Chapter 5. Finding and understanding ancient irrigated agricultural fields in southern Arizona

Were Early Agricultural period (2100 B.C.–A.D. 50) maize cultivators in Southern Arizona sedentary farmers or seasonally mobile forager-farmers? Ethnographic analogs and ethnographically derived middle range theory support both claims. One argument for sedentism has been the abundance of large subterranean storage pits. These are often presumed to have been used for long-term food storage. This study of wetlands-indicator spores recovered from those pits indicates that the pits were often saturated and could not have been used for long-term food storage; these findings support the general contention that Early Agricultural period maize cultivators were seasonally mobile and tried to fit early agriculture into a subsistence regime focused on wild foods.

Metric analyses of recently excavated maize (Zea mays, L.) cupules and cob fragments from Early Agricultural period (2000 B. C.-A.D. 50) sites in southern Arizona indicate that early maize cultivars produced small cobs with small cupules. Although it is risky to generalize about the yield potential of a plant that may have no compelling modern analogues, this work provides further support for the claim that ancient Tucson Basin maize plants provided relatively low yields as compared with more recent varieties.

We examine the changes in funerary rituals from the Early Agricultural period (2100 BC–AD 50) to the Early Preclassic period (AD 475–750) and how these changes concurrently reflect changes in social relationships between the dead, their families, and the community. The predominant mortuary ritual in the Early Agricultural period was inhumation, possibly emphasizing a variety of identity intersections of the dead and the mourners in the treatment of the body while creating collective memories and remembrances through shared ways of commemorating the dead. An innovation in funerary practices in the form of secondary cremation appeared in the Early Agricultural period and was slowly but broadly adopted, representing new social dynamics within the society. Thereafter, secondary cremation became the main funeral custom. During the Early Preclassic period, the variation in body position and the type and quantity of objects found with individuals decreased. It is possible that the vehicle for displaying different identity intersections changed and was not placed in the body, per se, as much as in previous periods. However, the transformation characteristics of these funeral rituals and the increase in community investment could have fostered the building or reinforcing of stronger social ties that highlighted a “collective identity.”

This study examines phenotypic variation and biological distances estimated using morphological traits from three Early Agricultural period (EAP) (2100 BC-AD 50) site-complexes in the Sonoran Desert of southern Arizona and northern Sonora. The hypothesis tested is that EAP forager-farmers were phenotypically homogenous as suggested by patterns in material culture and works to refine inferences regarding gene flow and biological affinity during subsistence transitions. Seven measurements from 62 EAP male and female crania were collected and used to calculate phenotypic variances, biological distances, and FST values with RMET 5.0 software. Analyses were applied to both pooled site-complex samples and to males and females separately. Results show differential variation between site-complex population samples, multiple significant biological distances, and significant FST values for the EAP regional sample that indicate widespread phenotypic heterogeneity rather than homogeneity. Significantly lower than expected variance in the Cienega Creek male sample is inferred to suggest a small closely related population present during the Cienega phase. Greater than expected male variation is attributed to higher frequencies of gene flow in the La Playa and Santa Cruz River site-complex samples. These EAP males are inferred to be more mobile across the Sonoran Desert landscape and representative of multiple biological affinities compared with females. This study provides evidence supporting the canalization of phenotypic variation when associated with human populations becoming increasingly sedentary due to transitioning subsistence practices.

An integrated approach to surveying an Early Agricultural period landscape: Magnetic gradiometry and satellite imagery at La Playa, Sonora, Mexico

Early irrigation systems in southeastern Arizona: the ostracode perspective

Late pre-Classic Hohokam (A.D. 750–1150) upland desert adaptations of the middle Gila River Valley in southern Arizona are still rather poorly understood. Current site and feature distribution data from Florence Military Reservation indicate that late pre-Classic groups used the upland or bajada zone in a varied and complex manner. First, a variety of agricultural technology was employed, including floodwater farming, dry farming, and to a lesser degree, simple irrigation-based agriculture. Second, a wide range of occupation types have been encountered in these bajada zones, consisting of villages, farmsteads, field houses, agricultural field sites, and more specialized resource processing sites. And, third, a flexible mobility pattern existed, where primary habitations such as rancheria-like villages and small farmsteads were situated along alluvial fans of Cottonwood Canyon Wash. This habitation zone has produced a diversity of floodwater, dry, and irrigation-based farming practices associated with residential areas, trash mounds, and a ball court; the combination of farming technology and presumed ceremonial features may have contributed to group aggregation, at least on a seasonal basis. From this habitation zone, specialized task groups and domestic units repeatedly used field houses and large agricultural fields out on creosote flats, and smaller dry farming loci, on more elevated ridge tops.

Continuing research on the Early Agricultural period has bolstered our understanding of early farming technology, community structure, and chronology. Environmental factors clearly affected the pace of agriculture’s spread, as did social interaction and population movement. Recent projects have contributed new information on how irrigation communities were organized, and how early farmers worked on the landscape. Much of the research conducted over the past thirty years has been conducted under the aegis of Section 106 of the National Historic Preservation Act of 1966. Methodological and theoretical advances have broadened the scope of study, but international and interdisciplinary cooperation remain goals to further this research.

An irrigated farmer's field at Hafizabad village in Dera Ismail Khan District of Northwest Frontier Province of Pakistan was sampled at a regular grid spacing of 50x15 m from surface (15 cm) to study the spatial variability of soil properties and wheat yield. The farm measured 250x75 m. Soil samples collected were analyzed for soil pH, lime content, organic matter, mineral nitrogen (N), ammonium bicarbonate (AB)‐DTPA‐extractable phosphorus (P) and potassium (K), and soil texture. A uniformly trial on wheat with a uniform rate of 120 kg N ha‐1, 90 kg P2O5 ha‐1, and 60 kg K2O ha‐1 was laid out. The results showed that the soil P had the highest coefficient of variation (CV 46%) followed by organic matter (36.20%) and clay content (33.81%). Grain yield had also a considerable variation in the field (CV=31.84%). Geostatistical technique of semivariogram analysis showed that mineral N, AB‐DTPA‐extractable K, sand, silt, and clay content had the strong spatial structure. Maps of soil fertility and crop productivity of the farm was prepared using modern geostatistical technique of kriging. The farm was divided into different management zones based on these maps for fertility management.

Field irrigation is the largest consumer of freshwater in the world covering 63 million hectares in the 1900s to 300 million hectares in the early 2000s to provide a multitude of benefits and ecosystem services to people around the globe, such as consistent food supply, higher crop productivity, and shared resource collectivism. Field irrigation intensifies land use mostly in the arid and the semiarid regions where precipitation cannot fully satisfy human and crop water demands. Climate change impacts the distribution and the timing of water availability into humid regions as well through increases in drought frequency and intensity, further augmenting the demand for irrigation. However, designing and operating irrigation infrastructure and scheduling practices for an agricultural region requires sound contemporary and historical knowledge of the local circumstances vis-à-vis humans, crops, soils, hydrology, and climate. Sub-Saharan Africa stands as a large-scale narrative of poorly performing field irrigation against decades of investments due to designs exclusive to the socioeconomic ecosystems. Optimal water allocation in the water–energy–environment–food nexus to achieve the greatest social and economic benefit for the region invariably a task of continuous cocreation between many actors. Therefore, field irrigation remains a challenging project and most of the agricultural water use worldwide—both from groundwater and surface water—remains suboptimal in terms of design, water allocation, and monitoring for farmers, communities, and regulators. Many diversions of surface water for irrigation in both economically developed and developing countries are small-scale temporary infrastructures in and outside official plans and permits, which altogether results in severe aquifer depletion worldwide with negative impacts on food safety, economy, environment, and society. Traditional surface flooding is the dominant mode of irrigation globally and mostly applied on new agricultural fields, whereas water-saving irrigation methods are practiced on fewer and older fields. Water-saving technologies involve either scheduling of regulated deficit irrigation or local water storage to optimize crop water supply, which may be combined with drip irrigation, biodegradable soil amendments to retain soil water, and plastic mulches to minimize evaporation, whereas the use of partial root zone drying and biochar mostly remain at the experimental stage. Global analyses over the late 20th and early 21st century find no water saving by water-saving technologies at field scale because increased return flow from newly irrigated fields surpasses the reduced soil evaporation from old, irrigated fields, whereas regionally, return flow to fresh aquifers is a benefit rather than a loss, which results in some water savings. At the same time, increased crop transpiration exceeds regional water savings, which explains the paradox between the wide application of water-saving technologies and more severe regional water shortage. With nonscientific decisions on when and where to irrigate practiced by most farmers worldwide, scheduling remains the top priority task in field irrigation, as both too little and too much water leads to yield decreases and loss of nutrients to the environment. Where water is abundant, scheduling aims to keep crop transpiration and yield at a maximum with minimum use of irrigation water. In dryer areas, this luxury can rarely be sustained unless the irrigation area and therefore production is reduced. Instead, regulated deficit irrigation may be practiced on drought-tolerant crops and cultivars. Regulated deficit irrigation seeks to limit crop transpiration to a fraction of the maximum during less drought-sensitive growth stages. In this way, crop water use efficiency increases, and yield per m3 of water rather than m2 of land is maximized. Remote sensing of soil and crops through satellite and aerial multispectral and thermal products have the potential to enhance irrigation scheduling by precisely quantifying and distinguishing crop transpiration (beneficial water consumption) from soil evaporation (nonbeneficial water loss) in space and time and to facilitate regulated deficit irrigation and other water-saving measures. However, irrigation management significantly falls behind in adapting state of the art information and communication technologies. With a global rise in frequency and duration of droughts, the lack of irrigation infrastructure in humid regions and of water availability in semiarid regions induces enormous losses in agricultural production and social well-being and unveils an urgent need for a macrolevel drought governance approach in order to strengthen multisectoral water management and mitigate climate change damage to human and natural assets.

During the Early Agricultural period (2100 BC–AD 50), preceramic farmers in the Sonoran Desert invested considerable labor in canal-irrigated field systems while remaining very residentially mobile. The degree to which they exercised formal systems of land tenure, or organized their communities above the household level, remains contested. This article discusses the spatial and social organization of Early Cienega–phase settlements in the Los Pozos site group, an Early Agricultural site complex located along the Santa Cruz River in southern Arizona. At Los Pozos, the formal spatial organization of seasonal farmsteads suggests that despite continued residential mobility, multihousehold lineages maintained distinct territories. Enduring “house groups”—likely lineal groups—are associated with disproportionately large cemeteries, suggesting the revisitation of ancestral territory through occupational hiatuses. However, variability in the formality and permanence of Early Cienega–phase settlements throughout the region indicates a flexible continuum of occupational mobility. These higher-order affiliations were only expressed in persistent settlements near highly productive farmland, where the relative priority of households over improved land might be contested.

Chemical characterization and adsorption of oil mill wastewater on Moroccan clay in order to be used in the agricultural field

Correspondence: Min Qin (mqin@aiofm.ac.cn) Nitrous acid (HONO) and nitrogen oxides (NOx) play a crucial role in tropospheric photochemistry by contributing to the hydroxyl radical (OH) and influencing atmospheric oxidization capacity. Recent research has found that soil HONO emissions are considered to be the main source of atmospheric HONO. Here, an aerodynamic gradient (AG) method combined with a BroadBand Cavity Enhanced Absorption Spectrometer (BBCEAS) system was developed to measure HONO and NOx emission flux from agricultural fields in the Huaihe River Basin. Measurements were taken at two different heights and included various agricultural management activities such as rotary tillage, flood irrigation, fertilization, transplanting rice seedlings, and top-dressing. For HONO and NO, upward fluxes were observed (0.07 ± 0.22 and 0.19 ± 0.53 nmol /(m2·s)), while NO2 was deposited to the ground (-0.37 ± 0.47 nmol /(m2·s)). The maximum emission fluxes of HONO and NO occurred at around 24°C, which is close to the optimal temperature (25°C) for soil microbial nitrification processes. This indicates that surface microbial processes may contribute to gas emissions. Specifically, during rotary tillage, continuous peaks in HONO flux and NO flux were observed. POH(HONO)net and POH(O3)net were 1.42 ppb/h and 1.35 ppb/h, respectively, with HONO and O3 photolysis accounted for 51% and 49% of the total yield. The peak of POH(HONO)net coincides with the peak of HONO emissions from agricultural fields, revealing the significant contribution of agricultural HONO emissions to atmospheric oxidizing capacity. After irrigation in agricultural fields, the increase in soil moisture content (~80% water filled pore space) restricts oxygen availability, thereby suppressing the HONO emission. Overall, this study provides valuable insights into the dynamics of soil HONO and NOx emissions in agricultural fields, shedding light on their environmental implications and the role of agricultural activities in atmospheric chemistry. Acknowledgments: This work was supported by the National Natural Science Foundation of China (U21A2028) and the National key Reearch and Development Program of China (2022YFC3701100).  

Although advances in remote sensing have enhanced mapping and monitoring of irrigated areas, producing accurate cropping information through satellite image classification remains elusive due to the complexity of landscapes, changes in reflectance of different land-covers, the remote sensing data selected, and image processing methods used, among others. This study extracted agricultural fields in the former homelands of Venda and Gazankulu in Limpopo Province, South Africa. Landsat 8 imageries for 2015 were used, applying the maximum likelihood supervised classifier to delineate the agricultural fields. The normalized difference vegetation index (NDVI) applied on Landsat imageries on the mapped fields during the dry season (July to August) was used to identify irrigated areas, because years of satellite data analysis suggest that healthy crop conditions during dry seasons are only possible with irrigation. Ground truth points totaling 137 were collected during fieldwork for pre-processing and accuracy assessment. An accuracy of 96% was achieved on the mapped agricultural fields, yet the irrigated area map produced an initial accuracy of only 71%. This study explains and improves the 29% error margin from the irrigated areas. Accuracy was enhanced through post-classification correction (PCC) using 74 post-classification points randomly selected from the 2015 irrigated area map. High resolution aerial photographs of the 74 sample fields were acquired by an unmanned aerial vehicle (UAV) to give a clearer picture of the irrigated fields. The analysis shows that mapped irrigated fields that presented anomalies included abandoned croplands that had green invasive alien species or abandoned fruit plantations that had high NDVI values. The PCC analysis improved irrigated area mapping accuracy from 71% to 95%.

La Playa (SON:F:10:3) is an archaeological site in Sonora, Mexico that contains the remains of an extensive preceramic earthen irrigation canal system. Modern floodplain erosion has destroyed the majority of these canals, but geoarchaeological investigations on areas of the system that remain reveal much about this early agricultural technology. Comprehensive dating using accelerator mass spectrometry14C on gastropods, charcoal, and soil humates and single‐grain optically stimulated luminescence (OSL) dating on canal sediments revealed that multiple irrigation systems were used at La Playa during at least two periods during the Early Agricultural period (~750–350 B.C. and ~ A.D. 50–250).14C and OSL age estimates from canals are in agreement with the earliest direct dates on maize from La Playa (A.D. 20–240), indicating that the introduction of maize corresponds to a significant investment in the modification of the floodplain environment for canal irrigation. The late phase of canal use (~A.D. 50–250) occurs before destructive floodplain erosion at the site. This is contemporaneous with local cultural changes, including the development of a new ceramic tradition, changes in burial practices, and changing subsistence strategies. These results demonstrate the utility of the combined14C and OSL approach for dating ancient earthen canals.