Analysis of Environmental Factors for Orchids: The Effect of Fertilizer on Growth

Orchidroots generally live in symbiosis with fungi, known as mycorrhiza. The fungi penetrate theorchidroots, and eventually their own tissues are absorbed by theorchidroots as nutrients. In any case, however, the nutrients supplied by the fungi are insufficient. In other words, orchids cannot rely entirely on fungi for nutrients and still need fertilization. In their natural state, orchids mostly grow in environments where the substrate (soil, sand and gravel, humus, etc.) is loose and well drained, and epiphytic orchids in particular attach themselves to rock walls or tree trunks with slight accumulations of soil or moss and gathered humus. They cannot take up too many nutrients, nor do they need too much fertilizer. Fertilizer that is too concentrated will instead harm orchids and may even cause death. This idea also appears in the ancient Chinese experience of growing orchids. For example, Yang Kui of the late Tang Dynasty held in his "On Cultivating Orchids" that if one imitated vegetable growers and "drew filthy water to irrigate them," that is, watered them with human excrement and urine, the seedlings would inevitably "suddenly wither, and the roots would soon rot." Huang Tingjian also wrote the line "water them with tea dregs and they will be fragrant." Both mean that orchids should not be given concentrated fertilizer, or death will result. This is obviously caused by toxic salts accumulating in the substrate and not being leached away properly. Early foreign orchidcultivationmanuals also held that it was enough to casually add some bone meal, clay balls, blood meal, and humus. But modern research shows that rational fertilization is very necessary for promoting orchid growth, especially for commercial production or large-scalecultivation. Orchid fertilizers can be divided into two types: organic fertilizers and inorganic fertilizers. Organic fertilizers include cattle (horse, sheep) manure, bone meal, blood meal, oilseed cakes (soybean cake, rapeseed cake, cottonseed cake, tea seed cake, etc.), humus, and so on. Inorganic fertilizers are chemical fertilizers, mainly nitrogen fertilizers (ammonium sulfate, ammonium nitrate, ammonium bicarbonate, ammonium chloride, urea, etc.), phosphorus fertilizers (superphosphate, potassium hydrogen phosphate, ammonium phosphate, monopotassium phosphate, etc.), and potassium fertilizers (potassium sulfate, potassium chloride, potassium hydrogen phosphate, etc.). In addition, trace amounts of iron (Fe), manganese (Mn), magnesium (Mg), calcium (Ca), copper (Cu), cobalt (Co), boron (B), zinc (Zn), molybdenum (Mo), etc. are also needed. Orchid fertilizers must be used with great care to avoid damaging the roots and causing death. Organic fertilizers must be fermented for 2 to 3 months before use. The dilution ratio can be based on adding 20 to 30 times water to the organic fertilizer, or even more dilute. Taking cattle manure as an example, it should be diluted until pale yellow, then clarified and the residue removed before use. Chemical fertilizers generally need to be diluted 1000 to 10000 times, that is, 0.01% to 0.1%. For seedlings, the ratio of nitrogen, phosphorus, and potassium fertilizers (referring to the ratio of actual nitrogen, phosphorus, and potassium content) is generally 3:1:1, while for mature plants it is 1:1:1. If the goal is to promote better flowering, it is 1:3:1, plus an appropriate amount of trace elements. From repeated visits to some orchid growing operations in Japan, Europe, and the United States, the author learned that they generally do not advocate using base fertilizer, fearing that if the amount is not well controlled, toxic salts will accumulate and harm the roots. Instead, they advocate using diluted liquid fertilizer sprayed on the leaf surface with a fine-nozzle sprayer; it is better to make it more dilute and apply it more often than to make it too concentrated and space the applications too far apart. Usually in spring and summer it can be applied once a day, and the dilution factor can be even greater; or it can be alternated with watering, once every 2 to 3 days, so that the water can wash away lingering fertilizer salts, causing less harm and giving better results. One must not take the lazy approach, that is, applying once a month with the concentration increased 10 times. This accords with the old Chinese experience, namely, "it is best to apply frequently and lightly, and avoid sudden heavy applications." Of course, considering difficulties such as labor and time, it can also be appropriately extended to 3 to 4 times per week. This depends entirely on thegrowermaking a decision based on actual conditions, and one must not mechanically copy the experience of others. The fertilization season generally begins in late spring and stops in late autumn, and some types can begin earlier. The best time to fertilize is when the temperature is moderate (18 to 25°C); avoid fertilizing above 30°C or below 10°C. Fertilizing when the temperature is too high will harm the orchid itself; when the temperature is too low, it will not be absorbed and the fertilizer will be wasted. (Chen Xinqi, Ji Zhanhe)