気候スマート農業の効果を示すモデル群(Suite of Models Shows Some Positive Effects of Climate-Smart Ag Practices)

2025-09-08 ノースカロライナ州立大学 (NCState)

ノースカロライナ州立大学の研究チームは、気候スマート農業(Climate-Smart Agriculture:CSA)の効果を評価するため、アメリカ中西部ミシガン州と南部テキサス州にある長期農業実験施設のデータを3種類の生物地球化学モデル(APSIM、Daycent、RothC)で「モデルアンサンブル」として解析しました。対象としたCSA実践は、不耕起(no-till)、被覆作物(cover crop)、残渣保持(residue retention)など。過去30年以上のデータを基に、今後25年を見据えた通常シナリオと、温室効果ガス排出が急増する最悪ケース両方で評価を実施しました。結果、通常シナリオ下ではミシガンで不耕起+残渣保持が土壌炭素貯留を促進し、不耕起・被覆作物・肥料削減が温室効果ガス排出を低減。テキサスでは多くの実践で炭素貯留が進み、不耕起だけでも排出の逆転が示唆されました。一方、最悪ケースでは全体的に効果が低下。研究では、複数モデルを組み合わせるアンサンブル解析が、単独モデルには見られない洞察を与え、将来の予測精度を高める手法であると強調されています。

<関連情報>

米国二つの長期農業研究サイトにおける気候適応型農業の管理代替案:モデルアンサンブル事例研究 Management alternatives for climate-smart agriculture at two long-term agricultural research sites in the United States: A model ensemble case study

Ellen D. v. L. Maas, Debjani Sihi
Agronomy Journal  Published: 05 September 2025
DOI:https://doi.org/10.1002/agj2.70146

気候スマート農業の効果を示すモデル群(Suite of Models Shows Some Positive Effects of Climate-Smart Ag Practices)

Abstract

Greenhouse gas (GHG) emissions reduction efforts are underway to mitigate climate change worldwide. Climate-smart agriculture (CSA) practices have been shown to both increase soil organic carbon (SOC) inputs and reduce net greenhouse gas emissions (GHGnet). We evaluated the GHGnet of several management practices with three biogeochemical models (APSIM, Daycent, and RothC) at two sites with contrasting soils, climates, and cropping systems. Additionally, two future climate scenarios (baseline and high-emissions) provided alternative outcomes of SOC, N2O, and CH4 by 2050. In Michigan, most biochar and residue retention with no-till treatments increased SOC stocks; leguminous cover crops, no-till, and reducing fertilizer input lowered N2O emissions. The lowest biochar treatment lowered GHGnet in the baseline climate scenario, but all other management treatments increased GHGnet under both baseline and high emissions, and all management scenarios increased a mean of 8.0 Mg CO2-equivalent GHG (CO2e) ha−1 from baseline to high emissions. Conversely, in Texas, most treatments increased SOC, and N2O was relatively constant. Every no-till treatment reversed GHGnet in both the baseline and high-emissions climate scenarios but all management scenarios increased a mean of 0.6 Mg CO2e ha−1 under high emissions. At both sites under high-emissions climate change, cover crops and no-till resulted in the lowest GHGnet overall. Overall, the study showed that no-till, especially with residue retention, and cover crops are important CSA practices to lower the GHGnet of agriculture, but there remains much room to find even more effective solutions to adapt to climate change.

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