Where the dilution factor is the larger number of the fertilizer injector ratio and the conversion constant C is determined by the units desired: Unit If you know the rate of fertilization (in ppm N), the percentage of nitrogen in the fertilizer, and the injector ratio, then calculations are simplified by the following formula: Amount of fertilizer to make 1 volume of stock solution Without recourse to tables or bags, growers can use formulas to calculate the amount of fertilizer needed. Information is also provided on fertilizer bags. Most of the manufacturers of commercial fertilizers and fertilizer injectors have produced tables that simplify this task. Growers must accurately determine the amount of fertilizer needed to mix stock solutions of fertilizers. The preparation of fertilizer stock solutions is of paramount importance. Many growers prefer injectors with adjustable ratios so that different fertilizer rates can be applied to crops with different nutrient requirements. Some injectors (Hozon, Smith Measuremix) have a fixed (nonadjustable) injector ratio whereas other injectors (Anderson, Dosmatic, Dosatron, M-P Mixer Proportioner) have adjustable ratios. Thus, the injector ratio determines the concentration of the stock solution that is needed to deliver a particular rate of fertilization. If both injectors were to deliver 200 ppm of nitrogen from the same fertilizer, the stock solution for the 1:200 injector would have to be twice as concentrated as the one for the 1:100 injector. A 1:200 injector will deliver 200 gallons of dilute fertilizer for each gallon of concentrated stock solution (or 100 gallons of dilute solution per ½ gallon of stock). For example, a 1:100 injector will deliver 100 gallons of dilute fertilizer solution for each gallon of concentrated stock solution. This is important for standardizing fertilizer recommendations since the percentage of nitrogen varies markedly among the water-soluble N-P-K fertilizers sold commercially.įertilizer stock solutions are mixed according to the fertilizer injector ratio: each injector will deliver a certain amount of stock solution for each increment of irrigation water that passes through the injector. Thus, the advantage of parts per million terminology is that we can state the concentration of a fertilizer solution independent of the fertilizer analysis. But what actually does this mean? If we use a fertilizer such as 20-20-20 with 20% nitrogen, 13½ ounces are needed to make 100 gallons of a 200 ppm N solution, whereas with a 15-15-15 fertilizer containing 15% nitrogen, 18 ounces are required to make 100 gallons of a 200 ppm solution. For example, it is often recommended that 150 to 250 ppm N be applied in the irrigation water on a "constant feed" basis for fertilizing many floricultural crops. Parts per million is a convenient unit of measurement for indicating the concentration of fertilizer solutions. Rates of fertilization are often given in parts per million (ppm) of nitrogen (N). Additionally, most growers apply water-soluble fertilizers at a dilute concentration on a "constant feed" basis (with every watering) to insure an adequate supply of the essential elements for plant growth. Applying fertilizers in a liquid form with a fertilizer injector is more convenient than broadcasting or top-dressing with dry fertilizers. These devices "inject" a small quantity of concentrated fertilizer solution ( stock solution) into the irrigation line so that the water leaving the hose ( dilute solution) supplies the proper concentration of fertilizer. Fertilizer injectors are used by most growers to apply water-soluble fertilizers to plants. Some nutrients (such as calcium and magnesium) may be mixed into the growing medium prior to planting, but most of the nutrients are applied after planting using water-soluble fertilizers. Proper fertilization of greenhouse crops is essential for producing high-quality plants.
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