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



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 what phosphorus is, where it comes from, how it 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!


Phosphorus and water quality

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.


What about the fish?

In basic terms, the more phosphorus in the lake, the less fish. Phosphorus facilitates the growth of weeds and algae. As algae die and decay, the water is robbed of dissolved oxygen. This can devastate fish populations if it occurs for a long period of time or the fish have nowhere else to go.


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 that saves homeowners time and money.  More information on how to have your soil tested can be found HERE.


Lake-Friendly Living Guide 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

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

Lake-Friendly Living Guide: Septic Maintenance

Lake-Friendly Living Guide: Alternative Septic Systems

Lake-Friendly Living Guide: Eliminating Pollutants

Lake-Friendly Living Guide: Conserving Water


This online series of Lake-Friendly Living Guide posts were funded through a grant from the Watershed Institute.

Categories: community, Hopatcong, Jefferson, Lake Hopatcong, Mt. Arlington, News, Roxbury, Water Quality