Soil Mapping Units Research Articles

Assessing geopedological soil mapping approach by statistical and geostatistical methods: A case study in the Borujen region, Central Iran

Geopedology, using geomorphologic and supervised classification bases, has been proposed as a soil surveying method. It undertakes a systematic approach to map soilscapes. This approach tries to reduce the budget of accomplishing soil surveys as well as increasing the purity of mapping units. But to what extent it has been succeeded is the question. The main objective of this research was to validate the geopedological mapping methodology by statistical and geostatistical methods in the Borujen region, Central Iran. After a primary interpretation of the study area on air photos (1:20 000 scale), 94 pedons were excavated on a 125 m square sampling grid in the sample area for geostatistical studies. To achieve the statistical aims, a geomorphic unit which encompassed the maximum surface of the sample area (and also the study area) was selected and the biggest delineation of this unit with 19 pedons was considered. The credibility of generalizing the results of the geopedological approach for the studied unit was tested by comparison with 15 pedons in a similar unit outside the sample area, named the validation area. Properties of the soils, including percentage of clay, rock fragments (2–75 mm) and total carbonates in the soil family control section, percentage of organic matter in the A horizon and its thickness, were selected for statistical and geostatistical analyses. Univariate and multivariate statistical analyses obtained from the units in the sample and the validation areas, showed that the means of soil variables were similar. A high difference between A horizon thickness variances in the sample area and the validation area affected the significance of the variation test in the univariate and multivariate results. Our study demonstrated that, when comparing the same factors from sample and validation areas, the spatial distribution and spatial dependency level of soil attributes were different. Therefore, although the geopedological approach tries to distinguish more homogeneous soil mapping units, it is still not able to fully define and represent the real variability of soil properties and show the chaotic behavior or nature of the soils. We recommend further investigations on different techniques of stratifying the landscape in order to better analyze and understand the soil-forming processes and the nature of soil variability and to improve sampling and mapping approaches. We suggest that the additional determination of the phases of landforms and phases of soil series will improve mapping in the future.

Reservas de materia orgánica en suelos y distribución espacial en la cuenca del Río Grande de Arecibo

Se estudió la influencia de los factores orden de suelo, fase y uso de terreno sobre la distribución espacial del carbono orgánico (SOC) y nitrógeno total del suelo (SON) en la cuenca del Río Grande de Arecibo, Puerto Rico. Los objetivos eran cuantificar las reservas de C y N en suelos y el potencial de secuestro de C de la cuenca. Se tomaron muestras de suelos representativos de la cuenca de un área de 39,361 ha (o 87.3% de la totalidad del área de la cuenca) bajo bosque secundario, pastura y uso agrícola. Los suelos de la cuenca almacenan 5.02 x 10s Mg de SOC y 0.48 x 10s Mg de SON a una profundidad de 100 cm. Las medias ponderadas de SOC y SON a 15 cm de profundidad fueron 4.33 kg C/m2 y 0.390 kg N/m2, respectivamente, y a una profundidad de 100 cm fueron de 11.13 kg C/m2 y 1.08 kg N/m2, respectivamente. La interacción entre unidad de mapa y uso de terreno representó el mejor estimado de SOC por la mayor resolución espacial. Suelos bajo bosque secundario y pasturas tuvieron mayor SOC (12.8 y 9.79 kg C/m2, respectivamente)(P < 0.05) que suelos bajo uso agrícola (7.90 kg C/m2) a una profundidad de 100 cm. El SOC a una profundidad de 15 cm fue similar entre Oxisoles y Ultisoles, los que juntos fueron mayores que los Inceptisoles con valores de 5.85, 4.77, y 3.18 kg C/m2, respectivamente. Estimamos que la cuenca puede secuestrar 46,627 Mg C adicionales, lo cual representa un aumento de 1.0% sobre el nivel actual de C.

Land Management Effects on Near‐Surface Soil Properties of Southeastern U.S. Coastal Plain Kandiudults

The National Cooperative Soil Survey is evaluating techniques for better characterization of near‐surface, management‐dependent soil properties associated with soil change (decade to century time scale). The U.S. Soil Taxonomy and soil surveys have been developed with emphasis on subsoil properties to reduce the impacts of management on taxonomic placement. Considering the importance of near‐surface properties on ecosystem function, however, some degree of characterization of these properties is essential. The objectives of this study were to evaluate land use effects on management‐dependent soil properties, C stocks, and soil quality of mature longleaf pine (Pinus palustris Miller) systems relative to more intensively cultivated land use systems in the southeastern U.S. Coastal Plain. Sites in Thomas County, Georgia, representing well‐drained, upland Kandiudults, were selected in each of three land use systems for comparison of near‐surface soil properties. Studied land use systems were mature, multi‐aged longleaf pine forest (LL), slash pine (Pinus elliottii Engelm.) plantation (PP), and conventional row crop (RC) systems. Concentrations of microbial biomass C (0–5 cm) in LL were 69% greater than RC, and LL sequestered 64% more total organic C than RC systems. Inputs of fertilizer were evident in RC (0–30 cm) based on greater exchangeable K (433% greater in LL), base saturation, and extractable P (1700% greater in LL). The soil infiltration rate was 1015% greater in LL than in PP. Principal component analyses indicated that 80% of data variability was explained by exchangeable bases, C pools, and hydraulic soil properties. Clustering suggested that near‐surface soil properties were more similar by land use than by taxonomic‐based soil map units. Land use changed many of the investigated surface soil properties (0–30 cm) at these Coastal Plain sites, resulting in functional and interpretive differences of these soils within similar taxa.

Mineração de dados para inferência de relações solo-paisagem em mapeamentos digitais de solo

O objetivo deste trabalho foi desenvolver uma metodologia para mapeamento digital de solos na escala 1:100.000 com a aplicação de técnicas de mineração de dados a descritores de relevo e a dados de mapas geológico e pedológico preexistentes. Foi criada uma base de dados digitais a partir de cartas topográficas e temáticas, que permitiu elaboração do modelo digital de elevação (MDE) da folha Dois Córregos, SP (escala 1:50.000). A partir do MDE, foram calculados os parâmetros geomorfométricos declividade, curvaturas em planta e perfil, área de contribuição e distância diagonal de drenagem. A matriz que associou esses dados georreferenciados foi analisada por meio de árvores de decisão, no ambiente de aprendizado de máquina Weka, o que gerou um modelo de predição de unidades de mapeamento de solos. A acurácia geral do modelo aumentou de 54 para 61% com a eliminação das classes com probabilidade nula de ocorrência. A associação da mineração de dados com sistemas de informações geográficas permite a elaboração de mapas digitais passíveis de uso em estudos que requeiram menor detalhamento que aqueles realizados com o mapa original.

Soil sampling based on field spatial variability of soil microbial indicators

Microbial indicators exhibit a high spatial heterogeneity which often masks comparison of the effects of different soil management treatments. It is therefore desirable to use a proper sampling design which integrates spatial heterogeneity at field level. Thus, the objectives were: (1) to study the spatial heterogeneity of biological and chemical soil variables, and (2) with obtained maps of spatial variability to test different sampling strategies to assess the usefulness of this ‘new’ soil map unit. 63 soil samples were collected according to a 10 m × 10 m grid on a 0.48 ha plot. On each of these samples, 10 variables were measured: soil water content, cation exchange capacity (CEC), organic carbon (OC) and total nitrogen (N), C/N, soil microbial biomass (SMB), labile soil organic matter (LOM), mineralisable C (C min) and N (N min), inverse of specific respiratory activity (1/SRA = SBM/C min). The spatial heterogeneity of each variable was charted with geostatistics. The biological variables exhibited spatial variability of the same order of magnitude as physicochemical parameters. From the maps, zones with different levels of organic matter, microbial biomass and specific respiratory activity were identified. The spatial patterns of SMB and SRA were related to CEC (positively for SMB and negatively for SRA), pointing out the effects of soil protection on microbial biomass and availability of organic substrates. The definition of these zones for a pool of variables (OC, N, SMB, LOM, CEC) is useful at 3 levels: (1) to record the initial values of the measured variables for each plot, (2) to integrate these zones as blocks in experimental design for future experiments, and (3) to focus analysis of specific biological mechanisms such as activity of micro-organisms.

Utilization of remote sensing data and GIS tools for and use sustainability analysis: case study in El-Hammam area, Egypt

Abstract The North-Western Coast of Egypt (NWCE) represents one of the high priority regions for future development in the country. El-Hammam area is located in the NWCE with an area of 94752 acres and is one of the main challenging regions for sustaianble development. In this study, we have used remote sensing and soil data in combination with GIS tools, for land use sustainable analysis (SLU) in El-Hammam area. The SLU was established based on various factors such as: land capability and suitability, water resources availability, economic return from water and financial return from land and water. A physiographic soil map for the study area was prepared using remote sensing and GIS. Multiple field surveys were carried out for collecting information on various soil map units (SMUs) and their profiles. Laboratory analysis for the collected samples was performed, and then the soil properties were stored as attributes in a geographical soil database linked with the SMUs. Furthermore, land capability assessment was done to define the suitable areas for agricultural production using a capability model built in ALES software. Results indicate that the area currently lacks high capability and moderate capability classes. By improving the soil properties, the soil can attain potential capability; and 55630 acres will become marginally capable. The assessment of soil physical suitability for different land use types (LUTs) were analysed in ALES software, in order to generate the most suitable areas. The results from the land suitability analysis indicated that, 17114 acres are moderately suitable for wheat and sorghum; whereas 15823 acres are moderately suitable for barley and 12752 acres are moderately suitable for maize, olive and figs. Finally, the SLU was investigated based on two scenarios; (1) the most SLU under the conditions of shortage of irrigation water: clover, barley and sorghum against figs, as the irrigation requirements for barley and sorghum are low; (2) the most sustainable land use in the conditions of irrigation availability will be wheat and maize against figs and guava. From the results it is quite evident that GIS combined with modeling approaches are powerful tools for decision making in the study area.

Soil resource assessment and mapping using remote sensing and GIS

In this study digital image processing for physiographic analysis and soil resource mapping of Solani watershed was carried out using satellite remote sensing data and GIS. Digital image processing of satellite data facilitated in accurately delineating and identifying various soil mapping units. The physiography of the study area is mainly influenced by denudational and colluvial processes in the upper part and by sedimentation processes in the lower part. Topography of the land and nature of parent material along with the time factor seemed to have played a vital role in the genesis of soils. Majority of the mapping units are Typic Haplustepts with Entisols and Inceptisols being the major soil orders. The soils of the Siwalik hills experiences severe erosion, which prevents the maturation of soil profile. The present study demonstrated that satellite remote sensing and GIS is a valuable tool for physiographic analysis and soil resource mapping.

An approach to extrapolate categorical agricultural soil data to nonmapped areas using majority vote

AbstractSoil maps are indispensable base material for planning processes and risk analyses. For many studies, however, area‐wide uniformly scaled soil maps are not available. Our objective was to develop a GIS‐based method for providing information for NoData areas of the Medium‐Scale Agricultural Site Mapping (MMK). NoData areas represent nonagricultural zones, in this case especially forests. A grid‐based methodology for extrapolating soil mapping units of agricultural areas to the entire landscape was developed and tested in Mecklenburg–Western Pomerania (total area 23,170 km2). The principle of the extrapolation method is based on a statistical neighborhood analysis implemented by the moving‐window technology considering selected site features as geology, altitude, and relief energy. Results were illustrated exemplarily for soil‐moisture conditions, which are expressed as “hydromorphy association types”. Four different indicators were derived to ensure a spatially differentiated evaluation of the extrapolation quality. The precision with which it is possible to extrapolate already mapped MMK units in terms of the hydromorphy association type was used to validate the extrapolation method. Evaluation of the results was based on the percentage of Correctly Extrapolated Pixels (CEP), which were derived from a confusion matrix. The percentage of CEP was 26% when the 15 single classes of the hydromorphy association type were considered separately. The percentage of CEP rose up to 65% after grouping the hydromorphy association types into three practically combined categories. It could be demonstrated that the extrapolation technique applied represented an objective and relatively fast and cost‐effective method to obtain an area‐wide MMK mapping.

Application of a very detailed soil survey method in viticultural zoning in Catalonia, Spain

<p style="text-align: justify;"><strong>Aims</strong>: The aim of this study was to implement a very detailed soil survey methodology in 1,243 ha of vineyards in Catalonia (Spain) and analyse its suitability for viticultural zoning.</p><p style="text-align: justify;"><strong>Methods and results</strong>: The Soil Taxonomy at series level was used as the basis for classifying soils and delineating soil map units at 1:5,000 scale. A principal component analysis showed that most of the variability of soil properties, which was explained by factors related to water stress, iron chlorosis and vegetative growth, was not reflected exactly in the soil map unit classification. A k-means clustering analysis was proposed in order to group soils according to their potential for vine growing.</p><p style="text-align: justify;"><strong>Conclusion</strong>: A very detailed soil survey method, based on Soil Taxonomy, could be used as a basic map for viticultural zoning, when was directed at the differentiation of zones of distinct suitability for vineyard growing, by means of cluster analysis.</p><p style="text-align: justify;"><strong>Significance and impact of study</strong>: This study showed how very detailed soil maps, which can be difficult to interpret and put into practice, can be valorised as viticultural zoning maps by means of a simple methodology.</p>

Soil and Plant Property Differences Across a Chronosequence of Humid-Temperate Tallgrass Prairie Restorations

The potential effects of grassland restoration in the warm-temperate humid zone of the midsouthern United States have received much less attention than that in the upper midwest or Great Plains. Restoration response will likely differ from that observed in other regions under different climate regimes. The objective of this study was to evaluate the effects of prairie restoration on near-surface soil properties and vegetation characteristics across a chronosequence of tallgrass prairie restorations (i.e., 3, 4, 5, and 26 years old) and a local native tallgrass prairie in the Ozark Highlands. Soil bulk density, pH, electrical conductivity, extractable P, K, Ca, Mg, Na, S, Fe, Mn, Zn, and Cu, organic matter, and total N and C in the top 10 cm, aggregate stability, soil surface carbon dioxide flux, and aboveground and belowground plant dry matter and N and C contents were determined along a 60-m transect established in the soil mapping unit most similar among each ecosystem between Fall 2005 and Fall 2006. All soil properties evaluated differed (P < 0.05) among the prairie ecosystems. Most extractable soil nutrients decreased, whereas soil organic matter and total C increased with restoration age and tended toward that observed in the native prairie. Soil surface carbon dioxide flux did not differ systematically (P = 0.20) among prairie ecosystems, but maximum fluxes were observed at approximately 50% water-filled pore space. Neither aboveground biomass nor necromass dry matter differed, although root biomass and C and N contents late in the 2006 growing season differed among prairie ecosystems. The known historic presence of tallgrass prairie throughout the Ozark Highlands suggests that current and future tallgrass prairie restorations can be ecologically successful in the region, but the combination of topographic, edaphic, and climatic conditions of the region may also provide unforeseen challenges to restoration managers.

Soil and Vegetation Differences from Peridotite to Serpentinite

Pedologists and ecologists generally consider peridotite and serpentinite together as common serpentine soils or substrates. A detailed survey in the Klamath Mountains, CA, with separate soil map units on peridotite and serpentinite revealed appreciable differences in geomorphic and pedologie features between these types of ultramafic rocks. Slopes tend to be steeper on peridotite and the soils redder. More Alfisols (Luvisols) were found on peridotite, and more Mollisols (Phaeozems) on serpentinite. Very shallow soils (7% of the area), which are mostly Mollisols and Entisols (Leptosols), are more common on serpentinite. Barrens are commonly fragmental colluvium (talus) on peridotite and erodible, slightly to moderately stony summits and slopes on serpentinite. The most obvious vegetation differences related to parent material are on very shallow and shallow soils, with more coniferous trees (Pinus jeffreyi [Jeffrey Pine] > Calocedrus decurrens [Incense Cedar] > Pseudotsuga menziesii [Douglas Fir]) and Quercus durata (Leather Oak) on peridotite, and more Ceanothus cuneatus (Buckbrush) and Vulpia microstachys (Annual Fescue) on serpentinite soils.

Assessment of Soil Limiting Factors Effect on Land Productivity at Wadi El-Faregh Area, West of Delta, Egypt

Agricultural expansion in Egypt is the central tool to maximize agrarian production. Generally, agricultural development has multiple mechanisms and sequent procedures in which land evaluation has the superiority. The major concept of land evaluation is to assess limiting qualities of land capability for maximum land utilization through land use planning. This study aimed at evaluating the influence of soil limiting characteristics on its productivity in a newly reclaimed area at Wadi El-Faregh area. Studied area which extends over 3000 feddans was surveyed by digging forty five soil profiles representing current farms and dominant problems. The soil could be classified as Typic Torripsamments, Lithic Torripsamments and Typic Quartzipsamment with differentiating seven soil mapping units differ in profile depth, soil salinity, lime content and soil texture. Field investigations showed that 66.3% of the studied area has deep profile, while shallow depth covers only 5.7% of the area. Sandy loam soil texture is dominant over 61.1% of the area, and the rest of area has either sand or sandy clay loam texture. Most of the area considered non to moderately saline, while only 10.7% is salt affected. The studied area is non calcareous to moderately calcareous over 83.6%, while 16.4% of the area has high lime content. Gravel content is negligible except for some limited sites over 3.5% of the area having moderate surfacial gravels. Well water samples have relevant quality for agricultural purposes except for well no. 6 and 7 which were affected slightly with salts. Limiting properties of land capability may be concluded as dominant sand content, shallow profile depth at some sites, salt and/or lime some affected sites and poor fertility status. The studied area is evaluated as order Suitable and classified into two capability classes; Fair representing 83.6% as productivity index ranged between 41.0 – 57.3%, and Poor extending over 16.4% of the area with productivity index varied from 29.5 – 35.9%. Best recommended winter crops are wheat, barely, alfalfa and faba bean, while in summer they are sorghum, sunflower and peanut. Seven different fruit trees are suitable in the studied area with the following sequence: date palm, olive, grape, apple, citrus, pummel and guava.

The effect of survey density on the results of geopedological approach in soil mapping: A case study in the Borujen region, Central Iran

Landscapes are considered to be complex systems that are hierarchically structured and spatially scale-dependent. Geopedology allows a systematic approach in geomorphic analysis for soil mapping that extrapolates the results obtained at sample areas up to similar units. This paper examines the influence of sampling intervals on the accuracy of geopedological results in the Borujen region, Central Iran. After a primary interpretation of the study area on air photos (1:20 000), a geomorphic unit that encompassed the maximum surface of the sample area (and also the study area) was selected and was surveyed at three different scales: 500, 250 and 125 m intervals. The credibility of generalization of the results of the geopedological approach for the studied unit was tested by comparison with three profiles in a similar unit outside the sample area, named the validation area. Although the type of mapping unit in the sample area and the validation area was the same (complex) at the three different scales, the dominant soil in the validation area was different in comparison with the sample area at 125 and 250 m intervals. The results indicate that the geopedological approach to soil mapping is better carried out in reconnaissance or exploratory surveys. Comparison of soil types between the unit in the sample area and the validation area at three scales indicated that by increasing the taxonomic accuracy, the hidden aspects of the soils may be more identifiable. Therefore, although the geopedological approach tries to distinguish more homogeneous soil mapping units, it still is not able to fully define and represent the variability and apparent chaotic nature of the soils. We recommend further investigations on different techniques of stratifying the landscape in order to better analyze and understand the soil forming processes and soil variability and to improve sampling and mapping approaches.

Global pedodiversity, taxonomic distance, and the World Reference Base

This paper discusses the study of taxonomic distance and pedodiversity by (1) deriving taxonomic distances for the World Reference Base for Soil Resources (WRB), (2) calculating pedodiversity indices at the global scale using the soil map of the world at a scale 1:25M, and (3) comparing traditional diversity measures which are based on abundance of soil individuals to measures that are based on taxonomic distance. Based on dominant identifiers in the WRB soil groups, taxonomic distances were derived between the soil groups and plotted in feature space. Using this information the soil's mean taxonomic distance for the world was calculated. The mean taxonomic distance combines the abundance and taxonomic relationship between soil groups and appears to be a useful index of pedodiversity. There is a good relation between mean taxonomic distance and climate or soil classes; areas with extreme temperatures and precipitation have the lowest pedodiversity. It was observed that areas with more detailed soil mapping units exhibit the largest pedodiversity and it was concluded that the measure of pedodiversity depends amongst others on the detail of the soil survey in an area.

Carbon stocks in Scottish peatlands

AbstractVarious estimates have suggested that the peatlands of Scotland are a significant deposit of fixed carbon. However, these have been based upon rather imprecise estimates of peat depth. Using previously unused archived data, we have mapped peat depth across the country and then used these values to obtain an improved value of the total carbon stock within peatlands, as well as indicating their spatial distribution. We included peat deposits that occur in combination with other soils in soil map units other than ‘blanket’ or ‘basin’ peat. We obtained an area‐weighted mean peat depth of 2.0 m, which is slightly shallower than previous estimates. Using values of bulk density and % carbon from the Scottish soils database, the total peatland carbon stock came to 1620 Mt, which represents 56% of the total carbon in all Scottish soils.

PEMETAAN BAHAYA LONGSORAN BERDASARKAN KLASIFIKASI STATISTIK PEUBAH TUNGGAL MENGGUNAKAN SIG: STUDI KASUS DAERAH CIAWI-PUNCAK-PACET, JAWA-BARAT

Regarding environmental degradation in Puncak and its surrounding area due to the rapid landuse changes during 1981-1994, some mitigation schemes for soil erosion have been implemented but landslides. Data on landslide and its causative factors (landuse, soil, geology, slope, climate, and terrain mapping unit) and their relationships in the area are still not available. The objective of this research is to develop the method and procedures to map landslide hazards by using GIS (Geographical Information System) univariate-statistical analysis applied to the area as a case study. For this purpose, three methods to classify and to map landslide hazards were evaluated. They were respectively developed by considering: (a) unweighted density total number of the landslide, Method#1, (b) density total number, weighting value, and age of landslide, Method#2, and (c) density total number, weighting value, age, and activity level of the landslide, Method#3. The density number is counted by overlying· each of the landslide maps and each of the causative factors maps used, and from this step, the weighting value is derived. The resulting density number of landslide given as a cumulative percentage and the corresponding weighting value were then plotted on an X-Y graph. From the graph, the level of landslide hazard is classified by applying: (1) standard classification procedure as the default statistical analysis given by the software used, and (2) natural classification procedure as it based on the nature of the curve slope of the cummulative graphic. The result given by the three methods were varied but in general, they gave landslide hazard maps with a similar pattern in which the very high and very low hazard levels in the study area increased during the period of 1981-1994. Of the three methods, applying the natural classification gave a better result than that of the standard classification procedure. Method#2 and Method#3 were better than Method#1 in predicting the future landslide occurrence. Apparently, Method#3 should show the best result but the effect of conversion from raster to vector data in GIS significantly reduced the quality of the resulting map.

Comparative Land Evaluation approaches: An itinerary from FAO framework to simulation modelling

The FAO framework for Land Evaluation (LE) has been the primary procedure used worldwide to address local, regional, and national land use planning. Despite its widespread and long-term application, the process has been criticised by the scientific community for its qualitative and empirical base, which is not effective to address many new agro-environmental challenges where the dynamic characterisation of the interrelated physical and chemical processes taking place in the soil landscape is a must. In today's environment, the LE expert is asked to choose the best LE methodology considering costs, complexity of the procedure and benefits in handling a specific land evaluation. Unfortunately very little scientific literature supports this choice especially in terms of the comparison of different LE approaches. In this scenario, we performed a forage maize land suitability study by comparing different methods having increasing complexity and costs. The study area was comprised of approximately 2000 ha and was located on the Lodi Plain (Po Valley) of North Italy. The primary land use in the region is forage maize and this study was designed to assess forage maize biomass. Methods were developed and applied to compare the efficacy of procedures of increasing complexity. The range of the 9 employed methods ranged from standard LE approaches to the extensive use of simulation modelling (SWAP and CropSyst), using as data input pre-existing soil information (soil map 1:50,000) and also hydraulic properties measured as well estimated by PTF(pedotransfer functions). The different methods were compared based on both predictive ability and cost. Independent estimates of forage maize biomass were obtained by locally tested remote sensing measurements, and predictive ability was estimated using statistical indexes including correlation, relative variance, and ANOVA to evaluate the mean differences in maize biomass. The level of expertise required to apply a specific methodology was a factor in the cost of the LE. In addition, an increase in method complexity corresponded to a higher quality/quantity of input parameters and as a consequence higher costs. Generally, more complex methods gave better results in terms of their predictive ability but this occurred in much discontinuous steps; this finding contradicts a simplified view on the better performance of more complex and mechanicistic methods. Methods operating on measurements resulted in increased performance relative to those operating on PTF. Furthermore, methods operating on “true” soils without aggregations (i.e. soil-mapping units) exhibited higher performance.

Geoarchaeology of a Strath Terrace in the Upper Ohio Valley, West Virginia

Soil characterization and distribution on a narrow ridge strath terrace bordering the Ohio River in the northern panhandle of West Virginia was evaluated to determine the stratigraphic context of the cultural remains of two prehistoric archaeological sites. Five soil map units were delineated in the project area based on the distribution of regolith materials and associated soil characteristics. Shale and sandstone residuum in the central crest of the ridge is covered with a laterally discontinuous mantle of Pleistocene alluvium, 0.25 to &gt;1.2 m thick, and a continuous mantle of Late Pleistocene loess, 0.25 to 1.1 m thick. Hapludalfs formed in the loess over alluvium, or in loess over residuum, indicate moderate to long‐term (e.g., 12,000 yr) pedogenesis. On steep shoulder slopes, Dystrudepts in shallow residuum with little to no loess indicate limited pedogenesis and possible early to mid‐Holocene erosion. Panhandle Archaic inhabitants of Site 46Br31 (∼6090–3400 yr BP) harvested freshwater mussels from the Ohio River below the ridge, and after consumption discarded the shells on the shoulder slopes at the southern end of the ridge. The resultant shell middens, largely disturbed by 20th century relic hunters, form a complex map unit of Dystrudepts and Udorthents. The distribution of soils on this ridge and the associated archaeological remains indicate that the successive occupations of prehistoric Native American inhabitants lived on the same ground surface. The resultant cultural remains were not buried or stratigraphically separated. The modern soil surface is an approximate, although eroded, remnant of the occupied ground surface. The vertical distribution of artifacts reflects several millennia on a mature soil surface with an evolving biomantle.

Residual soil nitrate in irrigated Southern High Plains cotton fields and Ogallala groundwater nitrate

Nitrate (NO3) is the most important contaminant of the Ogallala aquifer in West Texas, especially in counties south of Lubbock. Twenty percent of the wells in the 11-county study area of West Texas had >10 mg L-1 (ppm) NO3-N in the groundwater. The source of this NO3 is not clear. Leaching of residual soil NO3 from the 1.2 million ha (3 million ac) cotton land is a possibility, but it may take several decades for percolating water to reach the depth of the Ogallala groundwater. In this paper, soil profile NO3 data from eight cotton fields from five counties across the Southern High Plains of West Texas are presented. Soils were sampled to 90 cm (36 in) in four depth increments. Nitrate-N levels in the surface 0 to 15 cm (0 to 6 in) soil were low, averaging 15 kg N ha-1 (13 lb ac-1). However, extractable NO3-N content averaged 58 and 96 kg NO3-N ha-1 (52 and 86 lb ac-1) in the 0 to 60 (0 to 24 in) and 0 to 90 cm (0 to 36 in) soil profiles, respectively. Soil profile NO3-N was greatest in calcareous soils, soils with petrocalcic horizons and in Acuff loam soils. Soil profile NO3-N content or profile distribution was not consistently related to soil type. We also compiled and analyzed Texas Water Development Board irrigation well NO3-N concentrations by county and soil map unit. Well water NO3-N was greatest in Lynn county (12.8 mg L-1) and lowest in Hale county (2.7 mg L-1). Groundwater NO3-N and soil map unit data were not related in a consistent pattern in terms of soil texture. Well depth and well water NO3-N concentration were negatively correlated (r = -0.56). Irrigated cotton producers should test their well water for NO3, as this can be a significant source of N. Good N management requires N fertilizer applied at rates appropriate for yield goals for specific irrigation systems and water availability, resulting in minimal residual soil NO3 at harvest. Deep soil sampling, i.e. 0 to 60 or 90 cm (0 to 24 or 36 in) can help maximize profits and protect NO3 contamination of the Ogallala aquifer.

Characterizing and Classifying Variability in Corn Yield Response to Nitrogen Fertilization on Subfield and Field Scales

Marked spatial and temporal variability in yield response to N fertilizer observed in individual yield response trials creates a high degree of uncertainty when estimating economic optimum rates (EORs) of N for a group of trials and when extrapolating these rates from one location to another. A survey was conducted to characterize and classify variability in yield response to N on subfield and field scales. Fertilizer N was applied at five rates (56, 84, 112, 140, and 168 kg N ha−1) in many (6–12) replicated strips within three 18‐ to 24‐ha no‐till fields during two corn (Zea mays L.) growing seasons. Yield responses or yield differences between two adjacent strips were measured in 22 to 25 grid cells ha−1 within each field. Cumulative probability distributions (CPDs) were used to estimate the probability that a given N rate produces a yield response less or equal to a specified quantity. The yield responses were classified into potential categories with different N fertilizer requirements using apparent soil electrical conductivity (ECa), digital soil map units, and relative elevation. Analysis indicated that the classifications explained &lt;3% variability in yield response to N applied in the near‐optimal range, where probabilities of receiving positive and negative marginal returns were the same. Presenting probabilities of yield response observed at different ranges of N fertilization may provide the basis for assessing the uncertainty associated with the variable effects of weather and variable supply of N when assessing economic risk and benefits of N fertilization in large‐scale on‐farm studies.