Gardening and Growing Tips Shared: Practical Experience to Help You Avoid Detours

Since the nutrient concentration orchids need is only 1/4 to 1/6 of that of most fast-growing plants, understanding the composition of the water used for watering orchids is essential. Although fresh, unpolluted rainwater is best, it may be hard to obtain. The assessment of a water source can be divided into two parts: 1. Total salt content 2. Analysis of the content of various salts Salt content: A fairly accurate and practical method for measuring the salt content of water is to measure the water's electrical conductivity (EC). Pure water conducts almost no electricity, but most salts dissolved in water do conduct electricity, and the water's conductivity or electrical conductivity is directly related to the concentration of salts in the water. The unit for measuring conductivity can be MHOM (the reciprocal of the resistance unit ohm) or expressed as siemens (S). For orchid water, the conductivity you measure is very small, just a few millionths of a siemens, called microsiemens, expressed with the symbol μS; 50 means 50μS, 100 means 100μS. The instrument used to measure conductivity is called a conductivity meter. Instruments commonly used to measure the conductivity of liquids fall into two categories: one type reads in MHOM (μS); the other type reads total dissolved salts (TDS). TDS is calibrated with a coefficient and reflects parts-per-million content (PPM). But TDS obscures the fact that different salts have different conductivities (for example, urea dissolved in water conducts almost no electricity). In horticulture, the conductivity unit siemens is mostly used, but urban water source analysis reports mostly use TDS to express analysis results. The two readings can be converted easily; roughly, 1000μS is equivalent to 666 TDS. The choice of conductivity meter can be based on the type of plant you grow. For orchids, a reading range of 1-1999μS with temperature compensation is fairly ideal, because conductivity is affected by temperature. Since orchids require a lower nutrient concentration, using water with a low salt content is very important. The table below gives a water quality assessment for orchids: Water conductivity Assessment ====================== Below 50μS Very good 50-100μS Good 100-200μS Acceptable Over 200μS Poor Analysis of the content of various salts: The content of various salts in water is just as important to us as the total salt content. In developed countries, some orchid or other plant associations provide their members with analysis results of the content of various salts in the local water source. The unit of the data provided is PPM, that is, the number of milligrams of a certain salt contained per liter of water. Water in many regions is fairly hard, meaning the salt content is relatively high, and most of it contains relatively high levels of calcium and magnesium carbonates. For example, most areas of northern China with little rain. Excessive calcium and magnesium will be toxic to orchids. It is not hard to understand that using water with a low salt content allows us to better control the balanced nutrition of orchids. By the way, a reminder to our orchid-growing friends in the north: adding organic acids (oxalic acid, citric acid, etc.) to water to neutralize the alkalinity of hard water carries a certain risk! True, these organic acids can indeed lower the water's conductivity at the same time, but conductivity cannot reflect the content of all salts, such as the urea mentioned earlier. Adding other salts to water that is already too high in salt does not seem appropriate, and I hope everyone acts with caution. Since I am shallow in learning and scant in talent, please criticize and correct any inappropriate points in this article. Beijing Du Xiao