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Analysis of the stagnation of wheat yields in France
Nadine.Brisson,
Philippe Gate, David Gouache,
Gilles Charmet, François‐Xavier Oury
The issueA steady growth trend for wheat
yields in Europe during the second half of the 20th century due to
progress in genetics (HI)use of inputs for reducing
environmental limitations (nitrogen fertilizers, irrigation, pesticides)
climate effects : variability around this trend
A decline in this growth trend for the two last decades
WHY ?
0
1
2
3
4
5
6
7
8
9
1940 1950 1960 1970 1980 1990 2000 2010 2020
t ha‐1 1996 (P value=0.00082)Yield average progression 0.123 t ha‐1 year‐1
YIELD
Possible causes of yield leveling‐off
Genetic : is there un upper limit to genetic improvement ?
Agronomic : did changes occur in the management of fields (nitrogen fertilizers, use of pesticide preceding crop, soil organic matter) more or less driven by political or economic causes ?
Climatic : does climate change have a responsibility ?
Various sources of dataType of data
Nature of data Source of data period
Statistical surveys
Production, area
AGRESTE1 FAO2 1956 2007
Practices ONIGC 3 ARVALIS4 AGRESTE
1994 2009
Controlled trials
Damage
ARVALIS
2001 2008
Yield and optimal practices
1981 2008
Yield of each variety
INRA5NT
I NRA T CTPS6
T
1970 2008 1982 2008 1994 2008
Soil survey
Soil organic matter INRA 1990 2004
Modelling
Weather yields METEO FRANCE7 1956 2007
1 AGRESTE : Statistical service of the French ministry of Agriculture2 FAO : Food and Agriculture Organization of the United Nations3 ONIGC : French National Office for Arable Crops4 ARVALIS : French technical institute for cereal crops5 INRA : French National Institute for Agronomic Research6 CTPS : French Technical Committee for Breeding7 METEO FRANCE : French meteorological service
The observations in France
0
1
2
3
4
5
6
7
8
9
1940 1950 1960 1970 1980 1990 2000 2010 2020
t ha‐1 1996 (P value=0.00082)Yield average progression 0.123 t ha‐1 year‐1
YIELD
A regular increase of yield since the beginning of the fiftiesA significant stagnation since the middle of the nineties
(rising + plateau model with Fisher’s test)
without significant modifications in wheat areas
The observations in Europe
A general trend in Europe
Exceptions : Germany
(reunification)
southern countries (durum wheat, increase in the year‐to‐year variability)
SWITZERLAND UNITED KINGDOM
ITALY NETHERLANDS SPAIN
DENMARK FRANCE GERMANY
1990 ** 1996 **
1994 1993 **
1989
1995 ** 1996 ** 1999
Year of stagnation** very significant P<0.01
no star P>0.05
The observations in France at a departmental level
77 % of cereal‐growing departments show a significant stagnationYear of stagnation between 1991 and 1998Southern departments : same behavior than southern countries
* * *
* *
** **
** ** **
** **
MF
MF
MF
MF
MF
MF
Genetic causes
No stagnation : very good linear fit r2 > 0.95A continuous progress between 0.10 and 0.12 t ha‐1 yr‐1More important for untreated trials (progress not at the expense of
resistance to fungal disease)
INRA ‐TREATED INRA ‐UNTREATED CTPS ‐TREATED
Suppression of the year effect by a step by step procedure, accounting for the number of genotypes common to 2 successive years
Agronomic causes1) Nitrogen fertilizers
A decrease from 2000 of about 20 kg N ha‐1Efficiency (number of applications) stable since 2000Corresponding to ≈ – 0.1 t ha‐1 (technical references) ,
or ≈ ‐ 0.015 t ha‐1 yr‐1
170
180
190
200
210
1990 1995 2000 2005 2010
kg N ha-1
AGRESTEONIGCARVALIS
a
1.5
2
2.5
3
3.5
1990 1995 2000 2005 2010
N application
number
AGRESTE
ONIGC
ARVALIS
b
Agronomic causes2) Fungicide treatments
No trend in IFT (indicator of treatment frequency)
No relationship between damage and fall in yields
5
5.5
6
6.5
7
7.5
8
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
2001 2002 2003 2004 2005 2006 2007 2008
t ha-1t ha-1
damages on the left yield on the right
1 2
3
Evolution of damage – yield. Identification of three cases: • 1 with low damages and low yields, •2 with high damages and low yields and• 3 with high damages and high yields. •Source: AGRESTE, ARVALIS damage trials
Agronomic causes3) Preceding crop
From 1999, decrease in legumes and increase in rapeseedYield rapeseed < Yield legumesCorresponding to ≈ ‐ 0.035 t ha‐1 yr‐1
0%
10%
20%
30%
40%
50%
1994 1996 1998 2000 2002 2004 2006 2008
proportion of wheat
preceding crop
wheat rapeseed legumes other crops
a
5
6
7
8
9
10
1994 1996 1998 2000 2002 2004 2006 2008
t ha-1
wheat rapeseed legumes other crops
b
Agronomic causes4) Soil organic matter
Soil organic matter (organic C in g kg‐1) evolution between 1990‐1994 and 2000‐2004 periods. Source : INRA
Contrasted situationsNo trend
Agronomic causesSynthesis
≈ ‐ 0.015 : nitrogen fertilization≈ ‐ 0.035 : preceding crop
≈ ‐ 0.050 t ha‐1 yr ‐1 : agronomic causes
Climate cause :Estimate of a climatic yield with crop modeling
PANORAMIX (Gate, 1995) : “high‐input” agriculturebased on relationships between yield componentsassumes no nitrogen deficiencysoil water balance initialized at WP after harvest.main climate influence : water stress and thermal
stress during grain filling
STICS (Brisson et al., 2003, 2009) : “low‐input” agriculturebased on carbon balanceincludes nitrogen processes (plant and soil)continuous water balancenumerous climate‐crop interactions (direct and
indirect)
Climate causePANORAMIX STICS
Linear relationships fit better than bilinear but r2 not significantIncrease in the year‐to‐year variability towards the end of the period
Climate cause
Always negativeMore important with PANORAMIX (not positive effect of
mineralization stimulation by temperature : STICS)
locations
Estimation of the climatic penalty of wheat yield (t ha‐1 yr‐1 ) between the two periodsstatistically defined (year of change of slope) PANORAMIX STICS
Amiens ‐0.008 (1983) ‐0.074 (1998)
Bourges ‐0.039 (1993) 0.000 (1997)
Dijon ‐0.107 (1993) ‐0.038 (1999)
Rennes ‐0.002 (1993) ‐0.001 (1992)
Toulouse ‐0.022 (1980) 0.000 (1982)
Nîmes ‐0.078 (1988) ‐0.016 (1984)
Mean (std) ‐0.043 (0.042) ‐0.021 (0.030)
Test of the bilinear model Differences in slopes and year of slope change
Climate cause
Between ‐0.02 and ‐0.05 t ha‐1 yr‐1
Low input High input
Main climatic impacts :Negative
heat stress (Northern regions)water stress (Southern regions)
PositiveN mineralization
Not easy to combine at a national level
Synthesis
genetics
climate and agronomy
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
positive negative
t ha‐1 an
‐1
Evaluation of the progress and and the penalty of bread wheat in France since 1999
‐0.06
‐0.04
‐0.02
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
climate agronomy genetics
t ha‐1 an
‐1
1999
1970Evaluationof the causes of yield evolution in bread wheat in France (year of the beginning of the evolution)
1990
Still a gap between genetic progress and depressive effects of climate and agronomy
Up scaling of climatic analysis at the national scale ?Other causes ?Agronomic causes started in 1999 : reinforce climatic causesSensitivity of intensive agriculture to climate (in contradiction with
prospective SRES scenario studies)
Reference
Brisson, N.,Gate, P., Gouache, D., Charmet, G., Oury, F.X., Huard, F., 2010. Why are wheat yields stagnating in Europe? A comprehensive data analysis for France. Field Crops Res.119 : 201‐212.