Keeping Fresh Water Sources Safe & Viable
Minimizing Phosphorus Runoff with New Technology
Phosphorus, a vital nutrient for plant growth, is a double-edged sword. While it fuels healthy crops, excess phosphorus can wreak havoc on fresh waterways. When lost from fields, excess phosphorus contributes to a process called eutrophication, where algae blooms deplete lakes and rivers of oxygen and harm aquatic life.
Understanding Phosphorus Loss: The Pathways
Phosphorus can leave fields in three main ways:
- Erosion: Soil erosion carries phosphorus-laden soil particles directly into waterways. This often happens during heavy rainfall events on sloped fields with minimal ground cover.
- Runoff: Dissolved phosphorus washes away with surface runoff water, especially after fertilizer application or manure spreading.
- Leaching: In some situations, particularly with sandy soils, dissolved phosphorus can seep through the soil profile and contaminate groundwater that eventually feeds streams and lakes.
Phospholutions, a sustainable fertilizer company, is bringing technology to market that reduces runoff potential by 78% and leaching by 84%.
Phospholutions VP of Sustainability, Steve Levitsky, explains that Phospholutions’ new technology, RhizoSorb, uses 50% less phosphorus and maintains crop yields as good or better than traditional phosphate fertilizer.
“Of that 78% reduction in runoff, 50% comes from the fact that you are applying less P,” says Levitsky. “The balance of the reduction comes from RhizoSorb. RhizoSorb acts like a sponge in the soil that holds onto water extractable P, so when water runs over the soil profile, you’re not losing that phosphorus.”
Case Study 1: The Chesapeake Bay
The Chesapeake Bay, the largest estuary in the United States, is a stark example of the consequences of excess phosphorus runoff. Decades of agricultural practices contributed to significant algal blooms, creating vast oxygen-depleted “dead zones” detrimental to marine life. The Chesapeake Bay Program sites phosphorus and nitrogen as the two nutrients of concern, and says phosphorus reaches the bay from three sources:
- Wastewater treatment plants
- Urban, suburban and agricultural runoff
- Air pollution
The primary metric to manage nutrient runoff into the bay is called Total Maximum Daily Load (TMDL) and is a set of limits provided by the EPA on nitrogen, phosphorus, and sediment. The goal of the Chesapeake Bay program is to meet federal clean water quality standards by 2025.
Sophisticated modeling tools approximate the reductions of nitrogen, phosphorus and sediment between 2009 and 2023. Phosphorus entering the bay decreased 17% from 17.2 million pounds in 2009 to 14.2 million pounds in 2023, meeting 67% of the goal to reduce phosphorus by 2025.
The model shows that between 2022 and 2023, the agriculture sector was responsible for 26% of phosphorus reductions and the wastewater sector was responsible for 67% of the reduction.
Levitsky, in a former sustainability role for a poultry company, collaborated to help understand the challenge in the Chesapeake Bay and identify how his company reduced impact. Levitsky says that Phospholutions’ RhizoSorb technology would have a material impact in reducing phosphorus runoff into the Chesapeake Bay.
“Theoretically speaking, if every farm in the Chesapeake Bay watershed implemented RhizoSorb rather than the traditional fertilizer program, we could be down to 11 million pounds of phosphorus and immediately meet the 2025 goal,” says Levitsky. “Not only can we meet this environmental goal, but farmers maintain and, in some cases, improve crop yields. It’s a win-win for farmers impacted by regulations that reduce phosphorus, and the communities affected.”
Case Study 2: The Lake Erie Watershed
Lake Erie, another major body of water facing significant challenges, demonstrates the impact of phosphorus runoff. Harmful algal blooms (HABs) plague the lake, fueled by phosphorus from agricultural runoff and urban wastewater. The Lake Erie watershed is the most populated of the Great Lakes basins and provides drinking water to 11 million people. Of the great lakes, it is most exposed to stress from urbanization, industrialization, and agriculture. Agricultural and urban lands in southwest Ontario (Canada) and northwest Ohio contribute significant sediment loads to the lake.
There is a joint initiative between the U.S. and Canada to improve the water quality of Lake Erie called the Lake Erie Binational Nutrient Management Strategy. As of 2022, phosphorus load targets are largely not being met and load reduction trends are difficult to discern, as shown in the chart below.
Initiatives to combat this problem involve promoting best management practices (BMPs) among farmers in the watershed.
Best Practices to Minimize Phosphorus Runoff
Fortunately, there are several strategies farmers can implement to minimize phosphorus runoff and protect vital fresh water sources:
- Effective Nutrient Management: Apply fertilizer only when necessary and in precise amounts based on soil test results. Utilize new technology, such as Phospholutions’ RhizoSorb, to maintain yield while preventing phosphorus runoff.
- Right Source, Right Rate, Right Time: Choose fertilizers with low solubility in water. A controlled release phosphorus fertilizer option is RhizoSorb from Phospholutions, which is a direct replacement for MAP/DAP. Tools like split-application methods, where fertilizer is applied in stages throughout the growing season, can further optimize nutrient use.
- Cover Crops: Planting cover crops during fallow periods protects soil from erosion and reduces phosphorus movement. Cover crops hold soil particles in place, minimizing erosion-related losses. Their root systems also help filter and absorb dissolved phosphorus before it reaches waterways.
- Buffer Strips and Riparian Management: Establishing buffer strips of vegetation along waterways filters runoff water before it enters streams and lakes. Native grasses, trees, and shrubs in buffer strips take up and utilize phosphorus, preventing it from entering water bodies.
- Precision Agriculture: Utilizing technologies like GPS and variable rate applicators allows for targeted fertilizer application, reducing waste and minimizing the risk of over-application in specific areas.
- Manure Management: Develop a comprehensive manure management plan. Store manure properly in covered structures to prevent leaching and runoff. Consider incorporating manure into the soil at appropriate times and rates to maximize nutrient utilization by crops.
New Solutions Lead the Way to Safeguarding Fresh Water Resources
Farmers play a critical role in safeguarding freshwater resources. Minimizing phosphorus runoff not only protects lakes and rivers but also translates to economic benefits.
Phospholutions’ Levitsky says RhizoSorb is beneficial for farmers striving to meet environmental initiatives to retain freshwater.
“With RhizoSorb, you’re going to put less phosphorus down. You’re going to save money. And there is going to be less phosphorus runoff. That’s the bottom line,” says Levitsky.
Reduced fertilizer waste leads to cost savings, while healthy waterways support fisheries and recreational activities, contributing to the economic well-being of surrounding communities. Working together, farmers and environmental scientists can ensure a future where productive agriculture coexists with healthy and thriving fresh waterways.
Additional Resources:
- For information on specific BMPs in your region, consult with your local extension office or soil and water conservation district.
- The Chesapeake Bay Program: https://www.chesapeakebay.net/
- The Lake Erie Nutrient Management Collaborative: https://www.epa.gov/greatlakes/lake-erie-binational-nutrient-management-strategy
- The Environmental Protection Agency (EPA) on Nutrient Pollution: https://www.epa.gov/nutrientpollution