Speaker
Description
-
Introduction.
Cotton is Benin's leading export crop grown in different climatic zones. As a result of poor farming practices in agroecosystems leading to a decline in soil fertility, coupled with the phenomenon of climatic hazards, seed cotton yields of cultivated varieties are low. Given the context of soil degradation, agroecological practices are proposed as an alternative to conventional cropping systems. The emerging challenge for breeders is therefore to select new cultivars adapted to innovative cropping systems (Gouleau et al., 2021). Crop simulation models can be used to assess growth and yield of different crop genotypes (G) in different environments (E) by using environment-specific weather, soil, and crop management (M) practices (Boote et al., 2001) and help understanding the direct effect of each plant trait or a combination of traits on the G by E interactions for crop yield and other complex traits. The objectives of this study were (i) to evaluate the relative contribution of plant traits driving the G by E by M interactions for cotton yield using CSM-CROPGRO-cotton model from DSSAT, and (ii) to identify morpho-physiological traits for yield enhancement in agroecological cropping systems in Benin. -
Materials and methods.
The experimental study was conducted from 2020 to 2023, in two sites (Savalou and Soaodou) representative of contrasted cotton-growing regions of Benin. Approach consisted of (1) carrying out field experiments for the calibration and validation of CSM-CROPGRO-cotton model and determining the yield performance of cotton genotypes (2) launching a sensitivity analysis of the genetic coefficients from the crop model to determine the best values for traits adapted to agroecological cropping systems. According to a split plot design, the experiment compared four cropping systems with cowpea/maize//cotton rotation, namely Conventional Tillage (CT) with a plough, Conventional Tillage with Incorporation of biomass (CTI), Conservation Agriculture with Strip Tillage (CA_ST) and CA with No Tillage (CA_NT). In the three innovative cropping systems (CTI, CA_ST, CA_NT), legumes (Crotalaria spp., Stylosanthes guianensis) were sown as relay intercrops with maize while cotton was sown as a sole crop. Six different cultivars originated from Benin, Argentina, Uzbekistan, Nicaragua, and USA were compared as subplots in every cropping system. Among other parameters, crop model was parameterized for soil properties and water dynamics, and calibrated for phenology and growth, using a dataset under optimal conditions, then evaluated on other data from the same sites and 2 years. -
Results.
The agreement between simulated and observed data was strong for extractable soil water (fig 1a), and LAI (fig 1b) but fair for seed cotton yields (fig 1c). Our results confirmed that CSM-CROPGRO can be used to simulate the growth and yield of cotton in different environments and cropping systems and for the estimation of genetic coefficients (fig 1d). The availability of soil nitrogen was better in agroecological systems. The cultivars TAMCOT_CAMDE, S188 and OKP768 resulted in higher yields in the agroecological cropping systems under CA. The traits LFMAX, SLAVR, FL-LF and PODUR were responsible for yield differences and GxExM interactions. -
Discussion.
Maximum leaf photosynthetic rate (LFMAX) is related to traits that maintain high photosynthesis (Boote et al., 2001). In fact, increasing the value of this trait resulted in a decrease of SLAVR, indicating leaf thickening for leaf types like okra S188 or TAMCOT_CAMDE ensuring better nitrogen mobilization and radiation use efficiency, especially in CA systems. Increased availability of nitrogen in CA_ST and CA _NT made it possible to maintain green leaf area, delayed senescence of leaves (FL-LF) and a longer accumulation of reserves during seed filling (PODUR) (Wells et al., 1982) leading to an increase of boll weight. -
References.
-
Gouleau, A., Gauffreteau, A., This, P., Tailliez-Lefebvre, D., Gombert, J., Gouache, D., & Bakan, B. (2021). Saisine du Comité Scientifique CTPS-Quelles variétés pour l’agroécologie ? https://doi.org/10.17180/MEZ5-YV03.
- Boote, K. J., M. J. Kropff, and P. S. Bindraban (2001). Physiology and modelling of traits in crop plants: implications for genetic improvement. Agric. Syst. 70, 395–420.
- Wells, R., L.L. Schulze, D.A. Ashley, H.R. Boerma, and R.H. Brown. (1982). Cultivar differences in canopy apparent photosynthesis and their relationship to seed yield in soybeans. Crop Sci. 22:886–890.
| Keywords | tillage; water status; cover crop; nitrogen; CSM-CROPGRO-cotton. |
|---|
