DOES CROP DIVERSIFICATION IMPACT PLANT-SOIL INTERACTIONS ?
MIRA Sébas7an(1 ,2) , MOUGEL Christophe (2), LE CADRE Edith(1)*
(1) AGROCAMPUS OUEST, Joint Unit Research Soil, Agro- and Hydrosystems, Spa7aliza7on, Rennes – France.
(2) INRA, Joint Unit Research Gene7cs, Environment and Plant Protec7on, Le Rheu – France. * contact person email : [email protected]
Take home messages
Acknowledgement Authors thank Chaire Agriculture Ecologiquement Intensive for its financial support and technical staff from both INRA and AGROCAMPUS OUEST for their help during harvesFng and collecFng data.
Results and discussion
PLOT 1 : monoculture PLOT 2 : intercropping
Sunshine
Bulk soil properties (pH, SOM, CEC, texture)
Rain & [CO2]
Rhizosphere
Rhizosphere
Cultural practices (inputs, tillage)
Hypothesis (1) : Bulk soil ≠ Rhizosphere along a cultural cycle Hypothesis (2) : Rhizosphere effect is maintained along a gradient
of diversifica7on
Context and objec7ves
Plants modify physical and chemical proper3es around their roots1 The rhizosphere is an hot spot of biological ac3vity²
Rhizosphere func3onning may explain plant performances3
References
1 : Hunter, P. J., Teakle, G. R., & Bending, G. D. (2014). Root traits and microbial community interacFons in relaFon to phosphorus availability and acquisiFon, with parFcular reference to Brassica. FronFers in Plant Science, 5, 27.
2 : van der Pu[en, W. H., Bradford, M. A., Pernilla Brinkman, E., van de Voorde, T. F. J., & Veen, G. F. (2016). Where, when and how plant-soil feedback ma[ers in a changing world. FuncFonal Ecology, 30(7), 1109–1121.
3 : KulmaFski, A., Beard, K. H., & Heavilin, J. (2012). Plant-soil feedbacks provide an addiFonal explanaFon for diversity-producFvity relaFonships. Proceedings of the Royal Society B: Biological Sciences, 279(1740), 3020–3026.
Material and methods
BULK
SOIL RHIZO
SPHERE
Soil samples (4 replicates)
Rhizosphere Soil (RS) & Bulk Soil (BS)
- Phosphate & Nitrate fluxes estimated using Anion Exchange Membranes
(ANV Selemion)
- Enzymatic activities
Indicator used : BS – RS / BS + RS
3 winter wheat plots (Triticum aestivum)
Dynamic sampling : 6 dates of sampling per farm
April 24th--- May, 2nd--- May 14th --- May, 28th --- June, 11th --- June, 25th
0 20 40 60 80 100 120 PHOS
GLU
PAK ARN
Stem elongation (April, 24th)
0 20 40 60 80 100 120 PHOS
GLU
PAK ARN
Booting (May, 2nd)
0 20 40 60 80 100 120 PHOS
GLU
PAK ARN
Heading (May, 14th)
0 20 40 60 80 100 120 PHOS
GLU
PAK ARN
Flowering (May, 28th)
0 20 40 60 80 100 120 PHOS
GLU
PAK ARN
Development of fruit (June, 11th)
0 20 40 60 80 100 120 PHOS
GLU
PAK ARN
Ripening (June, 25th)
Farm A
Farm B
Farm C
Wheat Wheat IRG + CC Maize
2016 2017 2018
Faba bean Wheat Rapeseed Wheat
2015 2016 2017 2018
Cover crop
Cover crop Cover crop
2014 2015 2016 2017 2018
Wheat clover Maize Red Barley Rapeseed +
red clover Faba bean
3 farms - 3 degrees of diversification
Stem elongation Booting Heading Flowering Development of fruit Ripening
Figure 1 : Nitrate (1) and phosphate (2) fluxes (ng/day) in rhizosphere (green) and bulk soil (red) measured with a method using Anion Exchange Membranes (AEM). Bars indicate standard errors.
Differences are significant (p < 0,05) between soil samples for each date of sampling.
6 5
4 3 2
1 0
350
300 250 200
150 100
50 0
(1) N=4 (2) N=4
Boo7ng Heading Flowering Development of fruit Ripening Boo7ng Heading Flowering Development of fruit Ripening
Diversification +++
Diversification +++
Diversification +
Figure 2 : Enzymatic activities (PHOS = acid phosphatase, PAK = alakaline phosphatase involved in P cycle, ARN = Arylamidase involved in N cycle , GLU= Glucosidase involved in C cycle) in mU/g of soil in rhizosphere (green) and bulk soil (red). Differences are significant (p < 0,05) between soil samples for each date of sampling.
Bulk soil > Rhizosphere Bulk soil < Rhizosphere
0 1 -1
Bulk soil = Rhizosphere
Boo7ng Heading Flowering Development of fruit Ripening
Stem elonga7on Boo7ng Heading Flowering Development Ripening of fruit
Diversification +++
Diversification ++
Diversification +
v NO3- & PO43-- fluxes
Low diversifica7on à BS ≠ ≠ RS v EnzymaFc acFviFes
High diversifica7on à BS ≠ ≠ RS
Figure 4 : Differences in enzymatic activity of alkaline phosphatase between bulk soil and rhizosphere in function of diversification degree and plant growth stage. Differences are significant (p < 0,05)
between soil samples for each date of sampling.
Figure 4 : Differences in nitrate (green variations) and phosphate fluxes (red variations) between bulk soil and rhizosphere in function of
diversification degree and plant growth stage. Differences are significant (p < 0,05) between soil samples for each date of sampling.
v Soil analysis should collect rhizosphere soil (and not only bulk soil) to explain plant performances
v Rhizosphere is a dynamic compartment as variables are greatly influenced by plant growth stage and species
v Intensity of crop diversificaAon (duraAon of the crop rotaAon and number of culAvated species) impact rhizosphere funcAonning
v NO3- fluxes in BS > NO3- fluxes in RS à NO3- uptake by the plant v PO43- fluxes in BS < PO43- in RS àplant effect on P availability v EnzymaFc acFviFes RS > EnzymaFc acFviFes in BS
à higher microbial ac7vity in RS
