Simulating the Response of Drought–Tolerant Maize Varieties to Nitrogen Application in Contrasting Environments in the Nigeria Savannas Using the APSIM Model

This paper assessed the application of the Agricultural Production Systems sIMulator (APSIM)–maize module as a decision support tool for optimizing nitrogen application to determine yield and net return of maize production under current agricultural practices in the Nigeria savannas. The model was calibrated for two maize varieties using data from field experiments conducted under optimum conditions in three locations during the 2017 and 2018 cropping seasons. The model was evaluated using an independent dataset from an experiment conducted under different nitrogen (N) levels in two locations within Southern and Northern Guinea savannas. The results show that model accurately predicted days to 50% anthesis and physiological maturity, leaf area index (LAI), grain yield and total dry matter (TDM) of both varieties with low RMSE and RMSEn (%) values within the range of acceptable statistics indices. Based on 31-year seasonal simulation, optimum mean grain yield of 3941 kg ha⁻¹ for Abuja, and 4549 for Kano was simulated at N rate of 120 kg ha–¹ for the early maturing variety 2009EVDT. Meanwhile in Zaria, optimum mean yield of 4173 kg ha–¹ was simulated at N rate of 90 kg ha⁻¹. For the intermediate maturing variety, IWDC2SYNF2 mean optimum yields of 5152, 5462, and 4849 kg ha⁻¹, were simulated at N application of 120 kg ha⁻¹ for all the locations. The probability of exceeding attainable mean grain yield of 3000 and 4000 kg ha⁻¹ for 2009EVDT and IWDC2SYNF2, respectively would be expected in 95% of the years with application of 90 kg N ha⁻¹ across the three sites. Following the profitability scenarios analysis, the realistic net incomes of US$ 536 ha–¹ for Abuja, and US$ 657 ha⁻¹ for Zaria were estimated at N rate of 90 kg ha⁻¹ and at Kano site, realistic net income of US$ 720 ha–¹was estimated at N rate of 120 kg ha⁻¹ for 2009EVDT.For IWDC2SYNF2, realistic net incomes of US$ 870, 974, and 818 ha⁻¹ were estimated at N application of 120 kg ha⁻¹ for Abuja, Zaria, and Kano respectively. The result of this study suggests that 90 kg N ha⁻¹ can be recommended for 2009EVDT and 120 kg N ha–¹ for IWDC2SYNF2 in Abuja and Zaria while in Kano, 120 kg N ha⁻¹ should be applied to both varieties to attain optimum yield and profit.