Lake-Friendly Living Guide: Fertilizers, Phosphorus, and Water Quality

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| By Lake Hopatcong Foundation: This weekly series focuses on action-oriented ways to protect Lake Hopatcong, and this week's topic examines how phosphorus affects our waterways.

The goal of our Lake-Friendly Living Guide series is to engage the public in action-oriented ways to protect Lake Hopatcong.  In this installment, we examine how phosphorus affects our waterways and the best fertilizers to use if fertilizers are necessary. Check in each week to learn more about what you can do for our lake!

In Lake Hopatcong, phosphorus is the limiting nutrient, which means that everything aquatic plants and algae need to grow and thrive, such as sunlight, warmth, and water is available in excess, except phosphorus.  Phosphorus has a direct impact on plant and algal growth in our lake. The more phosphorus, the more plants and algae there will be in our lake.  Even the smallest increase in phosphorus can impact the water quality in our lake.

Where does phosphorus come from?

Phosphorus has many sources. Small amounts of phosphorus exist naturally in lakes and streams but human activities from residential and agricultural areas contribute a significant amount of phosphorus. Stormwater runoff travels across land and picks up phosphorus from fertilizers, eroded soil particles, septic systems, and pet waste and discharges it into nearby streams and the lake.

Eliminate or use only lake-friendly, phosphorus-free fertilizer

One of the best things you can do for Lake Hopatcong is to eliminate fertilizers from your regular lawn care. For more information about smart lawn care that focuses on long-term soil health while reducing chemicals and phosphorus, see our previous post: Lake-Friendly Living Guide: Smart Lawn Care. If you must use fertilizers, make sure to use only lake-friendly, phosphorus-free fertilizers.

To make sure your fertilizer is lake-friendly and phosphorus-free, simply check the fertilizer bag. The phosphorus content is measured as phosphate and appears as the middle number in a series of three numbers printed on the bag. A “zero” in the middle means your fertilizer is phosphorus-free.  It’s that simple.

The two main nutrients in lawn fertilizers are phosphorus and nitrogen. Plants in your yard and lawn grass, rely mostly on nitrogen to promote growth. Phosphorus is usually needed in only small amounts.  However, in a lake eco-system, the opposite is true, weeds and algae mostly need phosphorus and need very little nitrogen. The problem is that much of the unused phosphorus from fertilizers added to your lawn washes into the lake, and stimulates excessive algae and weed growth.

It’s the law

Since January 5, 2011, phosphorus-free fertilizer is the law in New Jerse. For more information CLICK HERE.

New Jersey law governs the application of phosphorus and nitrogen fertilizer.  The law applies to both homeowners and landscape contractors.  The intent of the law is to reduce the high levels of nitrogen and phosphorus from fertilizers which impact the water quality in many of the state’s water bodies.

WHEN NOT to apply fertilizer:

  • Between November 15th and March 1.
  • When the ground is frozen or saturated with water.
  • During or just before a heavy rain.

WHERE NOT to apply fertilizer:

  • To driveways, sidewalks, and other impervious surfaces. Sweep up or remove any fertilizer that may land on impervious surfaces.
  • Within 25 feet of a water body. The protective buffer can be reduced to 10 feet if using any of the following: a drop spreader, rotary spreader with a deflector, or targeted spray liquid fertilizer.

Hiring professional lawn care fertilizer applicators:

  • Professional fertilizer applicators must be certified, or trained and working under the direct supervision of a certified applicator. Rutgers University administers the online training and certification program and maintains a list of certified fertilizer applicators available HERE.

Why and how to test your soil

Most lawns in the Lake Hopatcong watershed do not need a fertilizer with phosphorus. Homeowners can learn about what their lawns may need for proper application of various nutrients through a soil test. Homeowners can mail a soil sample to the Soil Testing Laboratory at Rutgers University.  Soil testing is an environmentally friendly practice which saves homeowners time and money.  More information on how to have your soil tested can be found HERE.

Next up in our Lake-Friendly Living Guide series: Septic Maintenance

Previous posts:
Lake-Friendly Living Guide: Stormwater Basics

Lake-Friendly Living Guide: Go Native! Install Vegetative Buffers and Rain Gardens

Lake-Friendly Living Guide: Smart Lawn Care

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Featured Shop Local Coupon:

The following is one of many Shop Local coupons so you can support your local businesses during this difficult summer on Lake Hopatcong.

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See All Shop Local Offers Here

How to Join Shop Local: If you are a business within the Hopatcong, Jefferson, Mount Arlington or Roxbury areas contact or 973-288-1865 to join Shop Local free of charge.

How to Use Shop Local: Just Print or have a copy of the Coupon on your Cell Phone to show when purchasing from local businesses.

How to Get your Shop Local Picture Online: When every you purchase from a Shop Local Businesses take your picture and send it to #ILoveLH #LHShopLocal or email to

History of Shop Local:

Shop local was started by the Lake Hopatcong Foundation in 2013 as a way to support local businesses and to encourage the communities around the lake to think of the lake as their “downtown,” creating a more cohesive community around our lake. Hopatcong Lake Regional News stepped in in 2019 to keep this important initiative running and take it to the next level.

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