19年的研究表明，我们低估了堆肥能促进碳捕获的程度

It's no secret that organic farmers believe in compost, but just what role compost plays in soil's ability to store carbon - and keep it out of the atmosphere, where it contributes to climate change - has been less clear.

有机农民相信堆肥已经不是什么秘密了，但是堆肥在土壤储存碳的能力中扮演着怎样的角色——并且不让碳进入大气层，因为这是造成气候变化的原因——一直不太清楚。

A recent study out of the University of California, Davis suggests that compost plays a larger role than once thought in building soil carbon.

加州大学戴维斯分校(University of California, Davis)最近的一项研究表明，堆肥在土壤碳排放中发挥的作用比人们曾经认为的要大。

It also found that carbon levels fluctuate more in deeper soil than most evaluation methodologies tend to account for. In practical terms, the findings could mean compost has been undervalued by agricultural incentive programs, and that we've been measuring carbon levels in soil all wrong.

研究还发现，深层土壤中的碳含量波动比大多数评估方法所考虑的要大。在实际操作中，这些发现可能意味着堆肥被农业激励计划低估了，我们一直在测量土壤中的碳水平都是错误的。

Nicole Tautges, co-author of the study, says it wasn't a surprise to find that compost is good at helping soil store carbon - it's where exactly it does this that was revealing.

这项研究的合著者Nicole Tautges说，发现堆肥在帮助土壤储存碳方面很好并不令人惊讶，这正是堆肥的作用所在。

"The surprising piece was that it raised soil carbon between one and two meters deep. Because the big question is, 'How does the carbon get down there when we're only applying it in the top foot?'" adds Tautges, the chief cropping systems scientist at the UC Davis Agricultural Sustainability Institute.

“令人惊讶的是，它使土壤的碳含量增加了1到2米深。因为最大的问题是，‘当我们只把碳涂在脚上的时候，碳是怎么落到脚上的?’”加州大学戴维斯农业可持续研究所首席作物系统科学家陶茨补充道。

In the study, which was published this summer in the journal Global Change Biology and conducted at a long-term research site the university initiated in 1993, the researchers measured soil organic carbon at five different depths down to two meters over a period of 19 years.

这项研究于今年夏天发表在《全球变化生物学》(Global Change Biology)杂志上，并在该校1993年启动的一个长期研究基地进行。在这项研究中，研究人员在19年间测量了5个不同深度至2米以下的土壤有机碳。

They compared the carbon levels across a number of different cropping systems - conventional, conventional with cover crops, and one that included the application of compost alongside cover crops.

他们比较了几种不同种植系统的碳水平——传统的、传统的覆盖作物，以及一种包括在覆盖作物旁边施用堆肥的种植系统。

Researchers found that systems using cover crops alone not only failed to store more carbon, they actually lost significant amounts of carbon in the soil below about a foot deep. The system that used both cover crops and compost, however, had significantly increased soil carbon content over the length of the study - about 0.7 percent annually.

研究人员发现，仅使用覆盖作物的系统不仅不能储存更多的碳，实际上还会在约一英尺深的土壤中损失大量的碳。然而，在整个研究过程中，覆盖作物和堆肥的系统显著增加了土壤的碳含量——大约每年增加0.7%。

That may sound like a small number, but it's enormous in the context of soil, where change is slow and gradual. The "4 per 1,000" initiative has called for a 0.4 percent increase in soil carbon annually around the globe as a way to combat climate change.

这听起来可能是一个很小的数字，但在土壤变化缓慢而渐进的背景下，这个数字是巨大的。“千分之四”倡议呼吁全球每年增加0.4%的土壤碳，以应对气候变化。