氣候智慧型稻麥輪作之建立

Abstract

在氣候變遷下，全球糧食生產皆可能受到巨大衝擊，而台灣糧食自給率僅有33%，過度依賴各種進口穀類使台灣糧食安全受到威脅。其中，農業佔全球10%溫室氣體排放量，為減緩農業所造成之環境衝擊及增加台灣糧食自給率，稻麥輪作為一個可行的栽培模式之一，但在台灣稻麥輪作的環境衝擊並不清楚，因此本試驗利用生命週期評估(Life Cycle Assessment, LCA)技術，對整體稻麥輪作系統進行生命週期熱點分析及評估，並利用兼具'調適(Adaptation)”與'減輕(Mitigation)'的氣候智慧型農業(Climate Smart Agriculture)概念進行改善，以期建立本土氣候智慧型稻麥輪作栽培系統。 本試驗選用台中區農業改良場與台中大雅為試驗地點，進行一年三作之 稻-稻-麥 輪作栽培之生命週期分析，其中分析的系統邊界包含整地、育苗、灌溉、田間操作及收穫後加工等，最終以單位面積及單位重量白米與小麥榖粒評估各式環境衝擊，如溫室效應潛勢、優養化及酸化等。結果顯示，主要的環境衝擊皆來自於田間釋放，其總差異可高達50%，以每期作而言，碳足跡介於3~53 tg CO2 eq /ha；以單位糧食生產而言(單位：kg CO2 eq / kg white rice；單位：kg CO2 eq / kg wheat grain)，稻麥輪作生產過程中的碳足跡介於1.3~10，雖然田間排放為主要熱點，但可藉由不同農業操作進行改善，以本試驗結果而言，肥料管理為最有效之方法，而其他整地調整與二期休耕等操作雖然在本試驗評估中沒有一致的效果，但在其他長期研究中仍有一定程度的改善。因此低整地、精準施肥的稻麥輪作為台灣可發展的氣候智慧型稻麥輪作系統。

Food security is an important issue for all countries around the world, especially when food production has been challenged under climate change. The food self-sufficiency ratio of Taiwan is around only 33 % weighted by energy in 2013, with importing excessive cereal grains as a serious threat to Taiwan. Also, there is about 10 % artificially greenhouse gas emission generating from agriculture production. Therefore, it is suggested to mitigate the environmental impacts from agriculture production system and increase the degree of food self-sufficiency ratio of Taiwan. Rice-wheat rotation is a possible innovative cropping system for Taiwan, which integrate with the upland-lowland rotation, wheat production and labor saving. In the present study the analysis of environmental impacts of rice-wheat rotation system was performed by the tool of life cycle assessment and hot spots of the impacts for the cropping system were determined. This study is aim to establish a local climate-smart cropping system which is high yield, high quality, energy saving, food production and eco-friendly. In the study, a two-year rice-wheat rotation experiments at TDARES (Taichung District Agriculture Research and Extension Station) and Daya (Taichung) since 2012 winter was conducted. The system boundary of life cycle assessment consisted of production of farm inputs (such as fertilizer, pesticide and seed), tillage, irrigation, farming practice and post-harvesting, and used the function unit as kg grain and per hectare in evaluating the environment impacts from crop production. In this study we selected energy consumption, global warming potential, acidification, and eutrophication as environmental impact items to evaluate rice-wheat system. According to the research results, the main environment impact came from field emission and the variation was up to 50 %. In each crop, the GWP (Global warming potential) was 3~53 tg CO2 eq /ha and 1.3~10 kg CO2 eq/ kg grain. Although field emission was the main hot-spot, it still could be improved by modified fertilizer management. In this study, fertilizer adjustment was the most effective way to mitigate the field emission, while other adjusted strategies such as tillage and second crop period fallow didn’t show consistent mitigation effects. But there is still some positive effect of non-tillage and changing crop residue retention ratio has been confirmed in several long-term field research. In all, minimum tillage and suitable fertilizer management seemed to be the suitable practice for establishing climate-smart rice-wheat rotation system.