biological nitrification inhibition (bni) in plants: implications for nitrogen-use efficiency and...
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Biological Nitrification Inhibition (BNI) in Plants – Implications for Improving Nitrogen-use efficiency and
Reducing Nitrous oxide Emissions from Agricultural SystemsA Genetic-Mitigation Strategy
GV SubbaraoJIRCAS, JapanGV SubbaraoJIRCAS, Japan
CollaboratorsCIAT
CIMMYTICRISAT
Tottori University
Participation from JIRCAST. Ando
K. NakaharaT. YoshihashiT. Ishikawa
BNI-Mitigation Technology
Team
Year1950 1960 1970 1980 1990 2000 2010 2020
Nitr
ogen
eff
icie
ncy
in c
erea
l pro
duct
ion
(meg
a to
nnes
cer
eal g
rain
/meg
aton
ns fe
rtiliz
er a
pplie
d)
20
30
40
50
60
70
80
Why NUE is <30% in most agricultural systems?
Uncontrolled rapid nitrification in agricultural soils
NUE (Nitrogen use efficiency)
Global food production has doubled since the advent of Green Revolution
(1960 – 2000), but Nitrogen fertilizer consumption has increased 10-fold
Nearly 70% of the N fertilizer applied is lost to the environment
Amounts to a direct annual economic loss of
US$ 90 billion*[*based on - a) world annual N fertilizer production is 150 million Mg; b) 0.45 US$ kg-1 urea]
Nitrogen applications have reached a point of
diminishing returns i.e. we are applying more andmore nitrogen to get similar yieldsand this may continue in future
N-fertilization efficiency is declining in cereal production
Nitrogen fertilizer consumption worldwide in 2010
>120 Tg (million metric tons)
Energy cost of nitrogen fertilizer – 1.8 to 2 L diesel oil per kg N fertilizer
1.70 billion barrels of diesel oil (energy equivalent) is needed to produce this nitrogen
fertilizer
BNI Concept
Ammonium(NH4+)
Nitrite(NO2-)
Nitrate(NO3-)Ammonia-oxidizing Bacteria Nitrite-oxidizing BacteriaBL
BL
BL BL
Microbial-N
Imm
obili
zatio
n
Min
eral
izat
ion
Nitrate leaching
Denitrification
N2O, NO and N2
N lost from agricultural system
N lost from agricultural system
Concept of Biological Nitrification Inhibition (BNI)
BNI-Mitigation Technology?FAO workshop on "The Role of Agricultural
Biotechnologies in Sustainable Food Systems and Nutrition", 15-17 Feb. 2016,
Rome, Italy
Plants release two categories of BNIs
Hydrophobic Hydrophilic
BNI Activity
Mostly confined toRhizosphere
May move out of Rhizosphere
Plant -rootproduced
nitrificationinhibitors
BL
BL
BL
BL
BL
BL
BL
BL
BL
BL
BL
BL
BL
BLBL
BL
BL
BL
BL BNI-Mitigation Technology
Subbarao G V et al. PNAS 2009;106:17302-17307
©2009 by National Academy of Sciences
Brachiaria pastures release a powerful nitrification inhibitor from root systems
Chemical structure of
BrachialactoneA tricyclic terpenoid with a unique 5-8-5
membered ring system and a g-lactone ring
B. humidicola
FAO workshop on "The Role of Agricultural Biotechnologies in Sustainable Food
Systems and Nutrition", 15-17 Feb. 2016, Rome, Italy
BNI-Mitigation Technology
Brachialactone’s mode of inhibitory action on Nitrosomonas
CompoundConcentration in the in vitro assay, mM AMO pathway HAO pathway
Crude-root exudate (methanol extract) 63.4 + 0.8 63.8 + 0.8Brachialactone 5.0 59.7 + 0.9 37.7 + 0.9Nitrapyrin 3.0 82.3 + 1.5 8.1 + 1.2
Inhibition (%)
Outer Membrane
Inner Membrane
Periplasm
Nitrosomonas
mM
Brachialactone
Brachialactone–HAO Docking simulation
Receptor: N.oceani HAOLigand: Brachialactone
Autodock vina 1.1.2
Heme P460
Brachialactone
Docking simulation hypothesized that brachialactone could bind to the gateway of the ligand pocket.
Brachialactone is too large to bind to the reaction center.
Nishigaya, NIASJIRCAS-NIAS collaboration
Estimations for the BNIs release from B. humidicola
• Active root biomass in a long-term BH pasture being 1.5 Mg ha-1
• (Root mass up to 9.0 Mg ha-1 has been reported in BH pastures)• BNI release rates can be 17 to 50 ATU g-1 root dry wt. d-1
• Estimated BNI activity release d-1 could be 2.6 x 106 to 7.5 x 106 ATU
(CIAT 679) (CIAT 26159)•1 ATU being equal to 0.6 mg of nitrapyrin
• This amounts to an inhibitory potential equivalent to the application of 6.2 to 18 kg of nitrapyrin application ha-1 yr-1
Does it work in the field?FAO workshop on "The Role of Agricultural
Biotechnologies in Sustainable Food Systems and Nutrition", 15-17 Feb. 2016,
Rome, Italy
BNI-Mitigation Technology
Cumulative N2O emissions (mg of N2O N per m2 per year) from field plots of tropical pasture grasses (monitored monthly over a 3-year period, from September 2004 to November 2007)
Subbarao G V et al. PNAS 2009;106:17302-17307©2009 by National Academy of Sciences
Brachiaria pastures suppressed N2O emissions from the fieldCan BNI function in plants be exploited to develop low-N2O emitting systems then?
BNI capacity in root systems – Field plots
No BNIcapacity
Highest BNIcapacity
BNI-Mitigation Technology
Photo: J. W. Miles
Characterization of residual effect of BNI from B. humidicola pasture on maize productivity and Nitrogen use efficiency (2012-2015)
Suppressing soil nitrification with BNI-enabled Brachiaria pastures
JIRCAS-CIAT partnership
Can it improve NUE in maize when it is planted after Brachiaria pasture?
BNI-Mitigation Technology
120 kg N ha-1
BNI-Field Non-BNI-Field
120 kg N ha-1
Nitrogen Fertilizer Applied (kg N ha-1)
0 50 100 150 200 250 300
Mai
ze G
rain
Yie
ld (k
g ha
-1)
0
1000
2000
3000
4000
5000
6000
BH-BNICropped-No-BNI
BNI-Field
Non-BNI-FieldHigh-nitrifying field
4th year of maize crop after removing BH
Nitrogen Fertilizer Applied (Kg N ha-1)
40 60 80 100 120 140 160 180 200 220 240 260
Agr
onom
ic N
itrog
en U
se E
ffic
ienc
y(K
g G
rain
yie
ld K
g-1 N
app
lied)
10
15
20
25
30
35
40
45
BH-BNICropped - No-BNIBNI-Field
4th year of maize crop after removing BH
Non-BNI-FieldHigh-nitrifying field
Maize yields and NUE are substantially higher in BNI-fields compared to non-BNI
fields
A healthy maize crop N-deficient maize crop
Proof of concept for BNI function in sorghum A field study at ICRISAT
JIRCAS-ICRISAT partnership
FAO workshop on "The Role of Agricultural Biotechnologies in Sustainable Food
Systems and Nutrition", 15-17 Feb. 2016, Rome, Italy
O
O
OH
O 63-66 Mbp
Sorghum roots release a nitrification inhibitor from roots
Sorgoleone
Sorgoleone production is controlled by chromosome 1
JIRCAS-ICRISAT partnership
Chromosome-1
A Genetic-Mitigation Technology?
200N 200N+Sorgoleone 200N+DCD0
0.20.40.60.8
11.21.41.61.8
Integrated N2O emission
Treatments
N2O
em
issio
n (u
g N
2O-N
)
a
b
c
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44-8-327
121722273237
N2O emission
200N200N+Sorgoleone200N+DCD
Days of incubationN2O
em
issio
n (n
g N
2O-N
(g d
ry so
il)-1
hr-
1 m
-2)
Sorgoleone additions to the soil suppressed N2O emissions
BNI-Mitigation Technology
Genetic improvements in sorgoleone release from sorghum root systems lead to lower N2O emissions?
Introducing high-BNI capacity into wheat Developing low-nitrifying and low-N2O emitting wheat production systems
JIRCAS-CIMMYT partnership
FAO workshop on "The Role of Agricultural Biotechnologies in Sustainable Food
Systems and Nutrition", 15-17 Feb. 2016, Rome, Italy
Plant species0 1 2 3 4
BN
I act
ivity
rele
ased
from
root
s(A
TU g
-1 ro
ot d
ry w
t. d-1
)
0
5
10
15
20
25
30
35
NH4-N grownNO3-N grown
Nobeoka Chinese Spring
L. racemosus
Wild-wheat has high-BNI capacity
Leymus racemosus
Leymus does not release BNI when grown with NO3
--N where pH of RE-collection solution will be of >6.0
RE collection
pH 4.0
RE collection
pH 7.5
JIRCAS-CIMMYT partnership
A Genetic-Mitigation Technology?
FAO workshop on "The Role of Agricultural Biotechnologies in Sustainable Food
Systems and Nutrition", 15-17 Feb. 2016, Rome, Italy
n
N-inputs into Agriculture
175 Tg N(120 Tg N from N-
Fertilizers + N-fixed from legumes)
Plant protein-N53.5 Tg
Nitrogen flow in Human-centric Ecosystems (where most ecological components are
directed to serve human society)
AnimalProtein-N3.5 Tg Human-N
0.3 Tg
123.5 Tg N
LostAgriculture
48.0 Tg N Lost
Livestock5.0 Tg N LostSewage systems
N2O, NO, N
2
NO3
- leaching
If there were no N losses from agricultural systems and recycle most of the N excreted from animals (i.e.
manure) only a small fraction of N needs to be replaced by fertilizer N inputs annually
FAO workshop on "The Role of Agricultural Biotechnologies in Sustainable Food
Systems and Nutrition", 15-17 Feb. 2016, Rome, Italy
Nitrogen pollution epidemic in China
Nitrification facilitates movement of N from agricultural soils to water-bodies (ground water, freshwater lakes, rivers and to oceans) and cause algal
blooms The negative consequences of Green Revolution?
FAO workshop on "The Role of Agricultural Biotechnologies in Sustainable Food
Systems and Nutrition", 15-17 Feb. 2016, Rome, Italy
Year1850 1900 1950 2000 2050 2100 2150
N2O
Em
issi
ons i
n Tg
0
2
4
6
8
10
12
14
16
18
AnthropogenicNatural
Projected
Nitrification and denitrification are the primary drivers for N2O emissions from agricultural systems and account for >70% of global N2O emissions
Green Revolution
IPCC set a target to cut GHG emissions by 2050 to limit global temperature raise to
<2CA requirement set by COP-21
–The Paris Agreement
There is an urgency to develop next-generation technologies to reduce N2O emissions from agricultural systems
Exploiting BNI-Mitigation Technology could be one such powerful strategy
FAO workshop on "The Role of Agricultural Biotechnologies in Sustainable Food
Systems and Nutrition", 15-17 Feb. 2016, Rome, Italy
Based on Khalil and Rasmussen 1988Annals of Glaceology 10:73-79
Year1880 1900 1920 1940 1960 1980 2000 2020 2040 2060
N2O
con
cent
ratio
n in
the
atm
osph
ere
(ppb
v)
280
300
320
340
360
380
400
N2O concentration in atmosphere
(ppbv)
The Choices We Make Will Create Different Outcomes
With substantial mitigation
Without additional mitigation
Change in average surface temperature (1986–2005 to 2081–2100)
Source: IPCC AR5 synthesis report
FAO workshop on "The Role of Agricultural Biotechnologies in Sustainable Food
Systems and Nutrition", 15-17 Feb. 2016, Rome, Italy
FAO workshop on "The Role of Agricultural Biotechnologies in Sustainable Food
Systems and Nutrition", 15-17 Feb. 2016, Rome, Italy
Benefits from Genetic-Mitigation using BNI-Technology
It will not require expensive or cumbersome management changesNo additional cost to the farmers once BNI trait is introduced into staple crops/pasturesLarge-scale impacts are potentially achievable as adoption is only through seedDelivery of BNIs through root systems is more effective than synthetic nitrification inhibitors as fertilizer additivesNo negative environmental consequencesNo health issues on food or feed qualityCan bring long-term benefits by changing potential soil nitrification, microbial-ecologyIf properly integrated into cropping systems, BNI-technology can improve soil-N retention and contribute to the sustainability of production systems
1st International BNI Workshop held during 2-3rd March 2015 at JIRCAS, Tsukuba, Japan
FAO workshop on "The Role of Agricultural Biotechnologies in Sustainable Food
Systems and Nutrition", 15-17 Feb. 2016, Rome, Italy