I’m still not seeing this as other than a short term problem: it just means that the farmer has to plough his fields ASAP (and probably to a greater depth than usual) to let the oxygen in, just like they do every spring and autumn anyway. Especially deep ash falls can be dealt with by bulldozers and other earthmoving equipment. Not a trivial exercise, of course.
Except that volcanic ash gets into engines and fouls them. The tractors or earthmoving equipment probably wouldn’t work very well for very long. Plowing with animals (assuming modern farmers have the animals to do the job) probably wouldn’t work that much better, because of the effect of volcanic ash on lungs. I wonder if you can get or improvise a face mask for a horse or ox, and how well it would work if the animal didn’t like it.
Wouldn’t this be similar in effect to spreading six inches or more of e.g. sand or brick dust on a field and then ploughing it in? I would have thought that switching the sand/clay/organic mix of the topsoil so radically would have a pretty big impact on what crops you could grow, never mind all the funny volcanic chemicals you might get in there as well.
Ploughing is what Altair33’s cite recommends. Ditto on the earthmoving equipment. And an increased maintenance schedule. It’s just a question of the scale of the problem: where there’s a modest ash fall, ploughing’s only a real problem if the ground is frozen, otherwise it’s just an inconvenience to plough out of season. And for heavy ash fall or light ash fall on frozen ground, the farmer puts the bucket (?) or blade attachment on the tractor. Canny farmers might stockpile the ash for later use.
Yes, it could be a real problem with major short term food issues but arable farmers, if supported, will be able to cope. And in the medium term, with the added richness of the volcanic soil, it could turn out to be a huge blessing.
Livestock is another issue altogether. And the biggest issue, of course, in the short term, is people: cities will quickly run out of water that’s safe to drink.
I’d say breathing may be a major issue for everyone in the fallout zone.
-XT
From Altair33’s cite, it would seem to depend upon how much there is. A small amount (a couple of inches at most) and you plough it in; a large amount and you scoop it off. But really, if Yellowstone were to blow, a few years of food issues are very different from the decades or centuries that it could be and a small price to pay for the survival of the American arable food industry.
That depends upon what you define as recovered. From a purely natural view, the areas around Mount St. Helens are “recovering” at their own pace. However, fertile farm land inundated by volcanic ash would have a completely different recovery timeline. It’s not merely ash on the ground. It’s also the disruption of water runoff, lakes and streams, bacteria, insects, animals, etc., in addition to ordinary plant life.
As a slight hijack, clear-cutting has been found to cause long-term damage to a watershed beyond the land itself. Streams and rivers within a clear cut suffer greatly as well, including aquatic life. Some of the natural salmon runs studies have found salmon returning to spawn in streams within clear cuts produce poor quality salmon, if they spawn at all. And this is years after a clear cut. Imagine a massive volcanic ash blanket. Now we are talking decades, perhaps centuries for some “normalcy” to return, if it ever does.
There is also an acidic component to volcanic ash which effects soil fertility in the short term. Eventually volcanic ash has a positive effect. The problem being that ‘eventually’ may be years or decades down the pike and if your best agricultural areas are saturated then it may be tough times getting food out of them for your short term needs.
-XT