Over the last 15 summers, bright green algae have turned the waters of western Lake Erie into a toxic stew, unsuitable for swimming, fishing, or even drinking if not properly treated. The biggest contributor to harmful algal blooms? Phosphorus, a chemical used to manufacture fertilizers, matches, steel, and fireworks.
The Maumee River watershed, 4.2 million acres spanning Ohio, Indiana, and Michigan, delivers the majority of external phosphorus to Lake Erie. Everything from city streets, backyards, manufacturing plants, livestock, and cropland contributes 89% of the “nonpoint” sources of phosphorus. The Great Lakes Water Quality Agreement—signed by Canada and The United States—aims to reduce the phosphorus entering Lake Erie by 40% by 2025, with a goal to hit that target in at least nine out of 10 years. But reaching that goal is a complicated issue. There is no one-size-fits-all approach.
Where do we start? By talking about best management practices, or BMPs. That means, activities that benefit you and your environment. For example, in your backyard, you might rake and bag your leaves. Maybe you mow your lawn and sweep up grass clippings to keep them from flowing into the sewer next time it rains. Or you compost or reduce food waste. These are all best practices or ways you manage your phosphorus impact.
Since 80% of the Maumee River watershed is used for agriculture, let’s see what farmers do. Farmers use BMPs to help improve water quality in a watershed. And more is better when it comes to BMPs. According to recent research at CFAES, bundling practices a variety of ways makes a bigger impact.
How do farmers decide which practices to bundle?
Just like people, fields have different features, even on a single farm. One field might be hilly, another might have more sand in the soil, and a third might be located right by a stream. Does it make sense to add a wetland on a hillside field? Probably not. Allowing flexibility for farmers’ preference, equipment needs, and workforce, while taking into account each field’s characteristics, is one way to reduce the flow of phosphorus in the Maumee River watershed.
Here are a few BMPs farmers use:
Cover crops seem like a strange concept. Farmers spend time and energy planting a cover crop between “cash” crops—crops they can sell for a profit. They may not even harvest the cover crop. They just let it dry out and decay. Why?
Cover crops help recycle nutrients, improve soil health, control weeds, and slow erosion—the movement of soil due to rain, wind, and ice. Water washes through the field, taking soil and fertilizers with it. The sediment and nutrient rich water ends up in a body of water, such as a pond, stream, or river, which feeds the algae in Lake Erie, causing the growth of harmful algal blooms!
So, what types of cover crops do farmers plant? Each crop provides different benefits: adding nutrients, insect control, suppressing weeds, and other soil improvements. Cover crops can be:
- Ryegrass
- Sweet Clover
- Teff
- Oats
- Sunflower
- Barley
- Cereal Rye
- Winter Canola
- Buckwheat
Cover crops are one way to help prevent phosphorus loss from the field. Current cover crop use in the Maumee watershed is about 5-10%.
For cover crop “recipes,” visit the Ohio State University Extension Agronomic Crops Network or Midwest Cover Crop Council.
Here are Ohioline fact sheets to get started:
- Sustainable Crop Rotations with Cover Crops (SAG-9)
- Cover Crop Fundamentals (AGF-142)
Not only do buffer strips provide habitat for butterflies and wildlife, they also act as a barrier between farmland and ditches or streams. Grasses, sedges, ferns, and rushes keep soil from washing off the field and help filter out agricultural chemicals. Once planted, buffer strips continue to reseed and maintain themselves. Slightly more than a quarter of farms in the Maumee watershed use buffer strips.
Learn more at Ohio State University Extension AgBMPs website.
Soil is a mixture of sand, clay, loam, and silt with plants, rocks, organic matter, and microorganisms creating pockets for plant roots, air and water. Water is essential for plant growth, but if all the soil spaces are filled with water, the plants will drown. The unusually wet spring of 2019 showed how too much water affects when crops are planted and harvested, as well as crop yields.
Farmers can control the amount of water that stays in their fields through the use of subsurface drainage. Installed below the surface, drainage pipes, called tiles, redirect the excess water to the edge of the field or a retaining pond either through gravity or pumps. Farmers can choose to control drainage by adjusting the flow to improve crop yield while reducing nutrient loss through the tiles. While tile drainage reduces soil erosion, research is mixed on whether it slows phosphorus runoff and improves water quality.
Learn about soil-water-plant systems on the AgBMPs website.
Tillage is the process of turning over the soil before planting a crop. Fertilizers are also folded into the soil through tilling. With no-till farming, crops are planted without turning over the whole field, just the row where seeds are planted. The idea is the everything leftover from last season’s harvest or cover crop—stems, leaves, bits of plant matter—stays on top of the soil and slowly disintegrates, adding organic material that holds water and prevents wind from blowing off the topsoil. At the same time, by not disturbing the ground as happens through traditional tilling, all the rich organic matter stays in the soil.
Farmers who adopt continuous no-till practices, or seasonal no-till on at least one crop, can save money on labor and fuel costs, improving productivity and profits. The benefit to the land is improved soil structure, reduced wind erosion and water runoff, and increased soil health. Read more about no-till practices here and a news story here.
Current no-tillage rates in the Maumee River watershed are 30% continuous no-till and 35% season no-till.
It’s easy to think fertilizer reduction is the only solution when talking about harmful algal blooms. But it’s not that simple. Phosphorus is a vital nutrient for plants in the growing season. Instead, tweaks in the amount (rate) of fertilizer used, when fertilizer is applied (timing), the types of fertilizer selected (types), and the way (method) farmers spread fertilizer can be considered to optimize fertilizer use.
Crops need fertilizers during different stages of the growth cycle. Manure applied in the fall or spring only, or half fall/half spring, only slightly impacts total phosphorus loading—the amount of phosphorus that ends up in Lake Erie. Spreading fertilizers on top of the soil increases phosphorus loss, while tilling fertilizer into the soil results in minor reductions. Even better? Injected fertilizers—placing liquid manure into the soil at planting time—or other methods of adding solid fertilizer beneath the soil surface show the most promising results.
A combination of reduced fertilizer use and injecting fertilizer into the soil in the fall could reduce phosphorus from leaving the Maumee River watershed by 26%! Now bundle in some of the above BMPs and we have the potential to make a real difference for water quality in Lake Erie.
Visit Ohioline for more information:
- Opportunities for Sub-surface Nutrient Placement in Ohio (FABE-564.01)
- Remote Sensing in Precision Agriculture (FABE-554.1)
Martin, J.F., Kalcic, M.M., Aloysius, N., Apostel, A.M., Brooker, M.R., Evenson, G., Kast, J.B., Kujawa, H., Murumkar, A., Becker, R., Boles, C., Redder, T., Confesor, R., Guo, T., Dagnew, A., Long, C.M., Muenich, R., Scavia, D., Wang, Y., Robertson, D., 2019. Evaluating Management Options to Reduce Lake Erie Algal Blooms with Models of the Maumee River Watershed. Final Project Report - OSU Knowledge Exchange. Available at: go.osu.edu/HABRI_final_report_2019
These facts and statistics are just a small portion of the information available about Lake Erie and harmful algal blooms (HABs). Researchers from Ohio State and other partners published an extensive report summarizing the findings of a three-year project. The team explored bundling best management practices and their impact on reducing HABs. Check out their work at the link in the citation below!