The correct method for applying chemical fertilizers to orchids

OrchidsFor normal growth, development and flowering, orchids need not only a certain amount of light, ambient humidity, moisture in the potting medium, clean air and appropriate temperature, but also correct fertilization methods to regulate their nutritional needs during growth. Apart from the three major nutrient elements nitrogen, phosphorus and potassium, trace elements (iron, boron, zinc, molybdenum, manganese, copper, etc.) are also indispensable. First, nitrogen is the basic substance that makes up proteins and is also a main component of chlorophyll, enzymes, ribose, vitamins and alkaloids; phosphorus is an indispensable element in many phospholipid compounds and enzyme molecules; potassium can improve the colloidal state of protoplasm and the degree of photosynthesis, enhance the plant's stress resistance, reduce disease and prevent lodging. These three major elements, nitrogen, phosphorus and potassium, are vital to plant survival, so inorchidfertilization they are the first consideration: urea is an ideal nitrogen fertilizer; for phosphorus and potassium fertilizer, potassium dihydrogen phosphate is preferable (though other phosphorus and potassium fertilizers are not excluded). Urea is also called carbamide, with a nitrogen content of 44-46%, and is a neutral fertilizer. After application, it can only be absorbed by plants after being converted into ammonium carbonate through the action of urease secreted by microorganisms. Its conversion rate is related to humidity and temperature; when humidity is adequate, the higher the temperature, the faster the conversion. When the biuret content in urea does not exceed 1% (or is lower), it has a stimulating effect onorchidgrowth; when it exceeds 2%, it becomes toxic. Applying urea as a foliar fertilizer is both economical and effective, with a spray concentration of about 0.5%. Potassium dihydrogen phosphate can prevent premature senescence of functional leaves, enhance photosynthesis and promote the formation of carbohydrates. Using potassium dihydrogen phosphate as a foliar fertilizer is relatively ideal, with a concentration of 0.1-0.2% being suitable. Trace element fertilizers (including fertilizers of iron, boron, zinc, molybdenum, manganese, copper, etc.) are also essential nutrients for the normal growth and development of orchids: because iron (Fe) can directly or indirectly participate in the formation of chloroplast proteins, and many respiratory enzymes in plants contain iron; iron can promote plant respiration and accelerate physiological oxidation. The commonly used iron fertilizer is ferrous sulfate, and it is better to apply it mixed with organic fertilizer (such as green manure or fermented pig urine water), mixing only just before use; it must not be soaked together with organic fertilizer for a long time, because the oxides produced during soaking are toxic to orchids. Ferrous sulfate can also be sprayed as a foliar fertilizer at a concentration of 0.2%; boron (B) plays a certain role in the growth of roots, stems and other organs, the development of young meristematic tissues, and flowering. Boron can also accelerate the transport of carbohydrates, promote photosynthesis and the metabolism of nitrogen in the plant, and can also enhance disease and drought resistance. For boron fertilizer, boric acid is best, containing 17% boron; it is a white crystal, easily soluble in water, and its aqueous solution is weakly acidic, with a foliar spray concentration of 0.1%; zinc (Zn) is a component of enzymes in plants and can promote photosynthesis, respiration and the synthesis of carbohydrates; the formation of chlorophyll and auxin in plants is related to zinc. Zinc can enhance drought, cold, salt and disease resistance. The commonly used zinc fertilizer is zinc sulfate (ZnSO4-7H2O), containing 23% zinc; ZnSO4·H2O contains 35-40% zinc; the genuine product is a white crystal, and the foliar fertilizer concentration is a 0.05% zinc sulfate solution; molybdenum (Mo) enables the absorption and utilization of nitrogen, especially nitrate nitrogen (it can only combine with organic acids to form amino acids and then synthesize proteins after being reduced to ammonium nitrogen). Molybdenum can increase the activity of phosphoric acid and promote the synthesis and transport of sugars and starch in plants. It can alleviate plant chlorosis caused by excessive manganese, zinc or copper in the soil or by iron deficiency, and is beneficial to photosynthesis. The commonly used molybdenum fertilizer is ammonium molybdate, containing 54% molybdenum, with a foliar spray concentration of a 0.02-0.05% ammonium molybdate solution. When applying molybdenum fertilizer, attention should be paid to residual toxicity and controlling the amount used. The role of manganese (Mn) in plants is multifaceted; it is related to the activities of many enzymes, is an enzyme activator, and participates in photosynthesis, nitrogen transformation, carbohydrate transfer and some oxidation-reduction processes. The commonly used manganese fertilizer is manganese sulfate, containing 24-28% manganese. Manganese sulfate can have several different numbers of water of crystallization, for example, 3, 4, 5, 6, 7... molecules of water of crystallization. The foliar fertilizer concentration is a 0.05% manganese sulfate solution; copper (Cu) is the core element of the activation group of various oxidase enzymes in plants and plays an important role in catalyzing oxidation-reduction reactions. Copper can promote the formation of chlorophyll, and copper-containing enzymes are related to protein synthesis. The commonly used copper fertilizer is copper sulfate, containing 24-25% copper, easily soluble, and for foliar spraying a 0.02% copper sulfate solution is used. Fertilization timing: for nitrogen, phosphorus and potassium fertilizers, apply once every 2-3 weeks in May-June and from late August to early October; for iron and boron fertilizers, apply 2-3 times in May-June and once in September; for molybdenum, manganese and copper fertilizers, apply 1-2 times in May-June; for zinc fertilizer, apply once in mid-to-late May. Variegated varieties (editor's note: that is, striped-leaf orchids) should be given little or no nitrogen fertilizer. Fertilization should be carried out when sunlight and temperature are suitable; do not fertilize on cloudy and rainy days, and it is also unsuitable to fertilize when the temperature is below 12°C or above 30°C. Feng Guoqing