Phosphorus is an excellent nutrient for healthy grass growth but is noticeably absent from lawn fertilizer. If it is so beneficial to lawn growth, why isn’t it included in most common residential lawn fertilizers?
Some lawn fertilizers do not have phosphorus because of the nutrient’s potential for environmental damage. Several states have banned the inclusion of phosphorus in lawn fertilizers after discovering that phosphorus runoff can cause algal growth and oxygen depletion in rivers and lakes.
The rest of this article will explain why phosphorus is no longer used in a number of lawn fertilizers, how phosphorus can cause environmental issues, and in what cases phosphorus is still used. I will also share some useful tips for choosing the right fertilizer for your lawn.
Why Phosphorus Is Missing from Most Lawn Fertilizers
The three primary nutrients turf needs to flourish are nitrogen, phosphorus, and potassium often referred to on fertilizer labels as “N-P-K.” These letters will usually dictate the percentage of each nutrient present in the fertilizer.
One of these three essential nutrients, phosphorus, is missing from most lawn fertilizers. It’s such an essential nutrient, leading many new gardeners to wonder why it isn’t being used anymore.
Phosphorus was commonly used in lawn fertilizers until multiple studies in the early 2000s indicated that as the phosphorus from lawn and agricultural fertilizers ran off, it spilled into drains and irrigation systems that led to nearby rivers and lakes. As a result, nearby bodies of water suffered from nutrient deficiencies.
When phosphorus was found to be causing environmental damage to the rivers, streams, and lakes, the pressure was on to stop using fertilizers containing phosphorus in order to protect the environment. During this time, companies like Scotts removed phosphorus from their fertilizers altogether.
While phosphorus is excellent for helping restore health to both residential and agricultural lawns, it is not necessary if the lawn is relatively healthy to begin with. Because of this, many lawn fertilizers were reformulated to omit phosphorus.
Several states have laws limiting phosphorus use. However, eleven states in the United States have completely banned the use of phosphorus in lawn fertilizers.
These states include the following:
- New York
- New Jersey
The Negative Impact of Phosphorus on the Environment
In general, phosphorus negatively impacts the environment in the following ways:
- Contaminating the water systems through rain and snow runoff
- Aiding in the overgrowth of algae in bodies of water like rivers, streams, and lakes
- Preventing recreational use due to the growth of toxic algae
- Causing low-level oxygen in affected areas
I will discuss these items in more detail below:
Contamination of Bodies of Water
When using phosphorus in lawn fertilizer, the runoff leaks into water systems and can cause harm to our water’s delicate ecosystems.
When fertilizer runs off of residential and agricultural lawns and leaks into our water systems, it eventually leads to bodies of water like streams, creeks, lakes, and rivers. Runoff occurs when it rains or snow melts, and fertilizer from lawns is washed into the water systems.
Large amounts of phosphorus can be detrimental to aquatic animal life because it limits the availability of other nutrients in the water, such as dissolved oxygen.
Causing Algal Bloom
Phosphorus aids the growth of grass because of the large amounts of nutrients it provides, but when phosphorus starts providing those nutrients to the wrong place, it can cause problems.
The significant nutrients provided by phosphorus not only aid in lawn fertilization but also in the growth of algae when it reaches these important bodies of water. The result is algae overgrowth, which can be harmful to the fish and other types of aquatic life.
Preventing Recreational Use of Rivers and Lakes
The recreational use of the body of water can also be limited or even entirely prevented by algae overgrowth because algae can cause adverse reactions to humans and animals if consumed.
It’s not uncommon to unintentionally swallow water while swimming. However, if this type of algae is present in the water, it can make you sick.
The algae also consume oxygen as they decay, which can cause low levels of oxygen in the areas where the algae are most concentrated. Low oxygen levels can harm animal life and their habitats, causing a disruption in the ecosystem.
Because of these major environmental issues, most fertilizer companies chose to remove phosphorus from their fertilizer as many states began banning the use of phosphorus altogether.
Is Phosphorus Still Used in Any Type of Fertilizing?
Most states that have outlawed the use of phosphorus in fertilizer specify the conditions in which this fertilizer is banned. For example, the Washington State law specifies that phosphorus cannot be used in any fertilizer labeled for use on turf.
Phosphorus tends to be banned or simply removed from turf fertilizers. However, some types of fertilizers containing phosphorus are still used today.
Such fertilizers can be used for the following:
Fertilizer containing phosphorus is not banned for agricultural use. The ban is focused mainly on residential and commercial turf.
Establishing a New Lawn
In some states, like New York State, phosphorus-containing fertilizer may be used on non-agricultural turf only if the lawn is being established for the first time.
Necessary Turf Improvement
Some state laws, including Massachusetts, allow for the use of phosphorus-containing fertilizers on residential or commercial lawns only in the case that a soil test has proven that phosphorus is necessary to restore the health of the lawn.
Choosing the Best Turf Fertilizer for Your Lawn
When choosing a lawn fertilizer for your turf, it is essential to know what nutrients your grass needs for optimal health and select your fertilizer accordingly.
Things to Consider
Before you choose a fertilizer, you’ll need to:
Take note of the current condition of your lawn and assess the improvements you’d like to make. Choose the right fertilizer depending on your goal (i.e., increase green coloring, encourage growth, kill weeds, etc.)
The Type of Grass
If you already have grass on your lawn, you’ll need to figure out precisely what type it is. Many grass types need to be fertilized at different times of the year and have varying needs for optimal growth.
Soil Test Results
A soil test is an excellent method for checking potential issues in the soil’s pH level. Various grass species have different pH level preferences that can range from 5 to 7, so if your soil test comes back above or below the ideal pH, you’ll know you need to make some adjustments.
A Realistic Schedule
Take a look at the calendar and consider your daily schedule. Some fertilizing treatments take more time and care to manage than others. So if you don’t have a lot of time to dedicate to lawn maintenance, you’ll want to choose a fertilizer with lower-maintenance time-releasing capsules.
Kids, Pets, & Toxicity
Some fertilizers contain chemicals that can be toxic when ingested or rubbed in the eyes. If you have small children or pets that use your yard and won’t understand or remember your request that they stay off the lawn for a while, you will need to get a fertilizer that is safe and non-toxic.
Types of Fertilizer
Once you’ve considered your personal needs for lawn fertilizer, you’re ready to head to the home and garden store. There are many different types of lawn fertilizer, but they will usually be labeled well with benefits, ingredients, and any cautions or warnings a particular fertilizer might have.
The most common types of lawn fertilizers are:
These granules come in slow-release or quick-release and can be spread evenly over your lawn using a mechanical spreader or a shaker and then watered to encourage the fertilizer to release and enter the soil. Depending on the type, granular fertilizers can last 3 to 12 weeks.
Liquid fertilizer absorbs quickly, which is beneficial for the lawn, but requires more attention on your part. Because of how quickly it is absorbed, liquid fertilizer usually needs to be reapplied every 3 weeks. Liquid fertilizers typically come in a concentrated form and are mixed with a recommended volume of water before being applied to the lawn.
Lawn fertilizers typically do not contain phosphorus because of the chemical element’s ability to cause environmental harm to nearby bodies of water. Phosphorus encourages algal growth in lakes, rivers, and streams that can be toxic to aquatic life, people, and animals.
Many states have banned the use of phosphorus in fertilizers for home and commercial turf, causing the fertilizer companies to remove it from their products altogether.
Some exceptions allow for the use of phosphorus in fertilizer, including establishing a new lawn, fertilizing agriculture, or fertilizing turf with a soil test that deems phosphorus necessary.