The Nitrogen Balance of Three Long-term Agroecosystems on a Boreal Soil in Western Canada

Journal Article · Mon Sep 01 04:00:00 EDT 2008 · Agriculture, Ecosystems & Environment, 127(3-4):241-250

DOI:https://doi.org/10.1016/j.agee.2008.04.007· OSTI ID:974512

Ross, Shirley M; Izaurralde, Roberto C; Janzen, H H; Robertson, J A; Mcgill, William B

Nitrogen (N) budgets can be used to quantify the flows of N in agroecosystems and to account for differences in losses and retention of N. The objective of our study was to develop 24-year N budgets for three diverse cropping systems on a boreal soil at Breton, Alberta, Canada: AER an agroecological 8-year rotation, with N inputs from legumes [fababean (Vicia faba L.), red clover (Trifolium pratense L.), alfalfa (Medicago sativa L.)] and manure; CF - a continuous perennial grass legume forage system, with N inputs from fertilizer (18 kg N ha-1 yr-1) and white clover (Trifolium repens L.); and CG - a continuous annual grain system, with N fertilizer (90 kg N ha-1 yr-1). We were able to compile detailed N budgets, demonstrate accumulation of soil N, and attribute differences in N flow and permanence to treatment effects. For AER and CG, net inputs almost exactlymatched gains in soil N. The AER system had the highest N flow and the largest net N accumulation. Soil total N mass to 30 cm depth increased in all systems during 1980 2005, but increases were smaller in CG (0.59 Mg N ha-1) than in AER (1.90 Mg N ha-1) and CF (1.63 Mg N ha-1), showing the effect of legumes, perennial species, and manure in the latter systems. The proportion of total N inputs retained as soil N with organic N inputs in AER (44%) was about twice that with synthetic N fertilizer in CG (23%). The CF system had the lowest productivity and the least N loss to the environment (4 kg N ha-1 yr-1, compared to 28 for AER and 24 for CG). The proportion of N inputs lost to the environment was 16% for AER and 24% for CG. In CF, gains of soil N exceeded apparent net N inputs, perhaps because we under-estimated N inputs from clover. Estimate of legume N input was one of the larger sources of uncertainty. The study affirmed the value of N budgets in evaluating agroecosystem performance, and identified AER and CF as productive and sustainable systems due to their minimal reliance on external N inputs and small N losses to the environment.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 974512
• Report Number(s): PNNL-SA-61735; KP1702020
• Journal Information: Agriculture, Ecosystems & Environment, 127(3-4):241-250, Journal Name: Agriculture, Ecosystems & Environment, 127(3-4):241-250 Journal Issue: 3-4 Vol. 127; ISSN 0167-8809
• Country of Publication: United States
• Language: English

Related Subjects

09 BIOMASS FUELS
ALBERTA
ALFALFA
CANADA
CLOVER
CULTIVATION TECHNIQUES
FERTILIZERS
FORAGE
GRAMINEAE
MANURES
NITROGEN
PERFORMANCE
PRODUCTIVITY
RETENTION
ROTATION
SOILS
VICIA
nitrogen budget
nitrogen balance
long-term experiments
cropping systems
soil nitrogen
biological nitrogen