Nutrients like nitrogen and phosphorus are washed through a landscape during rains, which is both expensive to farmers, who need the nutrients to grow crops, and potentially harmful to downstream waterways.
So farmers employ a range of tactics to keep nutrients in the soil where crop roots can use them.
But in order to know what works, they need to know when and where the nutrients wash off their fields. Measuring nutrients downstream of farms is one way to understand what flows off the land, but not all nitrogen and phosphorus are the same.
Some come from fertilisers farmers apply, but some come from natural processes in the land, and some even come from wooded regions or development upstream from farms.
Gurpal Toor, a professor and extension specialist in the Department of Environ-mental Science and Technology at the University of Maryland in the United States, is tracing the different types of nitrogen and phosphorus flowing into drainage ditches, tile drains, and overland flow at the edges of farm fields during rainfall events.
He has set up a network of sophisticated monitoring stations across the state of Maryland to identify what flows off the land every few minutes when it rains.
He and his team have been collecting runoff samples and associated data over the past few years to capture a detailed picture of nutrient loss at different times and during different types of rainfall events.
“What we are trying to do here with some of these advanced sensors is actually get more high intensity, high-resolution data so we can see what is happening at the beginning, in the middle, and at the end of the storm because that’s going to tell us a different side of the story,” Prof Toor explained.
The goal of this research is to identify opportunities to reduce the nutrient losses and to keep more nitrogen and phosphorus in the crop fields so plants can use it.
“Any pound of nitrogen that’s running from the field is an economic loss, and fertilisers are not cheap,” he said.
“We want to make sure that nutrients stay in the field. So we need to give farmers better tools.”
That would benefit farmers and waterways, because if Prof Toor’s work can reduce the nitrogen or phosphorus flowing from crop fields into surface waters, it will reduce the nutrients reaching nearby streams and creeks flowing into the Chesapeake Bay.
And those tools can be applied to other waterways throughout the world.
This work is supported by the Harry R Hughes Center for Agro-Ecology, the Maryland Department of Agriculture, and the US Department of Agriculture National Institute of Food and Agriculture.
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