Environmental Science · Environmental Engineering
A study used satellite images, farm records and soil–water modeling to map nitrate loss within fields in a drinking-water protection area. Low-yield zones had higher nitrogen surpluses and modeled nitrate concentrations than high-yield zones.
Satellite images often average bare-soil data over long periods, but the colors can change even under similar conditions. Using seven years of Landsat 8 and Sentinel-2 reflectance data from more than 27,000 European sites, researchers found that changes in solar angle interacting with rough bare soil explain most of the temporal variation, while surface moisture contributes less.
Mediterranean dryland crops face cycles of drought and then sudden rain. In a year-long field experiment, researchers found that the biggest bursts of nitrogen pollution in the form of nitrous oxide and nitric oxide followed rewetting, especially when plants had been stressed by drought. Soil texture changed how much inorganic nitrogen built up, but it did not lead to proportionally larger gas spikes.
