Phosphorus Management Considerations

The Quick and Dirt-y on Dissolved Reactive Phosphorus (DRP)


A hot topic in soil health and nutrient loss over the last few years has been Dissolved Reactive Phosphorus (DRP), a form of phosphorus that is dissolved and readily available to plants and algae. DRP differs from the phosphorus loss we usually hear about, which is tied to soil particles, also known as Particulate Phosphorus (PP). To help understand the basics of DRP, ISAP spoke with the following experts: Dr. Andrew Margenot, Associate Professor in Crop Sciences at University of Illinois; Dr. Shalamar Armstrong, Associate Professor of Agronomy at Purdue; Pete Fandel, Professor of Agriculture at Illinois Central College; and Dr. Shani Golovay, Research Manager at the Illinois Nutrient Research and Education Council. Below is a summary of key points provided by our expert panel. If you’d like to learn more, go “Beneath The Surface” and read detailed responses from our experts.

Phosphorus loss primarily occurs in two pathways: Dissolved Reactive P (DRP) and soil bound “Particulate” P (PP). While DRP can be lost in runoff, leaching (in sandy soils), or via tile drainage, PP is lost via sediment and surface runoff. Typically, the majority of P is lost via soil erosion, making conservation practices that reduce erosion the primary defense against P loss.

Soil erosion is the primary pathway for phosphorus loss from agricultural fields. Controlling soil erosion through reduced tillage and cover crops can minimize phosphorus loss.

University of Illinois assistant professor and ISAP network expert Dr. Andrew Margenot explained that dissolved reactive P (DRP) is important because it can be transported via surface runoff and to drainage tiles and is a form of immediately bioavailable P, not just to plants but also to algae. DRP is therefore a contributor to algal blooms and eutrophication of surface waters.

Phosphorus management is full of tradeoffs. While no-till and broadcast P fertilizer increases surface concentrations of P, which may leave fields at higher risk for DRP loss, tillage greatly increases potential for PP loss. Our ISAP experts recommend subsurface P, plus strip-till, as a way to reduce potential for both DRP and PP loss while using tillage.

Different cover crops impact phosphorus loss in different ways. Purdue Associate Professor and ISAP network expert, Dr. Shalamar Armstrong, recently completed a study showing that when compared to no cover crop, radishes had a greater or equal potential for DRP loss, while cereal rye and annual ryegrass significantly reduced potential for DRP loss.

Cereal rye cover crops reduce erosion and have been shown to reduce potential loss for dissolved reaction phosphorus.

Residues (especially high carbon, late terminated overwintering grasses) may slow P loss by keeping it immobilized in residue longer than residue from young grasses, brassicas and legumes that break down more quickly. 

The jury is still out on Edge of Field practices and stopping DRP loss. Buffers and wetlands are great for halting PP loss, but as wetlands eventually fill with soil, they have the potential to emit DRP from trapped sediment.

For a comprehensive P loss reduction strategy, our experts recommended the following key strategies: 1) reduce soil erosion, 2) follow the 4R principles of nutrient management, and 3) understand your soils and cropping system and their influence on P loss potential. 

Farmers can reduce phosphorus loss by following the 4R principles of nutrient management: Right Source, Right Rate, Right Time, and Right Place.


While more research certainly needs to be done on DRP and its management, ISAP emphasizes continued focus on the strategies that have been proven successful: reducing tillage, implementing cover crops, and use of 4R principles. Whether they be in-field or edge of field practices, farmers can and do have a real impact on the amount of nutrients leaving their fields. ISAP and its network of specialists and researchers can be a great resource on the current best practices for reducing nutrient loss. 

Special thanks to ISAP network experts Dr. Andrew Margenot (UIUC), Dr. Shalamar Armstrong (Purdue), Pete Fandel (ICC), Dr. Shani Golovay (NREC)

ISAP Coordinator