Epsilon Archive for Student Projects

Abstract

Nitrogen has historically been a limited resource both in natural and agricultural environments.
The invention of synthetic nitrogen fixation has revolutionized agriculture, increased food
production, and reduced reliance on both symbiotic nitrogen fixation and manure for maintaining
soil fertility. High nitrogen losses from the agro-food system to the natural environment have
resulted in serious consequences for environmental and human health, however. This study
compares the current Swedish agro-food system with those of the mid-1800s and 1930s, prior to
the general adoption of synthetic fertilizers and during periods of adoption and then widespread
use of crop rotation systems. The aim is to understand how each period’s agro-food system
affected nitrogen flows, and more specifically the soil nitrogen balance in order to find out
whether or not past agro-food systems were removing more nitrogen from the soil than they were
putting in. The nitrogen flows of the Swedish agro-food system for the years 1866, 1937, and 2023
are measured and mapped out using an approach called the Generic Representation of Agro-Food
Systems (GRAFS).
The results of the study show a large soil nitrogen surplus in 2023, a slightly positive balance
for 1937, and a soil nitrogen deficit in 1866. While uncertainties are substantial, these results
indicate that farmland was being depleted of nitrogen in 1866 and, to a lesser extent, in 1937. The
depletion of soil nitrogen improved between 1866 and 1937, most likely thanks to the intensive
use of crop rotations with leguminous crops.