The Decision Support System for Agricultural Technology Transfer (DSSAT) was used to quantify the impact of climate change on maize yield and the potential benefits of the use of drought-tolerant maize variety over non-drought tolerant variety in savanna ecological zones of Nigeria. Projections of maize yields were estimated for three locations representing different agro-climatic zones and soil conditions, in the mid-century (2040–2069) and end-century (2070–2099) under representative concentration pathways scenarios (RCP 4.5 and 8.5) against the baseline period (1980–2009). Relative to the baseline period, the ensemble Global Circulation Models (GCMs) predicted significant increase in minimum and maximum temperatures and seasonal rainfall across the sites. In the mid-century, ensemble GCMs predicted temperatures increase between 1.7–2.4 °C for RCP4.5 and 2.2–2.9 °C for RCP8.5. By end-century, the temperature increases between 2.2–3.0 °C under RCP4.5 and 3.9–5.0 °C under RCP8.5. Predicted seasonal rainfall increase between 1.2–7% for RCP4.5 and 0.03–10.6% for RCP8.5 in the mid-century. By end of century, rainfall is expected to increase between 2–6.7% for RCP4.5 and 3.3–20.1% for RCP8.5. The DSSAT model predictions indicated a negative impact on maize yield in all the selected sites, but the degree of the impact varies with variety and location. In the mid-century, the results showed that the yield of the non–drought tolerant maize variety, SAMMAZ-16 will decline by 13–19% under RCP4.5 and 19–28% under RCP8.5. The projection by end-century indicates a decline in yield by 18–26% under RCP4.5 and 38–47% under RCP8.5. The yield of the drought-tolerant variety is projected to decline by 9–18% for RCP4.5 and 14–25% for RCP8.5 in the mid-century and 13–23% under RCP4.5 and 32–43% under RCP8.5 by the end-century. The higher temperatures by both emission scenarios (RCP 4.5 and 8.5) were primarily shown to cause more yield losses for non-drought-tolerant variety than that of the drought-tolerant variety. There will be 1–6% less reduction in yield when drought-tolerant variety is used. However, the higher yield reductions in the range of − 13 to − 43% predicted for the drought-tolerant variety by the end of the century across the study areas highlighted the need to modify the maize breeding scheme to combine both tolerances to drought and heat stresses in the agro-ecological zones of northern Nigeria.

The soils of the Nigeria savannas are particularly low in nitrogen (N) and phosphorus (P) and negatively affects maize productivity. The main objective of the study was to evaluate the interactive effect of N and P fertilizers on maize growth, grain yield, nitrogen uptake and N use efficiency. Field experiments were conducted during the 2015 and 2016 cropping seasons at Iburu in southern Guinea and Zaria in northern Guinea savanna zones of Nigeria. The treatments consisted of three levels of nitrogen (0, 60, and 120 kg N ha^-1) and three levels of phosphorus (0, 13, and 26 kg P ha^-1). The experimental design consisted of three replications in a split-plot design, with N as the main plot and P as the subplot. Our results show that the response of maize to N depends on the application of P. Higher yields were obtained with the combined application of 120 kg N ha^-1 and 26 kg P ha^-1 in both locations. With no P applied, plant N uptake (PNU) was greater at N rate of 120 kg ha^-1 at Iburu while in Zaria, it increases with increase in N from 0 to 60 kg ha^-1. When P was applied at 13 kg ha^-1, the PNU increased by 52 and 66% at Iburu while in Zaria the increases were 51 and 57% each with N application of 60 and 120 kg ha^-1, respectively, compared with zero N rate. The values for N recovery efficiency (NRE) and agronomic efficiency (AE) were lower for N rate of 120 than for 60 kg ha^-1 irrespective of P application rate at both locations. The N utilization efficiency (NUTE) however was higher at 120 N kg ha^-1 under 26 kg P ha^-1across locations. It can be concluded from these results that in low fertile soils environments such as the Nigeria savannas, N fertilizer should be applied along with P fertilizer for optimum growth, grain yield and nitrogen use efficiency of maize.

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.

Use of small doses of imazapyr and pyrithiobac for seed coatings of imazapyr-resistant maize hybrids (IR-Maize) offers an effective means to control Striga hermonthica. Field trials were conducted in Bauchi and Kano States of Nigeria in 2014 and 2015 under heavy Striga infestation to evaluate the potential effectiveness of herbicide coated hybrids maize on Striga control in farmers’ field. Results showed that herbicide coated seeds reduced number of emerged Striga per m² and Striga damage symptoms in farmers’ fields in all the locations. In Kano the number of emerged Striga was 4.9 to 7.9 times less in herbicide treated hybrids in comparison with those of the same hybrids planted without herbicide treatment. The Striga-resistant open pollinated variety (OPV) (TZL COMP1 SYN) had 6.7 to 8.0 times more Striga than the treated hybrids. In Bauchi, the number of emerged Striga on the untreated IR-maize hybrids were over four-times higher on the treated IR-maize hybrids than on the untreated hybrids. The Striga-resistant OPV check had four-times more Striga than the treated IR-maize hybrids and twice more than the untreated IR-maize hybrids across the two years. However, the effects of herbicide seed coating on grain yields were not consistent because of strong seasonal effects. The result revealed that coating of imazapyr-resistant hybrid maize seeds with imazapyr was effective in reducing Striga infestation in farmers’ fields. Although herbicide seed coating did not give consistent yield advantages of the hybrids over the untreated checks, a combination of herbicide seed treatment and genetic resistance to Striga would serve as an effective integrated approach that could significantly reduce the parasite seed bank from the soil and prevent production of new seeds. The IR-hybrids and the OPV checks contained Striga resistance/tolerant genes that protected them against drastic yield loss in the Striga infested fields in both Bauchi and Kano.

In the context of climate change, the sowing date and cultivar choice can influence the productivity of sorghum, especially where production is constrained by low soil fertility and early terminal drought across the challenging agro-ecologies of north-eastern Nigeria. Planting within an optimal sowing window to fit the cultivar’s maturity length is critical for maximizing/increasing the crop yield following the appropriate climate-smart management practices. In this study, the APSIM crop model was calibrated and validated to simulate the growth and yield of sorghum cultivars with differing maturing periods sown within varying planting time windows under improved agricultural practices. The model was run to simulate long-term crop performance from 1985 to 2010 to determine the optimal planting windows (PWs) and most suitable cultivars across different agro-ecological zones (AEZs). The performance of the model, validated with the observed farm-level grain yield, was satisfactory across all planting dates and cropping systems. The model predicted a lower mean bias error (MBE), either positive or negative, under the sole cropping system in the July sowing month compared to in the June and August sowing months. The seasonal climate simulations across sites and AEZs suggested increased yields when using adapted sorghum cultivars based on the average grain yield threshold of ≥1500 kgha⁻¹ against the national average of 1160 kgha⁻¹. In the Sudan Savanna (SS), the predicted optimum PWs ranged from 25 May to 30 June for CSR01 and Samsorg-44, while the PWs could be extended to 10 July for ICSV400 and Improved Deko. In the Northern Guinea Savanna (NGS) and Southern Guinea Savanna (SGS), the optimal PWs ranged from 25 May to 10 July for all cultivars except for SK5912, for which predicted optimal PWs ranged from 25 May to 30 June. In the NGS zone, all cultivars were found to be suitable for cultivation with exception of SK5912. Meanwhile, in the SGS zone, the simulated yield below the threshold (1500 kgha⁻¹) could be explained by the sandy soil and the very low soil fertility observed there. It was concluded that farm decisions to plant within the predicted optimal PWs alongside the use of adapted sorghum cultivars would serve as key adaptation strategies for increasing the sorghum productivity in the three AEZs.

Increasing delays in the onset of the rainy season and extended dry spells in the Nigerian savannas are complicating the determination of optimal planting dates for rain-fed crops, which increases risks for farmers. This study evaluated the impact of planting dates on soybean [Glycine max (L.) Merr.] performance to identify optimal planting dates for different soybean varieties in two agroecological zones (AEZs) of Nigeria. The study involved six planting dates (15 June, 22 June, 29 June, 6 July, 13 July, and 20 July) and three soybean varieties (TGX-1835-10E, TGX-1951-3F, TGX-1904-6F). Results showed significant differences in growth and yield parameters based on location, variety, and planting date. In the Sudan savanna (SS), AEZ at BUK-Kano, optimal yields (>1500 kg ha⁻¹) were achieved when planting TGX-1835-10E and TGX-1951-3F from 15 to 29 June and TGX-1904-6F on 15 June. Planting beyond 29 June reduces yields by 12–55% for TGX-1835-10E and 27–63% for TGX-1951-3F. For TGX-1904-6F, planting after 15 June reduces yields by 27–90%. In the Northern Guinea savanna (NGS) AEZ at Zaria, optimal yields (>1500 kg ha⁻¹) were obtained when planting TGX-1835-10E and TGX-1951-3F from 15 June to 6 July, and TGX-1904-6F between 15 to 29 June. Delaying planting beyond these dates significantly reduced yields by 18–31% for TGX-1835-10E and 12–20% for TGX-1951-3F and 10–41% for TGX-1904-6F.