Argentine Pampas Research Articles

Histotaphonomy of a Pleistocene megamammal assemblage from Argentine Pampas

This work involves a multy-proxy approach of taphonomic features of the extinct giant ground sloth Lestodon armatus (Xenarthra, Mylodontidae). The study is based on paleohistological, mineralogical, and geochemical analyses from the Late Pleistocene Playa del Barco site (Buenos Aires Province, Argentina). Transverse thin sections of ribs and vertebrae were studied under light microscope, polarizing petrographic microscope, and scanning electron microscope (SEM), combined with chemical analysis using energy dispersive spectroscopy (EDS) and micro-X-ray diffraction (μXRD). The internal crystalline structure and mineral composition remains almost unaltered. The bone microstructure is well preserved in all the samples, although it was affected by different types of microfractures and infillings. Numerous radial microcracks were identified in the secondary osteons of all specimens evidencing wet depositional environment. The mineralogical and geochemical composition of the infillings and encrustations indicates that the enrichment with new elements was due to direct exchange with the sediments in which they were buried. Mineralogical evidence from the infillings allows to identify different diagenetic pathways; most of the skeletal elements were quickly buried in the vadose zone, while others were buried in the phreatic zone, directly or after some time immersed in a continental aquatic context. The fossildiagenetic information obtained from the Lestodon armatus fossils provides novel information to interpret and reconstruct the whole taphonomic history and the environmental and climatic conditions that favored the preservation of the Playa del Barco fossil assemblage during the end of the Last Glacial Maximum.

Soybean seed yield and protein response to crop rotation and fertilization strategies in previous seasons

Annual crops dominate Argentinean landscapes with a majority of fields dedicated to soybean production. Consecutive years with full-season soybean crops are frequent and this practice is associated with organic carbon losses affecting soil chemical and physical properties. It is proposed that more intensive and diverse cropping sequences coupled with targeted fertilization may allow keeping near-neutral nutrient and carbon balances while improving successive crops performance. We conducted four on–farm experiments along six seasons in the Argentine Pampas where three crop rotations and two fertilization strategies (high and regular rates of N, P, and S) were evaluated. Crop rotations involved were i) soybean monoculture, ii) a typical wheat-soybean/maize/soybean rotation, and iii) a more intensified rotation consisting of wheat-soybean/field pea-maize/soybean. After five years, soil organic carbon was consistently lower under soybean monoculture compared to that under more intensive and diverse rotations. During the sixth and last season, identically managed soybean crops were grown in all treatments to determine the influence of previous management history on soil, plant nutrients, and on crop performance. Results indicate that crop rotation largely influenced soybean seed yield (range from 120 to 690 kg ha−1 yield increase) mainly through changes in water use affecting solar radiation interception and, by a lesser extent, the conversion efficiency of radiation into biomass and partition to seeds. Comparatively, increased fertilization rates in preceding seasons resulted in a lower seed yield response (range from nil to 180 kg ha−1), which indicates that fertilization strategies alone are ineffective to restore productivity levels after years of soybean monoculture. However, in most cases, the high fertilization strategy in previous seasons resulted in greater soybean protein concentration in seeds and in overall protein yield.

Medium-term fertilization strategies on extensive grain cropping systems under water table influence

CONTEXTHistorical increases in grain yields have been associated with an undermining of soil organic matter (SOM) and a reduction of nutrient cycling capacity. Nutrient limitations for grain crop production are ubiquitous, and while yield and economic response to fertilization has been exhaustively evaluated on several crops across different environments, the focus has been mainly on individual crops rather than on the cropping system. Benefits of increased fertilization beyond a single cropping season need to be assessed to help preventing the current soil nutrient mining process in the Argentine Pampas. OBJECTIVESi) Evaluate the effect of different fertilization strategies over crop yields across rotation cycles and locations (and their interactions); ii) determine the relationship between crop yield response to fertilization and the physical and chemical soil variables; iii) evaluate the economic profit of each fertilization strategy; and iv) determine the residual effect on a soybean crop after six years following different fertilization strategies. METHODSThe study was conducted across environments in the Salado “A” Basin of the Inland Pampas of Argentina and included seven experiments with a crop rotation of soybean - wheat/second soybean - maize that was managed with different fertilization strategies (with increasing levels of nitrogen N, phosphorus P, and sulfur S), including a non-fertilized control, along six seasons. Additionally, an extra soybean crop was grown in the seventh year to determine the residual influence of previously imposed fertilization treatments. RESULTS AND CONCLUSIONSThe yield response to fertilization was highest under the more intensified treatments and larger for wheat (up to 150%) and maize (up to 100%) than for soybean (up to 40%) and second soybean (up to 30%). Overall crop yield response to increasing N and P inputs was negatively correlated with initial soil extractable P while the response to S was higher in sites with high proportion of sand and low SOM. The economic profit increased as fertilization was intensified although differences were not always significant across treatments within sites. On average, intensification resulted in an additional profit of U$S187 ha−1 compared to the typical fertilization strategy followed by farmers in the area without considering a residual positive yield response (10–13%) observed in a successive soybean crop. SIGNIFICANCEThis study provided elements to improve the understanding of complex interactions determining crop yield response to fertilization strategies to help optimizing long-term management decisions affecting the cropping systems with large impact at regional level.

Transformation of tall-tussock grasslands and soil water dynamics in the Flooding Pampa

Cow-calf production is the main practice within marginal agricultural lands of the world, like the Flooding Pampa of Argentina, where it promotes the transformation of native tall-tussock grasslands Paspalum quadrifarium into native short-grass grasslands or sown pastures. The effect of these land use changes on water dynamics are not well understood, especially in regions subjected to marked interannual drought and flooding cycles. Here we measured soil properties (infiltration rate, bulk density and soil organic matter), rainfall interception by the canopy, and soil moisture during two years with different annual rainfall. Then, we parameterized a hydrological model (HYDRUS) for inferring consequences of soil water fluxes on water regulation. Infiltration rate was significantly higher in native tall-tussock grasslands than native short-grass grasslands and sown pastures, bulk density was significantly lower in native tall-tussock grasslands than native short-grass grasslands and sown pastures, and soil organic matter was significantly higher in native tall-tussock grasslands than sown pastures. Simulated water dynamics during years of low annual precipitation (summer rainfall deficit), show that transpiration and evaporation from native short-grass grasslands represented 59 % and 23 % of total water balance, whereas transpiration and evaporation from native tall-tussock grasslands represented 70 % and 12 %, respectively. This result reflects the high productive capacity of native tall-tussock grasslands under dry conditions. In contrast, under high annual precipitation (excess during fall and winter), transpiration and evaporation from native short-grass grasslands represented 48 % and 26 % of total water balance, whereas in native tall-tussock grasslands represented 35 % and 9 %, respectively. These results suggest a low capacity of native tall-tussock grasslands to evacuate water excess, especially during fall and winter. The observed differences in water fluxes between native tall-tussock grasslands and native short-grass grasslands are important to understand water dynamics under different climatic conditions and could be useful for adaptation to climate change through ecosystem-based management.

Rural Landscape Simplification and Provision of Cultural Ecosystem Services. A Case Study in the Argentine Pampas

In recent decades, the rural landscape of the Argentine Pampas has undergone a process of simplification due to the increased land allocated to crops, replacing pastures and grasslands, with a substantial increase in soybean area. In 2016-2017, a survey was conducted to analyze changes in cultural ecosystem services in this region. Pergamino citizens relate landscape improvement in terms of aesthetic and recreational values to increasing its complexity since they prefer more winter crops, grazing areas, native vegetation, trees, and birds. The significant relationship between sociodemographic variables and preferences for landscape attributes is consistent with the notion that aesthetic perception is constructed from personal experiences and background.

Outdoor culture of Halamphora coffeaeformis in the semi-arid Pampa of Argentina: A comprehensive analysis of triacylglycerol production for biodiesel

The feasibility of microalgal triacylglycerol (TAG) production for biodiesel remains constrained by high production costs under outdoor conditions. The aim of this study was to evaluate the capacity of an Argentinian strain of the diatom Halamphora coffeaeformis grown in outdoor raceway ponds to produce TAG suitable for biodiesel. The strain was cultured in seawater enriched with a biofertilizer during summer and spring in the semi-arid Pampa of Argentina. The following variables were analysed: 1) growth rate; 2) TAG accumulation; 3) lipid content and quality; 4) dissolved nutrient and physicochemical properties; and 5) climatic conditions. Intracellular TAG accumulation was evaluated with fluorometry by Nile Red. The growth rate and biomass productivity of the species were similar in the two seasons, with approximate values of 1.35 div. day−1 and 61.25 kg.ha−1.day−1, respectively. Total lipid content increased about 4-fold with respect to inocula in the 2 cultures, reaching up to 44.7 % ash free dry weight (AFDW) in summer and 36.4 % AFDW in spring. However, lipid accumulation differed between seasons: neutral lipid accumulation began at 8 days of cultivation in summer and at 19 days in spring. Salinity was the main stressor that accelerated the TAG accumulation in the species, the nutrient levels did not reach limiting values. In spring, precipitation decreased salinity levels, reducing stress and delaying the onset of TAG accumulation. The biodiesel properties inferred from the fatty acid profile of the species meet international standards and their quality ensures good performance in cold climates. Furthermore, the reported lipid productivity of the species (~25.6 kg.ha−1.day−1) is higher than that of the soybean oil used commercially for biodiesel. Based on the results obtained, H. coffeaeformis has potential for exploitation as a renewable source of TAG for biodiesel production in arid and semi-arid environments with access to brackish or marine water.

Short-Term Effects of Cover Crops on Soil Physical, Chemical, and Biological Properties in the Southeastern Argentinean Pampas

ABSTRACT Cover crop (CC) inclusion in cropping sequences could ameliorate negative effects of continuous agriculture on soil properties. The use of CC as a sustainable management tool can reverse the soil degradation process and improve soil health in the short term. The present study evaluated soil properties following short-term cover cropping in on-farm conditions. Three strip-trial experiments were conducted. Treatments were: i) oat (Avena sativa), ii) vetch (Vicia villosa), and iii) control (without CC). Prior to CC chemical termination, shoot and root dry matter (DM) and DM nitrogen accumulation in CC shoot (Nac) were determined. After CC termination, we determined: soil bulk density (BD), penetration resistance (PR), infiltration (INF), aggregate stability, total and particulate organic carbon (POC), organic nitrogen, nitrogen mineralized in anaerobic incubation (Nan) and soil glomalin. On average across sites, grater shoot, and root DM were determined in oat than vetch, while Nac was greater in vetch. The POC and Nan increased by CC inclusion mainly in 0–5 cm soil depth. Improvements of over 50% in INF (0–20 cm) and 8% in BD (0–5 cm) were determined in CC treatments compared to control. The effects of CC on some soil parameters depended on the previous management practices (i.e. tillage system, crop sequences). In the short-term, CC inclusion improves some soil properties, depending on their sensibility to management practices.

Maize (Zea Mays L.) Yield Estimation Using High Spatial and Temporal Resolution Sentinel-2 Remote Sensing Data

ABSTRACT Maize (Zea mays L.) is one of the world’s most important annual cereal crops and its yield can be estimated for a wide variety of purposes. The objective of this work is to evaluate in which stage of crop the best fit between remote sensing data and real yield occurs to predict yield in corn seed crops. For this, polynomial regression models were used between spectral indices of vegetation and real yield in 10 days time’s windows covering the critical period for generation of performance. Subsequently, the predictive capacity of the best goodness of fit model was evaluated by comparing estimates with those made using a conventional field estimation method. This experiment was carried out in production fields located in Tandil and Loberia district inside of the Argentine Pampas Region in southeast of Buenos Aires province in summer (from january to march) of 2020. We found the highest level of adjustment between vegetal index and real yield (R2 = 0.91) in the time window of 110 to 120 days after sowing (DAS) corresponding to the end of the critical period. Then, the predictive performance was evaluated, satellite model shows an underestimation of 53 kg/ha (0.72% relative error) while the conventional method underestimated by 955 kg/ha (13% relative error). A close relationship between remote sensing data and grain yield at the end of the critical period of maize can be evidenced, and this information can be used to predict yield early in the southeast of Buenos Aires province. Using the methodology here developed it is recommended to analyze- time series of satellite vegetal index in maize crops in other regions and climates to make more robust the yield prediction system.

Rural Women Redefining Care and Agency in the Argentine Pampas

This article provides an ethnographic analysis of the agency of women who reside in the rural areas of the Argentine Pampas, based on their promotion and production of agroecological family horticulture. The recognition of these women’s agency through care – care of their children, global care, and green care – offers a significant challenge to some metrocentric and Eurocentric feminist perspectives that claim care work can only be oppressive for women. The first of these types of care empowers women to improve the nutrition of their children. It also relates to another underlying type of care, which is to provide a sufficiently robust education as to ensure their children have a better and alternative future. The second type of care has the power to socially transform the territorial space of the district’s countryside and its marginalized populations which, through care, acquire greater public and political attention. The third type of care empowers women to transform and care for the environment, and is exercised by not using pesticides in horticultural production and by disseminating knowledge on the matter. In line with discussions of postcolonial feminism (Abu-Lughod, 1986; Mahmood, 2001; Suárez Navaz, 2008), I argue that certain properties that are attributed to women relative to caregiving – by way of a dichotomous view of gender relations – fuel their agency: for these women the cultivation of vegetables is a form of agency that actively combats food, training and labor inequality.

The potential of glomalin-related soil proteins as a sensitive indicator of changes in different cropping systems in the Argentine Pampas

The potential of glomalin-related soil proteins as a sensitive indicator of changes in different cropping systems in the Argentine Pampas

The expansion of rainfed grain production can generate spontaneous hydrological changes that reduce climate sensitivity

As global warming intensifies climatic extremes, the need to understand their effects on farming systems, particularly under rainfed conditions, grows. During the last three decades the Argentine Pampas, a major global grain exporter, hosted an unprecedented expansion of cultivation under unirrigated and undrained conditions. Simultaneously, the extreme flatness and lack of water infrastructure favored groundwater level raises where agriculture expanded. However, the effect of climate extremes and elevated water tables buffering droughts but increasing flooding risk on the sensitivity of regional grain production remains unknown. Based on agronomic, weather, water table, and remote sensing data, we analyzed the production response to dry, wet, and flooded periods over the last 35 years, and to the ongoing water table raises during the last 15 years, focusing on sown and effective harvested area (harvested/sown area) and yield. Soybean and maize production increased 5.9 and 3.3-fold, respectively, as a result of area and yield growths. On average, droughts decreased production (−25 % for soybean and −14 % for maize) and wet periods increased it (+14 % for soybean and +17 % for maize) through their effects on yields and effective harvested area. Floods reduced production (−8 % for soybean and −10 % for maize) by decreasing sown and effective harvested area, leaving yields unaffected. As water tables rose, a positive yield effect during drought was detected, with counties with shallow water tables (< 3 m depth) halving yield cuts during dry years. Lacking water infrastructure, this South American grain belt is currently matching the annual production variability levels observed under intense irrigation and drainage in North America. The unexpected water table level raises of the Pampas had an overall positive effect on grain production, with flood disruptions being more than compensated by drought buffering. This balance may change in the future, calling for a deeper understanding of these complex relationships between climate, hydrology and agriculture.

Croplands in the Pampas of Argentina will become an atmospheric carbon sink in coming decades

Due to the possibility of using cultivated soils as atmospheric carbon sinks, studies are being carried out worldwide to estimate the potential of carbon sequestration in agricultural areas. In the Pampas, the soil organic carbon (SOC) stock has been calculated at regional scale but its temporal dynamic is unknown. Using information on land cover, yield trends of the main crops, SOC stocks at year 2008 and the AMG model validated with local experiments, the SOC balance of croplands in the Pampas was calculated between 2008 and 2050. Carbon inputs from grain crops were calculated using results of experimental field networks carried out in the Pampas and local coefficients were calculated for the effects of the cultivation of pastures and the adoption of cover crops on SOC. Between 2008 and 2025, the SOC balance of cultivated soils changed from slightly negative to nearly steady state as result of increases in yield and higher carbon inputs. If current rotations are maintained and the rate of increased crop productivity does not stagnate, the Pampas will become an atmospheric carbon sink between 2025 and 2050 as a result of the higher carbon inputs of crops. The adoption of cover crops will improve the balance of SOC but the main tool for sequestering carbon in soils is the replacement of part of the large area cultivated with soybean by greater biomass crops such as corn or the double crop in a year wheat/soybean. Soybean replacement will almost double the carbon sequestration rate compared to the current management and allow attaining the 4‰ goal around 2050. Pampean croplands could represent a sink for atmospheric carbon in the coming years and the management applied can determine how important the sink would be.

How much carbon do Argentine Pampas Pinus radiata plantations store?

Aim of study: To quantify the biomass and carbon stored in the main ecosystem components in Pinus radiata D. Don plantations across an age sequence in the Pampean region of Argentina.&#x0D; Area of study: Plantations were established on non-agricultural land, southeast of the province of Buenos Aires.&#x0D; Material and methods: Fourteen sites were selected of Pinus radiata plantations, 9-, 13-, 15-, 19- and 21-years-old, in a first forest rotation. Forty-two trees were destructively sampled, allometric functions were set and biomass was estimated for the different compartments (needles, branches, stem). Root biomass was estimated from equations adjusted by the sampling of twenty-four trees. At 4 sites, C-stock was determined in the tree component, in the forest floor and understory, and soil organic carbon (SOC) was determined to a 50 cm depth.&#x0D; Main results: C-stock in the tree component increased with stand age, whereas SOC and C-stock in the forest floor and understory were not related to stand age. The system-level C-stock was 273.1, 263.7, 269.7 and 324.1 Mg ha-1 for the 9-, 13-, 19- and 21-year-old stands. On average, 69% of the total system-level C-stock was in the soil, while 28% was in the tree biomass and 3% was in the forest floor and understory.&#x0D; Research highlights: The forestry component contributed to C sequestration with no changes in SOC-stocks reserves for the age range studied.

Are service crops an alternative for mitigating N2 O emissions in soybean crops in the Argentinian Pampas?

Service crops (or cover crops) play an important role in simplified agricultural systems. Service crops reduce agricultural external inputs and increase ecosystem services but their ability to mitigate nitrous oxide (N2 O) emissions is still uncertain. The main objective of this study was to evaluate N2 O emissions in soybean-soybean (Glycine max [L.] Merr) rotations that included different service crops. Treatments included continuous soybean with winter fallow and soybean with three service crops: oat (Avena sativa L.), vetch (Vicia villosa Roth.), and a mixture of oat and vetch in a randomized complete block design. Service crops were sown 2 months after soybean harvest and were terminated 2 months before soybean planting. Nitrous oxide emissions were determined during the fourth year of the field experiment. We found that service crops did not significantly affect overall mean N2 O emission rates, with mean emission rates from the fallow, oat, vetch, and oat-vetch treatments of 1.82±0.35, 1.95±0.34, 2.71±0.43, and 2.42±0.42 kg N2 O-N ha-1 per year, respectively. Service crops with low C/N ratios (vetch and oat-vetch mixtures) significantly increased N2 O emissions in spring, after their termination. Overall, soil inorganic N content (NO3 - or NH4 + ) was the main driver that explained the N2 O emissions from different treatments, whereas water-filled pore space controlled the temporal variability of emissions. Our results suggest that service crops with a very short growing season may increase soil N availability for cash crops, but do not reduce N2 O emissions due to long periods of high N availability without crops.

Materiality and Images: Ameghino’s Collection of La Antigüedad del Hombre en el Plata in the La Plata Museum

Florentino Ameghino’s works were fundamental for archeology in Argentina. His first collections were shown in the book La antigüedad del hombre en el Plata {Antiquity of Man in the La Plata Basin} (1880–1881), a synthesis of the previous prehistoric studies whose purpose was arguing in favor of an ancient antiquity of the human occupation in the Argentine Pampas, which granted his archeological investigations international recognition. In this article, we present the first results of a comprehensive study on the aforementioned collection, which is currently in the Archeology Division of the La Plata Museum. We identified the pieces based on the published images, we analyzed the lithic and ceramic artifacts and bone remains, and we contextualized the information on the archeological sites from which they came. We recognized the importance of the collection for this investigation and for its conservation, acknowledging work practices related to the identification, classification and communication processes of the materials in the early days of this discipline. The revision of this museum collection shows the constructive nature of the cultural heritage, reflecting on the subjects, wisdoms, and actions that take part in their furtherance throughout time.

Landscape configuration is an important predictor of sunflower yield in the Argentinean Pampas Region

Conventional agriculture is frequently associated with large-scale environmental degradation andlandscape homogenization. In contrast, ecological intensification incorporates natural habitat conservationand landscape complexity to improve important ecosystem services such as pollination and crop yields. Inan observational study of 105 fields in the Argentinean Pampas Region, we explored whether sunfloweryields were related to landscape composition (percentage of natural habitat) and configuration (field size andedge density), and covariates of agricultural management practices such as nitrogen fertilizer addition, seeddensity, sowing date and crop cultivar. Our mixed-effects models revealed that field size and edge densitiesbetween crop and natural habitat are important predictors of yield. For example, a doubling of edge densityfrom 40 m/ha to 80 m/ha predicted an 11.3% (269 kg/ha) yield increase, while a doubling in the field size from40 ha to 80 ha predicted a 6.1% (149 kg/ha) yield decrease. We suggest that pollination is an important driverof both effects as higher edge densities and smaller field sizes reduce wild pollinator flight distances to cropflowers and thus increases the chances for effective crop pollination. This study provides key information forsustainable management of sunflower agroecosystems.

Technological and Social Strategies for the Acquisition and Exploitation of Long-Distance Lithic Raw Materials in the Central Pampean Dunefields of Argentina

ABSTRACT The lithic raw material sources in the Pampas of Argentina present a very restricted distribution. This has generated various scenarios linked with the acquisition and conveyance of stones carried out by human groups in the past. We explore the mechanisms performed in the procurement, transport and exploitation of rocks by those hunter-gatherer societies that inhabited the Central Pampean Dunefields, an area where lithic resources are absent. The results obtained from five lithic assemblages from the Middle and Late Holocene points to a preference in the exploitation of Tandilia Hills stones through both periods, with an increase in rock diversity in the Late Holocene. Our data indicate a direct procurement of orthoquartzite and chert from Tandilia Hills, although the acquisition of the rest of the raw materials could have involved both direct and indirect procurement. These results may be related to the existence of more fluent exchange networks among Pampas hunter-gatherer groups.

Grain yield, yield components and nitrogen economy of irrigated second-crop common Buckwheat (Fagopyrum esculentum Moench) in a cold-temperate region

Common buckwheat (Fagopyrum esculentum Moench) is a species with great nutritional value and promising to be cultivated as a second crop in irrigated fields of cold-temperate regions with short growing seasons. However, little information exists regarding the nitrogen (N) economy of common buckwheat as a second crop following a high-yielding winter cereal. This study aimed to quantify grain yield, its components, and the grain protein content, and to evaluate N economy processes such as the initial N use efficiency (INUE), the N uptake efficiency (NUptE), the N internal efficiency (NIE) for biomass and grain yield and the N harvest index (NHI) among different treatments of N availability at sowing in four site-year experiments of common buckwheat as a second crop in irrigated fields of the southwestern Pampas of Argentina. The variety Mancan, used in this study, lasted between 73 and 92 days (888–1073 °C days) from sowing to harvest. Grain yield was highly correlated with achene number but not with achene weight. Grain yield ranged from 405 to 2725 kg ha-1, with an interaction between treatments and experiments, with major differences among experiments and minor differences among N availability treatments. Relative N uptake was maximized at a higher value of N availability (160 kg N ha-1) than grain yield (50 kg N ha-1), associated with higher responses of N uptake, vegetative N uptake and grain protein content than grain yield to N availability. However, NUptE featured a negative response to N availability in all experiments. NHI was highly variable among experiments, ranged between 0.51 and 0.83 and was affected by N availability in only two experiments. NIE for biomass and grain yield were 80 kg kg-1 and 36 kg kg-1, respectively, which were lower than those of most cereals but higher than those of other non-cereal grain crops. A short crop cycle of the variety Mancan, an average grain yield of 1594 kg ha-1 among experiments in this study, a low N availability requirement to maximize grain yield and high values of NIE for biomass and for grain yield suggest that buckwheat is a promising species for second crop sowing in cold-temperate regions.

Cation nutrient reserves decline markedly under intensive cropping of Pampas Mollisols

The availability of exchangeable cationic nutrients in soils, such as calcium (Cae), magnesium (Mge), and potassium (Ke), is vital for crops growth and development. However, the concentration of these nutrients can be diminished by land use and management practices. The objectives of this study were i) to determine the concentration of Cae, Mge, and Ke in uncropped soils or soils under continuous agriculture, ii) to determine the Cae, Mge and Ke decrease rate due to agriculture (dCae, dMge, and dKe, respectively), iii) to evaluate the relative contribution of edaphoclimatic and farming variables on dCae, dMge, and dKe, and iv) to evaluate the spatial variability of Cae, Mge, and Ke. Surface soil samples (0–20 cm layer) were taken in 2011 and 2018 at geo-referenced sampling locations within 507 agricultural production fields (AGR2011 and AGR2018) from the Argentinean Pampas region (PR). Additionally, surface soil samples were taken from areas under gramineous vegetation that had never been cropped at each sampling point. Path analysis explained 58, 42, and 56 % of the variability on dCae, dMge and dKe between 2011 and 2018, respectively. The main factors determining the depletion of these nutrients were the soybean relative harvested area for dCae, magnesium concentration in 2011 for dMge, and rainfall for dKe. The spatial variation of Cae, Mge, and Ke increased with the history of agricultural use of soils, particularly in the case of Ke and Mge. If the depletion of exchangeable cationic nutrients in the PR continues at current rates, their deficiencies for the main crops could become evident in the medium/short term, depending on the area. For this reason, it is necessary to continue surveying the evolution of soil Cae, Mge and Ke over time in the PR and other areas in the world with similar edaphoclimatic conditions.

Abrigo 1, Cerro El Sombrero: An Early Site in Eastern Argentina

ABSTRACT Late Pleistocene human occupations are well represented in the Tandilia Range, Argentine Pampas. Abrigo 1 is a small shelter in close relation to the main and better-known site on the hilltop of Cerro El Sombrero, with both sites including Fishtail points. The oldest levels at the shelter dated to 13,000–12,000 calendar years ago and yielded two Fishtail points. This paper deals with the analysis of the sedimentary context, stratigraphy, artifact distribution, and site formation processes at Abrigo 1. The sedimentary record is dominantly composed of geogenic sediments with a minor participation of anthropogenic material, mainly lithic artifacts. The geogenic input includes sediments coming from the physical and chemical weathering of the rockshelter’s quartzites and windblown sediments. Pedogenesis is the prevailing site formation process. Artifact distribution, the homogeneity of the assemblage, and refitting are considered relevant to assess site integrity. The results are compared to other early cultural contexts of the immediate vicinity.