Using Maize δ15N values to assess soil fertility in fifteenth- and sixteenth-century ad Iroquoian agricultural fields.

John P Hart,Remigio Paradelo Núñez,Robert S Feranec

doi:10.1371/journal.pone.0230952

Abstract

Native Americans developed agronomic practices throughout the Western Hemisphere adapted to regional climate, edaphic conditions, and the extent of dependence on agriculture for subsistence. These included the mounding or "corn hill" system in northeastern North America. Iroquoian language speakers of present-day New York, USA, and Ontario and Québec, Canada were among those who used this system. While well-known, there has been little archaeological documentation of the system. As a result, there is scant archaeological evidence on how Iroquoian farmers maintained soil fertility in their often-extensive agricultural fields. Using δ15N values obtained on fifteenth- and sixteenth-century AD maize kernels from archaeological sites in New York and Ontario, adjusted to take into account changes that result from charring as determined through experiments, we demonstrate that Iroquoian farmers were successful at maintaining nitrogen in their agricultural fields. These results add to our archaeological knowledge of Iroquoian agronomic practices. Our results also indicate the potential value of obtaining δ15N values on archaeological maize in the investigation of Native American agronomic practices.

Highlights

Native American farmers developed agronomic practices throughout the Western Hemisphere adapted to climatic and edaphic conditions and the degree of reliance on agricultural production for subsistence
While it is possible that some of the high δ15N values we obtained are the result of initial field clearance involving cutting down and burning trees and other vegetation ([42], p.7), given the probable lengths of time Iroquoian agricultural fields were in continuous cultivation, the effects of these activities on the isotopic compositions of the plants are insufficient to explain the range of δ15N values observed
One study found an initial increase in foliar δ15N values after wildfires, followed by sharp drop offs in the first post-fire decade [73]

Summary

Introduction

Native American farmers developed agronomic practices throughout the Western Hemisphere adapted to climatic and edaphic conditions and the degree of reliance on agricultural production for subsistence. Well known systems of groups who relied heavily on agricultural production include the terraced fields in the Andes of South America [1], the milpa systems of Central America [2], the irrigation systems of the American Southwest [3], and the ridge systems of the upper Mississippi drainage [4]. How these systems functioned is evinced by archaeological investigations of extant features, ethnohistorical documentation, and in some cases, ethnographic documentation. There is little direct archaeological information on how these agronomic systems were managed

Methods

Results

Conclusion