Evaluation of banana covercropping systems and model based selection of cover-crop species

Transcription

1 Evaluation of banana covercropping systems and model based selection of cover-crop species Tixier, P., Alvarez, S., Blanchard, M., Ripoche, A., Achard, R. Banana and plantain Research Unit, Martinique, France AGRO2010, Montpellier, August 30, 2010

2 Intensive systems were traditionally managed with bare soil Cover crop allows to reduce herbicide applications and erosion

3 Intercropping banana alters the functioning of the soil-plant system Shading Competition for resource

4 Outline 1. How to select the best cover crops? using models to evaluate species searching for optimal functional traits 2. What is the optimal management to maximize cover and minimize nitrogen competition? use a spatialized intercropping model

5 Cover-crops should satisfy multiple criteria Capacity to cover soil surface Capacity to compete weeds Minimize competition for water and nitrogen Commercial availability of seeds Authorization of importation Host status for pests Tolerate shading of the main crop Technical compatibility

6 Existing cover crop in banana fields Gramineous impatiens Glycine javanica

7 But, cover-crop may decrease growth and yield of banana Height (cm) m a m j T0 T1 T2 j Bare soil Cynodon dactylon Bracharia decumbens a s o Month And delay harvest up to 8 weeks

8 1. How to select the best cover crops? Select most promising species of cover-crops on the base of early measures in collections 3 main criteria Capacity to control weeds Do no compete the banana plants for nitrogen Be tolerant to shading from the banana canopy

9 A model based approach A simple growth model based on : Beer-Lambert equations to intercept light Radiation conversion rate following a parabolic curve 0.25 Dbiom(t) (kg m-2 w-1) Pmax PARopti PAR(t) (J m-2 w-1) Tixier et al. submitted

10 A model based approach Calibration using data of growth under different shading BIOM(t) (Ton ha-1) sp. CD n = 5 RMSE = Weeks after sowing Tixier et al. submitted

11 Simulation of the growth of cover-crop under the canopy of banana 3 3 indicators were defined on the base of : 2 - biomass in 15 first weeks of growth Weed control - biomass between 50 and 150 weeks Persistence under the shade - total demand of nitrogen N competition BIOM(T) (kg m-2) 1 BD CR PN SH SG PP NW DR Weeks since seeding Tixier et al. submitted

12 Competition for nitrogen 0.70 Selection for multiple criteria 0.60 MA N (kg m-2) DR PP SG SH NW AO CR CD PN BD BIOM0-15 (kg m-2) Capacity to compete weeds Tixier et al. submitted

13 Research of functional traits of the ideal cover-crop Maximal biomass conversion rate Pmax (kg m -2 w -1 ) PARopti (J m -2 w -1 ) Optimal radiation N of criteria satisfied Tixier et al. submitted

14 2. How to manage cover-crops? The addition of a cover-crop modifies the whole functioning of the system

15 These processes become more spatially heterogeneous over the field Water balance Nitrogen balance

16 These processes become more spatially heterogeneous over the field Large Inter-Row Intermediate area Banana Row Small Inter-Row

17 Using Nitrogen and water balance model in every zone of the field

18 The SIMBA-N nitrogen balance model Plant uptake Banana & covercrop Fertilization Mineral N in soil Crop residues Leaching Runoff Soil organic pool Dorel et al European Journal of Agronomy

19 Very distinct dynamics of nitrogen in the 4 zones Large Inter-Row Small Inter-Row N (kg.ha-1) N (kg.ha-1) Weeks since planting Banana Row Intermediate area Weeks since planting

20 Preliminary use of the model Dose of nitrogen X Bunch dry weight Zone of application

21 Preliminary use of the model Bunch weight 1st cropping cycle + Dose Kg N ha-1 y-1 - BR IA LIR SIR Zone of fertilizer application

22 Preliminary use of the model Bunch weight 1st cropping cycle Bunch weight 2nd cropping cycle + Dose Kg N ha-1 y-1 Evidence of a stronger effect of the zone of application for the first cropping cycle and for low fertilization - BR IA LIR SIR BR IA LIR SIR Zone of fertilizer application

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