Legacy Phosphorus

Legacy Phosphorus

Significant research and conservation efforts are ongoing across the greater Western Lake Erie Basin to develop and implement strategies to reduce nutrient loading and improve water quality in Lake Erie and other agricultural tributaries. One such particular nutrient getting attention from water quality researchers is phosphorus. 

The productivity of soil is largely dependent on the supply of nutrients that become available during the cropping season.  Crop growth is affected by the supply of plant available phosphorus in the soil, which is itself determined by the amount of phosphorus in the soil that is soluble in water and the rates of changes to it from other forms of phosphorus in the soil. Because many of Ohio’s soils are deficient in plant available phosphorus, the input of fertilizer and manure is required to optimize crop production. When applied on cropland, a small percentage of applied phosphorus is directly available for crops. Over the growing season, transformations take place in the soil making the remaining soil phosphorus available for the crops.  When the added phosphorus is not completely used by the crops, it accumulates in less available forms. This build-up of soil phosphorus is known as legacy-P. 

Legacy P can be defined in different ways, as it takes many forms and includes many time frames. It can be recently applied P that has been in the profile long enough to be immobilized. It can be P that was applied years ago and is still stored in the soil and subject to release. It can be P that moved with eroded soil and accumulated at the edge of fields. Or it can be P stored in the stream bed or stream bank system. Additionally, P moves between these various states as water moves it through the system.

Understanding Agricultural Phosphorus Loss Sources

In watersheds dominated by agricultural land use like the Western Lake Erie Basin, dissolved phosphorus losses from agriculture have been shown to represent a concern to water quality. Since 2007, dissolved phosphorus loss from croplands was identified as the primary cause of more frequent and intense algal blooms in Lake Erie. Since then, farmers and researchers continue to evaluate the sources and mechanisms of agricultural phosphorus losses and control.

For example, in a recent analysis by the USDA-ARS Soil Drainage Research Unit, and through using edge-of-field monitoring equipment, it was found that broadcasting liquid manure showed the highest rate of phosphorus loss when compared to other manure application methods like incorporating or injecting liquid manure into the soil. 

By identifying high-risk phosphorus loss sources, farmers can in turn determine which management practices are best for mitigating nutrient loss from newly applied fertilizer. But what about reducing legacy-P? 

Legacy Phosphorus vs. Newly Applied Phosphorus

“When mobilized, either through surface runoff or subsurface tile drainage, legacy phosphorus can get released into the land-to-freshwater transport continuum, acting as a continuing source of phosphorus to downstream water bodies for years, decades, or even centuries,” said Aaron Heilers, former Project Manager at Blanchard River Demonstration Farms Network. “Addressing the source and transport processes of legacy phosphorus is critical to helping farmers make better nutrient management decisions.” 

Agricultural phosphorus loss sources can be approximately divided into two categories, those derived from legacy-P and those derived from newly applied phosphors such as fertilizer. Differentiating between newly applied phosphorus and legacy-P allows researchers to account for total agricultural phosphorus losses.

In an analysis from the Ohio USDA–ARS Edge-of-Field Monitoring Network, data indicates that legacy-P contributes to 80% of phosphorus loss, and newly applied phosphorus, from that of either chemical fertilizer or manure, contributes to the remaining 20% of phosphorus loss.

Also important is recognizing the pathways of phosphorus loss from croplands. Surface runoff caused by rain events and erosion are well-recognized pathways of phosphorus loss. However, subsurface tile drainage is also identified as a primary pathway of phosphorus loss, accounting for over 60% of losses. These two dynamics and interrelated but conflicting processes, complicate strategies to change farm management to manage phosphorus loss.

Managing Legacy Phosphorus

There are numerous ways to manage general nutrient loss as it is released from croplands. One practice-based framework is the USDA–NRCS’s Avoid, Control, and Trap (ACT) conservation approach. 

This approach uses conservation practices to avoid loss, control transport, and trap lost soil resources and nutrient inputs. Avoiding practices would include nutrient management and the 4-R’s. Controlling practices include conservation tillage and cover crops. Trapping practices include buffer strips, wetlands, and riparian zone management. These practices help farmers reduce nutrient loss by lessening the amount of soil, nutrient and pesticide inputs leaving the field. 

Management practices specifically known to reduce the loss of legacy-P are less known. In a first known study of its kind, researchers from the USDA-ARS Soil Drainage Research Unit, The Ohio State University and Iowa State University, are beginning to evaluate the source contributions of legacy-P and newly applied phosphorus through edge-of-field data. 

To learn more about the conservation practices improving agriculture’s impact on downstream water quality in Ohio, visit the Practices page.

Improving Water Quality From Home

Improving Water Quality from Home

Research being done at the Blanchard River Demonstration Farm sites is helping researchers determine which conservation practices work best for reducing nutrient and sediment loss. This information is showing farmers and rural property owners what tools and practices they can implement on their farms and within their rural residences to improve agriculture’s impact on downstream water quality in Ohio.


Conventional Septic Systems vs. Wastewater Irrigation Systems

Nitrogen and phosphorus are essential nutrients all living things require. However, an overabundance of these nutrients in both ground and surface water can lead to dense plant and algae growth in lakes and other bodies of water, resulting in toxins in drinking water and excessive nutrient richness in lakes that have been known to cause harmful algal blooms.

In the rural landscape, poorly managed or outdated home septic systems – used to treat human waste and household wastewater – are one of many possible sources that can result in an overabundance of nutrients, such as nitrogen and phosphorus, reaching surface water. In addition, conventional home septic systems are typically not designed to remove phosphorus. According to a study from Ohio State University, “Phosphorus Reduction from Septic Systems,” phosphorus can come from a variety of contributors within the home, such as tap water, the kitchen sink disposal, human waste, and lawn care fertilizer.

With this in mind, the Blanchard River Demonstration Farms Network worked with Ohio State University researchers Mike Rowan and Karen Mancl, as well as other partners, to showcase how rural property owners can reduce nutrient discharge through an alternative septic system – a wastewater irrigation system. In contrast to a conventional system, this option allows wastewater to be reused through lawn and landscaping sprayers after the wastewater has been treated and disinfected. 

Benefits of Onsite Wastewater Reuse

  • Turns wastewater into clear, odorless effluent for reuse as irrigation for lawn and landscape vegetative growth
  • Reduces discharge of nitrogen and phosphorus to groundwater and streams
  • Low cost and low energy

Home Septic System Replacement at Stateler Family Farms

With a nearly 70-year-old septic system in need of replacement, the Statelers had two options: replace their existing system with a “new” conventional septic system or install a wastewater irrigation system. 

As traditional systems age, there is the potential for environmental degradation. Even if the Statelers replaced their outdated traditional system with a “new” traditional system, the possibility for excessive phosphorus to escape and impact downstream water quality would still exist. Not to mention that existing site conditions were not conducive to a replacement due to poorly drained soils and lack of appropriate depth to treat the wastewater. As a result, fill dirt would have been needed.

Treated wastewater being sprayed onto the landscape through a series of three above-ground sprinkler heads.

In comparison, a wastewater irrigation system would allow the Statelers to filter wastewater, disinfect pathogens and bacteria with ultraviolet light, and pump the treated wastewater through spray irrigation nozzles onto the landscape to be used by growing vegetation. This system reduces nutrient loss off-site that could potentially impact downstream water quality. 

Most soils in Ohio don’t allow for traditional leach fields, making alternative sewage systems more prevalent, explains Matt Deaton, a soil scientist with Deaton Soil Services in Eaton, Ohio. “Spray irrigation systems like that used at the Stateler site offer homeowners another option when considering solutions for their properties,” he says. “They’re the only systems where the wastewater is technically reused in an environmentally friendly way, as opposed to just being disposed of.”


Water Quality Improvements

With the installation of an irrigation system at the Statelers, wastewater biochemical oxygen demand (BOD), phosphorus and suspended solids were all reduced. The majority of the phosphorus removal from this system occurs through the spray irrigation system where phosphorus is absorbed by the soil and/or taken up by plants. The removal of BOD, nitrogen and suspended solids occurs prior to spray irrigating. The total cost of the installation, including all components, excavation, and labor for electrical installation, was $28,000. 


Wastewater Parameter Main Environmental Concern Conventional Septic System Wastewater Irrigation System % Reduction
Biochemical Oxygen Demand (BOD) Harmful to aquatic life 206 mg/l Not detected 100%
Nitrogen, KJELDAHL Surface and groundwater pollutant; lake eutrophication (algal blooms) 21.5 mg/l Not detected 100%
Nitrogen, Ammonia (NH3, NH4+) Toxic to aquatic life 3.26 mg/l 0.39 mg/l 88%
Nitrogen, Nitrate + Nitrite (NO2-, NO3-) Surface and groundwater pollutant; algal blooms; Infant Methemoglobinemia (Blue Baby Syndrome) Not detected 7.5 mg/l N/A
Phosphorus Surface water pollutant; lake eutrophication (algal blooms) 2.06 mg/l 1.94 mg/l 6%
Suspended Solids Increased BOD and phosphorus transport; harmful to streambed habitats  372 mg/l 7 mg/l 98%

Source: Jones & Henry Laboratories, Inc.


Water quality samples were collected at the Statelers prior to the new wastewater irrigation system installation and four months after installation. Upon completion, each wastewater parameter saw a reduction in nutrients with the exception of nitrogen. Within the irrigation system, organic nitrogen is converted to ammonia, which naturally converts to nitrite and nitrate. This explains the increase in nitrate and nitrite from not detected to 7.5 mg/l because the irrigation system provides for the complete cycling of nitrogen.  

To learn more about the conservation practices improving agriculture’s impact on downstream water quality in Ohio, please visit our practice pages

Home Septic System Replacement

Rural property owners can help reduce nutrient discharge through a wastewater irrigation system. This home septic system allows wastewater to be reused through lawn and landscaping sprayers after the wastewater has been treated and disinfected.

To learn more about this system and its research on water quality improvements, download the fact sheet below.

Conventional Septic Systems vs. Wastewater Irrigation Systems


From the Ground Up: Constructing an Animal Mortality Composting Facility


As a livestock producer with a passion for conservation, Duane Stateler knows the importance of a properly managed mortality composting system. So when he saw a gap in the efficiency of his own mortality composting barn, he worked with the Ohio Natural Resources Conservation Service (NRCS) to plan and construct a new facility that was economical, environmentally safe and bio-secure. 

“Our old setup we had was just an old barn that we used to raise pigs in, and we basically had three different driveways,” says Duane. “The three beds didn’t work out very well, as far as being able to turn. We needed to have at least five different beds to make the system work well.” 

The driveway beds Duane is referring to are an important part of turning carcass waste into compost – an environmentally and economically valuable resource. 

Creating an optimal environment in which microorganisms can convert the organic material into compost that can be used as a soil amendment or fertilizer relies heavily on the construction of the facility. 

“NRCS has practice standards for any practice that we build,” says Greg Wells, NRCS engineer. “Our practice standards not only provide the criteria by which we plan and site these facilities, but also give us a list of technical references that we use when building these types of facilities.”

Specifications for an animal mortality composting facility include reinforced concrete, pressure-treated lumber and rot-resistant materials. This guidance ensures that the facility will last well beyond its expected lifespan when built according to NRCS construction standards. 

The construction standards of a mortality composting facility encompass three areas: 1) An impervious weight-bearing concrete pad to support and allow heavy equipment to maneuver on; prevent seepage of nutrients and bacteria into groundwater; and provide a durable, all-weather surface to allow the process to continue year-round. 2) A covered roof or other water-repelling material to prevent excessive moisture on composting materials. 3) Rot-resistant building materials strong enough to withstand the force exerted by equipment such as preservative pressure-treated lumber, concrete, hot-dipped galvanized and/or stainless steel nails and fasteners. 

By creating a durable structure, Duane and other producers can experience the benefits to their operation. A properly managed mortality composting system is low-cost, environmentally beneficial and safe. 

Composting has low to moderate start-up costs and minimal operating costs. Availability and cost of a composting medium (sawdust, wood chips, straw, etc.) are the only significant ongoing operating requirements.

In addition, composting in a structure like this is enhanced and accelerated by mixing organic waste with other ingredients to optimize microbial growth. This allows for turning waste into a beneficial fertilizer and soil amendment, resulting in on-farm nutrient recycling. 

Lastly, composting allows immediate year-round disposal of carcasses so that disease is not spread. There is no entry of off-farm vehicles that can bring disease onto the farm from other operations, and the high temperatures in the compost pile kill pathogens. A well-functioning compost pile gives off little odor and does not harm or affect groundwater. Nuisances such as flies, vermin, and scavenging animals are also prevented. 

“Animal mortality composting facilities provide the farmer a way to dispose of animal carcass waste on-site in an eye-appealing manner,” says Greg. “And if it’s managed right, the farmer doesn’t have any water quality or odor concerns.”

Producers looking to implement this practice in their operations should take the next steps by contacting their local NRCS office for financial and technical assistance and check out the OSU Extension “Ohio Mortality Composting Certification Workshop.” 

To view the construction process of a mortality composting facility at the Stateler Family Farms demonstration site, visit the Animal Mortality Composting practice page.

2 Reasons to Seal Abandoned Water Wells

farm pump photoAbandoned or unused water wells can be found almost anywhere: on farms, industrial sites, and in urban areas. You may be able to easily spot a water well when they are marked by a windmill tower or an old hand pump. Others are not so clearly marked. Many abandoned water wells may lie hidden beneath weeds and brush, unsuspecting not only to children, hunters and animals, but an unlimited number of potential contaminants. Fuel, fertilizer, solvents, sewage, animal waste, pesticides, and other contaminants have all been introduced into groundwater through unsealed wells

Each year, many unused wells are abandoned when they no longer serve a safe or practical purpose for accessing groundwater. In addition, wells are often abandoned when homes are connected to community water supplies or the quality of the water supply has degraded. According to the Ohio Water Resources Council, there is no accurate accounting of how many abandoned wells are in Ohio, but it’s estimated that tens of thousands of unused wells exist. 

If you have a water well that is no longer in use on your farm or land, it’s important to properly seal it. Here’s why:

Protect groundwater quality

Throughout the landscape, there are potential conduits to drinking water underground, and water wells are one of those conduits. Old wells that have been abandoned are sometimes found in crop fields. By working with a qualified contractor through your local health department, you can properly cap the old well.

“By sealing any unused water wells that you have on your property, you are removing potential liabilities, “ states Jim Raab, Geology Program Supervisor, Division of Geological Survey at the Ohio Department of Natural Resources. “Sealing wells removes potential contamination pathways to the aquifer that you and your neighbors could be using for water supply.” 

Sealing the old well eliminates the potential for contaminants such as nutrients and pesticides from directly reaching the groundwater. As a rule of thumb, if a substance can be dissolved, carried, or mixed in water, it has the potential for entering groundwater through an unsealed abandoned water well.

Prevent physical hazards

One of the more obvious reasons for sealing an abandoned water well is the physical dangers they present for the public and wildlife. Many of Ohio’s domestic wells fall in between the five to eight-inch diameter range, posing a potential hazard for children and small animals. 

In addition, Raab says that “sinkholes” are another danger. Large holes in the ground develop when an improperly covered water well or buried dug well gives way. “These wells need to be sealed from the bottom to the top,” explains Raab. 

Sealing an Unused Well

It’s highly recommended to seal wells with the help of an experienced registered water systems contractor due to the equipment and knowledge involved. According to the Ohio Department of Natural Resources, the basic procedures for sealing an unused well are:

  • Remove all equipment such as pumps, pressure lines, etc. that may obstruct the placement and performance of the sealing agent. 
  • An attempt should be made to remove screens, casings and liners, although in many instances this may be difficult or impossible. If possible, the casing and/or liner should be slit, perforated, or ripped to allow the sealing agent to make the best possible seal.
  • If the casing cannot be pulled, it should be cut off below ground level. The depth at which the casing should be cut will depend on whether the well was classified as public or private; in most cases, four feet will be sufficient.
  • Ideally, the material used in sealing an abandoned well should reflect the surrounding geologic formations. Unfortunately, in most instances, the formations or their exact depths may not be known. Therefore, it is often hard to match the materials that should be used to the various formations. Many types of suitable materials are readily available for sealing abandoned wells. For best results, a bentonite clay should be placed in the well from the bottom up to the surface using a tremie pipe. As the well is filled, the tremie pipe should be moved upward until the entire borehole is sealed. This helps to prevent bridging of the sealing agent, which can occur when the sealing material is poured into the well. Some other acceptable sealing materials include neat cement or a combination of neat cement and bentonite.
  • The location of the abandoned well and the specifics of the sealing procedure should be recorded and then reported to the Ohio Department of Natural Resources and other appropriate agencies (e.g. Department of Health, Ohio EPA). 

To view the process of an old well capping at the Kellogg Farms demonstration site, visit the Abandoned Well Removal practice page. 

For more information about well abandonment and its impact on water quality, please visit our resource library. If you have specific questions, contact your local OEPA district office, health department, or the Ohio Department of Natural Resources.

Reducing Nutrient and Sediment Loss: Part 4

Research being done at the Blanchard River Demonstration Farms and other related sites around the state is helping researchers determine what practices work best for reducing nutrient and sediment loss. Over the last five years, on-farm research has shown that three practices in particular help reduce nutrient and sediment loss:

  • Following the 4R approach
  • Reducing soil erosion
  • Developing a water management plan

Research shows that phosphorus is leaving the farm via water, through both surface and subsurface runoff. Implementing practices that slow, stop and/or treat water before it exits the farm can greatly reduce phosphorus discharge downstream. However, the unpredictability of the weather can make this difficult. In fact, the frequency of rainfall events totaling 1 inch or more has almost doubled in most northwest Ohio towns. These intense rainfall events drive a majority of nutrients downstream each year.

By developing a water management plan, you can begin to identify where nutrients are potentially escaping your farm and determine appropriate solutions, such as drainage water management structures, phosphorus removal beds, two-stage ditches, reconstructed wetlands and filter strips.

Saturated Buffer

What is it: Saturated buffers are a new practice that redirects a portion of field tile drainage water into riparian zones rather than into surface waters like traditional tile outlets. Riparian zones are areas adjacent to streams. Diverted waters then filter through the soil in the riparian zone before entering surface water/streams. Research on saturated buffers is ongoing.

How it helps: The goal of the saturated buffer is to use the riparian zone as a sponge to treat the tile water leaving the field. Once the riparian zone is full of water, or saturated, the water is slowly released through the soil and the nutrients are removed. This process is most effective at reducing nitrogen by causing it to turn into a gas, or denitrify. Phosphorus removal is still highly variable and needs to be studied further.

Drainage Water Management

What is it: Drainage Water Management (DWM) is an NRCS-approved conservation engineering practice that manages water discharge from surface and/or subsurface agricultural drainage systems. A DWM structure holds water in root zones when crops need it and drains it when there’s too much.

How it helps: By adjusting the tile outlet elevation, a DWM structure manages the timing and amount of water discharged from agricultural drainage systems. From a water quality standpoint, DWM provides the most benefit by raising the tile outlet elevation immediately after harvest until early spring. A DWM structure can impact nutrient movement, primarily reducing nitrogen loss.

“If we can get by with free-flowing drainage only three or four months a year we can show that constant drip from the tile going into the steams. We will spend about $4,000 for 50 more acres of controlled drainage structures. If we would get a 5% yield increase in a couple of dry years, it pays for itself.” – Duane Stateler

Sites should be evaluated by SWCD and NRCS professionals to determine if this practice can address the resource concern of the producer. If reduction of phosphorus is the primary resource concern, then the producer should look to other practices that are more efficient at removing phosphorus.


This article was featured in the September/October 2021 edition of Our Ohio Magazine

After fall field work is complete, the structures are closed until mid-March. Then the structures are opened, allowing drainage water to flow freely to the outlet. After spring field work is completed (planting and sidedressing corn), the structures are closed again until two weeks prior to harvest. This allows the soil to once again drain freely so harvest equipment can enter the field. Once fall field work is complete, the structures are closed.

Five Years In: An Update on the Conservation Practices’ Research & Results

To dive into the latest research and results from the Ohio Demonstration Farm sites, take a look at our 2021 Project Update.

What you’ll find inside:

  • Ohio’s Water Quality Problem
  • About the Blanchard River Demonstration Farms Network
  • How to Improve Quality through Reliable Conservation Practices
  • The Impact of the Blanchard River Demonstration Farms Network
  • New Satellite Research Sites Added
  • Latest Research, Resources, and Tools
  • What’s Ahead for the Blanchard River Demonstration Farms Network
  • How to Implement Conservation Practices to Reach Your Land Management Goals
  • The Demonstration Farm Families and their Conservation Practices

Reducing Nutrient and Sediment Loss: Part 3

Research being done at the Blanchard River Demonstration Farms and other related sites around the state is helping researchers determine what practices work best for reducing nutrient and sediment loss. Over the last five years, on-farm research has shown that three practices in particular help reduce nutrient and sediment loss:

  • Following the 4R approach
  • Reducing soil erosion
  • Developing a water management plan

Keeping valuable topsoil on the farm is critical to sustainable agriculture, and reducing soil loss can play an important role in water quality concerns downstream.

Soil erosion is the gradual process of deteriorating or wearing away a field’s topsoil by water, wind or mismanaged human activities.

Improved soil health and the use of cover crops can reduce soil erosion.

Soil Health

Soil health is a condition of the soil and its potential to sustain function within its natural or managed ecosystems. Soil health can be evaluated by several indicators, including pH, aggregate stability, available water capacity, active carbon and organic matter.

How it helps: A healthy soil performs many vital tasks, including regulating water and filtering nutrients. By improving soil structure, water can better infiltrate the soil profile and be absorbed.

“If you’re going to choose a practice as a fix (for a problem), it better be right. That’s why I think this testing is so important.” – Chris Kurt

Interseeding cover crops into V5 corn at Kurt Farms.

Cover Crops

Cover Crops such as cereal rye, oats and winter wheat are planted to temporarily protect the ground from wind and water erosion and supply living roots to the soil during times when cropland is often not adequately protected.

How it helps: Keeping living roots in the soil as much as possible help improve soil health by adding organic matter and biological activity. The root structure of the cover crops also helps hold the soil in place during a season when the ground would otherwise be bare.

Preliminary research from edge-of-field studies shows cover crops can be excellent scavengers of nitrogen and help reduce the amount of what that leaves the field. Additional longer-term research is needed to develop conclusions about dissolved reactive phosphorus.


This article was featured in the July/August 2021 edition of Our Ohio Magazine

Rainfall Pattern Increase in Ohio

In recent years rainfall has been more frequent and intense. These rainfall patterns have continued to change over the last 30 years, trending upward. Aaron Heilers, project manager of the Demo Farms Network, discusses how these rainfall episodes affect soil nutrients and how farmers can properly manage their farms so they become more resilient.

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