Biostimulants to enhance Nutrient Use Efficiency in Crop Plants

Transcription

1 Biostimulants to enhance Nutrient Use Efficiency in Crop Plants Pr. Patrick du Jardin Plant Biology Laboratory Gembloux Agro-Bio Tech, University of Liège, Belgium

2 This talk Biostimulants are defined by their action on plants and this includes improved nutrition. Nutrient Use Efficiency ( NUE ) is a key concept, which can be defined in 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).

3 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), 3-14 DOI: /j.scienta

4 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

5 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), 3-14 DOI: /j.scienta

6 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 Plants following Biostimulants characteristics will of be the legally plant: defined in EU by claims (a) of nutrient agricultural use efficiency, functions. (b) tolerance to abiotic stress, (c) crop quality.

7 Crop intensification and Nutrient Use Efficiency (NUE) Grain yield Grain yield / N fertilizers supply Tilman et al. 2002, Nature 418:671

8 «Currently, only 47% of the reactive nitrogen added globally onto cropland is converted into harvested products, compared to 68% in the early 1960s.» N output (kg N.ha -1 ) / N input (kg N.ha -1 )

9 Nitrogen cycle, losses by leaching and volatilization Denitrification N 2 O NO N N 2 N 2 O NO NO 2 NO - 3 NO - 3 NO - 2 Nitrification Plant Uptake NO 3 - NH 4 + solution NH 4 + Ammonification Fertilizer NH 4+ NO - 3 urea NO Immobilization R-NH 2 Aminization Mineralization Soil Surface Plant & Animal Residues Readily Decomposable Residues (10-20%) Microbial Biomass (<10%) Fungi, Bacteria, Protozoa Actinomycetes, Algae Nematodes, Fauna N2 Fixation Fixation Legumes Non-symbiotic Symbiotic 3 2 Stable Humus (70-90%) 6 SOIL ORGANIC MATTER NO 3- Leaching (Organic N) (Havlin et al Soil fertility and fertilizers An introduction to nutrient management.) NO 3 - N Transformations (Italics) Volatilization NH 3 NH 3 NH NO 3 - NH 4+ Fixation 5 N 2 Fixation Fixation 7 Atmosphere N 2 Lighting Rainfall 2:1 Clay 1

10 Innovation for increasing Nitrogen Use Efficiency Denitrification N 2 O NO N N 2 N 2 O NO NO 2 NO - 3 NO - 3 N Transformations (Italics) Volatilization NH 3 NH 3 NH 4 + NO - 2 Nitrification Plant Uptake 4 NO 3 - NH 4 + solution NH 4 + Ammonification Fertilizer NH 4+ NO - 3 urea NO Immobilization R-NH 2 Aminization Mineralization Soil Surface Plant & Animal Residues Readily Decomposable Residues (10-20%) Microbial Biomass (<10%) Fungi, Bacteria, Protozoa Actinomycetes, Algae Nematodes, Fauna N2 Fixation Fixation Legumes Non-symbiotic Symbiotic 3 2 Stable Humus NO - 3 (70-90%) 6 SOIL ORGANIC MATTER NO 3- Leaching (Organic N) (Havlin et al Soil fertility and fertilizers An introduction to nutrient management.) NO 3 - NH 4+ Fixation 5 N 2 Fixation Fixation 7 Atmosphere N 2 Lighting Rainfall 2:1 Clay 1 Precision agriculture Slow and controlled release fertilizers Stabilized fertilizers (with urease or nitrification inhibitors) Biostimulants

11 2016/582010/EPRS_BRI(2016)582010_EN.pdf

12 How to increase NUE with biostimulants? AAAAAAAAAAAAAAAAAA NNNNNN = UUUUUUUUUUUU EEEEEEEEEEEEEEEEEEEE PPPPPPPPPPPPPPPPPPPPPPPPPP NNNNNN Yield / Fertilizer = Uptake / Fertilizer * Yield / Uptake Root growth Nutrient solubilization Nutrient import Stress tolerance Photosynthetic capacity Nutrient reallocation

13 Root ideotype for higher P use efficiency (Taiz et al. 2015)

14 Rhizobacteria control root development via the emission of VOCs (volatile organic compounds). Dr. Pierre Delaplace, PI

15 Effects of PGPR VOCs on root architectural traits INTRODUCTION Cluster 1 Cluster 2 Cluster 3 Total adventitious root length CONCLUSIONS Total secondary root length Total root length Mean secondary root length Secondary root number Cluster 4 Cluster 5 Secondary root density NB: a cluster is a group of PGPR strains showing statistically similar effects on plant traits.

16 P starvation and PGPR response in the model grass Brachypodium distachyon (L) P. Beauv. Caroline Baudson, PhD student Brachypodium distachyon (L) P. Beauv. P starvation response of B. distachyon (in sand supplement with mineral solution) Cultivation of B. distachyon on gravel in gnotobiotic condition

17 Solubilization of Ca 3 (PO 4 ) 2 by PGPRs in liquid cultures [P] ph P.f.: Pseudomonas fluorescens E.c.: Escherichia coli B.a.: Bacillus amyloliquefaciens A.v.: Azotobacter vinelandii

18 Co-cultivation of B. distachyon with PGPRs in gnotobiotic conditions (1) *** *** *** *** *** = Low soluble P = Low = High soluble P soluble P + insoluble P = Low soluble P = Low = High soluble P soluble P + insoluble P

19 Co-cultivation of B. distachyon with PGPRs in gnotobiotic conditions (2) *** *** *** *** *** *** Proposal: When plants are P-limited and PGPRs are C-limited, the latter seem to promote a high Rootto-Shoot ratio (to better feed on the exudates?).

20 PGPR inoculants and N(itrogen)UE in wheat Luan NGUYEN, PhD student Spring wheat in the greenhouse Soil:sand mixture (2:1) 3 rates of ammonium nitrate 3 pre-selected inoculants, of B. amyloliquefaciens, B. megaterium and A. brasilense Measurements after 30d and 60d (Nguyen et al Arch. Agronomy and Soil Science, in Press)

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

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

23 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 is depending on the context. Higher total nutrient uptake does not necessarily mean higher concentrations of nutrients in the harvested organs.

24 2016/582010/EPRS_BRI(2016)582010_EN.pdf

25 Agronomic additives: current urease inhibitors and nitrification inhibitors are synthetic molecules NBPT Thiosulfates Nitrapyrin DCD DMPP

26 but plants produce their own nitrification inhibitors.

27 Root exudates contain BNI ( BNI, Biological nitrification inhibitors) (Subbarao et al. 2015) (Subbarao et al. 2013)

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30 In the field, higher BNI activity is correlated with lower N 2 O emission. CON, control; SOY, soybean; PM, Panicum maximum; BH(...), Brachiaria genotypes (Subbarao et al. 2013)

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

32 Novel, bio-based fertilizers additives could be derived / inspired from biochemical activities naturally present in the soil Plant allelochemical compounds, in exudates or from plant residues, are potential sources of new biostimulants enhancing NUE.

33 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.

34 Thank you! Patrick du Jardin