A Primer on Moist-Soil Management

Managing seasonal wetlands for seed-producing natural vegetation has many advantages over planting crops

By George Seek

Since legendary waterfowl biologist Dr. Frank Bellrose first introduced the concept of moist-soil management during the 1940s, wetland biologists throughout the flyways have studied, practiced, and written countless handbooks and how-to articles about this technique. Without getting too far down in the weeds (pun intended), we can define moist-soil management as a practice that encourages growth of seed-producing native wetland plants by mimicking the seasonal wet and dry cycles of natural wetlands. Moist-soil habitats are typically wet in spring, dry in summer, and wet again in fall and winter. Well-managed moist-soil wetlands can produce up to 2,000 pounds of seed per acre. That means a single acre of moist-soil habitat can meet the energy demands of a few thousand ducks for one day.

The main idea behind moist-soil management is to let water do the work. This requires some infrastructure—dikes, levees, water-control structures, wells, and pumps—to regulate the timing and amount of water in managed units. That's why, in the past, this management technique was mainly practiced on federal and state lands. Today, with significant progress made in restoring wetlands on private lands, growing numbers of landowners are flocking to moist-soil management.

For waterfowl, moist-soil wetlands are the perfect one-stop shop during spring and fall migration. Compared to agricultural lands (the most common habitat type available to waterfowl), moist-soil habitats provide more nutrition, offer better cover, and support a greater abundance and diversity of species. Seeds of moist-soil plants also resist deterioration longer than grain seeds, and the plants themselves harbor a smorgasbord of protein-rich invertebrates, which provide important nutrients for waterfowl preparing for the rigors of nesting, egg-laying, and molting.

For private landowners, moist-soil management is a more cost-effective way to provide food and cover for waterfowl and other wetland wildlife than planting and flooding agricultural crops. Although flooded corn can provide excellent hunting and high-energy food for waterfowl during fall and winter, the cost of planting a single acre of corn can easily exceed $400—not to mention the money lost by leaving the crop in the field.

Moist-soil management is also relatively easy for many landowners to do on their own, with one important caveat. Wetlands are highly dynamic environments that can change dramatically from year to year, so moist-soil managers must be willing to work with, rather than against, natural processes to keep habitat productive and attractive for wildlife. Having been a wetland manager for almost 40 years, I've made every mistake possible when it comes to moist-soil management. The beauty of such wetlands is that they're resilient, and even if you make mistakes, nature has a way of fixing them.

Here are the three basic steps required to manage moist-soil wetlands for waterfowl and other wildlife:

1. Moist-soil management begins in spring, when the first task is to decide when to start drawing water off wetlands. Drawdown timing is usually described as early, mid-season, or late. Early drawdowns start within the first 45 days of the growing season, while mid- and late-season drawdowns take place during the middle and at the end of the growing season. As a general rule, the longer you can wait to draw water off, the better. The duration of a drawdown is equally important. Long, slow drawdowns are usually better than short, fast ones.

After the spring drawdown, pay attention to the plant response. Left unchecked, without a major disturbance such as a long flood or drought, seed-bearing annual plants such as smartweed, millet, and panic grasses are quickly replaced by less desirable perennials like bulrush, cattails, or even woody shrubs. Although these plant species are important components of diverse and healthy wetlands, most moist-soil managers prefer to maintain 50 to 70 percent of wetlands in the early, annual-plant stage of succession.

2. When summer arrives, it's time to decide whether intervention is needed to set back plant succession. If that's the case, disking, mowing, burning, spraying, or limited cropping should be conducted to eliminate undesirable vegetation. These management practices also help improve hunting and encourage waterfowl use by creating open areas for decoys and landing zones for waterfowl within stands of dense vegetation.

3. The final step is to flood moist-soil habitat in the fall. For those with a reliable water source, flooding a moist-soil wetland is just like drawing it down, except in reverse. In this case, it's best to add water over a long period of time. Gradual flooding will boost seed production in water-loving plants such as smartweeds and millet and create shallow mudflats, which are highly attractive to blue-wings during the early teal season. Making food available through gradual flooding extends the season both for ducks and hunters.

If possible, increase the water level throughout the fall migration. Research shows that water depths ranging from less than one inch to 18 inches will support the greatest diversity of waterfowl and other wildlife. However, every site is unique, so it may take some experimentation to determine the optimal timing and depth of flooding in a particular moist-soil management area.

That's all there is to it. Draw water off slowly in spring, do a little disturbance in the summer to set back plant succession, and put water back on again slowly in the fall. Just remember that wetlands change constantly, so moist-soil management is not the same recipe every year.

For me, the best part of this management technique is that I get to enjoy wetlands year-round (not to mention that hunting in a natural marsh is something special). Without a doubt, this has made me a better conservationist by giving me a broader understanding of the dynamic interactions of water, plants, and animals. As wetland managers, we too often focus on what we can do to improve waterfowl hunting in the fall rather than thinking about how we can meet all the life-cycle requirements of the birds that bring us so much enjoyment. Fortunately, moist-soil management provides us the opportunity to do both.

George Seek helped pioneer moist-soil management techniques during his 30-year career with the Missouri Department of Conservation.