Keep reading to learn how your pond may be affected by fertilizers and options to reduce it.
Owning a home usually comes with the territory of making sure your yard looks great, something that can be expensive in the time, money, and effort spent. Landscapers, gardeners, and homeowners often add fertilizers to their yard to ensure growth, but what happens if all of those extra nutrients make their way into water?
Fertilizers are used for the purpose of making up gaps in nutrients for terrestrial plants. There may be a few applications where water is lacking nutrients to support life, however, these situations are few and far between – Very rare! Excess nutrients that make their way into the water can do significant ecological and monetary damage.
These are a few ways that fertilization can enter water bodies, also known as ‘runoff’:
- Plants can only absorb so much water/nutrients at any one time. Once the plant has taken up its maximum capacity at the time, the rest of the fertilizer stays put until eventually water washes it away – precipitation events, rain, snow, flood, etc.
- Depending on where you are located, plants can go dormant and overwinter. If fertilizer is used when plants are dormant (winter or early spring) the nutrients will not be absorbed and will be left to wash away.
- If you live in an area where you must water your yard or landscaping – overwatering has the potential to increase nutrient runoff by saturating the soil and that water pulling nutrients from the soil/plants.
- With spring being high precipitation season as well as a higher amount of fertilization to get growth started, this is a time when increase runoff is seen because both extra fertilizer is being added and rain events are more frequent.
- After mowing your yard, clippings that are left can also be a source of nutrient runoff and lead to higher amounts of growth in neighboring surface waters. In addition to the actual debris breaking down and releasing nutrients, there can be unused amounts of fertilizers that are attached to those clippings… and you guessed it, can wash into surface water nearby.
- Impervious surfaces such as sidewalks, driveways, roads, and patios increase the distance water can travel carrying nutrients. Some of these surfaces are designed to carry water to retention ponds or sewer systems as a measure of flood control, with u
So, what do these extra nutrients do? Is it bad to have fertilizers wash into my pond?
Having more nutrients than required for growing sounds like a good thing – better to have too many than not enough, right? Sadly, having too many nutrients can cause all types of other problems!
One major problem you have probably heard of is ‘eutrophication’. Eutrophication happens when debris (and nutrients) make their way into the water and break down – releasing nutrients – allowing for macrophytes and algae to grow rapidly with the newly available nutrients. These rapidly growing plants and algae can become so densely that sunlight no longer penetrates deeper into the water column; sometimes referred to as ‘algal blooms’. (Algal blooms themselves create a whole slew of issues that will be addressed more deeply in another article we post.) The shading of deeper plants makes it impossible for them to complete photosynthesis leading to the first decline in dissolved oxygen in the water The shaded plants still respire and add carbon dioxide while they are alive. The algae cells themselves are short-lived and end up growing & dying rather quickly, generations dropping to the benthos (or bottom). Once at the bottom they begin decomposing, releasing gasses such as carbon dioxide, additionally, bacteria and other decomposers get to work mechanically and chemically breaking down the algae further – using up oxygen and dispelling carbon dioxide.
In addition to larger organisms like invertebrates, fish, turtles, etc. continue to live in the same environment. These organisms do not produce oxygen but do respire creating more carbon dioxide in the water column. The low dissolved oxygen level is called ‘hypoxia’, more specifically when dissolved oxygen is less than 2-3 milligrams per liter of water, and reaches ‘anoxia’ or anoxic conditions when dissolved oxygen levels become 0 milligrams per liter of water and most aquatic life can not survive. A pond having hypoxic or anoxic conditions can have several serious side effects such as aquatic life becoming sick or possibly dying. Depending on the time of year, this could lead to large-scale fish kills in Texas ponds due to warmer weather and the fact that warm water holds less oxygen than cold water. If the pond is left alone and eutrophication is allowed to continue on, eventually the build-up of nutrients and dead plant/animal matter will cause the water body to fill in and eventually become a wetland, and even further to a grassy meadow.
How can you prevent nutrient runoff?
These steps can help prevent additional nutrients from entering your pond, every little bit you can do will help!
- Leave yard clippings and let them decompose in the yard, returning nutrients to the soil. If clippings are large, mulch first. However, remove clippings that are near impervious surfaces or waterways.
- Try to reduce the number of fertilizers you are currently using. It’s possible that using slow-release fertilizers with a smaller amount will allow for better absorption throughout the season, instead of a large amount several times, over-fertilizing and the water washing them away. It is also recommended to pay attention to the weather and apply the fertilizer when there is not a chance of heavy rain for several days after.
- Apply fertilizers directly to the roots of larger plants in your landscaping with hay or mulch placed over to ensure the moisture stays in at the roots but creates a barrier to keep fertilizers in place
- Instead of cutting your grass short, try to let it grow and cut it to a 3-inch height. This height allows for the roots to grow deeper and more developed. The more root mass each blade of grass has the better water/nutrient absorption, as well as more soil-stabilizing ability and further reduction of erosion.
- Make sure to keep fertilizers away from obvious areas of water runoff– ponds, sewers, drainage ditches, etc., or surfaces that do not absorb water (impervious services).