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<p>Growing Degree Days (GDD), Length of Growing Period (LGP) and Aridity Index (AI) are key agro-climatic indices that regulate crop growth and yield stability. However, they are highly sensitive to rainfall and temperature variability, leading to pronounced changes even over short distances. Despite their importance, the spatial and temporal variability of these indices across microclimate zones in Nyamagabe District had not been assessed prior to this study; therefore, we used gridded daily rainfall, minimum and maximum temperature data for 62 grid points obtained from the Rwanda Meteorology Agency (1985–2021) to address this gap. K-means clustering was applied to delineate four near-homogeneous climate zones (Zone 1–4). Spatial variability and temporal trends of GDD, LGP, and AI were then analyzed using the coefficient of variation, modified Mann–Kendall test, and Sen’s slope estimator across the zones and three agricultural seasons (A, B, and C), where Season A is September–February (SF), Season B is March–June (MJ), and season C is June–September (JS). Higher-altitude zones (Zone 3 and 4) were cooler and wetter, with LGP reaching 94&#xa0;days and AI of 1.0 in season A, while lower-altitude zones (Zone 1 and 2) showed higher variability of LGP up to 90% in Season C. Two-way ANOVA revealed highly significant seasonal and zonal differences in GDD, LGP, and AI (p &lt; 0.05), with strong seasonal effects on AI, LGP and GDD. Significant increasing trends at 99.9% confidence level were observed in mid-altitude zones during JS, with 40&#xa0;°C·days per decade for GDD, 1.7&#xa0;days per decade for LGP, and 0.04 per decade for AI. The study highlights strong altitude-driven agro-climatic variability and changing climate conditions, emphasizing the need for urgent, zone-specific, climate-smart agricultural strategies, including appropriate crop selection, improved water and soil moisture management, and promotion of agroforestry tailored to local climatic conditions.</p>

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Agroclimatic indices variability and trends for agricultural planning in Nyamagabe district, Rwanda

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月16日

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  • Sylvere Kubwimana,
  • Runyambo Irakiza,
  • Boshuwenda André Chuma,
  • Richard Mind’je,
  • Constantin Dushimimana

摘要

Growing Degree Days (GDD), Length of Growing Period (LGP) and Aridity Index (AI) are key agro-climatic indices that regulate crop growth and yield stability. However, they are highly sensitive to rainfall and temperature variability, leading to pronounced changes even over short distances. Despite their importance, the spatial and temporal variability of these indices across microclimate zones in Nyamagabe District had not been assessed prior to this study; therefore, we used gridded daily rainfall, minimum and maximum temperature data for 62 grid points obtained from the Rwanda Meteorology Agency (1985–2021) to address this gap. K-means clustering was applied to delineate four near-homogeneous climate zones (Zone 1–4). Spatial variability and temporal trends of GDD, LGP, and AI were then analyzed using the coefficient of variation, modified Mann–Kendall test, and Sen’s slope estimator across the zones and three agricultural seasons (A, B, and C), where Season A is September–February (SF), Season B is March–June (MJ), and season C is June–September (JS). Higher-altitude zones (Zone 3 and 4) were cooler and wetter, with LGP reaching 94 days and AI of 1.0 in season A, while lower-altitude zones (Zone 1 and 2) showed higher variability of LGP up to 90% in Season C. Two-way ANOVA revealed highly significant seasonal and zonal differences in GDD, LGP, and AI (p < 0.05), with strong seasonal effects on AI, LGP and GDD. Significant increasing trends at 99.9% confidence level were observed in mid-altitude zones during JS, with 40 °C·days per decade for GDD, 1.7 days per decade for LGP, and 0.04 per decade for AI. The study highlights strong altitude-driven agro-climatic variability and changing climate conditions, emphasizing the need for urgent, zone-specific, climate-smart agricultural strategies, including appropriate crop selection, improved water and soil moisture management, and promotion of agroforestry tailored to local climatic conditions.