Assessment of the Impact of Climate Change on Rice Productivity: Modeling and Simulation Studies

Rice is the third most important cereal globally after maize and wheat. It is the main food crop for more than 60% of the human population and it occupies almost one-fifth of the total land area covered under cereals. There are two types of rice systems, namely paddy and upland rice. Paddy rice requires high irrigation amounts for proper growth and development and consequently its water use efficiency is low. On the other hand, upland rice has strong drought resistance and low water requirements. In this chapter, we used a modeling approach to assess the impact of future climate change on water requirements and water productivity of three cultivars of paddy rice planted in a two-year field experiment in Egypt using future climate scenarios developed by CMIP6, namely SSP1-2.6 and SSP5-8.5 in two time-intervals, namely 2060–2079 and 2080–2099. We also employed a simulation approach using SALTMED model to assess the impact of climate change under the above scenarios on the yield of upland rice grown under deficit irrigation. Furthermore, we reviewed the attempts to intercrop legume crops with upland rice to increase its productivity in a sustainable manner. The results indicated that the required irrigation water will increase under the two future scenarios, where the increase was the highest under SSP5-8.5 in 2080–2099. Consequently, water productivity will be also reduced under the studied future scenarios. Moreover, a two-year field experiment was implemented to assess the impact of climate change on upland rice grown under deficit irrigation treatments. The climate-suitability of upland rice cultivation in the future was tested by graphing the cutoff temperature (Tcut, 35 ℃) with maximum temperature (Tmax) under the studied future scenarios to determine the number of days that Tcut will exceed Tmax. The results showed that the frequency of Tcut, exceeding Tmax was the lowest under SSP1-2.6 in 2060–2079 and it was the highest under SSP5-8.5 in 2080–2099, which implied higher yield losses. An increase in the water requirements of upland rice was projected under the studied future scenarios. Using SALTMED model to project the yield of upland rice revealed that, under deficit irrigation, yield losses were higher than the values projected under full irrigation application and was the highest under SSP5-8.5 in 2080–2099. The above results suggest that the cultivation of upland rice will be more suitable to conserve water resources in the future. Furthermore, intercropping upland rice with legume crops, namely peanut, mung bean, and soybean proved to be effective in increasing the yield of upland rice and it could be implemented in the future to reduce the harmful effect of climate change on rice production.