1493_ Uncovering the New World Columbus Created - Charles C. Mann [129]
Irish farmers for centuries had grown crops by cutting out blocks of sod, flipping them upside down, and piling them into long, broad ridges separated by deep furrows—“lazy-bed” farming, as the system was known. (The name may come from an occasional English epithet for the potato: the “lazy root.”) Typically four feet wide, the ridges loomed a foot or more above the furrows. They looked strikingly like wacho, the ridged fields in Andean societies. Like wacho, they were built in boggy soils; the ridges warmed up more quickly in the morning and retained heat longer in the evening than the surrounding flatlands, an advantage in cold places like the Andes and Ireland. Constructed from several layers of sod, the ridges represented concentrations of good soil; farmers could plant them densely, which naturally stifled weeds. Because the ridges were not plowed, they had intact root systems that resisted erosion; the roots also ensured that grass returned quickly after harvest, restoring nutrients.
Unaware of these advantages, eighteenth-century agricultural reformers denounced the lazy-bed/wacho method as inefficient, an unproductive obstacle to modernization. Activists like Andrew Wight and Jethro Tull wanted farmers to release soil nutrients by deep, thorough plowing; to plant every possible bit of terrain; to charge the land with fertilizer (manure and then, when it became available, guano); to protect growing crops with ruthless weeding; and to maximize yields by efficient harvesting. Believers in technology, they viewed the newest factory-made harrows, drillers, and harvesters as God-given tools to accomplish these goals. Because these machines needed level land—they couldn’t climb up and down ridges—the lazy-beds had to go. On top of everything else, reformers said, the furrows between the ridges were a waste of space.
Wacho occupied a swath of northern Europe that reached from France to Poland and included Britain, Ireland, Scandinavian countries, and Baltic states. As the new methods took hold after about 1750, they disappeared. Wacho had almost vanished from Ireland by 1834, when reform enthusiast Edmund Murphy took a cross-country “professional tour” between Dublin on the east coast and Galway on the west, taking “particular notice of the potato crop.” Seeing few lazy-beds in areas where they had once been ubiquitous, he crowed that they were “completely superseded.… Nothing shows the rapid improvement in agriculture which is at present extending in this country more clearly.”
To examine the consequences of the shift to modern cultivation methods, Michael D. Myers, then at the University of Texas in Austin, experimentally created six fields in Northern Ireland: three lazy-beds and three of the level fields that replaced them. He discovered that the simple ridges and furrows created a complex geography, with surprisingly sharp temperature and humidity differences between the top of the ridge and the bottom of the furrow. Plant-disease specialists describe the temperature and humidity conditions that favor P. infestans in terms of “blight units”—the higher the number of blight units, the better the chance that blight zoospores on potato leaves will be able to germinate. Myers’s lazy-beds had roughly half as many blight units as the level fields. Blight spores were less likely to germinate in the comparatively warm, dry conditions atop the ridges. Because water drained into the furrows, it flowed away and beneath the growing tubers, carrying zoospores away from them. In addition, they had fewer noxious weeds and needed less fertilizer.7
Many Andean peoples have long grown potatoes in parallel ridges called wacho (bottom, in Bolivia near Titicaca), a practice that has been shown to discourage fungal diseases by drying wet soil. Lazy-bed cultivation, as