Embed Size (px)
Citation preview
Evaluation of banana cover-cropping 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
Intensive systems were traditionally managed with bare soil
Cover crop allows to reduce herbicide applications and erosion
Intercropping banana alters the functioning of the soil-plant system
Shading
Competitionfor resource
Outline
• 1. How to select the best cover crops ?using models to evaluate speciessearching for optimal functional traits
• 2. What is the optimal management to maximize cover and minimize nitrogen competition?
use a spatialized intercropping model
Cover-crops should satisfy multiple criteria
Host status for pests
Capacity to cover soil surface
Commercial availability of seedsAuthorization of importation
Capacity to compete weeds
Technical compatibility
Minimize competition for water and nitrogen
Tolerate shading of the main crop
Glycine javanica
Gramineous impatiens
Existing cover crop in banana fields
0
50
100
150
200
250
300
m a m j j a s o
Month
Hei
ght (
cm)
T0T1T2
But, cover-crop may decrease growth and yield of banana
And delay harvest up to 8 weeks
Bare soilCynodon dactylonBracharia decumbens
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 criteriaCapacity to control weedsDo no compete the banana plants for nitrogenBe tolerant to shading from the banana canopy
A model based approach
• A simple growth model based on :– Beer-Lambert equations to intercept light– Radiation conversion rate following a
parabolic curve
0.00
0.05
0.10
0.15
0.20
0.25
0 10 20 30 40 50 60 70 80 90 100 110PAR(t) (J m-2 w-1)
Dbi
om(t)
(kg
m-2
w-1
)
PARopti
Pmax
Tixier et al. submitted
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 5 10 15 20 25Weeks after sowing
BIO
M(t)
(Ton
ha-
1)
sp. CDn = 5RMSE = 0.080
A model based approach
• Calibration using data of growth under different shading
Tixier et al. submitted
Simulation of the growth of cover-crop under the canopy of banana
0
1
2
3
0 20 40 60 80 100 120 140Weeks since seeding
BIO
M(T
) (kg
m-2
)
BDCRPNSHSGPPNWDR
Tixier et al. submitted
3 indicators were defined on the base of :- 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
Selection for multiple criteria
BD
DR
NW
PN
SH
AOCR
CD
PP
SG
MA
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.00 0.10 0.20 0.30 0.40 0.50 0.60BIOM0-15 (kg m-2)
N50
-150
(kg
m-2
)
Tixier et al. submitted
Capacity to compete weeds
Competition for nitrogen
Research of functional traits of the ideal cover-crop
0 50 100 150
0
0.2
0. 4
0.6
Pm
ax(k
g m
-2w
-1)
0 50 100 150PARopti (J m-2 w-1)
Tixier et al. submitted
Optimal radiation
Maximalbiomass
conversion rate
N° of criteria satisfied
1
2
3
2. How to manage cover-crops ?
The addition of a cover-crop modifies the whole functioning of the system
Water balanceNitrogen balance
These processes become more spatially heterogeneous over the field
Large Inter-RowIntermediate areaBanana RowSmall Inter-Row
These processes become more spatially heterogeneous over the field
Using Nitrogen and water balance model in every zone of the field
The SIMBA-N nitrogen balance model
Dorel et al. 2008. European Journal of Agronomy
Mineral N in soil
Soil organic pool
Crop residues
Plant uptakeBanana & covercrop
Fertilization
LeachingRunoff
Very distinct dynamics of nitrogen in the 4 zones
0
10
20
30
40
50
60
70
80
0 20 40 60 80 100
Weeks since planting
N (k
g.ha
-1)
Large Inter-Row Small Inter-Row
0102030405060708090
0 20 40 60 80 100
Weeks since planting
N (k
g.ha
-1)
Banana RowIntermediate area
Preliminary use of the model
Dose of nitrogen
X
Zone of application
Bunch dry weight
Bunch weight 1st cropping cycle
Zone of fertilizer application
Dose
Kg N ha-1 y-1
+
-
Preliminary use of the model
BR IA LIR SIR
Bunch weight 1st cropping cycle Bunch weight 2nd cropping cycle
Zone of fertilizer application
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
Preliminary use of the model
BR IA LIR SIR BR IA LIR SIR
