Developing an Original Computational Model for Simulating the Effect of Intercropping Systems on Resource Use Efficiency in Semi-Arid Nigeria

Intercropping systems in semi-arid Nigeria achieve resource use efficiency advantages through temporal and spatial complementarity in light, water, and nutrient capture, but mechanistic understanding of these interactions has been limited by the absence of region-specific computational models capable of simulating intercrop resource dynamics under the variable and stress-prone conditions of the Sahel savanna. This study developed an original computational model for simulating resource use efficiency in cereal-legume intercropping systems under semi-arid Nigerian conditions, focusing on sorghum-cowpea and millet-groundnut combinations in Sokoto and Zamfara States. A computational model development methodology was employed, combining process-based modelling with multi-season experimental data from 6 on-farm trials conducted from 2021 to 2023. The model was constructed by coupling a modified APSIM-Sorghum module with an adapted APSIM-Cowpea module with novel intercrop light partitioning and root water uptake competition algorithms calibrated for the Sahel savanna soil and climate parameters. Model calibration used 2021 to 2022 data and validation used independent 2023 trial data. Validation statistics showed NSE of 0.72 for sorghum grain yield and 0.68 for cowpea grain yield under intercrop conditions, acceptable for operational use. Land equivalent ratio predictions were within 8 percent of observed values in 71 percent of validation scenarios. The model was applied to evaluate 12 intercrop design scenarios varying plant density and row ratio, identifying a 2:1 sorghum-cowpea ratio as optimal for combined biomass production. Expert review confirmed the model's original methodological contribution.

Keywords: intercropping simulation, APSIM model, resource use efficiency, semi-arid Nigeria, cereal-legume system