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TRANSCRIPT
Nicolas MARRONBernard AMIAUD
Daniel EPRONErwin DALLÉ
Alexandre LAFLOTTESéverine PIUTTI
European Agroforestry ConferenceMay 23-25, 2016 – Montpellier, France
Present geopolitical and environmental world context:
- Rarefaction of fossil fuels
- Needs to reduce CO2 emissions
Promotion of renewable energy sources
Biomass
Forest = first supplier currently
+ Short Rotation Coppice (SRC) plantations on agricultural lands
Introduction
1
Soil fertility
Profitability
Technical procedure
Environment
Biodiversity/ Landscape
Currently not attractive because not optimized
Tree plantations dedicated to biomass production
Introduction of nitrogen
fixators
SRC
2
3
Introduction of N fixators, woody or herbaceous
Tree plantations dedicated to biomass production
2 m
2.5 m
Poplar
CerealsAlfalfa
Alder
5 m
Po
pla
r
Ald
er
Alfalfa / Clover…
Po
pla
r
4
Mixture poplar / alfalfa
Poplarmonoculture
Mixturepoplar / alder
NN N
Our hypotheses
Mixture plantations introducing nitrogen fixators
5
Mixture poplar / alfalfa
Poplarmonoculture
Mixturepoplar / alder
Po
pla
r
Ald
er
Alfalfa / Clover…
Po
pla
r
NN N
15N labelling
Leaf gas exchanges
Canopy description / LAI
Root profiles
Growth / Biomass
Our hypotheses and the ways to test them
Mixture plantations introducing nitrogen fixators
6
Amance
Nancy
The experimental agroforestry plantation: location
Mixture plantations introducing nitrogen fixators
7
Power line
Block
2
Block
1
Block
3
N
The experimental agroforestry plantation: layout
Mixture plantations introducing nitrogen fixators
3.5 ha – 3500 trees – 100 tree lines
The experimental agroforestry plantation: maintenance
Mixture plantations introducing nitrogen fixators
8
- Instrumentation to monitor soil and weather conditions
- Protection of trees against game + mulching
- Weed control (mechanical, chemical)
- Watering during summer 2015
9
Already some undesirable treatment effects!
Mixture plantations introducing nitrogen fixators
MonocultureTree
mixtureAgroforestry
350
300
250
200
150
100
50
0
MonocultureTree
mixtureAgroforestry
Alder Poplar
Two-year old tree heights (cm)
Species ***Treatments ***
S×T ns
10
Already some undesirable treatment effects!
Mixture plantations introducing nitrogen fixators
Wheat yield in 2015
Mixture with alder: 40,3 ± 2,5 quintal ha-1
Monoculture: 49,0 ± 3,6 quintal ha-1
11
Aim: to determine the amount
of nitrogen fixed by the leguminous
Method: Symbiotic nitrogen fixation
Isotopic dilution: increase of soil 15N signal
with an input of a labelled fertilisant
(ammonium sulfate (15NH4)2SO4)
%Ndfa= 100 1 −𝑥𝐸
𝑙𝑒𝑔
𝑥𝐸𝑛𝑜𝑛
−𝑙𝑒𝑔
(Fried & Middelboe, 1977)
𝑥𝐸 (excess in 15N) = 15N × 100/(15N + 14N) − 0.003663
Transfers
Pnonleg(atm)= 1 − (𝑥𝐸𝑛𝑜𝑛 − 𝑙𝑒𝑔 𝑚𝑖𝑥𝑡𝑢𝑟𝑒 /𝑥𝐸𝑛𝑜𝑛 − 𝑙𝑒𝑔 𝑝𝑢𝑟𝑒)
Pnonleg(leg)= (𝑥𝐸𝑛𝑜𝑛 − 𝑙𝑒𝑔 𝑝𝑢𝑟𝑒 − 𝑥𝐸𝑛𝑜𝑛 − 𝑙𝑒𝑔 𝑚𝑖𝑥𝑡𝑢𝑟𝑒) / (𝑥𝐸𝑛𝑜𝑛 − 𝑙𝑒𝑔 𝑝𝑢𝑟𝑒 − 𝑥𝐸𝑙𝑒𝑔 𝑚𝑖𝑥𝑡𝑢𝑟𝑒)
(Chalk & Smith, 1994)
Percentage of 15N in excess
Percentage of N derived from the
atmosphere
N proportion in the non fixing species coming from
the biological N fixation
N proportion in the non fixing species coming
from the N fixing species