Isotopic signals in an agricultural watershed suggest denitrification is locally intensive in riparian areas but extensive in upland soils – data and code

The data and R code provided here are the underpinnings of a manuscript in the journal, Biogeochemistry (the manuscript title is parallel to resource title). Nitrogen use efficiency in cultivated agriculture is reduced by denitrification and by leaching of nitrate, which reduces water quality and is subject to denitrification downstream. Denitrification and leaching losses from dryland farming during fallow periods (no crop growing) can play a disproportionately large role in cropping system nitrogen losses. This work combines nitrogen mass balance with δ15N mass balance to estimate denitrification rates in soil relative to groundwater and streams.

Data includes solute concentrations and isotopic composition of nitrate and water in water samples collected from soil, groundwater and surface water. Soil solution chemistry was characterized in samples from tension lysimeters installed in two non-irrigated fields operated by cooperating farmers. Groundwater and surface water sampling between 2012 and 2017 included two wells, five springs, and three stream sites. Solute concentration and water isotope analysis was conducted in the Montana State University Environmental Analytical Laboratory. Nitrate isotope analyses were conducted at Woods Hole Oceanographic Institution. For detailed analytical methods, see the main manuscript.