Durum Wheat-Grain Legume intercrops An innovative way to design low inputs cropping systems

Transcription

1 11th Congress of European Society for Agronomy Durum Wheat-Grain Legume intercrops An innovative way to design low inputs cropping systems Laurent BEDOUSSAC 1, Etienne-Pascal JOURNET 2, Patrice ROUET 2, Eric JUSTES 2 1 Université de Toulouse; ENFA; UMR INRA-INPT/ENSAT 1248 AGIR 2 INRA, UMR INRA-INPT/ENSAT 1248 AGIR Castanet Tolosan, France Thanks to Master Students: Xavier Auzuret, Maud Matura, Stéphanie Ledoux and Coline Josse Laurent.Bedoussac@toulouse.inra.fr Eric.Justes@toulouse.inra.fr

2 Improve agricultural systems efficiency Intensification of agriculture in the last 5 years sometimes leads to: - Environmental contamination (water, soil, air) - Resistance to chemicals (e.g. Griffon 26) Pesticides use must be reduced Agricultural systems efficiency needs to be improved Diversification of agro-systems is one of the solutions (Malézieux et al. 28) Higher diversification can be achieved by intercropping species i.e. growing simultaneously 2 or more species in the same field for a significant period but without necessarily sowing or harvesting them at the same time (Willey 1979) Durum wheat Faba bean row-intercropping Durum wheat Winter Pea mixed on the line 1/11

3 Advantages and Disadvantages of intercrops Cereal grain legume spring intercrops are known to: Global yield ; Cereal grain protein content ; Stability over years (eg. Corre-Hellou 25, 26, 27; Hauggaard-Nielsen et al. 21, 23, 25, 26, 29) Improve the use of available resources (complementary use of light & N pools) We recently demonstrated similar results on winter intercrops (durum wheat-winter pea and durum wheat-faba bean intercrops) (Bedoussac and Justes, Plant and Soil, 21, Vol. 33, 19:35 and 37:54 ) Intercrops could improve agricultural systems efficiency Cereal grain legume intercrops are also known to: Insects, Diseases and Weeds which are sometimes main limiting factors (eg. Vandermeer 1989; Trenbath 1993; Altieri 1999; Kinane and Lyngkjaer 22) Intercropping can allow pesticides reduction Coherent with actual French/European agricultural policies: Reducing pesticides use by 5% in 218 European grain legume production But Lack of knowledge and references on winter intercrops Contradictory results in the literature about effects on pests 2/11

4 Objectives and general hypotheses of our work General aim of our work on intercrops: Understand intercrop functioning to propose optimal management by improving their efficiency Objective: Evaluate intercrop potentialities to reduce pests and diseases injuries Preliminary results focusing more on the data observed than on a functional analysis of biotic interactions Hypotheses: Intercrop efficiency to reduce weeds, pests and diseases depends on : - Species and cultivars i) Growth dynamics, ii) Cover architecture - Farming practices i) N available, ii) Sowing date and densities, iii) Sowing pattern - Weather and soil conditions 3/11

5 Material and methods: a wide range of field experiments 5 years experiments since 25 Field Experiments in conventional system and farm plots in organic farming Various pedoclimatic conditions in southern France 1 pea (cv. Lucy) and 1 faba bean (cv. Castel) 6 durum wheat cultivars and 1 soft wheat Various densities (substitutive and additive designs) and sowing dates Different sowing patterns: row intercropping and mixture on the row Various N availabilities: amount and dynamics 4/11

6 Results: 1. Is intercropping efficient to reduce weeds? Weeds in IC (t/ha) Y=X Weeds in intercrop (t/ha) Experimental fields Organic Farm fields Organic Farm fields Wheat-Faba bean trial Wheat-Pea trial Y=X Weeds in SC wheat (t/ha) Weeds in SC legume (t/ha) Legumes less competitive than wheat for weeds Intercrop efficient compared to sole crop legume (65% less weeds) Intercrop not efficient compared to sole crop wheat (54%more weeds) Weeds reduction in intercrop mostly due to the wheat because : - Lower inter-row compared to sole crop faba bean - Earlier growth compared to winter pea 5/11

7 Results: 2. Is intercropping efficient to reduce pea aphids? Experimental fields Experimental fields Y=X Intercropped Pea Sole Cropped Pea Aphids/plant in IC pea y =,78x +,2 R 2 =,72 Pea aphids/plant Aphids/plant in SC pea 13 Mar 1 Apr 8 May 5 Jun Weak population of pea aphids during these experiments Pea aphids reduced in intercrop (21% on average) Dynamic of pea aphids modified in intercrop Intercrop efficient to reduce pea aphids due to habitat modification? Temperature, Humidity, Plant recognition, Physical barrier, Predator 6/11

8 Results: 3. Is intercropping efficient to reduce weevils? Weevils/plant in IC Faba bean y = 1,27x + 4,45 R 2 =, Weevils/plant in SC Faba bean Y=X y =,53x -,2 R 2 =,53 More weevils on Faba bean than on Pea Intercrop reduces weevils compared to sole crop pea (52% less) Intercrop increases weevils compared to sole crop faba bean (95% more) Faba bean more attractive than Pea? More Faba bean resources due to higher dry weight than Pea? Pea more difficult to be find in intercrop because smaller than wheat? Greatest mobility/adaptability of weevils to a large range of habitats? 7/11 Weevils/plant in IC Pea Experimental fields Experimental fields Organic Farm fields Weevils/plant in SC Pea Y=X

9 Results: 4. Intercropping can reduce diseases Frequency (%) x Severity (%) 1 5 Neodur SC-N35 Neodur-Mix IC Pea-N35 Neodur-Line IC Pea-N35 L1823 SC-N Organic L1823-Line IC Faba bean-n Organic Frequency (%) x Severity (%) Pea SC-N Pea-Mix IC-N35 Pea-Line IC-N35 Faba bean SC-N Organic Faba bean-line IC-N Organic 3/4 17/4 1/5 15/5 1/4 15/4 29/4 13/5 27/5 Low Septoria attack (< 2%) Septoria reduced in intercrop Intercrop efficient to reduce septoria Ascochyta reduced in intercrop pea But not in intercrop faba bean Ascochyta appeared earlier in Pea Intercrop efficient to reduce ascochyta Barrier effect to propagation, microclimate modification, lower biomass? 8/11

10 but can also increase wheat diseases Index of attack (damage and severity) ( g ) 22-mai épis 22/5 Leaves Ears 1823 Nefer Neodur 1823 Nefer Neodur 1823 Nefer Neodur ICF ICP SC Intercrop with Fababean increased wheat oidium High faba bean LAI and Dry weight Barrier effect for fungicide treatment Modification of microclimate (T, H 2 O) No difference was found between SC and Intercrop with Pea 9/11

11 Conclusions: Intercropping could be efficient to reduce legume weeds: Species complementary for light absorption (Sequential growth; Smaller inter-row) to reduce diseases: Barrier effect to propagation ; Microclimate modification ; Less resources? to reduce pea aphids: Habitat modification ; Less resources ; Plant recognition more difficult? to reduce pea weevils but not faba bean weevils: Faba bean more attractive ; Taller than wheat ; Higher mobility of weevils? to increase yield & wheat protein in low N input systems: Complementary resources use: N (Nmin Vs. N 2 ); Light and Water 1/11

12 Perspectives Further Knowledge needed for designing cropping management systems to reduce weeds, pests and diseases and consequently the use of pesticides - Which are the best-adapted species and cultivars? - What are the effect of sowing densities and sowing pattern? Other question to solve: How to introduce Durum wheat-grain legumes Intercrop in the cropping systems to reduce pesticides use? 11/11

13 Thank you for your attention For more details: inra.fr/agir Plant and Soil (21) Vol. 33, 19:35 Vol. 33, 37:54

14 Is intercropping efficient to increase yield? 6 5 Total Intercrop yield (t/ha) y =,91x +,97 R 2 =, Experimental fields Experimental fields Experimental fields Experimental fields Organic Farm fields Organic Farm fields Wheat-Faba bean trial Wheat-pea trial Mean Sole crop yield (t/ha) IC yield higher than mean sole crop yield (+ 2% on average) IC efficiency depends on N-fertilization N-fertilization slightly increased wheat yield N-fertilization reduce pea yield IC more suited to low N systems

15 Is IC efficient to increase wheat protein content? 16 y =,79x + 3,7 R 2 =,56 IC wheat grain protein content (% DW) Experimental fields Experimental fields Experimental fields Experimental fields Organic Farm fields Organic Farm fields Wheat-Faba bean trial Wheat-pea trial SC wheat grain protein content (% DW) IC GPC higher than in SC The lower SC Wheat GPC the larger the increase Larger amount of N available per grain in IC because : - Lower wheat yield in IC than SC (less plants and legume competitin) - Similar amount of N available (the legume use mostly the N2 from air)

16 Intercropping increases legume N 2 fixation Percentage of N derived from air (%Nacc) Sole cropped Pea Nefer Lucy ; Unfertilized treatments Wheat (Nefer) Pea (Lucy) in unfertilized treatments 64% Intercropped Pea 82% 84% 52% N natural abundance method (Shearer and Kohl 1986) δ 1 %Ndfa = 15 N δ ref 15 N δ ref 15 N β δ 15 N ref = IC wheat β = -1 (Voisin et al. 22) pea Pea N 2 fixation in IC > SC The more wheat N acquisition the more pea N 2 fixation Complementarity for N pools use High pea N 2 fixation in IC (8-85 %Ndfa) 14 kg N/ha up taken from soil (only 15% of N available)

17 Intercropping improves light absorption Wheat growth earlier than that of pea and then slower 1 Wheat (Nefer) Pea (Lucy) Nefer Lucy in The whole IC absorbed more PAR than the SC Species complementarities in time & height growth PAR absorbed (% of incident PAR) FPARa IC N FPARa SC W N FPARa SC P N Degree days ( C.d) BUT IC less efficient than SC wheat with large amount of N

18 Evolution of cover rate in /5/28 N fertilization