Relationships for estimating N₂ fixation in legumes: incidence for N balance of legume‐based cropping systems in Europe

Abstract

Citation: Anglade, J., G. Billen, and J. Garnier. 2015. Relationships for estimating N 2 fixation in legumes: incidence for N balance of legume-based cropping systems in Europe. Ecosphere 6(3):37. http://dx.doi.org/10.1890/ES14-00353.1Abstract. Management of nitrogen (N) inputs into agricultural systems is of increasing interest due to the intensive use of synthetic fertilizers in modern cash crop systems, which has caused considerable environmental damage, including nitrate contamination of surface and groundwater, eutrophication of coastal marine areas and emission of greenhouse gases. The use of legumes grown in rotations or intercropping is nowadays regarded as an alternative and sustainable way of introducing N into low-input cropping systems. In order to develop a simple tool to assess biological nitrogen fixation (BNF) by legume pulse and forages within crop rotations, we conducted a systematic literature survey with a quantitative statistical analysis intended to define a robust relationship between measurable variables and N 2 fixation. We found highly significant correlations between total N accumulation in shoot matter and fixed N 2 in forage (y ¼ 0.79x À 0.49) and grain (y ¼ 0.70x þ 1.01) legumes. Accurately estimating the contribution of belowground components is more difficult because of a lack of relevant studies. Properly assessing BNF is crucial to evaluate the possibility of diversified legume based cropping systems achieving a balance between inputs and outputs, thus ensuring both short-term productivity and long-term sustainability. For a typical nine-year organic rotation in the Paris basin alternating legumes and cereals, the soil surface balance, calculated with the relationships obtained, indicated that N fluxes were balanced, leaving a surplus of only a few kg N/ha/yr, with legumes accounting for 86% of total N inputs.

Crops, Nitrogen, Water: Are Legumes Friend, Foe, or Misunderstood Ally?

“…Furthermore, we lack hard evidence that BNF itself produces 'excess N'. Instead, and provided crop legumes are not augmented with INF, there is every prospect of maintaining balanced N budgets when crop legumes are used as both a source of grain and N. Recent detailed analysis of the N balance of legume-based cropping systems in Europe [45] showed that for a typical legume-cereal rotation, there was little N (a few kg ha…”

“…Legumes are frequently noted as being 'drought sensitive', to the extent that farmers can be wary of growing them under dry seasonal conditions. A strong, N-based response to drought (accumulation of amino acids) was interpreted [45] as being a potential mechanism to account for slowing rates of N fixation for the perennial legume Medicago. For grain legumes, a very similar response was noted for Cicer [46], while Phaseolus accumulated ureides in foliage (but not nodules) under drought conditions that also inhibited BNF [47].…”

Alfalfa (Medicago sativa L.) overseeding on mature switchgrass (Panicum virgatum L.) stand: biomass yield and nutritive value after the establishment year

“…Several authors reported a positive response of switchgrass yields to increasing nitrogen (N) fertilisation levels (Gurezky et al, 2010;Nassi o Di Nasso et al, 2015). Nevertheless, nitrogen distribution associated to grass cultivation may increase the risk of eutrophication and directly and indirectly cause GHG emissions (Anglade et al, 2015). To cope with this problem, the use of a legume as intercropping species appears to be an environmental friendly option to increase N use efficiency.…”

Nitrogen Fluxes Into, Out Of, and Within a Virginia Permaculture Livestock Farm

“…For the 2014 and 2015 calculation, estimates of pasture BNF were updated using a robust pasture survey, legume sample analysis (using an elemental analyzer) and equations relating legume N content to rates of N fixation (Gorksy 2016, Anglade et al 2015). The pasture survey included sampling every meter along three 50-m transects (locations were determined using 3 randomly selected points in each field and a random direction).…”

“…Legume samples were collected (three per field), sorted (leaf materials, stem, roots), dried (at 60° for 24 hours or until a constant mass was reached), ground, and analyzed to estimate N content. Fixation was estimated as a function of stem N content (Anglade et al 2015). See Gorsky (2016) for full details.…”