Compared to the small‐scale situation, some constraints in large‐scale rice fields have caused crop growth models to fail to reach an acceptable estimate of yield. This study was conducted to investigate the possibility of enhancing the accuracy of the CERES‐Rice model prediction at a large scale through the use of Landsat 5 satellite imagery (termed ‘assimilation’). Firstly, the model was calibrated by data taken from local research. The model accuracy was then evaluated in 110 paddy fields over 26 000 ha (method A). Then the model was recalibrated by paddy yield estimated from Landsat 5 image (method B). The two methods were compared based on their results. The results revealed that RMSEn in simulating grain yield in small‐scale field experiments on the Hashemi cultivar for calibration and validation of the model were 9 and 8%, respectively (R2 = 0.7), which indicated the model's high accuracy in yield prediction. While RMSEn in simulating grain yield in large‐scale (methods A) was 22% (R2 = 0.54), the use of Landsat images in the assimilation method (method B) increased its accuracy dramatically to RMSEn of 12.7% (R2 = 0.72). Copyright © 2016 John Wiley & Sons, Ltd.

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This experiment aims to study the effect of water‐saving irrigation on rice production and methane emissions. Three irrigation methods, that is, flooding irrigation, deficit irrigation (DI) and alternate partial root‐zone drying (APRD), were employed in a 2‐year field trial. The experiment was conducted in a randomized complete block design with three replications. For the DI and APRD treatments, plots were not irrigated until the soil matric potential reached −10 (DI10 and APRD10), −30 (DI30 and APRD30) and −60 kPa (DI60 and APRD60). In the APRD treatments, two adjacent furrows of each plant row were alternately irrigated in consecutive irrigation events. The DI and APRD treatments did not affect yield components when the soil matric potential was −10 kPa. Applying APRD treatments increased irrigation water productivity by 45%, 51% and 31% for soil matric potentials of −10, −30 and −60 kPa, respectively. On average, water stress treatments reduced methane emissions by 78% compared to flooding treatment. On average, the APRD treatments decreased the water input by 10% compared with the DI treatments while achieving a 2.5% higher yield. This is the first study to outline the effect of APRD on methane emissions and rice production. These findings suggest that APRD could be a valuable strategy to mitigate methane emissions without risking rice yield reduction.