Assessing the Sensitivity of Maize in the Coastal Savanna Of Ghana to Climate Change

Abstract

Climate change is projected to negatively impact on cereal production in Sub Saharan Africa. This impact is projected to be exacerbated by the generally low soil fertility, thus requiring fertilizer as well as other integrated soil fertility management options in order to replenish the soil fertility and to increase crop productivity. This study was to assess the impact of climate change on maize production in the coastal savannah of Ghana using CERES-maize module of the Decision Support System for Agro-Technological Transfer (DSSAT) model. To achieve this, two independent experiments were conducted simultaneously in the major and minor seasons in 2014. In experiment I, one maize variety (Obatanpa) was planted on 3 different planting dates. Three levels of N fertilizer were applied (0, 45 and 90 kg ha-1) with and without biochar (10 t ha-1). Total of 45 kg ha-1 of P and K in the form of Triple Super Phosphate (TSP) and Potassium Chloride (KCl) respectively were applied as basal application. Experiment I was 3 factorial trials (3 x 2 x 3) arranged in RCBD. Experiment II consisted of three maize varieties, (Obatanpa, Omankwa and Abontem) with poultry manure (5000 kg ha-1) K and P applied at 45 kg ha-1 and inorganic N (90 kg ha-1) in the form of urea. The same treatments were imposed on the three maize varieties and repeated for three planting dates. Experiment II, was a 2 factorial (3 x3) trial arranged in RCBD with three replications. Part of the data from the 3 maize cultivars (Experiment II) were used to calibrate the CERES-Maize model while the remaining, together with those from experiment I were used to evaluate model performance. The effects of climate change on the 3 maize cultivars over the major and minor seasons were assessed. Thirty years’ (1980 to 2009) historical weather data were used to run the simulations and compared with those from projected weather data from 4 General Circulation Models (scenarios); CCSM4 (E), CFDL-ESM2M (I), HadGEM2-ES (K), and MPI-ESM-MR (R) with Representative Concentration Pathway (RCP) 8.5: each encompassing 30 (2040-2069) years; near term. Results from experiment I, showed that the combined application of biochar and inorganic fertilizer produced yields that were significantly higher than the sole application of either biochar or inorganic fertilizer. The 3 maize genotypes were significantly different in their grain yielding and total biomass production abilities. The model performance in predicting grain yield was good with d-values of 0.84, 0.78 and 0.62 for Obatanpa, Omankwa and Abontem, respectively. Total biomass was predicted with d-values of 0.78, 0.98 and 0.62 for Obatanpa, Omankwa and Abontem, respectively. Projected weather data across GCMs show an increase in maximum temperature from between 1.81 and 2.61°C and minimum temperature of 1.7 to 3.17 °C. Results indicated that climate change has significant effect on maize phenology. Days to anthesis could reduce by an average of between 6 and 10 % for Obatanpa, 6 to 9% for Omankwa and between 5 and 8% for Abontem cultivar for major season. In the minor season, mean reduction ranged between 5 and 9 % for all cultivars. Reduction in the duration of days to maturity in the major season ranged between 7 and 11 %, with 6 and 10% for the minor season for all cultivars across GCMs. Climate change impacts on maize total biomass and grain yield suggest significant yield reductions of between 16 – 49 % across all three cultivars and across GCMs in both seasons. The response of grain yield to mineral fertilizer application suggests that, the efficiency of fertilizer use will decrease under climate change. Sensitivity analysis revealed temperature as main driving force in reducing grain and biomass yield in maize. The use of shorter duration maize cultivars may not be an effective adaptation strategy to climate change due to the effect of temperature increases on shortening crop phenology and subsequently yield. Even though increased use of mineral fertilizers as an adaptation strategy will increase yield, the efficiency will reduce significantly under climate change. The production of maize in the Coastal savanna will be negatively impacted by climate change, hence the need to explore feasible adaptation strategies to mitigate the negative impact