Title of article :
The nitrogen balance of three long-term agroecosystems on a boreal soil in western Canada
Author/Authors :
S.M. Ross، نويسنده , , R.C. Izaurralde، نويسنده , , H.H. Janzen، نويسنده , , J.A. Robertson، نويسنده , , W.B. McGill، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2008
Pages :
10
From page :
241
To page :
250
Abstract :
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 exactly matched 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.
Keywords :
Nitrogen balance , Biological nitrogen , Long-term experiments , Soil nitrogen , Cropping systems , Nitrogen budget
Journal title :
Agriculture Ecosystems and Environment
Serial Year :
2008
Journal title :
Agriculture Ecosystems and Environment
Record number :
1285064
Link To Document :
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