Archaeologists working in eastern North America typically refer to precontact and early postcontact Native American maize-based agriculture as shifting or swidden. Based on a comparison with European agriculture, it is generally posited that the lack of plows, draft animals, and animal manure fertilization resulted in the rapid depletion of soil nitrogen. This required Indigenous farmers to move their fields frequently. In Northern Iroquoia, depletion of soil fertility is frequently cited as one reason why villages were moved to new locations every 20 to 40 years. Recent analysis of δ15N ratios of maize macrobotanical remains from Northern Iroquoia, however, suggests that Iroquoian farmers were able to maintain soil nitrogen in their maize fields. An expanded analysis of maize kernel δ15N ratios from three ancestral Mohawk villages indicates that farmers from those villages maintained soil nitrogen throughout the occupational spans of their villages. It further suggests that precontact Iroquoian agronomy was consistent with contemporary conservation agriculture practices.

在北美东部工作的考古学家通常将接触前和接触后早期的美洲原住民以玉米为基础的农业称为轮移或轮换。与欧洲农业相比，人们普遍认为，缺乏犁、耕畜和动物粪便施肥导致土壤氮的快速消耗。这要求原住民农民经常迁移他们的田地。在易洛魁北部，土壤肥力的枯竭经常被认为是村庄每 20 至 40 年迁移到新地点的原因之一。然而，最近对北易洛魁人玉米大型植物遗骸的 δ 15 N 比率的分析表明，易洛魁人农民能够维持其玉米田中的土壤氮。对莫霍克三个祖传村庄的玉米粒 δ 15 N 比率的扩展分析表明，这些村庄的农民在其村庄的整个职业生涯中都保持了土壤氮。它进一步表明，接触前的易洛魁农学与当代保护性农业实践是一致的。