Dirt: The Erosion of Civilizations - Kootenay Local Agricultural Society

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Hilgard rightly dismissed the popular idea that the source of soil fertility
lay in the organic compounds in the soil. Also rejecting the western
European doctrine that soil fertility was based on soil’s texture and its ability
to absorb water, he believed that clays retained nutrients necessary for
plant growth and considered reliance on chemical fertilizers a dangerous
addiction that promoted soil exhaustion.
Hilgard recognized that certain plants revealed the nature of the underlying
soil. Crab apple, wild plum, and cottonwoods grew well on calciumrich
soil. Pines grew well on calcium-poor soil. Hired by the federal government
to assess cotton production for the 1880 census, he produced two
volumes that divided regional soils into distinct classes based on their
physical and chemical differences. Hilgard stressed understanding the
physical character of a soil, as well as its thickness and the depth to water,
before judging its agricultural potential. He thought that phosphorus and
potassium in minerals and nitrogen in soil organic matter controlled soil
fertility. Hilgard’s census report noted that aggressive fertilizer use was
starting to revive agriculture in the Carolinas.
He also reported how Mississippi hill country farmers concentrated on
plowing valley bottoms where upland dirt had piled up after cotton plantations
stripped off the black topsoil. Great gullies surrounded empty
manors amidst abandoned upland fields. Hilgard thought that a permanent
agriculture required small family farms rather than large commercial
plantations or tenant farmers seeking to maximize each year’s profits.
With a view of the soil forged in the Deep South, Hilgard moved to
Berkeley in his early forties to take a professorship at the new University of
California. He arrived just as Californians began shaking off gold rush
fever to worry about how to farm the Central Valley’s alkali soils—salty
ground unlike anything back East. Newspapers were full of accounts of
crops that withered mysteriously or produced marginal yields.
The extent of alkali soils increased as irrigation spread across the golden
state. Every new irrigated field raised the local groundwater table a little
more. Each summer, evaporation pumped more salt up into the soil. Hilgard
realized that, like a lamp’s wick, clay soils brought the salt closer to the
surface. Better drained, sandy soils were less susceptible to salt buildup.
Hilgard also realized that alkali soils could make excellent agricultural
soils—if you could just get rid of the salt.
Hilgard fought the then popular idea that salty soils resulted from seawater
evaporated after Noah’s flood. The ancient flood idea simply didn’t
hold water; the dirt was full of the wrong stuff. California’s soils were rich
dirty business