Oct. 14 (UPI) -- The contents of rural trash heaps outside several ancient Negev settlements suggest farmers during the Roman Imperial Period and Late Antiquity, between the 1st and 10th centuries AD, used livestock dung for fertilizer and as a main fuel source.
For the study, published Wednesday in the journal PLOS One, researchers analyzed trash mounds outside of Shivta, Elusa and Nessana, agrarian settlements that flourished during the Late Byzantine and Early Islamic periods, from the 4th through the 10th century AD.
By studying the varying concentrations of livestock dung, grass, wood and ash, researchers were able to gain new insights into shifting refuge management techniques and fuel usage among Negev's early agrarian societies.
"Our findings provide much-needed new insight into community specific responses to social and economic transformations in the Negev during a pivotal time in its history -- during the collapse of market-oriented agriculture and ruralization of the urban heartland near the end of the first millennium [AD]," researchers wrote in their paper.
Specifically, researchers found a consistent lack of raw livestock dung in all three trash mounds, suggesting sheep and goat dung fertilizer was vital to large-scale agriculture across the semi-arid region.
"Instead of being disposed of in trash dumps, dung would have been spread in agricultural plots," researchers wrote.
The discovery of bits of burned livestock dung within the trash heaps outside Shivta and Elusa suggests livestock waste was also used as a fuel source. Woody plant material was scarce in the region. The practice suggests livestock herds were plentiful and household fuel needs did not interfere with field fertilization.
Not all of the livestock dung collected by Negev herders was shoveled into fields and furnaces.
"In sharp contrast to the sustainable use of dung for fuel, and reasonably for fertilizer as well, raw dung was dumped and burned atop the mound outside Early Islamic Nessana," researchers wrote. "This is the first evidence of its kind from the Negev confirming the management of dung via controlled incineration."
The sizable layers of scorched dung outside Nessana suggests that by the Early Islamic period, economic disruption had made the practice of dung recycling unnecessary.
"Several of the Arabic documents written after the fall of Byzantine hegemony speak of the difficulties Nessana residents had in paying rising taxes, particularly those levied against farmlands and produce," researchers wrote.
With large-scale farming on the decline and trade networks crumbling, researchers suspect the market for commercial agricultural products collapses, as did the demands for dung as fuel and fertilizer.
"Nessana appears to have been transforming from an agricultural center into a more rural community persisting from smaller-scale domestic farming, semi-sedentary herding and wild game hunting," researchers wrote.
The study's authors said they hope their work will serve as reminder to archaeologists to look beyond buildings and city walls -- that important insights into the ancient socioeconomic shifts can be gleaned from refuge.