AbstractsBiology & Animal Science

Abstract Variability in seasonal precipitation, potential climate change impacts, competition for water among users, rising population and increasing food demands are putting pressure on agricultural water demands. For irrigated agriculture in Canada to play a major role in addressing current and future global food supply problems, more innovative and sustainable irrigation management approaches are required. In this context a decision support system that ensured more effective irrigation water allocation, application and optimisation was developed. Crop water requirements and irrigation schedules for bell pepper (Capsicum annuum L.) were obtained from greenhouse and field studies. Greenhouse experiments were conducted to determine appropriate irrigation water applications, agronomic and physiological response to water stress for peppers grown on clay and loamy sand soils. These studies involved four irrigation levels -120% (T120), 100% (T100), 80% (T80) and 40% (T40) of pan evaporation (Epan). The results showed that highest yields and water use efficiency were obtained with 120% Epan replenishment on loamy sand compared to clay soil. The corresponding crop water stress index (CWSI) at T120 was 0.18 to 0.20 on clay, and 0.09 to 0.11 on loamy sand. The fruit total soluble solids content was highest in the T40, and least in the T120 treatments.Given that the greenhouse results were obtained under controlled conditions, it was necessary to extend the research in the field. Experiments were conducted to determine the level of available soil water at which irrigation should be applied to prevent water stress and yield loss for peppers on a clay soil. Four irrigation thresholds, as a percentage of available water content, were investigated. These were: 85% (T1), 75% (T2), 50% (T3), and 25% (T4) available water content. A control of no irrigation (T5) was implemented. The crop water stress index (CWSI) and effects of elevated CO2 on the stomatal conductance and water applied were also investigated. The three CO2 levels studied were: ambient CO2 (~400 ppm), predicted CO2 for the year 2050 (550 ppm), and predicted CO2 for the year 2100 (750 ppm). Optimum marketable yields were achieved when 50% (T3) of the available water content had been depleted with a corresponding CWSI of 0.3 to 0.4. A decrease in stomatal conductance with increasing CO2 was observed. Irrigation water requirements decreased by 6-42% under elevated CO2 of 550 ppm, and 28-58% for elevated CO2 of 750 ppm. An integrated agricultural water demand model (IAWDM) was developed using a graphical user interface (GUI) in Matlab to estimate irrigation water requirements (IWR). A pre-requisite for the model development was to ensure that solar radiation (Rs) input data were of good quality. The suitability of nine (Rs) estimation methods, and their effects on reference evapotranspiration (ETo) were evaluated using data from eight weather stations across Canada. Based on Root mean square error (RMSE) of 1-6%, the Hargreaves and Samani (H-S) method gave best…