Methods of Application
Fertilizers can be applied either directly or indirectly to plants. When turf is fertilized, tree and shrub roots that extend into the turf area absorb some of the fertilizer, and are there before indirectly fertilized. Turf fertilization rates should be supplemented only if trees and shrubs are showing symptoms of nutrient deficiency.
Straight application of fertilizer could call for placement into the back fill soil or positioning in the planting hole at planting time. Neverheless, the more common variant of direct fertilizer application, broadcasting, is typically the most useful, especially proportional to cost. Just broadcasting the fertilizer over the soil atop the tree and bush roots and watering it in is generally enough. Compressed soil should first be aerated or raked.
The most sensible and efficient way to fertilize large trees is to scatter granular fertilizer on the surface of the soil and allow rain or irrigation water to transport the nutrients to the roots. Evenly broadcast the fertilizer over the area to be fertilized – that area covering the outer two-thirds of the distance between the trunk and the drip line and extending at least 50 percent of the crown radius beyond the drip line.
Another method is to put granular fertilizer into holes in the soil that are 4 to 12 inches deep. These holes are dug in a regular pattern at 2- to 3-foot intervals, in the same area as broadcast fertilizer is applied. Divide up the fertilizer among the holes. This technique does not insure consistent coverage to all feeder roots, especially in the upper few inches of the soil surface where the majority of the roots occur. High concentrations of fertilizers in these holes can also injure roots located bordering the hole.
An often utilized commercial process is to inject liquid fertilizers into the soil. A specialized injection probe is utilized and the fertilizer solution is injected under pressure. A corresponding probe device known as a 'root feeder' is sold at almost all garden centers. The elongated probe attaches to a garden hose and water-soluble plant food cartridges deliver nutrients and water directly into the tree root area. The tip of the injection needle bought to be entered four to twelve inches into the soil at two to three-foot intervals. Fertilizers appropriate for fluid injection are usually costlier per unit of nutrient and are often harder to apply than granular fertilizers.
Spikes are additional choice for tree or bush fertilization. These are rammed into the soil with a heavy hammer and can only be employed effectively when the soil is damp. The spikes do not even broadcast fertilizer around the tree's or bush's major feeder roots. Tree spikes are a pricey choice. Their popularity is founded on simplicity and ease of application.
Foliar feeding is a short-run answer when a nutrient inadequacy has been diagnosed. The leaves, buds and green wood are able to absorb some nutrients. Foliar nutrient sprays are put on with a pressure spray or siphon spray attached to a garden hose. The green-up from foliar spraying is fairly speedy but not long enduring. Generally deficiencies of micronutrients including iron, boron or manganese are rectified by seasonal foliar applications.
Micro-injection constituents the direct injection of necessary nutrients into the trunk of the tree or bush. It's an acceptable commercial use for remedying or invigorating trees demonstrating stress or decline symptoms. Nutrients can as well be solidified into gelatin capsules and imbedded in holes in the trunk. Micro-injection research is comparatively limited and results are often conflicting. Boring holes, imbedding or injecting fertilizer and sealing holes could lead to trunk disfigurement and decay. Foliar applications, injections or implants would better be used only when soil application of fertilizer is unrealistic. These routines are regarded as short-term remedies for nutrient deficiencies and pest infestations. In the final analysis, suitable soil and foliar applications must be applied for a permanent cure.
Placement of Fertilizer
Fertilizer should not be centered around the base or trunk of a tree or shrub, but should be applied over as much of the plant's root zone as possible. For trees and shrubs, fertilizer should be applied over an area twice as large as the crown spread. Since most landscape plant roots grow in the top foot of soil, surface, but not deep application, is recommended.
Factors Affecting Fertilizer Uptake
Numerous elements impact easily and well trees and bushhes assimilate fertilizers. The most significant uptake factors are:
- Fertilizer variant (inorganic, quick release, or fluid forms are assimilated faster than organic, slow-release, or dry forms)
- Soil type (clay particles and organic matter assimilate or bind more nutrients than sand, so fertilizer needs to be applied more frequently in sandy soils, but with less rates each time due to leaching potential)
- Soil moisture content and soil temperature (nutrient uptake is faster in moist warm soils)
- Plant vigor (plants under stress are more ineffective in assimilating available nutrients due to damaged or reduced root systems)
Fertilizer should be used when plants require it, when it will be most efficacious, and when plants can readily accept it. Late summertime and early autumn fertilization may hasten new growth that is not winter hardy, and summer drought could interfere with nutritive uptake, but spring, fall, and wintertime applications are satisfactory. A split application may be advantageous, applying half the annual rate in early spring and the balance in the fall as or after plants go dormant.
If water is unavailable, do not fertilizer altogether – plants will be unable to assimilate the nutrients. (During a dry time of year, fertigation – application of fertilizer by means of an irrigation system, can be beneficial.)
Tree and shrub fertilization is only one ingredient of total plant maintenance. Fertilization may not assist a plant if it is under stress from poor soil aeration or drainage, saturated soil, insufficient light or space, or excess pest problems. All factors influencing plant growth should be kept at optimum levels to ensure plant vigor.