Anthropogenic influences on Zuni agricultural soils

Abstract

Farmers in the Zuni area of the semiarid American Southwest have successfully cultivated maize and other crops for over three millennia without using artificial fertilizers. Zuni agricultural fields are among the oldest, more or less continuously cultivated areas in the United States. Traditional Zuni agriculture is based on runoff farming, a system whereby runoff and organic‐rich sediment generated in small watersheds are captured and directed onto fields for crop use. We conducted a study to compare soil properties associated with paired and unpaired cultivated, abandoned, and uncultivated fields to evaluate the long‐term effects of cultivation on soil quality. Sampling and analytical methods of this research are especially applicable to geoarchaeological studies of anthropogenic effects on soil fertility and agricultural sustainability in ancient and traditional historical farming systems. Results of the Zuni soil study indicate that cultivation has altered some soil properties, including bulk density, organic carbon, total nitrogen, and C:N ratios in paired fields, but there is no indication that agricultural soils are degraded. This assessment supports the perception of Zuni farmers that long‐term cultivation has not caused a decline in agricultural productivity. © 2005 Wiley Periodicals, Inc.

Biogeochemical studies of a Native American runoff agroecosystem

“…cultivated soils have higher organic matter and phosphorus levels than uncultivated soils primarily because of greater A-horizon thickness. These and other data already discussed suggest that overall, traditional Zuni agriculture has altered, but not degraded,soils (Homburg et al, 2005). This stands in contrast to clear trends toward decreased organic matter and microbial biomass with cultivation commonly reported in the literature for many modern agricultural fields under conventional cultivation (Sandor and Eash, 1991).…”

“…A distinctive feature of soils used for runoff agriculture is that they generally have thicker surface horizons than historically uncultivated soils used as references ( Figure 8a and Table II; Homburg et al, 2005). We infer that this is due, at least in part, to greater inputs of sediment from runoff processes.…”

“…Overall, data from this project suggest that nitrogen and phosphorus levels of Zuni runoff agricultural soils are sufficient to meet crop needs (Table III; Homburg et al, 2005; also see the next section on maize). In conjunction with soil chemistry studies, soil biology is a key area relating to soil nutrient dynamics that deserves much more study in relation to past and present runoff agriculture.…”

“…Altogether, study sites represent an approximately 30% sample of known runoff fields in the eastern Zuni study area. Field and lab methods used in this multidisciplinary study are detailed in Norton (1996Norton ( , 2000, Havener (1999), Homburg (2000), Sandor et al (2000), , Norton et al (2002Norton et al ( , 2003, in press a, in press b), and Homburg et al (2005). The rationale and limitations of paired-site methodology in studies of ancient agriculture are discussed in Sandor and Eash (1991).…”

“…These are sources of increased organic matter and associated nutrients for crops. The coatings may be associated with another finding, namely unusually high positive correlations between silt and organic matter (including nitrogen) in a number of runoff fields, which may reflect cotransport of silt and organic debris common with runoff processes (Table II; Nabhan, 1984;Norton, 1996;Homburg et al, 2005).…”