Increasing soil organic carbon (SOC) in Australian farming systems has the potential to offset greenhouse gas emissions. Even though methods for soil carbon (C) sequestration have been developed under the Australian Government’s Emissions Reduction Fund, the scope for farm-scale soil C sequestration is poorly understood. A pilot scheme was developed in Central West New South Wales to trial the use of a market-based instrument to encourage farmers to change farm management to increase SOC. This paper reports changes to SOC stocks measured on farms that were successfully contracted in the pilot. The 10 contracted farms were those that submitted the lowest bid per Mg CO2-e. Four land uses were contracted in the pilot: (1) reduced tillage cropping (reference); (2) reduced tillage cropping with organic amendments (e.g. biosolids or compost); (3) conversion from cropping land to permanent pasture; and (4) conversion from cropping land to permanent pasture with organic amendments. At each site a minimum of 10 locations (sampling points) were sampled and analysed for total carbon (LECO elemental analyser) and bulk density calculated. The SOC stocks (0–0.3 m) were assessed before (2012) and after the pilot (2017; calculated on equivalent soil mass of 2012), with 60% of sites showing a significant increase. Pasture had a higher rate of SOC sequestration than reduced tillage cropping (1.2 vs 0.28 Mg C ha–1 year–1, 0–0.3 m); and organic amendments had higher rates of SOC sequestration than without (1.14 vs 0.78 Mg C ha–1 year–1, 0–0.3 m). The results of the pilot demonstrated increases in SOC, using quantification methods consistent with the current Measurement Method of the Australian Government’s Emissions Reduction Fund policy used to generate Australian Carbon Credit Units. The results require careful interpretation as rates of sequestration are likely to be lower in the longer term than initial rates of change seen in this pilot (five years), and the pilot intentionally selected sites with initially low SOC, which ensured a greater opportunity to sequester SOC.

中文翻译：

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基于土壤碳市场的工具试点——以获取碳信用为目的的土壤有机碳封存

在澳大利亚农业系统中增加土壤有机碳 (SOC) 有可能抵消温室气体排放。尽管在澳大利亚政府的减排基金下开发了土壤碳 (C) 封存方法，但对农场规模土壤碳封存的范围知之甚少。在新南威尔士州中西部制定了一项试点计划，以试用基于市场的工具来鼓励农民改变农场管理以增加 SOC。本文报告了在试点中成功签约的农场测量的 SOC 储量的变化。10 个签约农场是提交最低每 Mg CO2-e 投标的农场。试点承包了四种土地用途：（1）少耕种植（参考）；(2) 使用有机改良剂（例如生物固体或堆肥）减少耕作；（三）耕地转为永久性牧场；(4) 从耕地转变为永久性牧场，并进行有机改良。在每个地点至少对 10 个位置（采样点）进行采样并分析总碳（LECO 元素分析仪）和计算的堆积密度。在试点之前（2012 年）和试点之后（2017 年；根据 2012 年的等效土壤质量计算）对 SOC 储量（0-0.3 m）进行了评估，60% 的地点显示出显着增加。牧场的 SOC 封存率高于减少耕作（1.2 vs 0.28 Mg C ha–1 year–1, 0–0.3 m）；和有机添加物的 SOC 封存率高于无添加物（1.14 vs 0.78 Mg C ha–1 year–1, 0–0.3 m）。试点结果表明 SOC 增加，使用与用于生成澳大利亚碳信用单位的澳大利亚政府减排基金政策的当前测量方法一致的量化方法。结果需要仔细解释，因为从长远来看，封存率可能低于该试点（五年）中看到的初始变化率，并且试点有意选择最初 SOC 较低的地点，这确保了更多的封存机会SOC。