Growth-stage-based deficit irrigation effects on the yield and water productivity of tomato

The sensitivity analysis of the Food and Agriculture Organization (FAO) CropWat 8.0 model is aimed at determining the dominant variable of the model in the study area. Hence, the sensitivity coefficient and the correlation of the reference evapotranspiration (ETo) in Afaka, Kaduna, Nigeria, with each of the climatic input variables of the model, namely, maximum temperature (Tmax), minimum temperature (Tmin), humidity (H), wind speed (WS) and sunshine hour (SSH), were evaluated. A perturbation method was used in the evaluation and the sensitivity coefficients were obtained in a decreasing order of 0.55, 0.42, 0.22, 0.09 and -0.08 for Tmax, WS, SSH, Tmin and H, respectively. Also, the correlation of ETo with each of the input parameters, irrespective of the others, show the following correlation coefficients, r; SSH (r = 0.8675), Tmax (r = 0.6979), Tmin (r = 0.6226), H (r = 0.19) and WS (r = 0.0742). Hence, radiation and temperature-based estimations of ETo were recommended as useful tools for ETo estimation in the face of limited or scarce data and are adaptable to areas with similar climate characteristics. This would also serve as a theoretical basis for future studies on the response of ETo to climatic change in the study area and other areas with similar climate.

The reference evapotranspiration (ETo) within Kaduna Central District, Nigeria was estimated from a 30-year climatological data using four different methods namely, Penman-Monteith (PM), Blaney Criddle (BC), Hargreaves (HGRV) and Piche evaporimeter (PiEv) (atmometer) methods. The study shows that the highest ETo values obtained from PM, BC and PiEv were 6.43 mm/day, 7.58 mm/day and 8.63 mm/day, respectively, and these occurred in February, except for HGRV which estimated its highest ETo (3.73 mm/day) in March. The lowest ETo values were obtained in August for all the methods. By means of the confidence index (c), agreement or concordance index (d) and correlation coefficients (r) statistics the BC, HGRV and PiEv ETo values were correlated with that of PM, as the standard. Results showed that BC, HGRV and PiEv gave c-values of 0.88, 0.48 and 0.67, respectively. Hence, BC-PM, HGRV-PM and PiEv-PM correlations were adjudged as excellent, bad and good, respectively, on the basis of criteria for interpretation of the performance of methods of ETo estimations. Blaney-Criddle reference evapotranspiration method gave the best estimate in comparison to the Penman-Monteith standard in the study area. Hence, the Blaney-Criddle ETo can be calibrated with the Penman-Monteith ETo and used effectively within the Kaduna Central District conditions for irrigation water management decisions. Keywords: Estimation and comparison, Reference evapotranspiration, Methods, Kaduna Central District, Nigeria.

The fuel consumption rates of a centrifugal water pump was evaluated with respect to varied system operating pressures and lateral lengths and irrigation period in a pressurized drip irrigation system (PDIS). The fuel consumption rates were found to vary among the operating pressures. The highest fuel consumption rate (1.04 l/hr) was obtained at 206.84 KPa while the least (0.43 l/hr) was obtained at 103.42 KPa. The differences in fuel consumption with respect to operating pressures were statistically significant but not significant with respect to lateral length. It was concluded that PDIS with pressure compensating emitters produce uniform EU irrespective of undulating terrains where uniformity of application can be adversely affected by gravitational effects.