous growth period, the calcium fertilizer can be supplemented by topdressing. Generally, 40 to 60 kg of hydrated lime is used per mu. The amount of lime used in sandy soil is appropriately reduced, not only adding calcium, but also It is beneficial to neutralize soil acidity, increase pH, and improve soil pellet structure. 80 kg of mature lime or 50 kg of plant ash can also be used to uncover the end of the membrane. The depth of the trench is 10 cm. The fertilizer is applied to the bottom of the trench and watered. Cover the membrane with the earth under water after infiltration. Or deep plowing and the use of plastic film cover cultivation methods to enhance its ability to retain water and fertilizer, maintain relatively stable soil moisture, reduce calcium loss. Can also be combined with disease-prevention spray using foliar fertilizer topdressing calcium, top dressing concentration of 0.3% to 0.5% is appropriate. Generally can be sprayed with 0.1% to 0.2% of calcium nitrate or 1% of superphosphate, spraying once every 15 days or so, even spray 3 to 4 times, the effect is good.
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