Fertilizer
The analysis or grade of a fertilizer refers to the minimum amounts of nitrogen (N), phosphorus (as P2O5), and potassium (as K2O) in the fertilizer, and is always printed on the bag, can, or bottle. A 10-10-10 fertilizer would represent 10 percent nitrogen, 10 percent P2O5, and 10 percent K2O. Therefore, in 50 pounds of 10-10-10, there are 5 pounds of N, 5 pounds of P2O5, and 5 pounds of K2O.
Fertilizers may be divided into two broad groups, organic and inorganic or chemical. An organic fertilizer is derived from a living plant or animal source. Nitrogen in an organic fertilizer is slow to become available for plant use because the organic nitrogen (NH2) must be reduced (converted) by micro-organisms to ammonium (NH4) or nitrate (NO3). The NH4 and NO3 forms are useable by plant roots.
Inorganic or chemical fertilizers are either mixed or manufactured and have the advantage of lower cost. High analysis, rapid solubility, and availability necessitate some caution when applying these fertilizers.
Slow-release fertilizers may be either inorganic or organic. They are characterized by a slow rate of release, longer residual, low burn potential, low water solubility, and higher cost.
There are several fertilizer categories of slow-release nitrogen fertilizers commercially available in garden centers including urea-formaldehyde (UF) and related urea based formulations, isobutylidene diurea (IBDU), sulfur coated urea (SCU), plastic coated (various formulations such as OsmocoteTM and NutricoteTM, salts (MagAmpTM), and natural organics such as composted sewage sludge.
Water soluble or liquid fertilizer is applied either to the soil or on the foliage. Many water soluble formulations are available for almost any specific need from plant starter, high nitrogen fertilizers, to minor element formulations. Chelated iron is used extensively for prevention and control of iron deficiency of azalea, rhododendron, oak, and sweetgum, among others.
Rates of Application
Studies have shown that approximately three pounds of actual nitrogen per 1,000 square feet per year is needed to maintain the health of woody plants in most landscape situations. If foliage color, annual growth, or general vigor is not normal, the application rate should be increased to five pounds of nitrogen per 1,000 square feet per year. Certain plants such as broadleaf evergreens, dwarf conifers, and alpine plants should be fertilized with one-half the above rates. If soil and foliar test results are available, follow the recommendations provided, otherwise the suggested rates given above could be used as a guide. Woody plants respond well to fertilizers with a 4-1-2, 3-1-2, 4-1-1, or 3-1-1 ratio such as 24-6-12, 18-6-12, 20-5-5, 12-4-4, respectively. Landscape plants respond to 3 to 4 times as much nitrogen as phosphorus, and twice as much potassium as phosphorus. An application of three pounds of actual nitrogen per 1,000 square feet using a 3-1-2 ratio would include one pound of P2O5 and two pounds of K2O.
To convert from actual nitrogen to fertilizer, divide the amount of actual nitrogen desired per 1,000 square feet by the percentage of nitrogen in the fertilizer analysis or grade. Example: How much 18-6-12 is needed to apply three pounds of nitrogen per 1,000 square feet? Answer: 16.6 pounds (3 / 0.18 = 16.6 pounds).
Timing Fertilizer Treatments
In the landscape, fertilizing once a year is preferable to less frequent applications, especially with newly planted materials. Applications twice a year in light sandy soils or in seasons of excess rainfall are suggested.
The best time to fertilize in the northern United States is autumn, generally after the first hard freeze in October and before the soil freezes in December.
The next best time to fertilize landscape plants would be prior to growth in early spring, between February and early April again in the northern United States. If fertilizer was not applied during the autumn or spring season, applications may be made up to July 1. Fertilizer applied after this midsummer date is not recommended, as it could delay acclimation to winter weather conditions.
Methods of Application
Fertilizer can be applied in the landscape via 1) liquid soil injection, 2) drill or punch bar holes in the soil, 3) surface application, 4) fertilizer stakes or spikes, 5) foliar sprays, and 6) tree trunk injection or implantation. Each serves a specific role depending on the site and plant health. Regardless of the method selected, the soil should be moist at the time of fertilizing to prevent fertilizer injury.
Liquid Injection into Soil
Liquid injection of soluble fertilizer into the soil is rapidly absorbed by the roots, and is an excellent method of correcting deficiencies quickly. Injection sites should be 2 to 3 feet apart, depending on pressure, and 6 to 9 inches deep. Fertilizing deeper than nine inches may place the fertilizer below the feeder roots. The addition of water to dry soil is desirable in summer or during periods of drought.
Drill Hole or Punch Bar
A major advantage of the drill hole system is the opening of heavy, compacted soils which allow air and fertilizer to penetrate the soil. This technique and liquid injection prevent excess growth of grass in turf areas. The drill holes should be placed in the soil in concentric circles or in a grid system around the main plant stem beginning 2 to 3 feet from the main stem and extending 3 to 6 feet beyond the dripline. Space the holes two feet apart and drill them 6 to 9 inches deep. The recommended rate of fertilizer for the area should be uniformly distributed among the holes.
After the fertilizer is applied, the holes can be filled with either organic materials such as peat moss or compost or inorganic materials such as gravel or calcined clay. The selection of organic or inorganic material will depend on the greater need for either water or air after the fertilizer is applied.
RELATED TAGS: WHAT IS FERTILIZATION,APPLICATION OF FERTILIZERS,FEED TO SOIL,FEED TO PLANTS,İNORGANIC MATERIALS,ORGANIC MATERILAS,USING MICRO ELEMENTS,MAKING MACRO ELEMENTS,TYPES OF APPLICATION OF FERTILIZERS,DRIP FERTILIZERS,FOLIAR FERTILIZERS,LIQUID FERTILIZERS MAKING,PRODUCTION OF FOLIAR FERTILIZERS.
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