Speaker
Description
Introduction
Intercropping offers the prospect of providing greater and more stable yield than sole-cropping in the face of climate change and increased climate variability. Cereal-legume intercropping is common in tropical cropping systems, but often with low legume density and limited or no nutrient inputs. Combining intercropping with integrated soil fertility management is a solution for promoting sustainable intensification. Long-term experiments investigating the impact of variations in soil and climate on intercrop performances are scarce throughout sub-Saharan Africa. Several models were designed to simulate intercropping, however their robustness and accuracy in reproducing intercropping functioning and performance have never been extensively evaluated for a range of tropical environments. This work aims to evaluate the robustness and accuracy of the STICS soil-crop model in simulating productivity and crop interactions for contrasting cereal-legume intercrops in tropical conditions.
Materials and methods
The STICS model (Beaudoin et al., 2023) was tested using data collected in on-farm and on-station experiments in Mali, Senegal, Burkina Faso, and Brazil. Various combinations of cereals (maize, sorghum, and millet) and legumes (pigeon pea and cowpea) were compared in sole cropping and intercropping. The experiments included contrasting spatial patterns, fertilizer inputs, crop varieties, sowing dates, and cereal/legume densities. The model was calibrated on sole cropping, and evaluated on intercropping. Observed and simulated partial Land Equivalent Ratio (pLER) was calculated to evaluate the ability of the model in simulating competition and complementarity effects in intercropping.
Results
We found that the STICS model had similar accuracy when simulating cereal grain yield of sole crops and intercrops. Model accuracy in simulating legumes was lower with intercropping compared with sole cropping. The model correctly reproduced competition and complementarity effects in intercropping between cereals and legumes in Mali and Burkina Faso and came close in Brazil (Figure 1). In Senegal, the model overestimated legumes’ pLER and underestimated cereals’ pLER, indicating that interspecific interactions where not correctly simulated for legumes with very low yields. Over all sites, the model simulated a reduction in legume yield due to light competition and a decrease in cereal yield due to competition for nitrogen. On the contrary, water stress had little effect on simulated yield, competition, and complementarity effects between crops.
Conclusion and prospects
This study provides evidence that the STICS model simulates intercropping with a good genericity and acceptable accuracy in contrasted tropical conditions, where legume yields are not too low. We are currently refining the calibration of the model and testing its latest version (beta version 11; Vezy et al., 2023) to better define the validity domain of STICS for tropical intercropping.
References
Beaudoin, N., Lecharpentier, P., Ripoche-Wachter, D., Strullu, L., Mary, B., Léonard, J., ... & Justes, E. (2023). STICS soil-crop model: conceptual framework, equations and uses.
Brisson, N., Bussiere, F., Ozier-Lafontaine, H., Tournebize, R., & Sinoquet, H. (2004). Adaptation of the crop model STICS to intercropping. Theoretical basis and parameterisation. Agronomie, 24(6-7), 409-421.
Justes, E., Bedoussac, L., Dordas, C., Frak, E., Louarn, G., Boudsocq, S., ... & Li, L. (2021). The 4C approach as a way to understand species interactions determining intercropping productivity. Frontiers of Agricultural Science and Engineering, 8(3), 3.
Baldé, A., Scopel, E., Affholder, F., Da Silva, F. A. M., Wery, J., & Corbeels, M. (2020). Maize relay intercropping with fodder crops for small-scale farmers in central Brazil. Experimental Agriculture, 56(4), 561-573.
Senghor, Y., Manga, A. G., Affholder, F., Letourmy, P., Bassene, C., Kanfany, G., ... & Falconnier, G. N. (2023). Intercropping millet with low-density cowpea improves millet productivity for low and medium N input in semi-arid central Senegal. Heliyon, 9(7).
Sow, S., Senghor, Y., Sadio, K., Vezy, R., Roupsard, O., Affholder, F., ... & Falconnier, G. N. (2024). Calibrating the STICS soil-crop model to explore the impact of agroforestry parklands on millet growth. Field Crops Research, 306, 109206.
Traoré, A., Falconnier, G. N., Ba, A., Sissoko, F., Sultan, B., & Affholder, F. (2022). Modeling sorghum-cowpea intercropping for a site in the savannah zone of Mali: Strengths and weaknesses of the Stics model. Field Crops Research, 285, 108581.
Vezy, R., Munz, S., Gaudio, N., Launay, M., Lecharpentier, P., Ripoche, D., & Justes, E. (2023). Modeling soil-plant functioning of intercrops using comprehensive and generic formalisms implemented in the STICS model. Agronomy for Sustainable Development, 43(5), 61.
| Keywords | intercropping, calibration, competition, complementarity, agroecology |
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