Till the soil to a 12-inch depth, and check the pH using a soil test kit. Cassava is not fussy about its soil, but it does prefer the soil to have a pH between 4.0 and 8.0. To raise a pH below 4.0, add lime. To lower a pH above 8.0, add peat. Apply the lime or peat according to manufacturer's recommendations.
Plant cassava as soon as the threat of frost is over. Lay the stalks along the broken soil line, spaced 3 feet apart. Cover the stalks with 1 inch of soil. Water the stalks immediately. Keep the soil evenly moist during the growing season with a combination of rainfall and supplemental watering with a garden hose.
Fertilize the soil around the cassava stalks two months after planting. Apply a 46-0-0 fertilizer according to manufacturer's specifications. Keep the fertilizer at least 6 inches from the stalks to prevent burn.
Pull weeds that grow around the cassava as soon as they develop, or they will compete with the cassava for water. If you prefer, spread 3 inches of mulch around the stalks to suffocate weeds and impede their growth.
Harvest cassava roots approximately eight months after planting the stalks. Cut the stems with a pair of loppers. Pull the roots out of the soil by hand with the help of a metal pry bar.