PREDICTING THE WATER REQUIREMENT, SOIL MOISTURE DISTRIBUTION, YIELD, WATER PRODUCTIVITY OF PEAS AND IMPACT OF CLIMATE CHANGE USING SALTMED MODEL Marwa M.A. 1* , A.F. El-Shafie 1 , O.M. Dewedar 1 , J.M. Molina-Martinez 2 and R. Ragab 3 1* Water Relations and Field Irrigation Department, Agricultural and Biological Research Division, National Research Centre, Cairo, Egypt. 2 Food Engineering and Agricultural Equipment Department, Technical University of Cartagena, 30203 Cartagena, Spain. 3 Centre for Ecology and Hydrology, Wallingford, United Kingdom. Abstract It’s important to study the effect of climate change on crops and water supplies, during this critical period of water scarcity and increasing food demand. These changes include evapotranspiration, which will affect crop growth and water requirement. This research work explores the impacts of climate change on water requirements, soil moisture distribution, yield and water productivity of peas. Two consecutive field trials were conducted during the 2017 and 2018 growth seasons of peas in El Nubaria zone, Egypt, on sandy soil conditions. Two irrigation schedules were studied, the first is irrigation at 30% depletion of field capacity, FC, the second schedule irrigation used actual weather station data under drip irrigation system. Under both irrigation schedules, measured and observed data were used for calibration and validation of the SALTMED model. The model was tested to study the impact of the future scenarios (RCPs, 4.5 and 8.5) for 2040, on water requirements, soil moisture content, yield and water productivity of peas, for the same study conditions. The field data indicated there was a high uniformity of soil moisture distribution under the 30% depletion of FC irrigation schedule, compared with the irrigation schedule using weather station data, for both seasons. The highest yield was (2.7 and 3.3 t ha -1 ) for 2017 and 2018 seasons, respectively, under the 30% depletion of FC irrigation schedule. The highest water productivity was (0.95 and 1.07 kg m -3 ) with total applied of water (2840 and 3070 m 3 ha -1 ) for 2017 and 2018 seasons, respectively, with irrigation at 30% depletion of FC. The calibration and validation of SALTMED model indicated there were a slight variations between the observed and simulated results, with high coefficients of determination, RMCE and CRM values for total dry matter, productivity, water productivity and soil moisture under both irrigation schedules and for both seasons. The predicted data using SALTMED model showed the crop water requirements will increase for RCPs, 4.5 and 8.5 scenarios of 2040. The predicted yield and water productivity tend to decrease in 2040 under both scenarios. In general, SALTMED model is a good tool for predicting total dry matter and yield and can run with different scenarios and under different conditions. Key words: Irrigation scheduling, weather station data, water productivity, peas, SALTMED simulation model, climate change (RCPs) scenarios, indicated that there is an increase in evapotranspiration (ETo) due to increasing minimum and maximum air temperatures. Abdrabbo et al., 2015 reported that ETo would increase by 4.7% to 19.6% for the Middle Egypt region. Water resources are a limiting factor for agricultural production, and water saving becomes a clear necessity. Also, in the near future, water scarcity will be a real big problem for the global economy. Therefore, water consumption, in all life activities, should be improved as a rare and important commodity (Marwa et al., 2017). Therefore, it is very important, when facing Plant Archives Vol. 20 Suppliment 1, 2020 pp. 3673-3689 e-ISSN:2581-6063 (online), ISSN:0972-5210 *Author for correspondence : E-mail: marwamahmoud30@yahoo.com Introduction The agricultural sector is one of the sectors that will be negatively affected by climate change, particularly in developing countries. These changes include temperature, and precipitation rate. The IPCC (2014) reported that climate change will affect evapotranspiration rates, thereby impacting soil moisture and consequentially crop water use. The predicted climate change in Egypt, based on different Representative Concentration Pathways