Spring is a time of renewal. As the weather warms up and the days get longer, plants break dormancy, rejuvenating turf and landscapes. That's why it's important to remember that, as plant growth increases, so does nutrient demand. A good spring fertilization program can help both your company and the properties it maintains to get off on the right foot this season.
There are a number of essential elements that are required for plants to grow and thrive. These nutrients can come from the air, rainfall, soil and fertilizer sources. If any one of these nutrients is not available at sufficient levels, plant growth will suffer. One key aspect of landscape installations and maintenance is the need to determine what nutrients are lacking and then supply them in the needed amount at the appropriate time.
For instance, fall fertilizer applications can encourage turf density and plant rooting going into the winter, while also providing adequate reserves for plants to survive the over-wintering process. However, when spring hits, the necessary nutrients must again be readily available to meet your turf and plant growing objectives—or there could be problems ahead.
TEST THE SOIL FOR NUTRIENT LEVELS
Test to know what the soil can supply and what is lacking. Mineral soil has a tremendous influence on landscape nutrition. It can hold, store and supply nutrients to the plants. Key factors such as soil pH can determine the availability of any nutrients present.
The best way to determine what a given soil can supply is to conduct a comprehensive soil test. Spring is a good time to conduct soil tests, and testing can easily be done at a number of state or commercial labs set up to handle this type of sample.
A soil sample must be representative of the site in order to be useful. Typically, it's a wise practice to collect a number of soil cores from locations around the site and then mix them together to provide a composite sample. Test results usually will come back in a graphical form as low/adequate or normal/high ranges with recommendations for boosting nutrient levels based on the types of plants you are feeding.
Any recommended nutrient addition rates usually will come back expressed in units of pounds of nutrient (or fertilizer source) per 1,000 square feet (or acres). This represents the amount that needs to be added to bring low nutrient levels up to an adequate supply level. Generally speaking, pH level is also reported with suggestions about how to adjust it by applying limestone, sulfur or acidifying fertilizers.
A soil test should identify the nutrients you need to add and guide you on the correct rate to add them. The idea for lean and efficient nutrient management is to utilize what is present in the soil and supplement the diet with only what's missing. If a soil already contains a high level of a specific nutrient (e.g. phosphorus), there is little need or advantage to plants in adding more in the form of fertilizer. More phosphorus than what's needed will not make a plant root or bloom any better.
SELECTING THE RIGHT FERTILIZERS
Obviously, there are many fertilizer products in the marketplace. A good method for selecting the best product is to study the label closely, making sure to understand exactly what you're getting.
There are many factors that might influence your purchase, but you need to go beyond the N-P-K analysis listed on the front of the bag to understand how any product might fill nutrient gaps in your fertilizer program. Cost per bag is an obvious factor, but there are a number of others that should be considered.
Actual nutrient content of all essential elements claimed on the guaranteed analysis. Sometimes your landscape may be severely lacking in micronutrients, not N-P-K.
Source of raw materials. Do they contain harmful salts, etc.?
Percent of coated or slow-release fertilizer that will feed plants for an extended period of time and cut back on the required number of applications needed per season.
Percent of soluble nutrients that can encourage quick growth spurts (requiring a lot of mowing) but not sustained feeding.
Presence of active ingredients in a combination product to control weeds, grubs and other unwanted pests.
APPLYING FERTILIZERS THE RIGHT WAY
Once you have selected an appropriate fertilizer program tailored to your landscape, proper application is critical to achieve the desired results. Broadcasting fertilizer at incorrect rates or at the wrong time will not yield success.
Rates should be based on the plant types you are feeding and whether you are in a maintenance mode or trying to encourage the quick establishment of a landscape. Extension websites, publications and even fertilizer labels will specify recommended application rates and timing for best results.
Inadequate rates will result in hungry, stunted and poorly developed plants. Applying excess nutrients can be expensive and wasteful, requiring frequent mowing and promoting thatch build-up and shallow roots, among other problems.
Over-fertilization also can lead to negative environmental impact, especially if applied improperly.
Some plants are heavy feeders while others are salt-sensitive, slow-growing or require lower nutrient levels. This can get complicated in a landscape filled with a mix of plant types. Turf fertilizer application should be targeted to feed the dominant turf species that are present.
A well-fed lawn will be thick and lush, discouraging the establishment of weeds. Conversely, excess feeding can encourage weak growth, making lawns susceptible to pests and diseases. Target application to the plants. Use of edge guards or sweeping up fertilizer from walkways is an environmentally conscious process that can cut down on fertilizer run-off into storm drains.
Fertilizer bag labels suggest generic rates and expected coverage per bag. Since bag rates may vary significantly from product to product, it's best to calculate the amount of nutrients you actually need to apply per unit area to sustain plants based on soil tests (i.e. pounds of N per 1,000 square feet), instead of blindly following a recommended rate.
Rates may be impacted by factors such as weather, irrigation timing and frequency, desired plant quality, species/cultivars growth differences, soil texture, organic matter content and whether clippings are removed or recycled.
If you consider these factors during the coming spring and make adjustments accordingly, you can optimize rates, minimize costs and produce favorable landscape environments for your customers.
Fred Hulme, Ph.D., is Director of Technical Services for The Scotts Company North America Professional Group.