Restoring the Chesapeake Bay, the nation’s largest estuary, has for decades proven to be a fraught enterprise, beset by the interests of researchers, farmers, anglers, multiple governments, and a host of others. A new approach, recently reported in Remote Sensing of Environment, could be an important tool in helping to heal or protect the Bay, as well as other watersheds.
Researchers report how they combined satellite images with data on farmer participation in a winter crop cover program to offer up a new sort of management model. “If we can mix cover crop innovation with a subsidy program, and measure areas where cover crops are performing well, then that gives us a chance to change farming practices for the better,” says coauthor W. Dean Hively, a research physical scientist with the US Geological Survey (USGS) Lower Mississippi Gulf Science Center in Beltsville, Maryland.
Some farmers plant winter cover crops such as barley, rye, and wheat in the fall after they’ve harvested summer crops. These cold-tolerant plants not only boost yields and soil health, they also help hold the soil in place; agricultural nutrients and sediments stay in fields rather than leaching into nearby waterways where they reduce water quality. When farmers kill off winter cover crops in the spring, the plants release nitrogen that is then made available for summer crops. “It creates a green bridge from one season to another,” says Hively.
The Maryland Department of Agriculture (MDA) has been paying farmers to plant winter cover crops as part of a cost-sharing program to support agricultural methods that can reduce the pollution in Chesapeake Bay. Over the last decade, acreage of winter cover crops has increased substantially in the state—up to about half of fields, says Hively. Fewer than 10% of fields in the Midwest have cover crops.
It’s important to better understand the impact of such measures—the environmental benefits of winter cover crops can vary significantly based on factors such as the choice of species, planting date, and seeding method. “Once you put cover crop on the landscape, then you need adaptive management—you need to know which cover crop practices work well and which practices are not working as well,” Hively says.
As part of a collaboration among the MDA, the USGS, the U.S. Department of Agriculture-Agricultural Research Service and NASA, Hively and his team compared the performance of various cover crop practices. They analyzed images and data to estimate cover crop biomass and the percent of vegetative ground cover as proxies for nutrient loss from agricultural systems. (Farmer privacy remains protected throughout the project.) Planting early—before the first frost—and opting for barley or rye over wheat resulted in greater accumulation of biomass and ground cover, and therefore better pollution protection for the Bay, the authors report.
The project’s power is in identifying not only which cover crops are used where, but also their growth, according to Sjoerd Duiker, a soil management professor at Pennsylvania State University. “If cover crops are not putting on a lot of growth then they also don’t do a lot of good for soil health or water quality improvement,” says Duiker, who was not involved in the study.
Currently, the MDA visits only a fraction of fields enrolled in the cost-sharing program to verify cover crop implementation. Use of the remote sensing imagery would allow the MDA to assess winter cover crop performance, support adaptive management of the incentive program, and potentially replace required field visits, according to the authors. “Instead of recruiting armies of people to drive through the country and do these surveys, it would be a great asset if you could do it from a satellite,” says Duiker.
But there will always be a role for researchers in the field, emphasizes Ken Staver, an agricultural research scientist at the University of Maryland. “We wouldn’t want to substitute this for on-the-ground expertise—people seeing what’s going on and communicating with farmers,” says Staver, who also wasn’t involved in the study.
Still, Staver says the project will help deliver large-scale assessments and the findings validate the set-up of the state’s incentive program. Farmers receive different subsidies based on a matrix of 72 different combinations of species, planting date, and planting method. The state pays farmers more for planting barley over wheat and for doing so earlier in the season, for example.
The model may be replicated elsewhere. In Pennsylvania, it could be used to estimate the general adoption of cover crops, Duiker says, independent of any incentive programs. “Many of our farmers are doing things on their own dime, so there is no record of it,” he says. “It’s very important to know about the adoption of best management practices. This kind of technology could help us with that.”