Simulating changes in cropping practices in conventional and glyphosate-resistant maize. II. Weed impacts on crop production and biodiversity
Environ Sci Pollut Res
Simulating changes in cropping practices in conventional and glyphosate-resistant maize. II. Weed impacts on crop production and biodiversity
Nathalie Colbach 0 1 2
Henri Darmency 0 1 2
Alice Fernier 0 1 2
Sylvie Granger 0 1 2
Valérie Le Corre 0 1 2
Antoine Messéan 0 1 2
Nathalie Colbach 0 1 2
0 INRA, UMR1347 Agroécologie , BP 86510, 17 rue Sully, F-21065 Dijon , France
1 Agroécologie, AgroSup Dijon, INRA, University Bourgogne Franche-Comté , F-21000 Dijon , France
2 Antoine Messéan
Overreliance on the same herbicide mode of action leads to the spread of resistant weeds, which cancels the advantages of herbicide-tolerant (HT) crops. Here, the objective was to quantify, with simulations, the impact of glyphosateresistant (GR) weeds on crop production and weed-related wild biodiversity in HT maize-based cropping systems differing in terms of management practices. We (1) simulated current conventional and probable HT cropping systems in two European regions, Aquitaine and Catalonia, with the weed dynamics model FLORSYS; (2) quantified how much the presence of GR weeds contributed to weed impacts on crop production and biodiversity; (3) determined the effect of cultural practices on the impact of GR weeds and (4) identified which species traits most influence weed-impact indicators. The simulation study showed that during the analysed 28 years, the advent of glyphosate resistance had little effect on plant biodiversity. Glyphosate-susceptible populations and species were replaced by GR ones. Including GR weeds only affected functional biodiversity (food offer for birds, bees and carabids) and weed harmfulness when weed effect was initially low; when weed effect was initially high, including GR weeds had little effect. The GR effect also depended on cultural practices, e.g. GR weeds were most detrimental for species equitability when maize was sown late. Species traits most harmful for crop production and most beneficial for biodiversity were identified, using RLQ analyses. None of the species presenting these traits belonged to a family for which glyphosate resistance was reported. An advice table was built; the effects of cultural practices on crop production and biodiversity were synthesized, explained, quantified and ranked, and the optimal choices for each management technique were identified.
GM crop; Model; Weed; Glyphosate resistance; Cropping system; Biodiversity; Yield gap; Harmfulness; Agroecology
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Introduction
Herbicide-tolerant (HT) crops, particularly those tolerant to
glyphosate, are grown on large acreages in some regions of
the world
(James 2013)
. Though these varieties simplify weed
management
(Bonny 2016; Brookes and Barfoot 2009;
Shaner 2000)
, the overreliance on glyphosate has led to the
development of resistant weeds
(Bonny 2016; Heap 2016;
Powles 2008)
. In contrast to the widespread annual use of
glyphosate in HT maize and HT soybean rotations in the
USA, the acreage of HT maize in Europe is almost nil today,
and maize is often rotated with other crops that are not treated
with glyphosate. However, glyphosate is frequently used
during summer fallow, and cases of weed resistance to glyphosate
have already been detected in arable fields with annual crops
(Collavo and Sattin 2014)
. Moreover, the introduction of HT
crops into the cropping systems may lead to other changes in
cultural practices which can also favour the evolution of
herbicide resistance, e.g. simplified rotations and/or simplified or
no tillage
(Beckie 2009; Boerboom 1999; Chauvel et al. 2009;
Colbach et al. 2016b; Colbach et al. 2017; Friesen et al. 2000;
Lievin et al. 2013; Moss and Clarke 1994; Moss et al. 2007)
.
This shift to herbicide-resistant biotypes potentially not
only increases weed harmfulness for crop production (e.g. yield
loss, harvest contamination, field infestion,
Mezière et al.
2015
b) but can also impair biodiversity. Indeed, weed flora
is a major part of wild plant biodiversity in arable lands and
provides habitat and food resources to a range of animals in
agricultural landscapes, among which pollinators
(Bretagnolle
and Gaba 2015)
or crop auxiliaries
(Taylor et al. 2006)
. The
management of glyphosate-tolerant crops can also lead to
shifts to different weed species, which has already been
analysed in recent studies
(Bigler and Albajes 2011; Bürger
et al. 2015; Heard et al. 2003)
. However, the particular effect
of herbicide resistance on weed-related functional biodiversity
(e.g. weeds as food resources) has yet to be investigated.
Because of long-term effects and the multiplicity of the
implicated factors, herbicide resistance is increasingly
investigated via modelling and simulations
(Cavan et al. 2000;
Colbach et al. 2016b; Gressel and Segel 1990; Maxwell
et al. 1990; Neve et al. 2003; Renton et al. 2014)
. These
models are, however, limited to a single species and neglect
the impact of weeds on crop production and biodiversity.
Therefor (...truncated)