Strategies for Preventing Algae and Aquatic Plant Problems in Farm Ponds

Overabundant aquatic plant and algae growth is one of the primary problems that pond owners face in Pennsylvania. While there are numerous methods for controlling plants and algae after they have already become a problem, preventing nuisance vegetation in the first place is far preferable because it will require less management and money in the long run. Since most excessive aquatic plant and algae growth is caused by high levels of nutrients, particularly phosphorus, one of the best ways to prevent plant and algae growth is by preventing nutrient pollution. Most ponds are water catchments, and incoming nutrients can accumulate over time. Luckily, there are many strategies that can be employed to minimize nutrients making their way into the pond.

The first step to controlling nutrients is determining the source of the problem. In the case of ponds, we need to consider the entire pond watershed, or all of the land that drains into the pond. We know that for pollution to occur, there must be two things: a source of pollution and a transport mechanism that carries the pollution from the source to the pond. For farm ponds, the source of nutrients could be fertilizer or manure applications, manure stacking or storage areas, exposed soil, animal concentration areas, and even septic systems. When livestock access ponds directly, they will deposit nutrients directly in the water. When there is no direct animal access, the transport mechanism is most often runoff carrying nutrients from uphill in the pond watershed down into the pond.  Solutions for reducing nutrient pollution in our farm ponds focus on addressing the source and/or preventing the transport of nutrients.

Nutrient/Manure Management

Just as the application of fertilizer and manure nutrients can promote crop growth, the nutrients can also facilitate the growth of algae and aquatic plants if they reach the pond. One way to reduce the source of pollution is to apply nutrients to fields based on crop needs. Farms in Pennsylvania that produce or use manure are required to have either a Manure Management Plan or a Nutrient Management Plan to help balance nutrient applications with the requirements of the crops. Plants can only consume a limited amount of nutrients in a growing season.  Applying more fertilizer or manure than a plant can take up is not only a waste of money but also increases the likelihood that the nutrients will be moved by runoff and become nutrient pollution in a farm pond or other water body. Similarly, applying manure or fertilizers immediately before heavy rainfall increases the likelihood that it will be moved by runoff, rather than being utilized by crops. Applying nutrients at the right rate and right time are two key pillars of proper manure and nutrient management.

Proper Manure Storage

Both temporary and permanent manure storage on farms have requirements to minimize their impact on surface water.  Nutrient and manure management regulations outline best practices for preventing nutrient pollution from manure storage and stacking areas. Permanent manure storage must be designed to have adequate capacity based on the amount of manure produced, bedding used, and additional inputs as well as considering how frequently the storage is emptied for manure applications. 

Generally, there should be no evidence of manure storage leaking, and storage facilities should be located at least 100 feet away from ponds and, in some cases, 200 feet away from ponds when located on steeper slopes.  Temporary infield manure stacks should also be located at least 100 feet away from ponds and should not be located on high-risk areas such as steep slopes, areas with concentrated water flow, or places with seasonal high water tables. Temporary, infield manure stacks should be land applied after 120 days or covered with an impermeable cover.  For more specific guidance related to manure storage and stacking regulations, please consult your operation's Manure Management or Nutrient Management Plan or your local County Conservation District.

Application Setbacks 

Another best management practice and requirement of a Nutrient or Manure Management Plan is creating manure application setbacks around environmentally sensitive areas, including ponds. Regulations require manure application setbacks ranging from 35 feet when a permanent vegetative buffer is in place to 100 feet when a vegetative buffer is not present. There are special scenarios in Pennsylvania when a plan called a Nutrient Balance Sheet is provided with manure imported from another farm that requires a 150-foot setback.  While not necessarily regulated the same way, keeping fertilizer applications away from the edge of the pond is also recommended.  Generally, the farther away nutrients are applied, the less likely it is that they will reach the pond. Setbacks also pertain to upslope streams or springs that supply the pond.

Riparian Buffers  

A great companion practice to manure and fertilizer application setbacks is the establishment of a riparian buffer. Riparian buffers involve planting or maintaining trees, shrubs, and/or perennial grasses or wildflowers along the banks of rivers, streams, lakes, and ponds. This permanent vegetation "buffers" the pond; that is, it lessens the impact of nearby land uses by increasing infiltration, filtering runoff, and capturing sediment, nutrients, or other pollutants. The plants' root matter also helps stabilize banks and prevent erosion and collapse.  Riparian buffers are touted as one of the best ways to protect water quality.  Like nutrient application setbacks, the wider the buffer, the greater the benefits.  A buffer with larger vegetation, such as trees and tall shrubs, can also help to shade the water which provides additional plant and algae control benefits by cooling the water and limiting direct sunlight. In addition to water quality, riparian buffers can provide additional practical benefits such as keeping livestock and equipment away from unstable banks, reducing property loss, and improving wildlife and pollinator habitats.

Fencing Out Livestock 

Surface water resources found on farms may be thought of as readily available drinking water sources; however, keeping livestock out of ponds provides both water quality and herd health benefits. The connection between livestock access to ponds and nutrient pollution is an easy one to make.  When livestock wade into ponds either to get a drink or to cool off, they will inevitably urinate and defecate directly into the pond.  The hoof traffic into and out of the pond or even just to the water’s edge will trample surrounding vegetation. This typically results in exposed soil and eroding banks, leading to increased sediment transport into the pond along with any nutrients bound to those soil particles. In some cases, producers may limit livestock access by creating specific stabilized access points for watering; however, when at all possible, it is always best to completely exclude livestock from the pond. 

While fencing livestock out of a pond may seemingly appear only to benefit water quality, there are several potential and documented benefits to herd health as well. One consideration is that pond water may not have desirable water quality for consumption.  While livestock drinking water requirements are not always easy to come by, water quality parameters like pH, nitrate, and bacteria are important and can be of concern. 

While pH levels are typically determined by the primary water source of the pond, nitrate, and bacteria levels are likely to be elevated in ponds impacted by manure. Drinking water far outside of the recommended pH range can lead to acidosis or alkalosis, reduced production, depressed milkfat, poor gains, lower feed intake, and more infection or metabolic problems.

Livestock drinking water with elevated nitrates could cause reproductive problems and reduced weight gain in young stock, although this depends on the amount of nitrate in the ration. 

Finally, the general recommendation for E. coli bacteria in livestock drinking water is that it should be absent. E. coli bacteria can alter and compete with the rumen microflora, reduce production, or cause illness in ruminants.  The water quality of Pennsylvania ponds is variable, and the only way to know the quality of your pond water is to test it.

Even if your pond water quality test results show acceptable water quality for livestock consumption, pond water is not considered to be the most palatable choice for livestock. The article Water Quality Matters for Cattle on Pasture, published by the Noble Foundation in 2019, summarized a study comparing the effect of water sources on the average daily gain of cattle. This study found that cattle will avoid water contaminated with as little as 0.005% manure, when given the choice. Knowing this, it is unsurprising to learn that this study also found that water pumped to a trough had greater palatability than water being consumed directly from a pond, even if the source of that pumped water was a pond. Consequently, pastured cattle gained 9-10% more weight when provided with water pumped to a trough, even when there were no significant differences in water quality between the pond water and the pumped water.

Another risk of allowing livestock to access ponds for drinking water is the potential exposure to cyanobacteria toxins. Cyanobacteria, commonly called blue-green algae, are photosynthesizing bacteria that can release toxins.  Typically, the toxin release happens in conjunction with a bloom, or an explosion of growth. Consequently, cyanobacteria blooms are frequently called harmful algae blooms (HABs). HABs are most common during hot, dry weather in ponds with seasonally low water flow, higher water temperatures, and abundant accumulated levels of nutrients. HABs can appear as scum on the surface that is sometimes compared to spilled paint or pea soup.  Livestock should never be permitted to consume water from ponds that you think may be experiencing a HAB because toxins can lead to diarrhea, lack of coordination, labored breathing, liver damage, and even death.

Erosion and Sediment Control

Most phosphorus enters a pond attached to soil particles that have been eroded by water and are suspended in runoff. In Pennsylvania, farmers can develop their own Agricultural Erosion and Sediment Control Plan (Ag E&S Plan) to outline how they will manage their farm to reduce accelerated soil erosion. Penn State Extension has a growing list of Agricultural Erosion and Sediment Control Planning Resources available online for farmers interested in developing their operation's Ag E&S Plan on their own. For assistance, farmers can reach out to their County Conservation District for help in developing an Ag E&S Plan or locating a consultant, or they can reach out to their local Natural Resources Conservation Service Center for assistance in developing a Conservation Plan. While either of these plans can be used to reduce erosion and sedimentation into nearby waterbodies, they will also help maintain productive topsoil to ensure crop yields and soil fertility remain sustainable for years to come. 

Considering in-field practices that help reduce erosion and increase water infiltration on fields uphill of the pond will retain topsoil and reduce sediment and nutrient pollution. Practices such as leaving crop residue after harvest, planting cover crops, utilizing no-till or reduced tillage, contour farming, contour strip cropping, implementing a conservation crop rotation, and installing terraces and diversions are all management practices to reduce soil erosion.  In livestock operations, preventing overgrazing can also minimize the impact of pastures on pond water quality.  Practices such as rotational grazing, ensuring proper stocking rates, and properly managing animal heavy-use areas can help maintain dense vegetation, minimize bare spots, and result in less sediment and nutrient runoff. In-pasture feeders and waterers should be located away from the pond and moved periodically to allow vegetation to reestablish. Permanent animal heavy-use areas should be stabilized with gravel or concrete and/or roofed to prevent erosion. Vegetated treatment areas can also be installed to adsorb nutrient-laden runoff from a heavy-use area. 

In addition to farm-specific practices, another option for erosion and sediment control is installing a sediment pond uphill of your farm pond. The purpose of the sediment pond is to capture any runoff before it reaches the pond and allow sediment to settle out in the sediment pond before water enters the main pond, either by way of infiltration or a riser pipe. Sediment ponds can be used when uphill erosion cannot be controlled; however, accumulated sediment will need to be dredged periodically to allow for continued erosion control.

Control Nuisance Goose Populations

Just as manure from livestock adds nutrients into a pond, so does the waste from wildlife. The most likely species of concern are large, resident flocks of Canada geese. An adult goose can produce 2 to 4 pounds of manure each day, resulting in close to 1,000 pounds of waste each year. Consequently, short, migratory stops are often not a large concern, but when geese remain and reproduce, they can deposit a significant and growing supply of nutrients. Luckily, there are several strategies that can be employed to deter geese. Often simplest and most effective strategy is establishing a vegetative buffer around the entire pond. Surrounding the pond with tall vegetation makes the pond harder for geese to access and limits their visibility, making them feel at risk to predators and deterring geese from spending time in the pond. Other barriers include fencing around the pond or covering the surface with a grid of monofilament line. If geese are nesting around the pond, the eggs can be oiled with corn oil to prevent eggs from developing, although this does require a permit from the U.S. Fish and Wildlife Service. Resident Canada geese can also be legally harvested in Pennsylvania during certain seasons by those with a Pennsylvania Migratory Game Bird hunting license and federal duck stamp. Chemical deterrents can also be sprayed around the pond; however, these can create different water quality issues when runoff washes into the pond.

Septic System Maintenance

 Human waste can create the same nutrient problems as livestock and wildlife waste.  For properties that have on-lot septic systems, it is important to maintain the septic system to minimize their potential impact on the watershed. An important step is to locate the septic system as far from the pond as possible. Regardless of where the septic system is located, proper management and pumping the septic system every three years is recommended to ensure the system is not overburdened and generating nutrient pollution. 

Conclusion

Controlling nutrients is key for preventing problems with aquatic plants and algae growth in ponds.  Without it, pond management will be limited to reacting to excessive growth after it has already started.  Simply reacting by eliminating overabundant plant and algae growth without addressing the underlying cause will often just create a different set of problems. For example, controlling submerged and floating aquatic plants with herbicides can lead to increased algae growth as the plant material decays and releases nutrients into the water. While prevention is best, if you are already experiencing problems, developing an integrated approach will often be necessary. These solutions will not only focus on killing nuisance plants and algae but will also involve learning more about the pond and its watershed, evaluating all of the possible control options, and taking steps to identify and control nutrient sources and transport mechanisms so that excessive algae and aquatic plant problems will improve over time.

Sources and Additional Information

Agricultural Analytical Services Lab. “Summary of Pond/Lake Water Samples.” Agricultural Analytical Services Lab (Penn State College of Agricultural Sciences). Accessed August 14, 2024.

Briggs, Nathan G., and Ronald  P. Lemenager. "Heavy Use Area Pads for Cattle." Penn State Extension, April 3, 2023.

Duppstadt, Leanna. “Livestock Water Quality.” Penn State Extension, June 17, 2024.

Duppstadt, Leanna, and Danielle Rhea. "Riparian Buffers for Field Crops, Hay, and Pastures." Penn State Extension, October 13, 2021.

Hebbert, Caitlin. “Water Quality Matters for Cattle on Pasture.” Drovers, June 27, 2019.

"Pennsylvania Manure Application Setbacks and Requirements" Pennsylvania Nutrient Management Program. 2014.

Rhea, Danielle, and Jennifer Weld. "Agricultural Erosion and Sediment Control Planning Resources." Penn State Extension, June 9, 2022.

Swistock, Bryan. "Interpreting Drinking Water Tests for Dairy Cows." Penn State Extension, May 13, 2024.

Swistock, Bryan, and Mark Hartle. Management of Aquatic Plants. University Park, PA: Penn State Extension. 2018.

The Pennsylvania State Conservation Commission. Pennsylvania’s Nutrient Management Act Program Technical Manual. 12.0 ed. October 2023.

Wulfhorst, Peter. "Pond and Lake Wildlife: Canada Geese." Penn State Extension. October 19, 2023.