Harvesting vegetation on riparian buffers barely reduces water-quality benefits

Date:
October 2, 2020
Source:
Penn State
Summary:
Allowing farmers to harvest vegetation from their riparian buffers
will not significantly impede the ability of those streamside tracts
to protect water quality by capturing nutrients and sediment --
and it will boost farmers' willingness to establish buffers.



FULL STORY ========================================================================== Allowing farmers to harvest vegetation from their riparian buffers will
not significantly impede the ability of those streamside tracts to protect water quality by capturing nutrients and sediment -- and it will boost
farmers' willingness to establish buffers.


==========================================================================
That is the conclusion of Penn State College of Agricultural Sciences researchers, who compared the impacts of six riparian buffer design
scenarios over two, four-year crop rotations in two small central and southeastern Pennsylvania watersheds. Two of the buffer scenarios included
the harvesting of switchgrass and swamp willow trees.

Allowing farmers to harvest vegetation from their riparian buffers
and sell it for biofuels -- not permitted under current Conservation
Reserve Enhancement Program, or CREP, federal regulations -- would
go a long way toward persuading farmers to establish riparian buffers, researchers contend. And farmers' buy-in is badly needed in Pennsylvania,
where hundreds of miles of new buffers are needed along streams emptying
into the Chesapeake Bay to help the state meet water-quality standards.

"This is the first long-term study in the Chesapeake Bay watershed to
model how harvesting vegetation affects riparian buffer performance
over the full length of a buffer contract," said researcher Heather Preisendanz, associate professor of agricultural and biological
engineering. "Allowing harvesting of the buffer vegetation -- either trees
or grasses -- minimally impacted water quality, with only slight annual
average reductions in the capture of nitrogen, phosphorus and sediment."
In addition, she noted, under the highest input loading conditions --
heavy runoff after storms -- buffers with lower removal efficiencies
removed more total mass of pollutants than did buffers with high-removal efficiencies, if they were between streams and fields with row crops
such as corn and soybeans.

The location of the buffer was most important.

The researchers, who modeled runoff and resulting pollution from
agricultural fields reaching the streams, studied riparian buffer
performance on Spring Creek in Centre County and Conewago Creek in
Lancaster County. Buffer design scenarios studied included 35-feet-wide
grass; 50-feet-wide grass; 50-feet-wide deciduous trees; 100-feet-wide
grass and trees; 100-feet-wide grass and trees, with trees harvested
every three years; and 100-feet-wide grass and trees, with grass harvested every year.

The research team developed these scenarios after considering feedback
from focus group meetings with farmers in the two watersheds. Farmers
indicated they wanted to be able to install buffers tailored to their properties with the prospect of generating limited revenue.

In the Spring Creek watershed -- which has been studied closely by Penn
State agricultural scientists for decades -- 16 years of daily-scale
nutrient and sediment loads from three crop rotations and two soils were simulated in a soil and water assessment tool. That data was used as an
input to a riparian ecosystem management model used nationally to better understand how a buffer's effectiveness changes as a function of input
load, buffer design and buffer management.

The simulation results, recently published in the Journal of Environmental Quality, suggest that for buffers of the same width, the farmer-preferred
grass vegetation outperformed policy-preferred vegetation of trees for sediment, nitrogen and phosphorus removal.

The findings of the research have important implications for informing
flexible buffer design policies and enhanced placement of buffers in
watersheds impaired by nutrient and sediment, Preisendanz explained. She pointed out, however, that more research may be needed to examine
tradeoffs between water-quality impacts and other ecosystem services,
such as streambank stabilization, habitat and stream shading.

"If incorporated into policy, these findings could remove one barrier
to farmer adoption of riparian buffers," she said. "Based on our
conversations with famers in focus groups, we think this approach --
government being more flexible with buffer designs and allowing harvesting
-- would go a long way toward farmers agreeing to create more riparian buffers." The state Department of Conservation and Natural Resources
currently is promoting "multifunctional" buffers, Preisendanz added. "Our
hope is that this work will help to inform tradeoffs of flexible buffer
designs and management options in this new program."

========================================================================== Story Source: Materials provided by Penn_State. Original written by Jeff Mulhollem. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Fei Jiang, Heather E. Preisendanz, Tamie L. Veith, Raj Cibin,
Patrick J.

Drohan. Riparian buffer effectiveness as a function of buffer
design and input loads. Journal of Environmental Quality, 2020;
DOI: 10.1002/ jeq2.20149 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201002153617.htm

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