MODELING CLIMATE CHANGE EFFECTS ON PLANTAIN (Musa spp.) WATER REQUIREMENTS AND YIELD IN ONDO STATE, NIGERIA

Abstract

ABSTRACT This study aims to determine the effects of potential climate change on crop water requirements (CWR) and yield of plantain (Musa spp) in three agro-ecological zones over Ondo State. Climate change scenario-Representative Concentration Pathways (RCP 4.5) derived from statistical downscaling of six global circulation model (GCM) outputs were applied as inputs to the CROPWAT model. The sensitivity of each GCM to accurately simulate the baseline and project climate was evaluated. Projections of average monthly minimum temperature (Tmin), maximum temperature (Tmax) and precipitation for future time periods of the 2050s (2035-2065) and 2080 (2070-2100) were developed for three regions, (Ondo North Agro-Ecological Zone-ONAEZ, Ondo Central Agro-Ecological Zone-OCAEZ and Ondo South Agro-Ecological Zone- OSAEZ) in Ondo State, relative to a baseline period of 31-year (1975-2005). Statistically-downscaled and baseline climate parameters outputs were used as inputs to the CROPWAT to estimate irrigation water requirements (IWR) and CWR of plantain. The comparison results of a baseline period (1975-2005) and projected minimum and maximum temperatures increased for all the selected six GCMs and across the three agro-ecological zones. CCCMA model predicted greatest annual Tmax increases of 1.30C-1.90C and 0.80C-1.50C at ONAEZ and OSAEZ for periods 2050s and 2080s respectively. The simulation for the MPI model at OSAEZ indicates highest minimum temperature changes of 2.5oC-3.2oC for periods the 2050s and 2080s. The outputs of CROPWAT model to estimate CWR and IWR showed that CCCMA consistently predicts seasonal highest increases of 26.7% (1085.4 mm) and 28.0% (1102.6 mm) for the periods of the 2050s and 2080s in comparison to crop water requirement (CWR) of 879.9 mm in ONAEZ. This trend is similar to the predicted changes in crop water requirement obtained in OCAEZ and OSAEZ respectively. Again, CCCMA model projected highest irrigation water requirements of 451.6 mm and 469.3 mm; 493.8 mm and 500.8 mm for OCAEZ and OSAEZ. These results correspond to IWR increase of 19.6% to 36.1% in ONAEZ, 20.3% to 39.9% in OCAEZ and 25.3% to 42.1% in OSAEZ for periods of 2050s and 2080s relative to the current period of 1975-2005. The results of regression analysis showed a positive relationship between precipitation and plantain yield, while maximum (Tmax) and minimum temperature (Tmin) indicated no significant relationship with plantain yield at P˂ 0.01 in all the AEZs. The trend analysis indicated an increase in Tmax of 0.046oC/year for Ondo North Agro-Ecological Zone (ONAEZ), while Ondo South Agro-Ecological Zone (OSAEZ) has the lowest increment of 0.003oC/year. Tmin for Ondo Central Agro-Ecological Zone (OCAEZ) increased by 0.007oC/year and decreased with 0.004oC/year and 0.030oC/year for ONAEZ and OSAEZ. However, analysis of precipitation events in the study areas from 1975-2005 showed that OCAEZ received the highest increase of 7.47 mm/year and decreased by 13.48 mm/year and 2.84 mm/year for ONAEZ and OSAEZ respectively. Largest plantain yield reduction percentage compared to the control-period for CCCMA model was -30.3% and -38.1% for the 2050s and 2080s whereas ICHEC model predicted the average lowest reduction of -7.5% and -12.5% for the short time and long periods in ONAEZ. In OSAEZ, plantain yield decreases varied from -6.3% to -8.4% for CNRM model, -6.1% to -6.7% (MPI) and -36.1% to -37.7% for CCCMA. In conclusion, overall simulations of climate change impact in OCAEZ showed that projected climate may likely have relatively low effects on plantain yield compared to the results predicted for ONAEZ and OSAEZ respectively. Also, poor agronomic and human factors affect plantain yield and production.