What are the challenges regarding phosphorus use?

Celebrating the 350th Anniversary of Phosphorus’ Discovery!

Did you ever wonder why your home and garden fertilizer has specific ratios of nutrients? Well, the story goes back even further – to the discovery of those elements! Phosphorus is one of the main “ingredients” for healthy plant growth. This year, 2019, is the 350th anniversary of the discovery of the element phosphorus, so the Soil Science Society of America (SSSA) and the American Society of Agronomy (ASA) are celebrating Phosphorus Week. We’ll have guest bloggers on Soils Matter this week, covering various topics. This fourth blog covers the challenges we face in our use of phosphorus.


In the first few blogs of this series, we learned that phosphorus is a necessary nutrient for healthy crops and high yields. However, growers must determine the right amount of phosphorus and place it on the fields at the right time, in the right place, and in the best form for that field/soil. If all of these factors are not managed carefully, then some of this phosphorus can run off. And this can impair the quality of our streams, rivers, lakes and coastal waters.

Challenges of too little and too much phosphorus

In addition, the raw material for phosphorus fertilizers, rock phosphate, is a finite, non-renewable resource. Despite successes in redistributing phosphorus globally as a fertilizer, there is an imbalance in the availability of phosphorus worldwide.  Around 30% of global cropland is currently lacking in phosphorus, limiting yields and reducing food security.  In contrast, cities and some agricultural areas (particularly concentrated intensive livestock farming areas), have too much phosphorus.

stream flowing over rocks
Farms, wastewater treatment plants and other sources can leak phosphorus into water bodies. Best management practices can stop this from happening. Credit: SV Fisk

Farms can be a source of phosphorus entering our water bodies. Over application of animal manures and fertilizers, and other practices, have been linked to phosphorus runoff.  This was acknowledged in the 1960s. Since then, scientists and farmers have worked to decrease phosphorus losses from agriculture.

Phosphorus is also used in nursery plants. Research continues on the best ways to manage run off in this industry – where the public buys trees, bushes, vegetables, etc. for their own gardens.

Cities are also areas of excess phosphorus accumulation because of the concentration of people and food consumption. Human and food waste is phosphorus rich. However, most of this waste doesn’t always get back to the farms where our food is produced. Much of this phosphorus gets into our sewers and wastewater or septic systems. Wastewater treatment plants successfully remove some of this waste phosphorus. However, the effectiveness of treatment can be variable and sewage effluent remains an important source of phosphorus entering water bodies in many highly populated areas. Scientists are working on ways to recycle phosphorus from urban wastes to use as fertilizers.

When waterbodies have too much phosphorus

Why are high levels of phosphorus a problem for waterbodies? Algae thrive on the excess phosphorus (and nitrogen) from agricultural runoff and sewage effluent, which is a major worldwide cause of water-quality impairment, known as “eutrophication”.

man on boat with computer and tubes that monitor phosphorus levels
Monitoring equipment deployed in the field allows us to measure changing phosphorus concentrations 24 hours a day, and 7 days a week. Data providing new insights into the sources and cycling of phosphorus in our streams, rivers and lakes. Credit: Helen Jarvie

Individually, algae may be tiny. But, when they proliferate, these algae can have big impacts on the use of our water resources. Rivers, lakes and coastal zones can become choked with green algal slime, limiting the penetration of light into the water.

Crucially, when the algae die off, decomposition uses up vital dissolved oxygen supplies in the water. This oxygen is essential for the survival of other aquatic creatures, including fish. Algal blooms can impact fisheries by creating vast “dead zones” of low-oxygen water. One example is the United States Gulf Coast. Water carrying phosphorus and nitrogen flows all the way down the Mississippi River to the Gulf. Habitats that should ordinarily be teeming with life are suffocated from eutrophication.

Algal blooms can also limit our use of water bodies. You may remember the Beijing Olympics, when a huge algal bloom off the coast of Qingdao threatened to disrupt the sailing events.

And, in some circumstances, the algae themselves can be toxic to humans, pets and livestock. During the 2014 Toledo, Ohio, water crisis, a toxic algal bloom in western Lake Erie resulted in release of toxin into the drinking water.  A “do not drink” advisory was issued for over 400,000 people.

The phosphorus paradox

We now face a “phosphorus paradox”. Too little phosphorus threatens our food security. Too much phosphorus is a major cause of water-quality impairment worldwide. Our future food and water security will be increasingly dependent on our ability to better manage phosphorus.  So, finding solutions to the “phosphorus paradox” are of monumental significance for humankind.

An important way forward will be recovering phosphorus from the phosphorus-rich wastes produced in intensive livestock and urban areas and recycling it back to areas where it is needed for food production. This potentially offers “win-win” opportunities; by reducing losses of waste phosphorus to water bodies, and by reducing our reliance on non-renewable rock phosphate reserves to grow our food.

Better decisions and innovative solutions in how we use and manage phosphorus are needed now, to ensure the continuing availability of this vital element to grow the food for future generations and reduce the “green peril” of algal blooms.

By Helen Jarvie, Centre for Ecology and Hydrology, UK

Read the other blogs in our phosphorus series!

The discovery and general uses of phosphorus

Why is phosphorus needed on farms? 

What are the sources of phosphorus for crops? 

Ten things we all can do to manage phosphorus better

To receive notices about future blogs, be sure to subscribe to Soils Matter by clicking on the Follow button on the upper right! Explore more on our webpage About Soils. There you will find more information about Soil Basics, Community Gardens, Green Infrastructure, Green Roofs, Soil Contaminants, materials for Teachers and more.

5 thoughts on “What are the challenges regarding phosphorus use?

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s