Biostimulants to enhance Nutrient Use Efficiency in Crop Plants

Pr. Patrick du JardinPlant Biology Laboratory

Gembloux Agro-Bio Tech, University of Liège, Belgiumpatrick.dujardin@uliege.be

This talk

• Biostimulants are defined by their action on plants and this includesimproved nutrition.

• Nutrient Use Efficiency (‘NUE’) is a key concept, which can be definedin different ways.

• In order to improve NUE:- Biostimulants and other bioresources offer options

complementing the existing tool box;- New regulatory advances pave the way to innovation in this area

(further discussed tomorrow during the workshop).

The very diverse nature of Biostimulants:

Substances• Humic substances• Seaweed /plant extracts• Protein hydrolysates and amino

acids• Chitosan and other

polysaccharides• Inorganic compounds

Microorganisms

• Bacteria• Fungi

Scientia Horticulturae (2015) 196 (30), 3-14DOI: 10.1016/j.scienta.2015.09.021

Many physiological triggers (substances and microorganisms)

Many cellular targets

Many whole-plant physiological responses

Converging agricultural functions related to:nutrition efficiency, abiotic stress tolerance, crop qualiy

Defining biostimulants by what they do:

A plant biostimulant is any substance or microorganism

applied to plants with the aim of enhancing nutrition

efficiency, abiotic stress tolerance and/or crop quality

traits, regardless of its nutrients content.

P. du Jardin (2015) Scientia Horticulturae. 196 (30), 3-14DOI: 10.1016/j.scienta.2015.09.021

Plant Biostimulants, as defined by the draft« CE-marked fertilising products » regulation (EU)

A plant biostimulant shall be a CE marked fertilising product stimulating plant nutrition processes independently of the product's nutrient content with the sole aim of improving one or more of the following characteristics of the plant:

(a) nutrient use efficiency,

(b) tolerance to abiotic stress,

(c) crop quality.

Plants Biostimulants will be legally defined in EU by claims of agricultural functions.

Crop intensification and Nutrient Use Efficiency (NUE)

Tilman et al. 2002, Nature 418:671

Grain yield / N fertilizers supplyGrain yield

N output (kg N.ha-1) / N input (kg N.ha-1)

« Currently, only 47% of the reactive nitrogen addedglobally onto cropland isconverted into harvestedproducts, compared to 68% in the early 1960s. »

Readily DecomposableResidues (10-20%)

Readily DecomposableResidues (10-20%)

Plant & Animal Residues

Soil Surface

SOIL ORGANIC MATTER(Organic N)

Stable Humus(70-90%)

Stable Humus(70-90%)

Microbial Biomass(<10%)

Fungi, Bacteria, ProtozoaActinomycetes, Algae

Nematodes, Fauna

NN22 Fixation

Fixation

SymbioticNon-symbiotic

Legumes

NONO33--

LightingRainfall

FertilizerNH4

+ NO3-

Plant Plant UptakeUptake

R-NH2NH4+

Ammonification Aminization

NONO22--

Mineralization

NONO33--

Nitrification

Immobilization

NN22

NN22O

NONO

NONO22

NONO33--

NO3- NH4

+

solution

NO3- Leaching

NO3-

Den

itrifi

catio

nD

enitr

ifica

tion

NN22OONONONN22

NH3

Vola

tiliz

atio

n

NH4+

NH3

2:1 ClayNH4+ Fixation

N Transformations (Italics)

3 2

1

4

5

6

9 8

7

NN 22Fix

atio

n

Fixat

ion

Atmosphere NAtmosphere N22

urea

(Havlin et al. 2014. Soil fertility and fertilizers – An introduction to nutrient management.)

Nitrogen cycle, losses by leaching and volatilization

Readily DecomposableResidues (10-20%)

Readily DecomposableResidues (10-20%)

Plant & Animal Residues

Soil Surface

SOIL ORGANIC MATTER(Organic N)

Stable Humus(70-90%)

Stable Humus(70-90%)

Microbial Biomass(<10%)

Fungi, Bacteria, ProtozoaActinomycetes, Algae

Nematodes, Fauna

NN22 Fixation

Fixation

SymbioticNon-symbiotic

Legumes

NONO33--

LightingRainfall

FertilizerNH4

+ NO3-

Plant Plant UptakeUptake

R-NH2NH4+

Ammonification Aminization

NONO22--

Mineralization

NONO33--

Nitrification

Immobilization

NN22

NN22O

NONO

NONO22

NONO33--

NO3- NH4

+

solution

NO3- Leaching

NO3-

Den

itrifi

catio

nD

enitr

ifica

tion

NN22OONONONN22

NH3

Vola

tiliz

atio

n

NH4+

NH3

2:1 ClayNH4+ Fixation

N Transformations (Italics)

3 2

1

4

5

6

9 8

7

NN 22Fix

atio

n

Fixat

ion

Atmosphere NAtmosphere N22

Innovation for increasing Nitrogen Use Efficiency

Precision agriculture

Slow and controlledrelease fertilizers

Stabilized fertilizers(with urease or nitrification inhibitors)

Biostimulants

urea

(Havlin et al. 2014. Soil fertility and fertilizers – An introduction to nutrient management.)

http://www.europarl.europa.eu/RegData/etudes/BRIE/2016/582010/EPRS_BRI(2016)582010_EN.pdf

How to increase NUE with biostimulants?

𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨 𝑵𝑵𝑵𝑵𝑵𝑵 = 𝑵𝑵𝑼𝑼𝑼𝑼𝑼𝑼𝑼𝑼𝑼𝑼 𝑵𝑵𝑬𝑬𝑬𝑬𝑨𝑨𝑨𝑨𝑨𝑨𝑼𝑼𝑨𝑨𝑨𝑨𝑬𝑬 ∗ 𝑷𝑷𝑷𝑷𝑬𝑬𝑷𝑷𝑨𝑨𝑨𝑨𝑷𝑷𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑼𝑼𝑷𝑷 𝑵𝑵𝑵𝑵𝑵𝑵

Yield / Fertilizer = Uptake / Fertilizer * Yield / Uptake

Root growth Nutrient

solubilization Nutrient import …

Stress tolerance Photosynthetic

capacity Nutrient reallocation …

Root ideotype for higher P use efficiency

(Taiz et al. 2015)

Rhizobacteria control root development via the emission of VOCs (volatile organic compounds).

Dr. Pierre Delaplace, PI

CONCLUSIONS

INTRODUCTIONEffects of PGPR VOCs on root architectural traits

88

63

271

236

196

473

0100200300400500

Total root length

Mean secondary rootlength

Secondary rootnumber

Secondary rootdensity

Total secondary rootlength

Total adventitious rootlength

Cluster 1

Cluster 2

Cluster 3

Cluster 4

Cluster 5

NB: a cluster is a group of PGPR strains showing statistically similar effects on plant traits.

P starvation and PGPR response in the model grass Brachypodiumdistachyon (L) P. Beauv.

Brachypodium distachyon(L) P. Beauv.

P starvation response of B. distachyon(in sand supplementwith mineral solution)

Cultivation of B. distachyonon gravel in gnotobioticcondition

Caroline Baudson, PhD student

Solubilization of Ca3(PO4)2 by PGPRs in liquid cultures

[P]pH

P.f.: PseudomonasfluorescensE.c.: Escherichia coliB.a.: BacillusamyloliquefaciensA.v.: Azotobactervinelandii

Co-cultivation of B. distachyon with PGPRs in gnotobiotic conditions (1)

***

******

*** ***

= Lowsoluble P

+ insoluble P

= Lowsoluble P

+ insoluble P

= Lowsoluble P

= Lowsoluble P

= High soluble P

= High soluble P

***

***

******

***

***

Proposal: When plants are P-limited and PGPRs are C-limited, the latter seem to promote a high Root-to-Shoot ratio (to better feedon the exudates?).

Co-cultivation of B. distachyon with PGPRs in gnotobiotic conditions (2)

LuanNGUYEN, PhD student

PGPR inoculants and N(itrogen)UE in wheat

• Spring wheat in the greenhouse• Soil:sand mixture (2:1)• 3 rates of ammonium nitrate• 3 pre-selected inoculants, of B.

amyloliquefaciens, B. megateriumand A. brasilense

• Measurements after 30d and 60d

(Nguyen et al. 2018. Arch. Agronomy and Soil Science, in Press)

Higher N uptake efficiency (N uptake / N supply) in PGPR-inoculated plants:

Nutrient uptake in ears (60-d plants):Total contents and tissue concentrations

Rhizobacteria and NUE-related plant traits: observations (and food for thought)

• PGPRs have the capacity to shape root development (e.g. by releasing volatile compounds).

• PGPRs include P-solubilizers, but their effect on plant growth isdepending on the context.

• Higher total nutrient uptake does not necessarily mean higherconcentrations of nutrients in the harvested organs.

http://www.europarl.europa.eu/RegData/etudes/BRIE/2016/582010/EPRS_BRI(2016)582010_EN.pdf

Agronomic additives: current urease inhibitors and nitrification inhibitors are synthetic molecules…

NBPT Thiosulfates

Nitrapyrin DCD DMPP

…but plants produce their own nitrification inhibitors.

Root exudates contain BNI(‘BNI’, Biological nitrification inhibitors)

(Subbarao et al. 2015) (Subbarao et al. 2013)

CON, control; SOY, soybean; PM, Panicum maximum; BH(...), Brachiaria genotypes

In the field, higher BNI activity is correlatedwith lower N2O emission.

(Subbarao et al. 2013)

There is a large variability of BNI activity between cultivars. This opens perspectives for breeding plants for higher NUE (in specificenvironments)!

Novel, bio-based fertilizers additives could be derived / inspired frombiochemical activities naturally present in the soil …

Plant allelochemical compounds, in exudates or from plant residues, are potential sources of new biostimulants enhancing NUE.

General conclusions

• There is need to increase NUE in crops.• Biological solutions can be derived from beneficial microorganisms

and natural substances.• There is a growing interest on Biostimulants, as reflected by the:

- raising awareness of the scientific community,- increasing R&D investment by the industry,- regulatory advances.

• Still a major need to demonstrate efficacy in diverse field situations and to better understand the action mechanisms of biostimulation.

Thank you!

Patrick du Jardin(patrick.dujardin@uliege.be)