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

Hannah Wenng,Eva Skarbøvik,Marianne Bechmann,Tore Krogstad

doi:10.1007/s13280-020-01359-z

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.

Highlights

The agricultural sector is under pressure to respond to energy and food security challenges and to reduce greenhouse gas emissions
The relationships between climate, land management and nitrogen concentrations were investigated in seven small agricultural catchments across Norway
For the first objective, the study found that climate change has affected the length of the thermal growing season, there was an increase in the thermal growing season length in four of the seven catchments, located in different parts of Norway; the south-east (Skuterud, Mørdre), the south-west (Time) and the north (Naurstad)

Summary

Introduction

The agricultural sector is under pressure to respond to energy and food security challenges and to reduce greenhouse gas emissions. Jeong et al (2011) showed an increase of the vegetative growing season (phenology) for the temperate zone in the Northern Hemisphere during the period 1982–2008 This may imply earlier timing of agricultural management in spring (e.g. seedbed preparation, sowing), the introduction of new crop varieties adapted to a longer growing season and higher yields (He et al 2018; Wirehn 2018). It is still unknown if a prolonged thermal growing season has or will have an impact on water quality. It is uncertain how soil mineral N will change due to higher temperatures (He et al 2018)

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