Enhancing the soil with nutrients is a requirement for healthy plant growth. Using the proper fertilizing methods is necessary to this end, but deciding which fertilizer to use can open a hornets nest of questions and predicaments. Honing in on the correct application amounts, timing and type of fertilizers requires thorough consideration.
All packages of fertilizer are labeled with three numbers which indicate the percentage of nitrogen, potassium and phosphorus included in the bag. Water-soluble nitrogen, denoted by the initials WSN, is in a simple form which dissolves rapidly. WIN, or water-insoluble nitrogen, is a slow-release nitrogen source. Ammonium nitrate, ammonium sulfate, calcium nitrate, and potassium nitrate are water-soluble types of nitrogen. WSN becomes available to the plant as soon as it comes into contact with soil water. Generally, nitrogen in an organic form, which must be broken down by soil microorganisms, dissolves slowly. The exception to this is urea, an organic fertilizer that quickly converts to an available form of nitrogen.
Water-soluble plant fertilizers have a strong leaching capacity. To maximize plant uptake, application should coincide with the time of optimum plant receptivity. Because fall application tends to lead to water degradation, an application of fertilizer in the spring, followed by small additional applications as needed, allows the plant the best chance for utilizing nutrients. Fertilizer should be placed at the root zone to minimize loss of nutrients due to leaching, runoff and off-gassing. Excess irrigation from rain or sprinklers will also increase leaching.
Because water-soluble fertilizers are usable by the plant immediately, quantity of application should be considered. Over-fertilization can cause burning, even death to the plant, as well as leaching and waste. It is better to provide smaller, frequent applications, than one large dose.
When confronted with a particular nutrient lack, a foliar spray of that nutrient can be used. Generally in a water soluble form, foliar sprays address issues in a short term manner. In order to correct the problem in the long run, corrections must be made at the soil level.
Water soluble fertilizers, when applied incorrectly are particularly subject to runoff, leaching and vaporizing. Runoff and leaching, under certain circumstances, are major sources of water pollution. Overuse and incorrect time of application allow seepage into the ground and surface waters. Excess fertilizer in ground water is responsible for birth defects and other health disorders. Correct application amounts, as well as accurate timing minimize these problems.