Conventional versus agro-ecological intensification: assessing the effect of conservation agriculture in maize cropping systems with the DSSAT model in Côte d’Ivoire (West Africa)

Abstract

Integrated soil fertility management options are being promoted as ways of adapting agricultural systems to sustain yields on highly degraded and poor soils encountered throughout West Africa. The efficiency of these practices may be affected by high variability and uncertainty associated with seasonal rainfall, especially for areas such as Côte d’Ivoire, where intra-seasonal rainfall has been observed to change from 1 year to another. The DSSAT crop simulation model was used in this study as a tool to evaluate the impacts of soil improvement options including inorganic fertilizer and conservation agriculture generating higher carbon sequestration and crop yield in maize agro-ecosystems. The model was calibrated using agronomic data for three cropping seasons from 2009 to 2010 in Goulikao (Center-West Côte d’Ivoire) and Ahérémou 2 (Central Côte d’Ivoire), respectively and validated against independent datasets of yield of 2003–2004 seasons in the buffer zone of the Lamto Natural Reserve, Central Côte d’Ivoire. The model predicted average maize yields of 1454 kg ha⁻¹ across the sites versus an observed average value of 1736 kg ha⁻¹, R² of 0.72, and RMSE of 597 kg ha⁻¹ after the default values for stable soil organic matter fraction used in the model were substituted by the estimated one. For the validation, the predicted higher maize yield was consistently related to fallow biomass inputs and different rates of fertilizer, thus generating a RMSE of total aboveground biomass and grain yield of 606 kg ha⁻¹ and 350 kg ha⁻¹, respectively. The impact of fallow residues and cropping sequence on subsequent maize yield was simulated and compared with conventional fertilizer and control data using 12 years historic climate time series. We conclude that soil fertility improvements through conservation agriculture can sustain grain yield at the same level as conventional inputs of urea against larger climate variability. However, this system may be substituted by conventional agriculture when climate forecast reveals a dry cropping season year.