Biology Department, The University of British Columbia Okanagan, Kelowna, BC, Canada.
Agriculture and Agri-Food Canada, Summerland Research and Development Centre, Summerland, BC, Canada.
Glob Chang Biol. 2021 Aug;27(16):3898-3910. doi: 10.1111/gcb.15680. Epub 2021 Jun 7.
Over the last 200 years, conversion of non-cultivated land for agriculture has substantially reduced global soil organic carbon (SOC) stocks in upper soil layers. Nevertheless, practices such as no- or reduced tillage, application of organic soil amendments, and maintenance of continuous cover can increase SOC in agricultural fields. While these management practices have been well studied, the effects on SOC of cropping systems that incorporate irrigation are poorly understood. Given the large, and expanding, agricultural landbase under irrigation across the globe, this is a critical knowledge gap for climate change mitigation. We undertook a systematic literature review and subsequent meta-analysis of data from studies that examined changes in SOC on irrigated agricultural sites through time. We investigated changes in SOC by climate (aridity), soil texture, and irrigation method with the following objectives: (i) to examine the impact of irrigated agriculture on SOC storage; and (ii) to identify the conditions under which irrigated agriculture is most likely to enhance SOC. Overall, irrigated agriculture increased SOC stocks by 5.9%, with little effect of study length (2-47 years). However, changes in SOC varied by climate and soil depth, with the greatest increase in SOC observed on irrigated semi-arid sites at the 0-10 cm depth (14.8%). Additionally, SOC increased in irrigated fine- and medium-textured soils but not coarse-textured soils. Furthermore, while there was no overall change to SOC in flood/furrow irrigated sites, SOC tended to increase in sprinkler irrigated sites, and decrease in drip irrigated sites, especially at depths below 10 cm. This work sheds light on the nuances of SOC change across irrigated agricultural systems, highlights the importance of studying SOC storage in deeper soils, and will help guide future research on the impacts of irrigated agriculture on SOC.
在过去的 200 年中，将非耕地转化为农业用地，极大地减少了全球上层土壤中的土壤有机碳（SOC）储量。然而，免耕或少耕、施用有机土壤改良剂和保持连续覆盖等做法可以增加农业领域的 SOC。虽然这些管理实践已经得到了很好的研究，但对于纳入灌溉的种植系统对 SOC 的影响却知之甚少。考虑到全球范围内灌溉农业用地的巨大且不断扩大的基础，这是减缓气候变化的一个关键知识空白。我们对通过时间检验灌溉农业用地 SOC 变化的研究进行了系统的文献回顾和随后的荟萃分析。我们通过气候（干旱）、土壤质地和灌溉方法来研究 SOC 的变化，目的是：（i）研究灌溉农业对 SOC 储存的影响；（ii）确定灌溉农业最有可能增强 SOC 的条件。总体而言，灌溉农业增加了 SOC 储量 5.9%，而研究时间长短（2-47 年）的影响很小。然而，SOC 的变化因气候和土壤深度而异，在 0-10 cm 深度的灌溉半干旱地区观察到 SOC 的最大增加（14.8%）。此外，在灌溉细质地和中质地土壤中 SOC 增加，但在粗质地土壤中则没有。此外，虽然漫灌/沟灌灌溉地的 SOC 没有总体变化，但在喷灌灌溉地中 SOC 趋于增加，在滴灌灌溉地中 SOC 趋于减少，尤其是在 10 cm 以下的深度。这项工作揭示了灌溉农业系统中 SOC 变化的细微差别，强调了研究深层土壤中 SOC 储存的重要性，并将有助于指导未来关于灌溉农业对 SOC 影响的研究。
