“We had time to address the amount of dredge material, placement
and plans to use the dredge materials as a resource for
agricultural uses, construction and engineering materials. It
could also be placed in water with proper permitting for
projects such as wetlands restoration.”
Vázquez-Ortega’s research directly ties into H2Ohio’s
collaborative approach to the issues facing Ohio’s water.
Specifically, her work looks at encouraging the beneficial use
of dredge material to improve water quality, reduce nutrient
impact and reduce sedimentation.
The greenhouse approach
To date, most of Vázquez-Ortega’s research has been done in
five-gallon buckets in a greenhouse. She and her graduate and
undergraduate students collected both the dredge material and
farm soil and mixed the ratios of dredge to farm soil. They used
ratios that included 100% farm soil, 90% farm soil and 10%
dredge, 80% farm soil and 20% dredge and 100% dredge.
“When my masters student, Russell Brigham told me, ‘We have
plants and the plants have flowers,’ I was super happy because
it’s one thing to grow the plants on a farm, but we were doing
it in a greenhouse,” she said.
According to Vázquez-Ortega, the final ratio may be only 2% to
5%. “The farmer will need to make an agronomic analysis of how
much to put on the soil to provide the necessary benefits, as
well as the cost to get the material to the farm and incorporate
it into the soil.
“By using the different ratios in the research, I wanted to
quantify the effect of the dredged material into the farm soil
and to look at soil health and soybean yield,” the only crop she
planted in the first year of the research. Corn is planted for
the 2021 research crop.
They have studied what they believe are the agronomic parameters
that farmers would be most interested in and how the dredge
material compares to the optimal values. The dredge material is
rich in organic content at about 5%, which is good compared to
the usual 2% to 3% in many Ohio soils, she said.
“We want to know if we put an amendment on a farm if it is good
for the soil, but we also want to know if there are any
contaminants in the material and if they accumulate in the soil
or in the plants to cause negative impact on animals or humans
consuming the product,” she said.
They are checking if microcystins are in the dredge material
because they have been associated with the harmful algal blooms
every year in the lake for the past several decades.
The other concern is heavy metal concentration in the sediment,
such as hydrocarbons and polychlorinated biphenyl (PCB) which
were banned in 1979, but whose half-life is resistant to the
“Are they similar to what is in a typical farm soil, and if so,
by putting dredge on the farm soil are we accumulating the heavy
metals or are they accumulating in the greens?” she said.
In addition to determining if there were contaminants in the
grain, she also wanted to find out whether the soil and dredge
material would allow a large amount of nutrients and heavy
metals to move into the percolated solution and eventually into
the water supply in a major rainfall event.
The preliminary results from the research showed that phosphorus
levels were elevated, calcium levels increased because the
dredge material was very rich in calcium and the organic matter
increased. Organic matter is important to farm soil health,
helping to retain the nutrients that will be released slowly and
providing the energy and food source for bacteria and fungi that
are essential for having healthy soil.
The root systems were more robust and there were no significant
differences in heavy metal content between farm soil and dredged
sediment. The same was true for heavy metal bioaccumulation in
Overall, the average yield increased slightly, “but most
importantly, by adding the dredge we did not see any decrease in
yield. The increase was not statistically different, but we did
not see any negative effects on crop yields,” she said.
The next step is to translate the results from the greenhouse
into actual farms. The Ohio EPA has sought farm field
demonstrations to determine if the greenhouse results hold up on
the farm. For more information about Vaquez-Ortega’s research,