Fertilizers and their Nutrients
Did you know that the nutrients that feed your yard’s grass, trees, shrubs and flowers are the same ones that help algae blooms grow in your lake? Excess nutrients and other garden products such as pesticides can run off the land or leach under ground, eventually making their way to lakes, ponds and streams causing water pollution. That’s why it’s important to identify what type of nutrients your lawn and garden needs and to follow label directions whenever using lawn and garden products.
The three primary plant nutrients essential for growth are nitrogen, phosphorus and potassium. Fertilizers can be purchased as “single ingredient” fertilizers (such as ammonium nitrate and urea for nitrogen, triple super phosphate for phosphorus and muriate of potash for potassium). “Combination” fertilizers such as 8-8-8 or 25-10-5 contain all three nutrients. The three numbers indicate the percentage of each nutrient in the fertilizer blend. For example, a 10-6-4 fertilizer contains 10 percent nitrogen, 6 percent available phosphate (which includes phosphorus) and 4 percent soluble potassium potassium.
Fertilizers are available in dry and liquid forms. They also can be classified by their solubility. Soluble fertilizers (liquid and dry formulations) release nutrients rapidly, whereas slow-release and organic fertilizers (typically dry formulations) release nutrients over a period of time.
Plants are not always able to immediately use all of the nutrients available in soluble fertilizers. Some water soluble nutrients may leach below root levels in the ground and be transported into the nearest lake or stream. Slow-release fertilizers, on the other hand, are designed to release nutrients at a rate more in line with plant needs. This means there is less likelihood that nutrients will leach into groundwater and enter your lake.
It’s important to test your soil before applying any lawn or garden fertilizers. Test results will tell you what type and how much, if any, nutrients are needed for optimum plant growth. Soil test kits are easy to use, take the guess work out of fertilizing and, in the long run, will save you money.
Phosphorus is a
nutrient that boosts
plant and algae growth in your lake!
Soil test kits are available at your local Penn State Extension Office and many lawn and garden centers. Follow the simple directions to collect and send in your soil sample (a nominal fee is charged for the analysis). A soil test will tell you the levels of available phosphorus and potassium in the soil as well as the soil pH (because nitrogen is so soluble, it’s not practical to test for it). A fertilizer recommendation, including nitrogen, will be included in your soil test results. If levels of phosphorus and/or potassium are sufficient, there is no need to apply those nutrients. Remember that grass clippings also contain nutrients your lawn needs to grow. A garbage bag of clippings contains up to 1/4 pound of usable organic nitrogen. Over the growing season, grass clippings can provide up to 50% of the nitrogen needed by your lawn. You can potentially reduce your fertilizer costs by mulching grass clippings back into the lawn.
The rate and timing of fertilizer applications are very important in maintaining a vigorous and healthy turf, as well as keeping the nutrients on your lawn and not in the lake. Apply only the amount specified, and water your lawn immediately after application. Never apply fertilizers if rain is forecast: you can control your sprinkler but not the weather! Use a calibrated spreader to ensure uniform distribution and help prevent over-application.
In general it is better to apply fertilizer in the fall than in the spring.
Spring applications may actually harm lawns by promoting more blade growth
than root growth. This can lead to shallow root systems that are unable
to sustain lawns through a drought or harsh winter. Fall applications,
on the other hand, promote deep, healthy root systems and hardy lawns.
Apply fertilizer in the fall after the average daily temperature drops
to 50°F for a week or so (usually in October). To calculate the 
average
daily temperature, add the daily high temperature to the daily low temperature
and divide by two. For example, 61° (daily high) + 37° (daily low) / 2
= 49° (average daily temperature).
Trees, shrubs, flowers and vegetable gardens all require differing amounts of fertilizer nutrients under different circumstances. In fact, many healthy trees and shrubs do not require annual fertilization. Contact your local nursery, Penn State extension office, or county conservation district for recom- mendations.