With spring comes the greening of lawns and gardens — and, by extension, the greening of rivers, streams and other bodies of water. The first is a good thing. The second — well, that’s decidedly bad.
As we finally dust off the winter doldrums and head outside to start gardening, it’s easy to get over-eager with the lawn fertilizer and a bit excessive when we’re preparing the flowerbeds. It’s also easy to shrug off, because unless you’ve really gone over the top and the lawn turns brown, the effects of over-fertilization aren’t that noticeable.
That is, until you look at the waterways: All that excess nitrogen and phosphorus gets bound to the soil, and is either washed away by the rain or carried underground to the aquifer — and you can guess where it ends up from there.
“More often … [nitrogen] contained in soil, crop residues, fertilizers, and manures dissolves in water,” states a fact sheet from the University of Delaware. “While some of the dissolved [nitrogen] also leaves in runoff, the majority leaches through the soil past the root zone in subsurface drainage. Dissolved [nitrogen] leaves through natural underground laterally flowing water, or through artificial drainage systems like tile drains or drainage ditches.”
And while even water plants can use some nitrogen and phosphorus, “agricultural and urban land practices add more [nitrogen] and [phosphorus] to surface waters than they would receive under natural conditions. When one or both of these nutrients exceed critical concentrations, pollution of downstream water bodies can occur. High concentrations of nutrients in water bodies fuels the overgrowth of algae which impacts the local ecology by blocking sunlight from reaching beneficial submerged aquatic vegetation.”
The term for this is “nutrient pollution.” While it may seem harmless — it’s just making plants grow more, right? — it “often leads to large daily fluctuations in dissolved oxygen levels. Dissolved oxygen is used by fish and shellfish to breathe. Organisms that can escape the potentially lethal low dissolved oxygen levels leave, while those organisms that cannot leave typically die,” the fact sheet states.
So what can you do to stop nutrient pollution? It’s simple: measure, precisely, the amount of fertilizer you put on your lawn and garden. Better yet, don’t fertilize your lawn at all. Honestly, is a green lawn worth the damage the runoff does to the ecosystem?
Another way to curb nutrient pollution is to create buffer zones on your property. A buffer zone is an area that catches, slows and filters water runoff before it enters a stream or river.
It can remove chemicals, excess nutrients such as phosphorus and nitrogen (which come from lawn and crop fertilization), and sediment that’s been washed away in a heavy rain.
One type of buffer zone is a rain garden, which can be used to capture and filter runoff by utilizing rocks, blended soils and water-loving native plants.
If a stream or river runs along your property, create a no-mow zone of 5 feet or more (the wider the better). This allows better filtration of runoff before it reaches the stream, while also maintaining an area for wildlife. It also saves you money on gas and stabilizes the stream bank by reducing erosion. You can even go a step further by planting native wildflowers and grasses to improve the process. And remember: Never, ever dump leaves, grass clippings or any other debris into a stream.
Porous paving stones and driveway materials are also an integral part of a buffer zone. Instead of traditional macadam or cement — materials that deflect water — porous materials allow runoff to soak into the ground, which aids in filtration and helps prevent runoff.
This spring, green your lawn and garden — not the waterways. Mother nature will thank you.