Tuesday, April 14, 2009

Ultisols and Alfisols

Ten days week ago, I posted an entry on John Majewski’s new book, Modernizing a Slave Economy: The Economic Vision of the Confederate Nation, focusing on Prof. Majewski’s discussion of land use and agricultural practices in the antebellum south, and in particular the fact that southern farmers placed only about one-third of their land in cultivation at any given time, versus two-thirds on average in the north. I left you hanging concerning Prof. Majewski’s conclusions as to why southerners retained the practice of shifting cultivation, which accounted for this discrepancy. This post continues and concludes that review.

In the antebellum period, northerners regularly made note of and denigrated the effects of shifting cultivation in the south: the large tracts of unimproved and worn-out land, interspersed with occasional farmhouses and small settlements. With equal regularity they assumed that the desolate appearance of much of the rural south was somehow attributable to slavery, which rendered the inhabitants slovenly and lazy:
David Wilmot . . . frequently associated slavery with soil exhaustion. “Sterility follows its [slavery’s] path,” he declared in 1846. A decade later, Representative Israel Washburn of Maine noted that “their [southerners’] lands are being worn out and exhausted. . . . [T]hey have not the enterprise, skill or means to renovate them.”

The contrast between the tidy, prosperous farms of the north and (in the words of William Seward) the “old and decaying towns, wretchedly neglected roads, and, in every respect, an absence of enterprise and improvement” in the south provided a powerful argument to Free Soilers. “No wonder,” Prof.Majewski observes, “that many northerners wanted to stop slavery spreading to the western territories. Shifting cultivation, they believed, was sure to follow.”

Modern historians have to a large extent adopted this analysis. “Historians have frequently pointed to some combination of slavery, cheap western lands, and ingrained traditionalism.” The relative abundance of land and mobility of slave labor, so the argument goes, allowed southerners to work a given piece of land to exhaustion, and then move on.

Prof. Majewski rejects all such explanations. Shifting cultivation persisted, he argues, because southern soil and weather made crop rotation impracticable or impossible. It turns out that most of the south has soil classified as part of the ultisol soil order. “Ultisols generally lack key nutrients for plant growth and tend to be highly acidic. The acidity makes it difficult for plants to fully utilize whatever nutrients are present, which means that fertilizing the soil will not raise crop yields unless the acidity is first neutralized.”

Shifting cultivation was ideally suited to this soil because the ash produced by burning “provided a quick infusion of important nutrients, and its calcium content helped neutralize the acidic ultisol soils.” Northern farms, in contrast, generally consisted of alfisol soils, which contained “an abundance of phosphorus, potassium, calcium, and other essential plant nutrients.” The rotation systems that northerners successfully used on alfisol soils simply did not translate to the ultisols of the south.

Other environmental facts – heat and rainfall patterns – also conspired against the south to make rotation impractical. “Important fodder crops such as hay and clover that supported continuous cultivation failed to thrive in the warm and humid southern climate.” Southern cattle tended to be stunted and produced less manure – another important element of the rotation system in the north – both because they had to be raised on less nutritious substitutes and because they fell prey to tick-spread disease.

Prof. Majewski appears to do an excellent job supporting his thesis that these environmental factors constituted the principal reason that southern farmed stuck with shifting cultivation. The core of his analysis involves the use of “multivariate regressions” to assess the impact of numerous variables, which are summarized as follows:
In summary, the regressions indicate that the environmental factors (soil types, typography, and climate) greatly influenced levels of improved land; they show a particularly strong association between alfisol soils and high levels of improved land. Ultisols and rugged topography (such as the mountains of Appalachia or the marshes of the coastal regions), on the other hand, led to low levels of improved land.

The book includes a 17-page “statistical appendix”, which I invite those more statistically literate than I to pick at for holes or discrepancies. What I found most interesting about the more detailed analysis there was the discussion concerning the relationship between slavery and shifting cultivation. It turns out, according to Prof. Majewski, that there is “a strongly positive” and “statistically significant” relationship between more slaves and higher levels of improved land.

Prof. Majewski cautions that “it is impossible to tell . . . whether slavery caused more land to be improved or whether slaveholders simply preferred to locate in areas with the best soils and the best access to transportation.” However the correlation does discredit the contrary claim, that slavery “caused” less land to be improved. “Slavery (or its absence) did not ‘cause’ shifting cultivation, strengthening the point that environmental factors plaed the most important role.”

Post-Civil War (and therefore post-slavery) evidence further buttresses this conclusion:
What makes the statistical results for 1860 even more compelling is that the same basic relationship holds for 1890 as well. Despite the greater availability of fertilizers, farmers in counties with poor soils cultivated far less land than farmers in areas with more favorable soils. The 1890 results cast further doubt that slavery and cheap western land caused shifting cultivation. Shifting cultivation, simply put, outlived both.

Prof. Majewski’s findings, if correct, point to a profound irony. Obviously, northerners came to adopt Free Soil ideology for a variety of reasons. But images of decrepit southern agriculture and agricultural lifestyles caused by slavery were a powerful weapon in the Free Soil arsenal, as some of the above quotes suggest. Was the assumption that slavery was the source of those images simply wrong? It would seem so.

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