Grass coverage in orchards has increasingly become a sustainable practice to improve soil quality, reduce soil erosion, increase water infiltration, and enhance biodiversity and ecosystem services. It is likely to gain further adoption as a promising nature-based measure to increase organic carbon and nitrogen storage in soil. However, there is still a lack of comprehensive global quantification regarding the accumulation and availability of soil organic carbon (SOC) and total nitrogen (STN) after grass coverage in citrus orchards. A global meta-analysis was conducted to comprehensively evaluate the effects of grass coverage on SOC and STN dynamics in citrus orchards, as well as the patterns influenced by various factors. Compared to clean tillage, the accumulation rates of SOC and STN were significantly enhanced with grass coverage, with an increase of 19.98 Mg ha⁻¹ yr⁻¹ and 2.27 Mg ha⁻¹ yr⁻¹ , respectively. The microbial biomass carbon (MBC), dissolved organic carbon (DOC) and available nitrogen (AN) exhibited significantly increases following grass coverage, with average enhancements of 13.90 %, 17.94 %, and 18.04 %, respectively. The primary factors influencing the variation in SOC and STN were identified as grass age and growth modes. When grass coverage reached or exceeded 10 years and was applied uniformly across the entire orchard (full coverage), there was a more pronounced increase in SOC and STN levels. The present study provides policymakers and orchard managers with science-based evidence to guide adaptive management practices that enhance SOC and STN stocks, improve soil conditions, and increase orchard resilience to climate change.

中文翻译：

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有机碳和氮在草覆盖的柑橘园土壤中自然积累


果园中的草覆盖已日益成为一种可持续的做法，以改善土壤质量、减少土壤侵蚀、增加水渗透以及增强生物多样性和生态系统服务。它可能会作为一种有前途的基于自然的措施来增加土壤中的有机碳和氮储存，从而进一步得到采用。然而，关于柑橘园草覆盖后土壤有机碳 （SOC） 和总氮 （STN） 的积累和有效性，仍然缺乏全面的全球量化。进行了一项全球荟萃分析，以全面评估草覆盖率对柑橘园土壤有机碳和 STN 动态的影响，以及受各种因素影响的模式。与清耕相比，草覆盖度显著提高了土壤有机碳和土壤碳氮的积累速率，分别增加了 19.98 Mg ha⁻¹ yr⁻¹ 和 2.27 Mg ha⁻¹ yr⁻¹。草覆盖率后微生物生物量碳 （MBC） 、溶解有机碳 （DOC） 和速效氮 （AN） 显著增加，平均分别增加 13.90 % 、 17.94 % 和 18.04 %。影响 SOC 和 STN 变化的主要因素是草龄和生长模式。当草覆盖率达到或超过 10 年并在整个果园统一施用（完全覆盖）时，SOC 和 STN 水平的增加更加明显。本研究为政策制定者和果园管理者提供了基于科学的证据，以指导适应性管理实践，以增强 SOC 和 STN 存量、改善土壤条件并提高果园对气候变化的适应能力。