When feeding dairy cows, a buffer helps maintain a balanced rumen pH by limiting the effects of excess acid. Outside of the cow, buffers in a farm’s fields serve a similar purpose for the water features around them.
Buffers planted along a streambank, which are referred to as riparian buffers, can be thought of as a stream or creek’s “last line of defense against everything we do uphill,” described Danielle Rhea. In a Penn State Extension webinar, the water resources educator discussed how planting or retaining native trees, shrubs, or tall grasses along the banks of water sources filters out pollution while stabilizing the streambank.
The practice can also be useful for farmers since streamside land can be challenging to farm and may be prone to flooding, debris, and erosion. When livestock have access to streams, rivers, lakes, or ponds, diseases can be transmitted.
The benefits of riparian buffers stem from the presence of perennial roots near the water, Rhea said. Especially near cropland, it is valuable to have plants that can bind to phosphorus and sediment runoff before it makes its way into the water source, and deep roots allow the plants to take up nitrates in the soil. “Roots growing along streambank helps to protect that streambank, almost like an armor,” she described.
Riparian buffers can be constructed in many ways and contain a variety of species to be effective, but there are still a few best practices. Width is an especially important consideration depending on your goals. Rhea explained that to receive conservation funding, buffers often need to be at least 35 feet wide. This is also the typical width necessary to filter nitrogen, while phosphorus runoff requires more like 50 feet, she noted. If you are simply aiming to stabilize the bank, less than 35 feet would be okay. For larger goals such as sediment control, flood management, or wildlife habitat, though, you will need an increasingly wider buffer, said Rhea.
Grass is a great choice
It may seem like larger plants would have more buffering capability, and though different plants will provide different buffering benefits, Rhea also pointed to a study recently done at Penn State that found no significant difference in sediment filtration between trees and grasses. This is promising for livestock farmers because it means grasses can provide valuable buffering benefits with no leaf litter into fields and the opportunity to graze or harvest forage.
Field and forage educator Leanna Duppstadt added that grass buffers are easy to implement and maintain while simplifying weed management. When used in pastures, they cut back on animals standing in water, stabilize the streambank by reducing animal traffic, and can help limit overgrazing.
As long as you aren’t receiving funds for your buffers, harvesting the grass can provide forage while possibly helping the buffers improve sediment and nutrient removal. Making hay or grazing is possible, said Duppstadt; just be sure to leave at least 4 inches standing, preferably 6 inches. “We want these to be a buffer first. We don’t want to be cutting them too low,” she reminded. Grazing should be done in a “flash” manner — allow the animals out for less than a day. Do it when it’s dry, cool, or at night so the animals aren’t encouraged to go in the water.
If you’re interested in grass riparian buffers, select species by considering if your main goals are for nutrient filtration, bank stability, or forage harvest. Duppstadt advised that including at least 30% legumes will provide enough nitrogen for the grasses to grow.