Richard E. Terry

Quantitative phosphorus measurement: A field test procedure for archaeological site analysis at Piedras Negras, Guatemala

Currently there is a wide interest in the use of chemical analyses for the evaluation of anthropogenically altered soils and other archaeological deposits. Because soil phosphorus levels increase in areas of human habitation, and leave a permanent signature that can only be removed by erosion of the soil itself, phosphorus mapping has become a popular field procedure to indicate areas of habitation where overt evidence of ancient occupance is absent. We have developed a methodology to obtain accurate acid-extractable phosphorus concentrations (mg/kg) in calcareous soils under the primitive field conditions of Piedras Negras, Guatemala. Predicated on Mehlich-II acid extractant and colorimetric methods, this procedure processed 36 samples per hour at very low cost per sample. Based on eight replicate measurements of a group of samples, the coefficient of variation of the procedure was 8.3%. Subsequent analysis of 35 soil samples in a controlled laboratory revealed a moderate correlation of 0.44 between the Mehlich-extractable phosphorus and total phosphorus. The correlation was 0.91 between the Mehlich procedure and Olsen bicarbonate extractable phosphorus, indicating that Mehlich-based results are similar to those obtainable using a traditional extractable phosphorus method on soils of neutral to alkaline pH. There was a moderate correlation between Mehlich P and ring-test rating (r = 0.42). The wider dynamic range of the Mehlich extraction, coupled with the use of a battery-operated colorimeter, facilitated the finding of a refuse midden within an area of phosphate enriched soils. Further tests indicated that phosphorus concentrations measured in the field deviated by only 7% from those made under controlled laboratory conditions.

In search of an ancient Maya market

Market economies are notoriously difficult to identify in the archeological record. This is particularly true in the subtropical Maya lowlands of Mexico, Guatemala, and Belize because most utilitarian items and consumables were made of highly perishable materials. We explore the hypothesis that ancient marketplaces can be identified through analysis of chemical residues in soils from open and easily accessible spaces in and about ancient Maya cities. We compared soil chemical signatures from a credible ancient marketplace location in the specialized trade center of Chunchucmil, Yucatan, Mexico to those from a modern marketplace at Antigua, Guatemala. We found extraordinarily high concentrations of phosphorus and zinc in the soil of Chunchucmils proposed marketplace and the same high concentrations correlate well with food preparation and vegetable sales areas at the modern marketplace. These methods hold promise in resolving the vexing question of how large ancient Maya urban populations were sustained.

EFFECTS OF POLYACRYLAMIDE AND IRRIGATION METHOD ON SOIL PHYSICAL PROPERTIES

The objective of this study was to observe the effects of irrigation method and polyacrylamide additions on selected soil physical properties. Polyacrylamide (PAM) was applied to fallow clay loam soil to the rate of 650 kg ha1. The PAM-treated plots were flood-irrigated at the rate of 5 cm wk-1. Untreated plots were either flood-or sprinkle-irrigated. Measurement of soil physical properties included bulk density, penetrometer resistance, aggregate stability, and infiltration rate. The surface bulk densities of sprinkle-irrigated soil and PAM-treated, flood-irrigated soils were significantly lower than the flood-irrigated control. The presence of a surface soil crust in the flood-irrigated control was evidenced by penetrometer resistance 10 times greater than the PAM or sprinkle-irrigated treatments. Aggregate stability was immediately improved from 17 to approximately 80% by the application of PAM. Improved aggregate stability (approximately 50%) lasted throughout the experiment. Infiltration rates of the PAM and sprinkle-irrigated treatments were approximately twice as great as those of the flood-irrigated control.

Domestic and Political Lives of Classic Maya Elites: The Excavation of Rapidly Abandoned Structures at Aguateca, Guatemala

The Aguateca Archaeological Project conducted extensive excavations of elite residences at the Maya center of Aguateca, which was attacked by enemies and abandoned rapidly at the end of the Classic period. Burned buildings contained rich floor assemblages, providing extraordinary information on the domestic and political lives of Classic Maya elites. Each elite residence served for a wide range of domestic work, including the storage, preparation, and consumption of food, with a relatively clear division of male and female spaces. These patterns suggest that each of the excavated elite residences was occupied by a relatively small group, which constituted an important economic and social unit. In addition, elite residences were arenas where crucial processes of the operation of the polity and court unfolded through political gatherings, artistic production, and displays of power.

Nitrous Oxide Emissions from Drained, Cultivated Organic Soils of South Florida

Due to the intense microbial oxidation of organic soils in the Florida Everglades, approximately 1400 kg N/ha are mineralized annually. Most of this nitrogen is lost to the atmosphere through denitrification in the soil. Nitrous oxide is one of the gaseous products of denitrification, therefore the objectives of this study were to determine the quantities of N2O emitted from these soils and to measure the effect of this N2O on ambient mixing ratios in the Everglades. Nitrous oxide fluxes from these soils ranged from 4 g N/ha/day, during dry periods, to 4500 g N/ha/day following rainfall events. Nitrous oxide emissions increased with increasing soil moisture. From April through the end of December 1979, a total of 165, 97, and 48 kg N2O-N/ha were emitted from fallow, St. Augustine grass, and sugarcane fields, respectively. There was a diurnal variation in the N2O mixing ratios of air 8 m above the soil in the Everglades. This diurnal fluctuation was affected by wind speed. There was a significant linear co...

Modeling nitrous oxide emissions from agriculture: A Florida case study

Abstract The DNDC (Denitrification-Decomposition) model is shown to simulate emissions of nitrous oxide (N 2 O), changes in soil nitrate, and nitrogen mineralization rates consistent with field measurements at three agricultural sites in Florida. As a case study of the potential policy relevance of a process-oriented biogeochemical model, we estimated N 2 O emissions to the atmosphere from all agricultural lands in Florida, a state with significant agriculture on both organic and mineral soils. Nine landscape classes (3 soil classes × 3 annual rainfall classes) were coupled with county-based data on crops (5 major crops + pasture + fallow), fertilization, irrigation, and representative areas, to generate 86 model scenarios. Annual simulations were run for each case, and county and state emissions were tabulated. Total N 2 O emissions from Floridas agricultural lands were estimated to be 0.024 Tg N 2 ON y −1 . Emissions were unevenly distributed with approximately 50 percent of the N 2 O being emitted from soils in six (of 68) Florida counties. Organic soils, while occupying only 9% of the total agricultural land area and receiving no nitrogen fertilizer additions, accounted for 38% of the states total N 2 O flux. Sensitivity studies suggest that the most effective means for mitigating N 2 O emissions would involve a combination of measures including reductions in drainage of organic soils, injection of fertilizers to soil depths of 10 cm or greater, and increased attention to precision irrigation. Biogeochemical modeling will be critical to developing an integrated framework for assessing policies for reducing N 2 O emissions from agricultural systems.

Root iron‐reduction capacity for genotypic evaluation of iron efficiency in soybean

Abstract Genetic resistance to Fe‐deficiency chlorosis is the most viable and economical means to overcome this problem in soybean [Glycine max (L.) Merr.], but current field evaluation is slowed and constrained by soil heterogeneity and environmental fluctuation. Highly resistant (Fe‐efficient) cultivars have been shown to reduce Fe3+ to Fe2+ more actively by the roots under Fe‐deficiency stress than highly susceptible genotypes. The objective of this study was to determine if Fe3+ reduction could be used to predict the degree of resistance or susceptibility to Fe‐deficiency chlorosis. Thirteen genotypes (both commercial and experimental) with known field susceptibility ratings were grown in a growth chamber in modified Hoagland solution. The more Fe‐efficient genotypes reduced Fe3+ earlier and to a greater extent than the less Fe‐efficient types. The sum of the seven daily Fe3+ reduction measurements was negatively correlated with field chlorosis ratings, as high as ‐0.864 (p > 0.01), and was a good pre...

Soil Chemical Analysis of Ancient Activities in Cerén, El Salvador: A Case Study of a Rapidly Abandoned Site

Activities performed over long periods of time tend to leave soil chemical residues as evidence of those activities. Some of the questions studied in this paper deal with the interpretive capabilities provided by chemical patterns. Soil samples from Ceren, El Salvador, a well-preserved site, were analyzed for extractable phosphorus and heavy metals. We compared in situ artifacts collected from the site with chemical signatures that indicate activity areas. We found that elevated concentrations of phosphorus were associated with food preparation, consumption, and disposal. Heavy metals were associated with the interior of the structure where pigments and painted gourds were found. In this case, where well-preserved, in situ artifacts were available for analysis, we found that chemical analysis was effective in locating human activity areas. Our findings indicate that chemical analysis can be used to guide interpretation in areas of poor artifact preservation with reasonable accuracy, and in archaeological sites that underwent gradual abandonment.

Mycorrhizal colonization and nutrient uptake of dry bean in manure and compost manure treated subsoil and untreated topsoil and subsoil

Abstract Eroded or leveled Portneuf silt loam soils (coarse‐silty mixed mesic Durixerollic Calciorthid) have been restored to topsoil productivity levels by manure application, but not by other organic sources such as cheese whey. In dry bean (Phaseolus vulgaris L. cv. Viva), only soil organic matter and Zn concentration of leaf tissue correlated with improved yields. Manure application could potentially increase or decrease mycorrhizal colonization depending on which factors dominate. Manured and unmanured soils from a long‐term field experiment were sampled and mycorrhizal spores were quantified, but there was no significant manure treatment effect on spore numbers. A greenhouse study was conducted to see if manure or composted manure freshly applied to subsoils would facilitate mycorrhizal colonization in dry bean roots compared to untreated topsoil or conventionally fertilized subsoil. Low level colonization (< 5%) was observed 21 days after planting and that increased to 58% by 56 days after planting...

Pelletized cyanobacterial soil amendments: Laboratory testing for survival, escapability, and Nitrogen fixation

The escape and growth of Microcoleus vaginatus from alginate pellets onto soil crusts under controlled laboratory conditions were examined. Soil crust samples were collected and placed in petri dishes. Selected samples were sterilized, and three treatmerits were established: 75 g m−2 Microcoleus pellets added to sterilized soil, 75 g m−2 blank pellets added to sterilized soil, and unsterilized soil with no additions. Chlorophyll a readings were significantly higher in unsterilized soils. Microcoleus biovolumes were highest in sterilized inoculated soils and significantly higher than sterilized untreated soils. Microcoleus filament density was significantly higher in Microcoleus‐inoculated soils than in the other two treatments. Nitrogen fixation activity was recorded in unsterilized soils after only 1 month, and rates increased as the experiment progressed. Microcoleus‐inoculated soils had significant nitrogen‐fixing activity during the last sampling period.