Climate effects on land management and stream nitrogen concentrations in small agricultural catchments in Norway

Abstract

Land use and climate change can impact water quality in agricultural catchments. The objectives were to assess long-term monitoring data to quantify changes to the thermal growing season length, investigate farmer adaptations to this and examine these and other factors in relation to total nitrogen and nitrate water concentrations. Data (1991–2017) from seven small Norwegian agricultural catchments were analysed using Mann–Kendall Trend Tests, Pearson correlation and a linear mixed model. The growing season length increased significantly in four of seven catchments. In catchments with cereal production, the increased growing season length corresponded to a reduction in nitrogen concentrations, but there was no such relationship in grassland catchments. In one cereal catchment, a significant correlation was found between the start of sowing and start of the thermal growing season. Understanding the role of the growing season and other factors can provide additional insight into processes and land use choices taking place in agricultural catchments.

Land‐use dominates climate controls on nitrogen and phosphorus export from managed and natural Nordic headwater catchments

“…Daily nutrient fluxes were obtained by multiplying daily water discharge with concentrations in the corresponding weekly/ fortnightly water sample. Daily concentrations were set to be constant for the period between outtake of composite water samples, most often every second week (Wenng et al, 2020).…”

“…Monitoring at all but one catchment started between 1990 and 1995. The catchments represent the main farming systems in Norway; cereal production in the eastern and middle parts of the country, vegetable production in the south, intensive dairy farming in the west, and more extensive grass production in the southern mountains and in northern Norway (Wenng, Bechmann, Krogstad, & Skarbøvik, 2020 4,298; 1,151 2,694; 911 4,440; 3,000 4,419; 1,481 4,231; 1 (1.8-7.8) 5.2 (2.9-8.5) MAP (mm) 824 (782-1,003) 691 (607-754) 1,203 (553-3,719) 760 (622-1,186) MAQ (mm) 168 (98-218) 336 (289-376) 1,150 (436-2,299) 523 (315-946 Abbreviations: MAP, mean annual precipitation; MAQ, mean annual discharge; MAT, mean annual temperature.…”

“…Spatial variation in totN export was strongly related to annual runoff in agricultural catchments, however, and implies that increases in runoff could lead to increased element export (e.g., Oygarden et al, 2014). It is likely that investigations of climatic and hydrological impacts on water quality and element export would benefit from a focus on seasonal trends and/or from including a longer time period (de Wit et al, 2008;Jeppesen et al, 2009;Jeppesen et al, 2011;Wenng et al, 2020).…”

Catchment effects of a future Nordic bioeconomy: From land use to water resources

“…Collectively the studies show the advantages of deeper exploration within, and between, monitoring data records for 'added value' insight into relationships between parameter groups and other informative (e.g. non-linear trend) behaviours; this is one aspect in Wenng et al (2020).…”

“…Harmonising this across themes such as land-water-air connections (e.g. Kaste et al 2020;Wenng et al 2020), improvement of data certainty (e.g. Skarbøvik et al 2020;Vermaat et al 2020) and informing the development of environmental impacts and mitigation measures (e.g.…”