The Dust Bowl: how's the recovery of all that topsoil going?

Question

I must admit this is very confusing: one gets different types of information from different sources that often contradict one another.

It is said that the main event occurred due to some misguided farming practices; that those practices allowed strong winds to pick up all the topsoil in the area, carry it east, and deposit it into the Atlantic, more or less in toto. This may not be altogether accurate, but that's the impression one gets from reading essays, articles, and the Wikipedia entry pertaining to the Dust Bowl.

That said, various sources maintain that it takes 500 years or more to form 1 inch of topsoil.

Others suggest coyly that the process can be expedited artificially by burying lots of organic garbage and introducing earthworms to it: a few years of this, and voila - we've got topsoil! (Few of them say how many years, exactly, and where's one supposed to get all those earthworms?)

Still other sources say that because of soil erosion and other intriguing factors we may be running out of arable land. And not just in Kansas either, but all over the globe.

With all of the above in mind, my question is: have the areas affected by the Dust Bowl recovered partially, completely, or not at all? How much of that land can be classified as arable once again?

Answer 1

Soil is not a single uniform material. When wind erosion takes hold, as in the infamous 'dust bowl' of the 1930s, it is the uppermost A horizon, and to a lesser extent the B horizon that is mainly lost. The lost soil takes with it most of the organic carbon, and it is this component that is most difficult to replace.

Rates of soil loss are primarily factors of the underlying geology and climate. A wetter and warm climate will regenerate soil very much faster than a cold dry climate. Basalt and shale will break down into soil much faster than, for example, quartzite or granite. The rate of rock weathering is not quite the same as the rate of soil formation.

As a first approximation, rate of weathering = rate of soil formation + rate of mass loss by various processes.
Wakatsuki and Rasyudin (1992) Rates of Weathering and Soil Formation, Geoderma, V52, 3-4, gives a good assessment of such rates.
Their best estimate is that soil formation occurs at 370–1290 (mean = 700) kg ha−1 yr−1. Or roughly 0.3 mm per decade, excluding the lost organic carbon. This is equivalent to about 3 mm of new soil generation since the great dust bowl.

In other words, no, the lost soil is nowhere near replenished yet. Moreover, the impact of climate change does not bode well for the future of soil regeneration.

Answer 2

There's No way to ascertain the level of soil reclamation since the 1930's the Soil Conservation service keeps track which I assume you can learn online if they have their data. Agronomic libraries May keep track of it. For one keeping tabs on something that affected over 200 million acres is spotty at best. The dust bowl occurred in six states, Texas, Oklahoma, New Mexico, Colorado, Nebraska and Kansas. In environments dominated by a mild or temperate climate, it takes roughly 200-400 years to form half an inch of top soil. in wet tropical areas soil formation is substantially faster, it takes 200 years However tropical plants gobble up nutrients at record pace. It's been 80 years since the dust bowl, so far top soil hasn't regenerated at a recognizable rate. We use fertilizers to keep the soil productive.