Yard owners all know fertilization is essential to proper growth, but how many truly understand the science behind the forms they come in or nutrients they contain.--NEWS PHOTO SCOTT SCHMIDT
We are in the throes of spring, grasses are knitting over the wounds of winter kill, dandelions have made their annual showing, and the first round of blooms have come and gone on many trees and shrubs, with lilacs, honeysuckles and apple tree blossoms having sweetened the air of spring.
In our urban landscapes, plants require specific nutrients to conduct their physiological processes. While soils can be abundant in these nutrients, they are not always readily available for uptake by the plant’s roots. That is where fertilizers come in, and while the topic of fertilizers is expansive, let us focus on the primary nutrients they provide for plant growth.
When looking at a fertilizer product in the store, there are usually three numbers of interest on the label, representing Nitrogen (N), Phosphorus (P), and Potassium (K), in that order. Sulphur (S) is occasionally shown as a fourth number on fertilizer labels. Each of the numbers represents the amount of that nutrient relative to the product’s weight, and the ratio of the nutrient to the other ones listed.
How do these nutrients effect plant growth?
Nitrogen (N)
Nitrogen plays a vital role in the above ground growth of a plant, primarily shoots, leaves, termed “vegetative growth,” rather than the flowering and fruit producing areas. Turf is particularly dependent on nitrogen, as it is the first nutrient absorbed from the soil by the fibrous root system.
Phosphorous (P)
As the second of the Big Three nutrients shown, phosphorous is integral to root establishment and growth. This key nutrient is often the highest number in “Plant Starter” or “Transplant” type fertilizers for that very reason, to enable roots to grow and mitigate the stress on the plant.
Potassium (K)
Finally, we have potassium, which is the last number listed. When it comes to plant resilience, this nutrient is essential, as it aids in the plant’s ability to respond to environmental pressures. Potassium also has a direct role in flower and fruit development, and so it should be of interest to gardeners looking to increase their yields.
Fertilizer comes in different formats.
Granular
Most lawn fertilizers will be in a granular form. The small pellets are often coated so that they dissolve when exposed to water over a longer period. That reduces the chance of fertilizer burn, which can happen when a high concentration of the fertilizer components contacts the lawn.
Liquid fertilizers are often reserved for commercial applications due to costs and the frequency with which they must be applied, as they tend to leach away more rapidly.
Stakes
Fertilizers stakes are often used for trees and shrubs. The stakes are placed into the topsoil at the drip line, which is the area below the widest part of a tree’s canopy. These are much easier to place if your turf has been watered recently, as they tend to break if forced into firmer ground. Quantity and placement distance will vary depending on the size of the tree and the fertilizer product used. The stakes dissolve over time with regular watering and that solution provides nutrients to the topsoil, which can be pulled into the roots.
Scheduling
Application times for fertilizer types vary. We want to feed plants the nutrients they require at a given time in the season. Spring is an ideal time for fertilizers to support top growth, root development and flower and fruit development, as well as to support new plants in the landscape.
An ideal fertilizer program is tailored toward a specific goal, because although our urban plants need these nutrients, too much of a good thing can have unintended consequences. Regular applications of lawn fertilizer that is high in nitrogen, for example, can stunt root growth and limit drought resiliency. Younger deciduous trees can be sensitive to large amounts of nitrogen in lawns and will push out ‘leggy’ or weakly attached new growth because of this nitrogen leaching into their root zones.
Fertilization is a broad topic, with many considerations, but hopefully some light has been shed on this topic for you. Happy gardening from all of us at Parks and Recreation and enjoy all the season has to offer.
Jeff Quinlan is the parks technician for the City of Medicine Hat, which involves technical support for the department through research, insect and disease monitoring (of trees), and public education/engagement through things like the Adopt a Tree program and the annual Litter Blitz. Quinlan is an ISA certified arborist with a Bachelor of Applied Science in Horticulture. Prior to being in Medicine Hat, Quinlan also worked as a Japanese Garden Technician for several years at Nikka Yuko, Japanese Gardens in Lethbridge. His gardening tips will appear in the News throughout the growing season.
