Complete Fertilizer - Forgetaboutit!

“In order to maintain the health of your plants, you need to regularly fertilizer with a balanced, complete fertilizer,” so says almost every gardening reference out there.  A long-held belief, routine application of complete fertilizer is viewed as a successful way to provide TLC for your lovely plants and lawn – a boost to help them grow big and strong.  Routinely using complete fertilizer is also viewed as a necessity among gardening enthusiasts.  Complete fertilizers supply three essential plant nutrients – nitrogen (N), phosphorus (P), and potassium (K) – and may also supply micronutrients in smaller quantities.  The general public is wholeheartedly in agreement with the need for complete fertilizers, as bags and bags of N-P-K fertilizer fly off the store shelves despite steeply rising fertilizer prices.  And who can blame them?  I mean, who really wants an incomplete fertilizer?

But most times our gardens and lawns don’t need complete fertilizers.  Too much of a good thing really isn’t a good thing.  In particular, the plant nutrient phosphorus has been shown to be at sufficient or excessive levels for many areas of the East Coast, including Long Island.  Continually applying fertilizers with phosphorus to these areas is not only a waste of money, but also a serious threat to the environment.  Stormwater runoff which carries phosphorus into our lakes and streams causes significant water quality issues and can lead to drinking water contamination and fish die-offs.     

Photo: Reducing the use of phosphorus fertilizers enhances the health of our surface waters. View from Center Island. 

Results from over 1500 soil samples from home gardens in Suffolk County show that we are severely overfertilizing our lawns and gardens.  These samples were submitted by landscapers, arborists, and homeowners, and were analyzed over a five year period by Cornell University’s Nutrient Analysis Laboratory.*  Based on the results, almost all home gardens in Suffolk County will not need supplemental phosphorus (80% of samples tested high or very high), and about half will not need supplemental potassium (over 50% of samples tested high or very high).  Instead, we need to focus on adjusting soil pH, maintaining adequate nitrogen levels, and adding organic matter like compost.  Results indicated that 60% of samples had less than 3% organic matter, which is crucial for holding water, nutrients, and air in the soil. 

Indiscriminate, routine use of complete fertilizers is not needed, and can negatively impact plants and the environment.  The only “routine” thing we should be doing in regard to fertilizer is taking a soil test.  A soil test will tell you which nutrients you need to supplement and how much.  A soil test helps identify problems, while providing the foundation for fertilizer recommendations and a sound nutrient management program.  AND all the numbers and fancy charts will surely impress your gardening friends!  This type of “prescription-based” fertilizing is much better for your plants and the environment.

Photo: Fertilize your plants based on the results of a soil test. Soil sampling at a Christmas Tree Farm in Huntington.

Prescription-based fertilizing is really taking hold.  In 2007, one of the largest tree care companies in the United States began requiring its arborists to take soil samples and fertilize trees and shrubs based on the test results.  Next year, in 2012, a New York State law will go into effect that prohibits the use of phosphorus on lawns except when a soil test demonstrates that additional phosphorus is needed.  (Phosphorus will still be allowed on newly established lawns during the first growing season to help stimulate root growth.)  This state law will also require retailers who sell any fertilizer with phosphorus in it to post warning signs about the restriction as well as the potential negative environmental impacts of phosphorus.  Not surprisingly, the Scotts Miracle-Gro Company, the world’s largest marketer of branded consumer lawn and garden products, just announced last month that it will remove phosphorus from its lawn fertilizers by the end of 2012, including the market-leading Scotts®Turf Builder® brand.  Our lakes, streams, fish, ornamentals, and lawns will be healthier because of these initiatives.   

Photo: A healthy lawn and a healthy environment are both possible when you fertilize according to best managment practices.

We shouldn’t think of fertilizing our lawns or gardens without phosphorus or potassium as “incomplete” fertilizing.  Instead, we should think of it as “prescription-based” fertilizing – we are providing our lawns and gardens with exactly what they need based on a soil test, while minimizing environmental harm.   And complete fertilizer?  Forgetaboutit!    

For more information on best management practices for Long Island lawns, visit:  http://healthylawns.suffolkcountyny.gov/bmps/bmps.htm

*Source: Rao, R., D. Moyer, Q.M. Ketterings, and H. Krol (2007). Suffolk Soil Sample Survey (2002-2006). CSS Extension Bulletin E07-46. 34 pages.