Archaeologists from the University of Colorado recently made findings at the village of Ceren archaeological site in El Salvador that the ancient Mayas cultivated manioc (also known as cassava):
A University of Colorado at Boulder team excavating an ancient Maya village in El Salvador buried by a volcanic eruption 1,400 years ago has discovered an ancient field of manioc, the first evidence for cultivation of the calorie-rich tuber in the New World.
The manioc field was discovered under roughly 10 feet of ash, said CU-Boulder anthropology Professor Payson Sheets, who has been directing the excavation of the ancient village of Ceren since its discovery in 1978. Considered the best-preserved ancient village in Latin America, Ceren's buildings, artifacts and landscape were frozen in time by the sudden eruption of the nearby Loma Caldera volcano about 600 A.D., providing a unique window on the everyday lives of prehistoric Mayan farmers.
The discovery marks the first time manioc cultivation has been discovered at an archaeological site anywhere in the Americas, said Sheets. ...
"We have long wondered what else the prehistoric Mayan people were growing and eating besides corn and beans, so finding this field was a jackpot of sorts for us," he said. "Manioc's extraordinary productivity may help explain how the Classic Maya at huge sites like Tikal in Guatemala and Copan in Honduras supported such dense populations."
You can listen to a podcast of Professor Sheets describing this new discovery at this link.
Ceren is a highly significant archaeological site:
Shortly after dinner started, one early evening in August about 595 AD, the Loma Caldera volcano of north central El Salvador erupted, sending a fiery mass of ash and debris up to five meters thick for a distance of three kilometers. The inhabitants of the Classic period village now called Cerén, a mere 600 meters from the volcano's center, scattered, leaving dinner on the table, and their homes and fields to the obliterating blanket. For 1400 years, Cerén lay forgotten--until 1978, when a bulldozer inadvertently opened up a window into the perfectly preserved remains of this once thriving community.(Source)
Ceren is registered as a UN Heritage site and has been called the "Pompeii of the New World." It is one of El Salvador's major archaeological sites. The University of Colorado has an elaborate web site letting you explore what has been unearthed at the site.
And if you don't know about manioc, here is information from Wikipedia:
The cassava, casava, yuca or manioc (Manihot esculenta) is a woody shrub of the Euphorbiaceae (spurge family) native to South America that is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates.
The root is long and tapered, with a firm homogeneous flesh encased in a detachable rind, about 1 mm thick, rough and brown on the outside. Commercial varieties can be 5 to 10 cm in diameter at the top, and 50 to 80 cm long.... The flesh can be chalk-white or yellowish; raw cassava tastes like a mixture of potato and coconut flesh, it breaks like a carrot, and darkens quickly upon exposure to the air....
The cassava plant gives the highest yield of food energy per cultivated area per day among crop plants, except possibly for sugarcane. Cassava roots are very rich in starch, and contain significant amounts of calcium (50 mg/100g), phosphorus (40 mg/100g) and vitamin C (25 mg/100g).