能源、气候与材料2022pnas.org
接近蜥脚类恐龙重量的农用车辆超出土壤功能极限
Farm vehicles approaching weights of sauropods exceed limits for soil function
进阶 · 约 45 分钟读完前置知识：土壤物理基础、农业机械、土壤压实与孔隙度
导读
这篇 PNAS 论文关注现代农业机械不断增大、增重（已接近蜥脚类恐龙的体重）是否会超出土壤可承受的限度，核心结论是重型农机带来的土壤压实可能损害土壤功能。作者将农机重量与土壤功能阈值联系起来，警告农业机械继续大型化可能不可持续。
HN 关注点：重型农机对土壤压实的现实影响、农民如何用宽胎和深松等措施应对，并延伸到 AI 时代是否该用更多小型机械替代巨型机械。
HN 评论精选
这几条评论里：质疑 1 补充 2 亲历 1
质疑土壤压实取决于接地压强而非单纯重量，农民已通过宽胎、曝气和耕作等方式应对，并会根据土壤选择机械。
每个农民都知道：重要的不是重量，而是土壤压实，而压实取决于重量除以拖拉机驱动轮接触地面的面积。这也是拖拉机轮胎那么宽、常使用高浮力轮胎的原因。农民对抗压实的另一办法是土壤曝气和耕作。拖拉机确实越来越大、越来越重，但农民对此很了解，通常会根据自家土壤选择何种机械和轮胎，因为搞错了可能损害土地产量。最后，作物常按行种植以便机械作业；跟在拖拉机后面走，你能看到拖拉机经过后土壤又回升，通常是因为土壤像海绵，拖拉机把水挤出来，过去后土壤会弹回。意识到脚下的地面如此有弹性有点奇怪，因为平时注意不到。
jacquesm查看英文原文
As every farmer knows: it's not the weight that matters but the soil compaction, and that's a function of weight over surface area of the contact patches of whatever drive train your tractor has. That's also why tractor tires are so wide, and high flotation tires are commonly used. Another way in which farmers combat soil compaction is by aeration and tilling. It's true though that tractors are getting larger and heavier, but farmers are pretty knowledgeable about these things and usually take them into account when deciding what kind of machinery (on what kind of tires) to use for their soil, after all, if they get it wrong they may end up negatively impacting the yield of their land. Finally, crops tend to be planted in rows for convenient mechanical processing, and while walking behind a tractor you can actually see the soil rise again after the tractor has passed, usually because the soil acts as a sponge, the tractor squeezes the water out and once it has passed the soil will spring back. It's a bit strange to realize that the ground you walk on is so springy because you normally don't notice it.
亲历亲历经验：种胡萝卜时用深松机加“鼹鼠”部件打破深层压实，否则胡萝卜长度会受影响。
在我们农场，我们会用一种叫深松机（ripper）的农具。它有一排刀片，能下探到 18 到 20 英寸来破碎土壤。每把刀片后面有一个直径 3.5 英寸的子弹形部件（叫 mole），会像真正鼹鼠一样在地下打出隧道。我们种胡萝卜，所以必须限制土壤压实，否则会抑制胡萝卜的长度。
ratsmack查看英文原文
On our farm we would use an attachment called a ripper. It was a series of blades that would reach down 18 to 20 inches to break up the soil. Behind each blade was a 3.5 inch diameter bullet shaped slug (called a mole) that would create an underground tunnel, not unlike what an actual mole creates. We grew carrots, so it was imperative that soil compaction was limited or it would stunt the length of the carrots.
补充土壤/真菌网络被压实后恢复极慢，历史林业案例也显示短期管理可能带来长期生产力下降。
在森林里破坏或挤压真菌，恢复需要几个世纪[1]。普鲁士开始科学林业后，约 100 年后森林生产力显著下降[2]。好日子还在后头。我不明白为什么我们明明掌握知识却视而不见。两本好书：[1]《树的隐秘生活》；[2]《Seeing Like a State》。
balb0a查看英文原文
When you destroy/squeez fungus in the forest it takes centuries to recover[1]. In Prussia when they started with scientific forestry, productivity of the forrest dropped significantly after around 100 years[2]. Good times to come. I wonder why we look the other way, even when we have all the knowledge on our hands. Two great books: [1]: The Hidden Life of Trees [2]: Seeing Like a State
补充质疑大型化逻辑：大型机械主要为省人力，AI 时代或许更多小型机械更有效。
我认为机械越来越大的原因之一是为了节省人力时间。如果我们进入一切由 AI 操作的时代，是否有可能许多小型机械比少数巨型机械更有效？
dhbradshaw查看英文原文
I think one of the reasons to get bigger and bigger is to save human time. If we get to a place where it's all AI, is there a chance that many smaller machines will become more effective than a few enormous ones?
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