利用田間試驗與模式模擬探討水稻田灌溉策略

Abstract

本研究以行政院農業委員會桃園區農業改良場(簡稱桃改場)之水稻田為研究場域，藉由田間試驗資料，並搭配Decision Support System for Agrotechnology Transfer (DSSAT)作物模式與CropWat灌溉管理模式，討論現有模式是否能夠完整評估水稻田水平衡與對應的作物產量，分析水稻田間歇灌溉方式對於土壤含水量變化、N2O排放、以及區域地下水變動的影響。研究結果顯示，DSSAT曬田時期高估土壤含水量，並且其模擬產量與實際值有顯著差異，可能原因為模式對於模擬氮吸收量有高估的疑慮；CropWat模擬上則易高估蒸發散量。本研究進一步透過驗證後之模式分析常見五種水田灌溉策略包含: Controlled irrigation (CI)、Intermittent irrigation (II)、Shallow-wet irrigation (SWI)、Alternate Wetting and Drying (AWD)、The System of Rice Intensification (SRI)。模擬結果顯示，SRI灌溉策略的節水成效最佳；CI與SWI採用之低湛水深的間歇灌溉策略能有效抑制脫硝作用所造成之N2O排放量。此外，在桃改場地區，採取節水灌溉並不會造成該區域地下水位嚴重衝擊。因此，本研究建議若能結合CI、SRI、SWI灌溉策略將能同時滿足節水，並考量到維持地下水位不大幅下降。

The focus of this study is to examine the impact of intermittent irrigation methods on soil moisture, nitrous oxide emissions, and regional groundwater dynamics in rice fields. Field data and models are utilized to assess the accuracy of the Decision Support System for Agrotechnology Transfer (DSSAT) crop model and the CropWat irrigation management model in evaluating water balance and crop yield. The study was conducted at the Taoyuan District Agricultural Research and Extension Station. Results indicate that DSSAT overestimates soil water content during drying periods and a significant disparity between simulated and actual crop yields. This discrepancy may be attributed to an overestimation of nitrogen uptake in the model. Additionally, the CropWat model tends to overestimate evapotranspiration. The study further analyzed five water-saving irrigation strategies for rice cultivation—Controlled irrigation (CI), Intermittent irrigation (II), Shallow-wet irrigation (SWI), Alternate Wetting and Drying (AWD), and the System of Rice Intensification (SRI)—using validated models. Simulation results reveal that SRI demonstrates the best water-saving performance, while CI and SWI, characterized by low water depth intermittent irrigation, effectively mitigate nitrous oxide emissions from denitrification. Furthermore, adopting water-saving irrigation practices at the Taoyuan District Agricultural Research and Extension Station does not have a significant impact on groundwater levels when employing the aforementioned irrigation strategies. In the end, the study recommends an irrigation approach that combines CI, SRI, and SWI to achieve water conservation while maintaining groundwater levels without significant decline.